Cognitive control refers to the ability to regulate cognitive processing according to the tasks at hand, especially when these are demanding. It includes maintaining and updating relevant information in working memory, inhibiting irrelevant information, and flexibly switching between tasks. Performance monitoring denotes the processing of feedback from the environment and the detection of errors or other unexpected events and signals when cognitive control needs to be exerted. These two aspects of behavioral adaptation critically rely on the integrity of the frontal lobes, which are known to show pronounced age-related performance decrements. By contrast, there is evidence that processing of rewards remains relatively intact across the adult lifespan. Hence, motivation may play an important role in modulating or even counteracting age-related changes in cognitive control functions. To answer this question, neuroscientific data can be particularly useful to uncover potential underlying mechanisms beyond behavioral outcome. The aims of this article are twofold: First, to review and systematize the extant literature on how motivational incentives can modulate performance monitoring and cognitive control in young and older adults. Second, to demonstrate that important pieces of empirical data are currently missing for the evaluation of this central question, specifically in old age. Hence, we would like to stimulate further research uncovering potential mechanisms underlying motivation-cognition interactions in young and in particular in older adults and investigating whether or not those can help to ameliorate age-related impairments. It is well known that many cognitive functions, mainly those from the domain of fluid intelligence, decline with increasing age . By contThe goal of this article is to review and systematize recent research examining the influence of motivational incentives on performance monitoring and cognitive control across the adult lifespan. Performance monitoring denotes the processing of environmental feedback, the detection and processing of errors and of unexpected events. It is an important prerequisite for the flexible adaptation of behavior to varying situational demands because it signals when our behavior was inadequate or did not lead to the expected goal. It is also a precondition for the implementation of cognitive control because it signals when (more) cognitive control is needed. Cognitive control is the ability to guide one’s own behavior and cognitive processes in a goal-directed way. It is a multidimensional construct comprising several core components, including the ability to select relevant information, to keep it active in working memory and protect it against irrelevant information .Tables 2). Thus, we will briefly summarize research findings in young adults and focus on older participants whenever possible. Finally, we will discuss the extant empirical findings on motivation–cognition interactions in the light of aging models on cognitive control functioning  and discuss caveats and limitations that this line of research is confronted with, in particular the lack of systematic evaluations of cognition-motivation interactions in older adults .These fundamental cognitive functions constitute the basis for more complex abilities like adaptive behavior, rational decision making, or self-regulation . They alA fundamental question is whether the processing of rewards and punishments changes across the adult lifespan. If younger and older adults process these incentives differently, this fundamental difference may have important implications for how and whether incentives can exert their influence over other cognitive processes.per se are not the main focus of this article, in the following we will present only a short summary on the main findings of this research area and direct the interested reader to the respective literature  studies have examined the activation of reward networks during the anticipation and the delivery of rewards by means of incentive delay tasks. In young adults, these studies have consistently found that anticipation and delivery of rewards and punishments activate parts of the ventral striatum , the insula, the dorsal midbrain, and the orbitofrontal cortex e.g., . This liper se, older adults show decreased functioning in processing reward prediction errors, i.e., the difference between expected and actual rewards  and several components have been associated with their detection .Performance monitoring involves a cognitive as well as an affective component, which are probably inseparably interwoven in daily life. For instance, receiving negative feedback from another person regarding our behavior is rarely just purely informative, but also has an emotional impact. Therefore, a separation of performance monitoring and motivational influences on performance monitoring is difficult. This is also reflected in recent research where oftentimes no differentiation is made between “abstract performance feedback” and “reward or punishment feedback.” Instead, it is assumed that even abstract performance feedback has a rewarding or punishing effect and thus has a motivational impact. Conversely, it is oftentimes implicitly assumed that monetary gains can be used as positive feedback and losses as negative feedback without affecting the basic monitoring processes cf. . For thiIn fMRI studies, evidence has accumulated showing that activity in the striatum varies as a linear function of reward magnitude. For example, per se, but to the size of the prediction error. This might or might not coincide with reward magnitude, depending on the study design. In contrast to the FRN, reward magnitude has been found to influence a later ERP component, the P300. The P300 is a large positive deflection following the FRN that is probably associated with working memory updating after unexpected task-relevant events  and compared to a neutral condition without incentives. Taken together, cues signaling potential rewards seem to be effective motivational incentives for young adults and enhance error and feedback processing when there is room to improve performance. To our knowledge, there are no similar studies examining the effect of motivational incentive cues on performance monitoring in old age. However, because performance monitoring is a prerequisite for behavioral adaptation which is impaired in older adults (see section “Reward Prediction Errors”), it would be crucial to know how it could be supported or even improved.Another approach to investigate motivational influences on performance monitoring is to compare the effects of different types of reward feedback. In the context of performance monitoring, the most commonly used types of feedback are abstract performance feedback, e.g., symbols informing participants whether their response has been correct/incorrect, and monetary feedback, i.e., amounts of money won/lost. Other types of feedback are scarcely investigated. However, different types of rewards can have a different subjective value and therefore have different motivational impact. Which reward is perceived as most motivating could also change across the lifespan. For instance, preserved cognitive functioning plays a key role in old age . Hence, In line with this idea, some studies have used social stimuli as feedback, like social acceptance or rejection  or emotiOnly a handful of studies have explicitly contrasted the effect of different types of rewarding feedback in the same paradigm. Importantly, although these behavioral studies use paradigms that are commonly used in the area of performance monitoring, one can only speculate which specific cognitive processes are affected by the incentives in these tasks. Here, neuroscientific measures can be extremely helpful. To this effect, Functional magnetic resonance imaging studies provide evidence that there are common as well as distinct brain areas involved in processing different types of rewards. Together, the existing data speak in favor of an anterior–posterior gradient in the orbitofrontal cortex, with primary reinforcers activating more posterior areas and more complex or abstract reinforcers activating more anterior regions . HoweverTo conclude, the above studies demonstrate that motivational factors consistently enhance performance monitoring and improve performance in young adults. Neuroscientific studies examining age-related differences in this domain are rare and longitudinal data are missing completely, so it remains an open issue whether or under which circumstances motivational factors can enhance performance monitoring in older adults and diminish age-related impairments. Still, some preliminary conclusions can be drawn from the existing studies. First, adding additional information to the feedback stimulus seems to be an inappropriate way to examine motivational influences in older adults. This may be due to limited processing resources, which force older adults to focus on the most relevant properties of a feedback stimulus cf. . Thus, tper se. In line with the vulnerability of the PFC to aging, many empirical studies to date have identified pronounced age-associated deficits in tasks requiring cognitive control, specifically as task demands increase . Finally, the recruitment of additional control processes is effortful and cannot be maintained for long periods of time, otherwise it would be optimal to keep cognitive control up-regulated for the duration of the task . Note that some of the studies reported in this section examine performance monitoring, however, with a specific focus on how it may lead to enhanced cognitive control. In Section “Performance Feedback as Incentive,” we will examine how subsequent task performance and cognitive control are affected by performance feedback, which is often used in a non-systematic fashion in a general attempt to improve performance. Section “Processing of Reward Feedback” will summarize how experimentally introduced rewards or losses act as incentives for engaging in effortful cognitive control, whereas Section “Dissociating Specific Processing Stages With Incentive or Task-Preparation Cues” will focus on the role of different incentives cues and how they might differentially influence cognitive control.In the following, we will review empirical evidence on whether and how motivation can moderate the amount or type of cognitive control recruited in service of task performance  compared to following a correct response feedback (p = 0.33). The authors attributed this particular difficulty in regulating response speed to age-associated deficits in the dopamine system responsible for precise motor timing. In line with the results reported above, both age groups were more accurate in producing a precisely timed motor response following positive compared to negative feedback  correct task performance, often consistently across many trials . While this approach will not capture potential trial-by-trial fluctuations of cognitive control, some strategic adjustments may rather be reflected in tonic activity. Taking advantage of this approach, formance . Thus, eTo summarize, rewards consistently modulate young adults’ behavior when provided contingent on individual performance. Positive incentives promote fast responses presumably via advance preparation, albeit sometimes at the expense of increased errors rates in rare task conditions requiring response inhibition. In these reward conditions, neuroimaging studies have identified a network of sustained activity predominantly in lateral prefrontal brain regions consistent with task maintenance. Introducing penalty incentives does not activate these areas and tends to have weaker impact on performance, associated with slower responses and a more conservative response criterion.To our knowledge, only three studies so far explicitly studied rewards in the context of aging in cognitive control paradigms. To summarize, tentative evidence available so far suggests that behavioral age differences in cognitive control persist when monetary rewards or losses are added to the informational content of performance feedback. Older adults appear to scarcely modify their behavior based on rewards. Conversely, young adults incorporate reward contingencies more flexibly, in particular when emphasis is placed on response speed. Hence, young adults might revise their current strategy, but not necessarily recruit additional control processes successfully . As a result, the precise impact of incentives often depends on which aspect of behavioral performance is examined. Notably, the scarce extant data point to an incentive-based shift in task strategy for the young, but not in older adults. Imaging data complement this picture with unspecific or de-differentiated brain activation patterns during advance preparation cf. . Howeverinc and LPC) were observed considerably earlier, suggesting that reward prospects modulate the temporal dynamics of conflict processing . Moreover, indices of effort put into task by each individual and age group, independent of behavioral outcome, could help to shed more light on complex motivation–cognition interactions and avoid circular argumentations. The precise implications of a lack of controlled processing in young adults with healthy PFC functions for potential aging effects in the same task remain unclear. Again, neuro-scientific measures can be fruitful for this endeavor in the future, but at present inter-individual variability in the strategies employed during a specific task or in cognitive reserve more generally, limit viable interpretations of task-unspecific brain activations. The DMC framework has been very instrumental in dissociating cognitive control processes, and spurred empirical evidence of how motivational factors can moderate cognitive control in young and older adults. Conversely, a clear taxonomy of paradigms used to investigate these effects and their implications cognitive control and its specific timing  is still missing to date.We report empirical findings demonstrating that incentives can modulate performance monitoring and cognitive control. Although studies examining age-related differences across adulthood are scarce, the existing ones indicate that under specific circumstances incentives can ameliorate age-related deficits. However, even apparently subtle inconsistencies between paradigms may have important implications seriously limiting the conclusions that can be drawn at this point. Clearly, future research is needed to clarify (a) the specific circumstances under which incentives can reduce rather than enlarge age-related impairments, (b) which types of incentives are most effective in which age group, and (c) the role of increased effort in overcoming individual differences in ability underlying performance differences in young but especially among older adults. Critically, due to compensatory use of differential strategies or increased effort, the true amount of age-related deficits may be systematically underestimated. While both ways to ameliorate performance deficits are useful and should be encouraged, they cannot be maintained over a longer period, hence it is important to differentiate between typical performance in old age and what can be achieved using all available resources and highest level of motivation. To achieve this, careful and innovative analyses on several aspects of behavioral performance are needed along with neuroscientific methods that together can shed light on the specific neuronal substrates and cognitive processes involved in successful task performance. We also noted several general caveats impeding research in this area, including the fact that participants differ in their long-term motivation to take part in research which can mask age-differences as long as (some) older adults are able to compensate. This substantiates the need to focus on neural activation patterns that can uncover both cognitive and motivational mechanisms underlying age differences in performance.All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Blood vessels can no longer be seen as just passive conduits for delivering blood. Endothelial cells lining blood vessels separate blood from surrounding parenchymal cells. This unique position allows endothelial cells to sense the presence of nutrients in blood plasma and to subsequently control their flux into tissue. Recent work demonstrates that the movement of metabolites across the endothelial barrier occurs in a highly regulated manner –3 and thThe organ-specific endothelium provides a rich set of membrane-bound and secreted factors (referred to as angiocrine factors), which coordinate organ development, tissue regeneration, the maintenance of stem cells and metabolism . TherefoHere, we discuss one such aspect, namely endothelial control of long chain fatty acid (LCFA) transport to myocytes and its implication for cardiac function. LCFAs are the most abundant energy source for cardiac muscle cells. Although still under debate, it is assumed that a significant amount of circulating LCFAs reach the cardiomyocytes after first being taken up by cardiac endothelial cells and subsequently being released again at the basal site. Their active transport across the continuous endothelium is facilitated by a receptor-mediated mechanism in which the scavenger cluster of differentiation-36 (CD36) is involved. Son et al.  have recTo present knowledge, little is known as to how endothelial transport of LCFAs is actively regulated. Vascular endothelial growth factor B has been shown to regulate the transcription of genes of the fatty acid transport protein (FATP) family in addition to its role in inducing blood vessel expansion in the heart ,7 Our grWhat are the functional consequences of a metabolic shift from fatty acid to glucose consumption? Under normal conditions, heart, skeletal muscle and brown adipose tissue rely on fatty acids for energy in order to meet their high ATP generation needs. During aging, but also in several experimental models of heart failure, cardiomyocytes shift to an enhanced reliance on glucose metabolism. Our recent work indicates that such a metabolic shift – by interfering with endothelial LCFA transport to myocytes – can already accelerate heart failure in mice. We cannot entirely rule out that loss-of-Notch-induced changes in vascular morphology could contribute to cardiac dysfunction, however, feeding mice with a ketogenic diet strongly improved cardiac function , therefoIn summary, endothelial-mediated active transport of metabolites can govern the function of the supplied organ by regulating nutrient availability to parenchymal cells, and should be taken into account in future therapeutic interventions in tackling aging-related disorders.


This review aims to summarize the advance in the field of nanosensors based on two particular materials: polymer vesicles (polymersomes) and polymer planar membranes. These two types of polymer-based structural arrangements have been shown to be efficient in the production of sensors as their features allow to adapt to different environment but also to increase the sensitivity and the selectivity of the sensing device. Polymersomes and planar polymer membranes offer a platform of choice for a wide range of chemical functionalization and characteristic structural organization which allows a convenient usage in numerous sensing applications. These materials appear as great candidates for such nanosensors considering the broad variety of polymers. They also enable the confection of robust nanosized architectures providing interesting properties for numerous applications in many domains ranging from pollution to drug monitoring. This report gives an overview of these different sensing strategies whether the nanosensors aim to detect chemicals, biological or physical signals. Polymer sensors play an important role in monitoring our environment and could become soon an essential part of our modern sensor devices , 2. AmonPolymersomes are interesting artificial vesicles to be considered for nanosensors due to their strong responsiveness to variety of stimuli. For example, the sensing mechanism of the polymersomes based on detectable fluorescence or color transition can be caused by diverse environmental triggers such as pH and redox potential. In recent years, nanosized polymersomes have also been developed to detect different ions, small molecules, macro-molecules or enzymes. In comparison to polymer micelles or nanoparticles, polymer vesicles are able to carry not only hydrophobic but also hydrophilic cargo within their core. In addition, many polymersomes are nontoxic for organisms but exhibit thicker and more robust membranes compared to their biological counterpart: liposomes. As a result, their unique architecture makes polymer vesicles very promising candidates for nanosensors.+ according to increased glucose metabolism [pH-responsive nanosensors are one of the most designed stimuli-sensitive vesicles since a lot of natural processes are highly pH-dependent, such as degradation of biomacromolecules. Moreover, vesicles sensing the decrease of the physiological pH value are very useful in cancer diagnosis, since tumor cells produce more Htabolism .+ which allows quantitative information about the pH area. Another strategy consists in the encapsulation of fluorescent benzoxazole (BZ) molecules in the cavity of polymersomes made of self-assembled mixed polydiacetylenes (PDAs) and phospholipids [For developing such biosensors, Quan et al.  encapsulholipids . In suchAlso, Palivan’s group prepared Horseradish Peroxidase (HRP) loaded polymersomes with an integrated pH responsive pore . The outArmes and coworkers presented a new type of polymersomes tagged with a pH-sensitive dye: a Nile Blue-based label . At low Recently, Craciun et al.  created Most reduction-sensitive vesicles contain disulfide bonds in the polymer membrane to achieve structure loss in the presence of reducing agents, like glutathione , 14. ThoRecently, Palivan’s group developed artificial organelles which enabled the detection of changes in glutathione concentrations . Protein2O2), dioxygen and adenosine triphosphate (ATP) to name but a few. Several strategies using sensitive polymersomes were developed for their detection. Vesicles produced through the assembly of conjugated polydiacetylene is one of them. Polydiacetylenes have been well studied for their chromatic-transition properties and have been successfully employed for the development of colorimetric biosensors since the polydiacetylenic structures can change color with environmental perturbations [Many different compounds and molecules can act as bioactive signals as hydrogen peroxide  and its derivatives among ions in water [2 has been used as the driving force for detection amide). Exogenous ATP could passively diffuse through the membrane and quenched the reporter polymer. Then, alkaline phosphatase hydrolyzed the reporter bound-ATP leading to partial recovery of its emission. Such system could be considered as a model for processes involving accumulation/consumption of ATP inside discrete vesicular compartments.In addition, a polymersome-based sensor for adenosine triphosphate (ATP) has been developed by Liedberg and coworkers . They en+, Na+ or H+ can be detected by polymersomes formed from a library of different poly(2-methyloxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyloxazoline) (PMOXAx-PDMSy-PMOXAx) triblock copolymers, thanks to a particular ion selective permeability. The insertion of gramicidin (gA) peptides in their membrane formed biopores that permit different ions to enter inside the vesicles cavities. This exchange across the membrane can be visualized through the encapsulation of dyes that are specific to these compounds: changes in fluorescence intensity are observed upon the entrance of these small molecules inside polymersomes [Moreover, several ions such as Kmersomes .Also, Zhang et al.  developeHammer’s group focused on the development of a nano-biosensing platform made of patterned microfluidic synthesized cell-sized polymersomes that are immobilized on a surface . These mEnzymatic sensors cover a wide range of applications and can be used to detect special types of cells , pathogenic micro-organisms or even genetically modified organisms. Kim et al. developed biohybrid polymersomes that respond to matrix metalloproteinase type 1 (MT1-MMP1) which plays an important role in metastasis associated-cancer cell trafficking . The senStaphylococcus aureus bacteria. Another group also focused on the detection of Staphylococcus, using PDA vesicles coupled to specific antimicrobial enzyme lysostaphin [Other enzyme-responding polymersomes are promising candidates for targeting bacterium. Haas et al. created a new hyaluronidase-sensing system based on hyaluronic acid and polycaprolactone that can be assembled into polymersomes by inversed solvent shift method . The triostaphin . A colorostaphin  developePhysical phenomena provide extremely convenient usage in vivo as they are deeply penetrating the tissue, relatively safe and easy to use. In that regard, a lot of studies have been focused on the development of responsive polymersomes to physical changes  –32. In fChen et al.  reportedPlanar polymer membranes nanosensors are seeing a constant increasing interest and offer undoubted advantages over conventional analytical methods providing quicker and essential information. Different methods to develop distinctive planar polymer membrane based nanosensors have been established, but still effort has to be made in order to improve their performance. Polymer based nanosensors allow us now to probe numerous chemical or biological analytes, from gas, ions to more complex structure like protein or oligonucleotides. In that regard, the polymer membrane will play a major role in the recognition efficiency of the sensing device. Planar polymer membranes can be used to immobilize active species or improve the sensitivity through an improved signal transduction. In all cases the polymer membrane is either designed or chosen to provide an appropriate signal or improve the sensing device efficiency. This part of the review will focus mainly on the planar polymer membranes of the nanosensor and their characteristic features as material of sensors, whether they serve as recognition material, used as part of the transduction mechanism or operate as intermediate mechanical support or pattern. We cover the topic under four main sections, multiple components polymer membranes, molecularly imprinted polymer membranes, conducting polymer membranes and nanoporous polymer membranes. Certain polymer membranes can belong to several class of polymer, for instance, a conducting multiple components polymer membrane.4I4-metal organic framework (MOF) based mixed matrix membrane for gaseous HCl sensing. The polymer membrane was prepared by one-step in situ self-assembly of a tri-armed oxadiazole-bridged ligand and CuI in a polyvinylidene fluoride polymer binder solution. A clear colour change was observed from light yellow to dark red when the membrane was exposed to different concentrations of gaseous HCl, , composite membranes or hybrid organic–inorganic membranes, all refer to the same type of polymer membranes, they are all multiple components polymer membranes. Such membranes have been developed to overcome limitations encounter with conventional organic or inorganic materials. In those types of membranes, the polymer is rarely the sensing material but rather the material in which the organic or inorganic element is embedded. In MMM based sensors, polymer membranes can be designed to support different types of recognition elements, from the simple chemical probe as inorganic particles to the more complex ones as nucleic acid, enzyme, antibodies or cells . For insCl, Fig. . The chaAnother example of polymer-MOF composite membrane was developed by Sachdeva et al.  in orderNumerous multicomponent membranes are used for biosensors . For inso-aminothiophenol (ATP) and the electropolymerization of o-aminothiophenol functionalized gold nanoparticles (ATP@AuNPs). The incorporation of gold nanoparticles has been proved to increase the sensitivity towards simazine compound by 23 times, compared to a bare gold electrode. The rigid structure formed from ATP@AuNPs electropolymerization also improved the selectivity of the SMZ imprinted sensor.Among the several types of sensing materials using polymer membranes, the molecularly imprinted polymer (MIP) membrane is one of the most specific materials, as it requires the imprint of the analyte itself to develop the sensing material. Other methods with specific receptors as enzymes, microbes or antibodies show high selectivity towards their analytes but are often more expensive with a poor chemical or temperature stability , 40. MIPThe same method was also applied for the detection of endocrine disruptors in different media . For insThe class of “conducting polymer” includes several types of material with electronic or ionic conductivity as well semi-conducting polymers, doped conjugated polymers, redox polymers, polymer composites and polymer electrolytes. The great design flexibility of conducting polymers make them a polymer of choice for different type of sensors and are broadly used in chemical or biochemical sensors –47.−1  (PNTA) polymer was synthesized and blended with a poly(vinyl chloride) (PVC) to form a membrane. The polymer membrane was then incorporated to an electrode and its stability and response to aliphatic alcohols were recorded. Measurements showed stability up to 1000 s for six different aliphatic alcohols, as well as a good discrimination ability towards these short chain aliphatic alcohols.In the same way than multiple component polymer membranes, conducting polymer membranes can be tuned to mesh with an alternative material and to improve sensitivity and selectivity of the conductive material. The counter part of the organic polymer can be a metal oxide, a metal, an organic material or carbon nanotubes, to name but a few . Mahato 12-poly(ethylene oxide)8, with an integrated conjugated oligoelectrolyte acted as conductive interface that provided efficient electron transfer to the photosystem I and the second block-copolymer was used to stabilize the protein. After functionalization of gold electrodes with the conductive bilayer membranes, they reported a photocurrent approaching 35.0 μA cm−2, which was among the highest observed so far for such system on a per protein basis  one part of the polymer without affecting the assembly or organisation of the other block. They offer unique morphologies or ability to form nanopores . BCP canPolymer biochemical sensing membranes are based on the same principle than biological ion channels. There are mainly two types of detection signal that rely on the variation of ionic current in channels: sensing by volume exclusion effect and sensing by electrostatic effect. In nanopore sensing, the transmembrane ionic current is proportional to the pore size. The crossing of an analyte through the nanochannel decreases the cross-section and consequently affect the current signal measured. The measured current signal reflects then the size and shape of the molecule , 60. ForIn the second type of polymer biochemical sensing membrane, the sensing property is mainly based on electrostatic effect. The inner wall of nanochannels is functionalized with distinct recognition molecules depending on the targeted analyte . Ali et The use of polymersomes or planar polymer membranes offer a large spectrum of possibilities for sensing devices that would be difficult to achieve using other materials and allow us to overcome barriers encounter with conventional sensors. Nanoscale control of the engineered nanomaterials remains one of the most challenging part in building nanosensor devices as the sensitivity and selectivity of such system depend not only on the recognition but also on the transduction mechanism that are directly linked to the structural conformation of the polymer material. Even though polymer sensor represents one of the most widely investigated type of sensors, polymersomes and planar polymer membrane nanosensors are still facing a development phase and tremendous effort still have to be made in order to be more widely adopted in industrial applications. One of the drawbacks that is linked with the use of nanomaterials is the identification of the potential impact on human health and on the environment. As efficient and performant as those material becomes, the development of such nanomaterials simultaneously opens the door to several unknowns that have to be considered.


Cylindrical panorama stitching is able to generate high resolution images of a scene with a wide field-of-view (FOV), making it a useful scene representation for applications like environmental sensing and robot localization. Traditional image stitching methods based on hand-crafted features are effective for constructing a cylindrical panorama from a sequence of images in the case when there are sufficient reliable features in the scene. However, these methods are unable to handle low-texture environments where no reliable feature correspondence can be established. This paper proposes a novel two-step image alignment method based on deep learning and iterative optimization to address the above issue. In particular, a light-weight end-to-end trainable convolutional neural network (CNN) architecture called ShiftNet is proposed to estimate the initial shifts between images, which is further optimized in a sub-pixel refinement procedure based on a specified camera motion model. Extensive experiments on a synthetic dataset, rendered photo-realistic images, and real images were carried out to evaluate the performance of our proposed method. Both qualitative and quantitative experimental results demonstrate that cylindrical panorama stitching based on our proposed image alignment method leads to significant improvements over traditional feature based methods and recent deep learning based methods for challenging low-texture environments. Panoramic images are able to provide a wide field-of-view (FOV) of a scene, which is demanded in a number of applications, such as remote sensing ,2, envirA novel light-weight regression convolutional neural network (CNN) architecture called ShiftNet, able to handle low-texture environments properly, is proposed to predict robust shift estimates. ShiftNet can be trained in an end-to-end fashion using a large synthetic dataset generated from a publicly available image dataset. The performance of ShiftNet is superior to recent CNN models in terms of both model size and inference accuracy.A global illumination invariant sub-pixel refinement algorithm is proposed to improve the accuracy of the initial estimate obtained by ShiftNet under either a strict horizontal translation motion or a translate and scale motion assumption. The refinement procedure is essential for cylindrical panorama stitching because the outputs of a CNN model are not accurate enough to produce visually pleasing results.Extensive experiments on a synthetic dataset rendered photo-realistic images, and real images were then tested to throughly evaluate the performance of the proposed method and comparative methods. Both qualitative and quantitative experimental results for challenging low-texture environments demonstrated significant improvements over traditional feature based methods and recent deep learning based methods.This work follows the third way and focuses on the problem of cylindrical panorama generation from a set of images, in which an essential step is to perform accurate image alignment. In an ideal scenario where the camera undergoes pure rotation around a fixed vertical axis passing through its perspective projection center and the amount of details in the target scene is sufficiently high, the alignment of two consecutive images can be simplified to a horizontal image displacement estimation problem, which can be readily fulfilled by classic image matching algorithms based on sparse local image features . HoweverThis remainder of this paper is structured as follows. By combining multiple images with overlapping FOVs, cylindrical panorama stitching provides an easy way to produce a high-resolution global image with large viewing angle . The mosThe most widely used image alignment methods are methods based on hand-crafted features. These methods first extract a set of image keypoints and compute their descriptors, and then find a set of putative feature correspondences by matching the descriptors, after which outliers in the initial correspondence set are eliminated and the geometric transformation between the two images is calculated within a RANdom Sample Consensus (RANSAC) scheme . In the During the last decade, deep learning has made remarkable advances in various applications in computer vision ,28,29,30Ranftl et al.  proposedAlthough feature based methods often provide excellent performance in cases when there are sufficient reliable features in the images, these methods often fail in low-texture environments , where not enough distinct features can be detected and matched. The greatest advantage of deep learning based methods over traditional hand-crafted feature based methods for solving geometric problem is its robustness to sparse scene structure, illumination change, and image noise. While it is straightforward to adopt existing homography estimation CNN models for robust image alignment by adjusting the output layer, such modifications have been shown not to be able to obtain sufficiently accurate estimates for cylindrical panorama stitching. To this end, this paper proposes a novel end-to-end trainable light-weight CNN architecture called ShiftNet to estimate the initial shifts between images, which is further optimized in a sub-pixel refinement procedure based on a specified camera motion model. Details on our proposed method and experiments with different types of datasets are presented in the following.This paper proposes a robust solution to cylindrical panorama generation for low-texture environments, with explicit modeling of global illumination change and camera motion. In this section, we first present an overview of the proposed pipeline and then present details on key components in the pipeline, including the geometry of cylindrical projection, the CNN architecture for initial image alignment, the sub-pixel refinement procedure, as well as the method for generating synthetic dataset for training and testing the proposed CNN architecture.As shown in In order to construct a cylindrical panorama, all the images captured with the camera need to be projected to cylindrical coordinates, and then stitched together according to displacement between each pair of consecutive images. In the following, we presents theoretical background on cylindric projection.f is the focal length of camera lens, In this paper, the pinhole camera model is used and the intrinsic parameters of the lens which can be obtained from calibration is assumed to be known a priori, based on which, an image can be projected to a cylindrical surface via cylindrical projection. An illustration of image formation is shown in the image at the upper-left corner of to scale .As illustrated in er O see . The proIn this way, an image point Y-axis only, thus both Let As explained in the previous subsection, horizontal shift estimation is crucial for cylindrical panorama stitching. While traditional methods based on sparse features are not reliable for low-texture environments, this paper proposes a customized light-weight regression CNN architecture called ShiftNet to robustly predict shift estimates in an end-to-end fashion.ShiftNet takes as input two channel-wise stacked It is noteworthy that the idea of using CNN to solve two-view geometrical problems has been investigated previously in the case of homography estimation ,32. WhilThe output of the initial alignment algorithm based on ShiftNet presented in the previous subsection is not accurate enough for cylindrical panorama stitching. A previous study  has showp in p under horizontal translation motion and translation and scale motion are denoted by Let Let In order to train a usable CNN model, a huge amount of data with accurate ground truth labels is essential. Since there is no available public dataset for the task of image alignment with ShiftNet, we generate pairs of image patches with random horizontal shifts based on background images randomly selected from the Microsoft common objects in context (MS-COCO) dataset , which cThe workflow for generating synthetic image patches is illustrated in In order to evaluate the performance of our proposed method, we implemented the algorithms described in The five comparative feature based methods are based on popular sparse local image features including SIFT, SURF, ORB, AKAZE, and BRISK. For this set of methods, the particular image feature detector is used to detect points of interest. Putative keypoint correspondences are established by nearest neighbor search via fast library for approximate nearest neighbors (FLANN) followed by a ratio test proposed by Lowe . OutlierAs for deep learning based methods, we compare our proposed ShiftNet with algorithms based on CNN models described in ,32. NoteThe three CNN models shiftnet, shiftvgg, and shiftvggsim are all implemented in PyTorch and the Adam optimizer  with momWe first evaluate the performance of various methods on the synthetic test dataset which was generated by a way described in Shown in The experimental results in To facilitate in-depth investigation, the distribution of average alignment errors (error larger than 5.0 pixels is not shown) with an error tolerance of 5.0 pixels for three deep learning based methods without and with sub-pixel refinement is shown in To facilitate visual inspection, representative qualitative results are shown in Next, we investigate the performance of different methods for the task of cylindrical panorama generation. To this end, experiments on a challenging image sequence generated from a publicly available synthetic dataset  were carIn order to fulfill panorama stitching for the above image sequence, there are 35 consecutive image pairs that need to be aligned and alignment failure in any of these 35 image pairs will lead to failure in the cylindrical panorama generation. Since the scene is texture-less for many images see c, image Since the motion of the virtual camera is rotated under precise control while rendering images, the ground truth translation between consecutive images can be calculated easily, making it possible to evaluate the alignment algorithms quantitatively. The average accuracy of image alignment on the 35 image pairs using six deep learning based methods are shown in More qualitative comparison of the generated cylindrical panoramas using different deep learning based methods are shown in Since shiftnet, shiftvggsim, and shiftvggsim_ht are all able to produce results hard to compare from the global view, thus we present in In order to test the robustness of different methods in practical scenario, we carried experiments on a public available real image sequence with 33 In the image matching process, all methods in sift, surf, orb, akaze, and brisk fail to establish good feature correspondences for at least two image pairs. The number of failure cases for each method is presented in Qualitative comparison of the generated cylindrical panoramas from the real image sequence using different deep learning based methods are shown in Not all the whole panoramas generated by all the deep learning based methods are presented, as they produce results hard to compare from the global view. Instead, in In addition, we made a comparison of cylindrical panorama stitching using the popular free demo AutoStitch  and commIn the process of cylindrical panorama generation, traditional image stitching methods based on hand-crafted features are unable to handle low-texture environments where no reliable feature correspondence can be established. In order to address the above limitation, a novel two-step image alignment method based on deep learning and iterative optimization is proposed. Specifically, an end-to-end trainable light-weight CNN architecture called ShiftNet is proposed to estimate the initial shifts between images, which is further optimized in a sub-pixel refinement processing based on a specified camera motion model. We carried out extensive experiments on a synthetic dataset, on rendered photo-realistic images, and on real images to evaluate the performance of our proposed and comparative methods. The qualitative and quantitative experimental results demonstrate that cylindrical panorama stitching based on our proposed image alignment method leads to significant improvements over traditional feature based methods and recent deep learning based methods for challenging low-texture environments. The use of deep learning based image alignment in many other potential applications such as satellite image stitching, multi-spectral satellite image registration, and environmental modeling and localization are directions worthy of further investigation.


This suggests the need for a “dynamic targeting” strategy aimed at optimizing tumor control by interfering with different molecular targets, at varying stages. Understanding the dynamic changes of this complex network under various perturbed conditions due to drug treatment is extremely challenging under experimental conditions let alone in clinical settings. However, mathematical modeling can facilitate studying these effects at the network level and beyond, and also accelerate comparison of the impact of different dosage regimens and therapeutic modalities prior to sizeable investment in risky and expensive clinical trials. A dynamic targeting strategy based on the use of mathematical modeling can be a new, exciting research avenue in the discovery and development of therapeutic drugs.With the advent of personalized medicine, design and development of anti-cancer drugs that are specifically targeted to individual or sets of genes or proteins has been an active research area in both academia and industry. The underlying motivation for this approach is to interfere with several pathological crosstalk pathways in order to inhibit or at the very least control the proliferation of cancer cells. However, after initially conferring beneficial effects, if sub-lethal, these artificial perturbations in cell function pathways can inadvertently activate drug-induced up- and down-regulation of feedback loops, resulting in dynamic changes over time in the molecular network structure and potentially causing drug resistance as seen in clinics. Hence, the targets or their combined signatures should  Cancer is a multifactorial and remarkably heterogeneous disease. Its initiation, progression, invasion, and metastasis processes all involve multiple molecular signaling mechanisms. The diversity of molecular and cellular properties across tumors from different patients, and even across cancer cells from the same patient, makes it extremely difficult to find a “one-size-fits-all” solution for therapeutic targeting of cancer. Thus, tailored targeted therapies based on each individual tumor’s characteristics are required in order to optimize treatment efficacy, minimize toxicity and drug side-effects, and ultimately lead to more cost-effective patient management by giving the most appropriate drugs at the optimum dose to every patient in need . This isFrom a systems biology perspective, cancer can be viewed as a network disease caused by dysregulation of molecular signaling pathways that determine various physiological cellular processes, such as growth, division, differentiation, and apoptosis . These sa priori which drug combinations are synergistically effective and which are not. Given the number of targeted drugs currently available and in clinical development, it is time-consuming and expensive to do unbiased screening of the large number of possible drug combinations at their clinically relevant dose and dosing schedules. Therefore, there is a major need for approaches that will allow us to identify effective drug combinations where two or more drugs work synergistically to suppress malfunctioning signaling.The disappointing response rate of targeted therapies is partly due to the resilience of oncogenic signaling networks that will often bypass a single hit through an abundance of the highly non-linear built-in feedback loops and alternative pathways that can compensate for therapeutic impact. To solve this “escape” problem, multiple therapies can be used together or in sequence, i.e., combination therapy, which can potentially block these parallel or alternative pathways activated in cancer cells . Since tTesting potentially clinically relevant drug combinations using mathematical models see Box  offers aMathematical modeling of cancer treatment. Mathematical modeling is not only useful in providing mechanistic explanations of the observed data and generating valuable insights into how the molecular signaling network adapts under various perturbed conditions, it can also be used to derive new experimentally and clinically testable predictions. Data-driven modeling approaches that integrate statistical analysis of large-scale cancer multi-omics  with clinical data have been used to identify key biological processes underlying cancer pathogenesis, prognostic biomarkers, and predictive signatures for drug response . On the compensatory mechanisms (which have emerged due to this rewiring) should help to improve treatment efficacy and patient outcome  xenograft model to confer resistance to EGFR inhibition through extensive analysis of a perturbation data set targeting epidermal growth factor receptor (EGFR) and insulin-like growth factor 1 receptor (IGF1R) pathways in a panel of colorectal cancer cells. Some studies  therapeutic interventions apply selective pressure on the cancer cells’ molecular network; secondly, this multi-target strategy will arguably be more toxic, and hence may cause more adverse side effects for the patient than necessary to achieve tumor control. Rather, the goal is to deliver optimal therapeutic efficacy at the minimum necessary level of side effects. As such, our dynamic targeting approach might just be the right answer in that it incrementally “probes” the network’s adaptive capabilities by applying a staggered amount of selective pressure. Also, effective targeting does not have to “take out” a target completely; it could instead be intended to modulate it up or down to redirect the network output. The second question is how frequently should the tumor system be re-examined in order to identify new targets or target combinations? While this is generally cancer type- and treatment-specific, it should also be patient-specific – yet remaining mindful of operational constraints and economics involved when translating this concept into a clinical setting. Still, in our opinion, every time a patient sees a diminishing therapeutic yield from, let alone fails a particular targeted treatment, the molecular network should be re-evaluated to potentially adjust the targeting strategy. We note that the timeline shown in This cascade of drug targeting, network rewiring, followed by subsequent target re-identification and reprioritization , in our opinion, should be repeated during the entire course of treatment. sequentially through “selection” imposed by targeted treatment and the perturbations it causes and reconfigurations the network stabilizes to. This is geared toward optimizing tumor growth control and as such differs from current combinatorics approaches  for the modest responses observed in current trials of targeted therapies. Focusing on long-term tumor control rather than eradication, we introduce a Both authors made a substantial contribution to researching data for the article, discussions of content, writing, and reviewing and editing of the manuscript before submission.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Delayed auditory feedback (DAF) is a classical paradigm for probing sensori-motor interactions in speech output and has been studied in various disorders associated with speech dysfluency and aphasia. However, little information is available concerning the effects of DAF on degenerating language networks in primary progressive aphasia: the paradigmatic “language-led dementias.” Here we studied two forms of speech output  under natural listening conditions (no feedback delay) and under DAF at 200 ms, in a cohort of 19 patients representing all major primary progressive aphasia syndromes vs. healthy older individuals and patients with other canonical dementia syndromes . Healthy controls and most syndromic groups showed a quantitatively or qualitatively similar profile of reduced speech output rate and increased speech error rate under DAF relative to natural auditory feedback. However, there was no group effect on propositional speech output rate under DAF in patients with nonfluent primary progressive aphasia and logopenic aphasia. Importantly, there was considerable individual variation in DAF sensitivity within syndromic groups and some patients in each group  apparently benefited from DAF, showing paradoxically increased speech output rate and/or reduced speech error rate under DAF. This work suggests that DAF may be an informative probe of pathophysiological mechanisms underpinning primary progressive aphasia: identification of “DAF responders” may open up an avenue to novel therapeutic applications. Speech production is a highly complex process that depends on an interaction of motor and perceptual mechanisms. A motor programme corresponding to speech sound representations establishes perceptual predictions about the speaker's vocal output, and the motor programme is in turn updated and fine-tuned based on auditory and other perceptual feedback arising from the act of speaking , 2. PertFor many years, it has been recognized that DAF may paradoxically improve the fluency of speech output in stutterers, albeit with substantial individual variability –13. SensCertain clinical and neuroanatomical observations suggest that further exploration of the effects of DAF in PPA syndromes may be warranted. The speech slowing and speech sound errors induced by DAF in healthy individuals closely resemble the speech production deficits that characterize nfvPPA , hintingIn this study, we assessed sensitivity to DAF in all major PPA syndromes—nfvPPA, lvPPA and svPPA—in relation to patients representing related dementia syndromes—behavioral variant frontotemporal dementia (bvFTD) and typical amnestic Alzheimer's disease (tAD)—and healthy older individuals. We scored measures of speech fluidity (output rate) and accuracy (error rate), key outcome measures that have been used in previous studies , 32. SinBased on previous evidence, we hypothesized that DAF in healthy control participants would lead to slowing of speech output and appearance of speech errors during both reading aloud and propositional speech under DAF , 5, 14. 1−42 profiles were available for four of the seven patients with lvPPA, all of which were consistent with underlying Alzheimer pathology based on local reference ranges . Demographic, clinical and background neuropsychological data for all participants are summarized in Table Five patients with nfvPPA , eight patients with svPPA , six patients with lvPPA , 11 patients with tAD  and eight patients with bvFTD  were recruited via a specialist cognitive clinic; 13 healthy older individuals  with no history of neurological or psychiatric illness also participated in the study. No participant had a history of childhood stammering or clinically relevant otological disease and all had screening pure tone audiometry using a previously described procedure , to provAll participants gave informed consent for their involvement in the study. Ethical approval was granted by the University College London and National Hospital for Neurology and Neurosurgery Research Ethics Committees, in accordance with Declaration of Helsinki guidelines.All participants completed two tasks designed to assess the impact of DAF on reading aloud and on propositional speech . We adapted a script (found at http://psychtoolbox.org/docs/BasicSoundFeedbackDemo) to record sound from a boom microphone attached to the Sennheiser PC350SE® headphones worn by all participants and play this sound back (resampled at 48kHz) via the headphones. Two versions of the script were used to run the NAF and DAF conditions. In the NAF condition, the recorded sound was played back to the participant with the shortest latency supported by the 2015 MacBook Pro® computer used to run the experiment ; while in the DAF condition, the recorded sound was played back with a 190 ms delay added to the minimum latency, resulting in a total delay of ~200 ms (range 190–210 ms). This latency range was chosen as corresponding approximately to the duration of a syllable in conversational spoken English and previously associated with maximal fluency disruption under DAF both in healthy individuals  omissions ; (ii) substitutions or misarticulations ; (iii) duplications or additions ; (iv) elongations ; (v) dysfluencies, . In analyzing the spontaneous speech condition, we included an additional category of grammatical errors.The total number of words produced in each condition was manually counted, and the speech output rate in words per minute (WPM) for each condition was then calculated as:In line with previous work , 5, an ot-tests for continuous variables and chi-square tests for categorical variables.Clinical and background neuropsychological data were analyzed using Stata v14.0®. Each patient group was compared to the healthy control group using independent-samples t-tests.Analyses of NAF and DAF data were run for the reading aloud and propositional speech task conditions separately. For each task condition, we derived change variables for speech output rate and speech error rate, calculated as the difference between NAF and DAF rates. Using these four change variables, each patient group was assessed for within-group change in speech output rate and speech error rate between the NAF and DAF conditions, using dependent-samples t-tests directed by the result for that group from the within-group analysis. Where assumptions of the general linear model were violated, an appropriate nonparametric equivalent test was used .Each patient group was then compared to the healthy control group using change scores as dependent variables, in independent-sample p < 0.05 was accepted in all cases.All tests were two-tailed, and a statistical significance criterion thresholded at F = 0.32, p = 0.572], handedness , gender , peripheral hearing ability  or education . Patient groups did not differ in mean symptom duration  or Mini-Mental State Examination score .Participant groups , in the nfvPPA group  and svPPA group  but not the lvPPA group ; speech also slowed significantly under DAF in the bvFTD group  but not the tAD group . Slowing of speech was attributable mainly to prolongation of syllable durations rather than silent pauses. During the propositional task, DAF produced slowing of speech output in healthy controls  and there was a trend toward a significant effect in the svPPA group  but no significant effect in the nfvPPA group  or lvPPA group ; speech slowed significantly under DAF in the tAD group  but not the bvFTD group .During the reading task, DAF produced significant slowing of speech output relative to NAF in healthy controls , in all PPA syndromic groups  and in the bvFTD group  but there was no significant effect in the tAD group . During the propositional task, DAF produced significantly more speech errors in the healthy control group  and svPPA group  but not the nfvPPA group  or lvPPA group ; a DAF effect was also shown by the tAD group  but not the bvFTD group .During the reading task, DAF produced significantly more speech errors in the healthy control group . For the reading task, the nfvPPA group showed a trend toward significantly less slowing of speech output under DAF than healthy controls ; no such trend relative to healthy controls was identified for any other patient group .For the propositional task, the nfvPPA group showed significantly less slowing of speech output under DAF than healthy controls  or during the propositional task .Change in error rates under DAF did not differ significantly between the healthy control group and any patient group, either for reading  and three of six individuals with lvPPA ; and speech error rate decreased for three of five individuals with nfvPPA  and one of six individuals with lvPPA (−6.3 PHW). Similar “paradoxical” effects on propositional speech output were exhibited by three of eight individuals with bvFTD  and two of 11 individuals with tAD , while no healthy individuals showed any such effect on propositional speech output.Under DAF during the propositional task, speech output rate Here we have shown that canonical PPA syndromes are associated with differential sensitivity to DAF at latency 200 ms; and that sensitivity to DAF is significantly reduced in nfvPPA, as indexed by a lack of effect on propositional speech output compared with a healthy older control cohort. Overall, both the healthy control group and most patient groups showed quantitatively or qualitatively similar profiles of DAF sensitivity, manifesting as speech slowing and increased speech error rates during propositional speech and reading aloud. The only exceptions to this pattern were exhibited by the patient groups with dysfluent PPA syndromes—nfvPPA and lvPPA—in which there was no overall slowing of propositional speech output under DAF. Our findings corroborate previous work in healthy individuals , 44, 45 a priori to show discrepant profiles of DAF sensitivity, reflecting the nature of the lesion they induce within the dorsal language network. The dorsal language and auditory cortical pathways behave as a functional unit, the progressive transcoding of information along these pathways supporting sensori-motor integration of speech output with auditory feedback about the speech signal produced  is likely to account for the absence of a significant group-level DAF effect for the lvPPA cases here. However, both the nfvPPA and lvPPA groups contained a substantial proportion of individuals who showed improvement in speech fluency under DAF: no such benefit was observed in any healthy controls. It is of interest that previous reports of therapeutic benefit from DAF have generally been based on single cases , 18. TheVarious explanations have been proposed to account for the apparently paradoxical benefit of DAF in some people with developmental stuttering, including amelioration of an intrinsic overreliance on auditory feedback during speech output, engagement of a language mirror neuron system and regulation of speech rate , 13, 56.This work has several limitations which should direct future work. Case numbers in each syndromic group were relatively small; larger cohorts would increase power to demonstrate group level effects and also allow any stratification into syndromic subgroups to be more adequately assessed. Relatedly, it will be relevant to compare the effects of DAF in neurodegenerative and vascular pathologies; and to study DAF sensitivity longitudinally in patients with dementia, since it is likely a priori that syndromic profiles transform as involvement of the language system becomes more widespread and compensatory mechanisms are exhausted . Measurement of objective speech parameters alone does not capture the full impact of DAF: in future work it will be important to garner patient caregiver impressions about speech fluency and quality the subjective effort associated with speaking under DAF vs. NAF . There aSensitivity to DAF is reduced in nfvPPA and (less robustly) in lvPPA relative both to healthy older controls and other canonical dementia syndromes. Importantly, there was considerable individual variation in sensitivity to DAF within syndromic groups and some patients in each group  apparently benefited from DAF, showing paradoxically increased speech output rate and/or reduced speech error rate under DAF. This work identifies several areas for future clarification, notably the pathophysiological mechanisms that underpin DAF effects and the characteristics of “DAF responders” with a view to future therapeutic applications.CH, RB, KJ, and JW contributed to the conception and design of the study. CH, RB, KJ, CM, LR, KD, SC, and JR were involved in the collection and/or analysis of data. CH, RB, and JW wrote the first draft of the manuscript. All authors contributed to manuscript revision, and read and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Drosophila melanogaster as a model system for mammalian development and behavior. Drosophila appear resistant to alcohol’s toxic effects and display many behaviors resembling intoxication  when exposed to alcohol vapors. Accordingly, investigators have begun to measure alcohol sensitivity in Drosophila and to identify genetic mutations associated with increased or decreased sensitivity. One mutant called cheapdate affects a signaling system that plays a role in many regulatory processes in a cell and which involves the compound cyclic adenosine monophosphate (cAMP). Additional Drosophila mutants with altered alcohol sensitivity carry mutations in other components of the cAMP signaling system. Because the cAMP system also is affected in human alcoholics, these results indicate that studies using Drosophila as a model system may identify genetic changes relevant to human alcoholism.Researchers frequently study the fruit fly  Drosophila melanogaster is one of the most widely used and successful genetic model systems for studying development and behavior. The usefulness of this model system is based on the fact that the genes and biochemical pathways underlying development and behavior have largely been conserved during evolution. As a result, many genes first identified in Drosophila have provided major insights into human and other vertebrate development and disease. Drosophila has a relatively sophisticated nervous system and is capable of many complex behaviors. For example, the flies can learn to associate certain events and to remember that association  that can be used to map novel mutations. Subsequently, such genetic techniques as germ-line transformationDrosophila genome has recently been published, and its analysis has revealed further similarities between flies and mammals  have been implicated as potential targets for alcohol. For example, flies carry homologs of the mammalian receptors for the brain chemicals  gamma-aminobutyric acid, serotonin, dopamine, and glutamate . Accordingly, fruit flies are resistant to alcohol’s toxic effects and can metabolize alcohol efficiently for use as an energy source or as a starting material  for the production of lipids  . To expls normal . These dDrosophila is to determine their inability to stand  after alcohol intake using an inebriometer. This instrument, which was designed originally to selectively breed alcohol-resistant flies  flies. Conversely, barfly mutants required higher alcohol doses than did wild-type flies to achieve sedation  that integrates randomly into the flies’ DNA and inactivates any genes located near the integration site   . AC promcheapdate mutant, other findings from Drosophila studies indicate that the cAMP signaling system appears to play a role in mediating alcohol’s effects. Thus, Drosophila mutants with disruptions in the gene encoding a certain type of AC also display increased sensitivity to alcohol  is more resistant to the acute effects of alcohol than are wild-type flies  and, therefore, is viable and relevant. However, it is too soon to speculate whether these genes will provide clues to alcohol addiction in humans.Drosophila genes that disrupt alcohol-related behaviors provides at least two potential benefits. First, identifying these genes could facilitate studies in vertebrates, particularly humans, because the vertebrate homologs could be investigated as potential candidate genes. Second, such analyses could provide researchers with tools to investigate in Drosophila the mechanisms underlying alcohol-induced behaviors in higher organisms. For example, identifying novel genes associated with alcohol-related phenotypes in mammals or humans may provide few clues for the development of therapy because of the difficulties of studying these genes in complex mammalian systems. The introduction of such genes into Drosophila, however, might allow researchers to identify the mechanism through which the novel gene acts in a simpler model system.The identification of


Exposure to alcohol during gestation can have profound consequences, but not all cells within the embryo are affected equally. Recent advances in molecular embryology have allowed an exploration of this variation. Much of this research has focused on the embryo’s vulnerability to the facial malformations characteristic of fetal alcohol syndrome. Studies using mice and chicks show that alcohol exposure at specific stages of early embryo development results in significant death among the cells destined to give rise to facial structures . This type of cell death is through activation of the cell’s own “self-destruct” machinery . Researchers have advanced several theories to explain how alcohol triggers apoptosis in the neural crest cells. These theories include deficiency in a type of vitamin A compound, retinoic acid; reduced levels of antioxidant compounds  that protect against damage from toxic oxygen molecules ; and interference with the cell’s normal internal communication pathways. Alcohol is capable of directly inducing abnormalities during prenatal development that can lead to lifelong and profound disabilities  are especially busy and are crucial in laying the foundation for future growth see . From itApproximately 2 weeks after fertilization, further cell rearrangement  begins to establish a multilayered, vertebrate body plan in the embryo. Three distinct “founder regions” of cells  form during gastrulation: the ectoderm, endoderm, and mesoderm. Unfolding genetic codes direct further development of each germ layer, transforming it from an initially undifferentiated set of cells to increasingly complex, genetically programmed tissue patterns that eventually become recognizable body structures. Thus, the skin and nervous system are formed from the outermost layer of cells , while the lining of the digestive tract, respiratory tubes, and their associated organs derive from the innermost layer . Between these two layers, the mesoderm spreads outward and will generate all the organs between the ectodermal wall and the endodermal tissue, including the cardiovascular system, bones, muscles, and connective tissue.The cells of the three germ layers interact with one another in an intricate sequence to coordinate the development of all the body structures. For example, a strip of mesoderm cells  lying directly beneath the ectoderm along the embryo’s midline causes a portion of the ectoderm to wrinkle and form two ridges see . The topAs the neural crest cells migrate, increasingly complex developmental activity in the embryo results in considerable progress toward a recognizable human form. Over the course of the fourth week, the heart begins to pump; arm and leg buds appear; and the groundwork is laid for the liver, lungs, eyes, spleen, and other body systems. The embryo doubles in length to become pea size. During the next several weeks, rapid progress in development and refinement continues as nerves sprout, lymphatic and coronary vessels appear, brain structures become visible, the intestinal loop forms, the kidneys begin to ascend, and many other milestones are achieved. Hands begin to develop in the fifth week, and finger rays appear in the sixth; feet and toe rays follow a week later. In the seventh week, bone begins to replace the skeleton’s cartilage foundation, eyelids form, and the first hair follicles appear. By the end of the eighth week of gestation, the embryo is just over 1 inch long, and all major body systems are in place. From this point onward, the embryo (now termed “fetus”) primarily undergoes further refinement and growth, which continue after birth at a slower rate until adult form and stature are attained.—Mary Beth de RibeauxGilbertSFDevelopmental Biology2d ed.Sunderland, MASinauer Associates1988GilbertSFRaunioAMEmbryology: Constructing the OrganismSunderland, MASinauer Associates1997LarsenWJEssentials of Human EmbryologyNew YorkChurchill Livingstone1998Mary Beth de Ribeaux is a science editor of Alcohol Health & Research World.Early diagnosis and intervention for children affected by prenatal alcohol exposure can reduce their risk for social difficulties later in life  . IdentifTo help define the risks associated with maternal alcohol use during pregnancy, researchers are seeking to understand the mechanisms of alcohol’s teratogenic effects on various tissues. The use of animal models to reproduce many of the deficits seen in FAS allows investigators to study alcohol’s teratogenic effects in detail under controlled treatment conditions. In addition, recent findings in molecular embryology have greatly advanced scientific knowledge about the signals and agents that govern normal embryo development. Applying this knowledge can help elucidate how prenatal alcohol exposure results in birth defects. It also can clarify our understanding of why certain physical defects are useful diagnostics for prenatal alcohol exposure, and it places these deformities within the overall criteria that define whether a potentially affected person may qualify for support services.This article first reviews current understanding about the embryo’s vulnerability to facial malformations and the alcohol-induced cell death responsible for producing such deformities. The article then explores several theories on how alcohol triggers cell death in embryos and concludes with a discussion of possible future research directions.Many toxic substances , including alcohol, are specific in their actions and affect only a subset of cells within the embryo. The timing of exposure plays a role in the embryo’s outcome as well: A given tissue’s susceptibility to disruption peaks during distinct timeframes of development . Thus, a close examination of the target tissue’s developmental history may reveal clues as to the toxicant’s mechanism and the basis for the tissue’s sensitivity. Such examination also may identify additional, previously unsuspected targets. For example, because the face, limbs, urogenital tract, and central nervous system all use the same set of genes to direct their growth and development, it is not surprising that certain toxicants or genetic mutations will disrupt all of these tissues to some degree.The concept of critical sensitivity windows is useful in examining how alcohol produces its teratogenic effects. Certain embryonic tissues, such as those of the face, heart, and urogenital tract, appear to be particularly sensitive to alcohol-induced malformations during the processes that establish location, growth, and three-dimensional shape as the tissues develop from their primitive origins. In humans, many of these early developmental events occur during a time when a woman may be unaware of her pregnancy, 3 to 6 weeks after fertilization. For example, alcohol is most likely to cause heart defects during the time when cellular signals are directing the heart’s division into its various chambers and great vessels, starting 4 weeks after fertilization.In work that was critical in drawing attention to alcohol’s early effects on the embryo, The fact that alcohol causes similar facial defects in people and rodents implies that alcohol probably affects embryonic events common to both species. Closer examination of alcohol-exposed mouse embryos revealed significant cell death within specific groups  of cells, including the primitive neural and facial tissues. In particular, cell death was observed in a group of cells called the neural crest see .Rats exposed to alcohol during late gestation or soon after birth experienced a similar death of cells within specific brain regions. The restriction of alcohol-induced cell death to selected brain regions supports the concept that alcohol affects specific target tissues. Moreover, the causative relationship between alcohol and cell death is reinforced by the fact that several alcohol-affected embryonic tissues later result in body structures that exhibit malformations consistent with underdevelopment. In addition to the characteristic facial defects seen in FAS, these malformations can include exencephaly, a condition in which the brain is exposed or extrudes from a skull defect; spina bifida, a congenital defect in which part of the spinal cord is exposed through a gap in the backbone; absence of the corpus callosum, a brain structure that helps link the two brain hemispheres ; and motor neuron losses in the spinal cord.Both chronic and acute alcohol exposures can lead to cell death in the mature liver, brain, and certain white blood cells , as observed in animal models and cell culture systems. In turn, such aberrant cell death might contribute to characteristic tissue diseases associated with repeated alcohol exposure . Although some of this cell death involves necrosis, much of it is consistent with the elicitation of another type of cell death called apoptosis, in which the cell “programs” its own destruction. Necrosis and apoptosis differ in several crucial ways. Necrosis occurs when cell metabolism ceases, leading to membrane disintegration and rupturing of the cell’s contents. In contrast, apoptosis depends on activation of the cell’s own internal cell-death machinery . Apoptotnormal embryo development is apoptotic. At critical times or locations, however, excessive cell death beyond the normal bounds of apoptosis could produce malformations within susceptible tissues, despite the embryo’s tremendous capacity to repair damage. The realization that alcohol and other teratogens can stimulate excessive cell death within the embryo was a conceptual breakthrough.Some apoptosis is a natural part of development. In adults, for example, apoptosis is often a desirable process used to remove damaged or mutated cells  that have escaped from the normal constraints on their growth. In embryos and fetuses, apoptosis shapes and remodels developing tissues by removing unwanted cell populations . Research has established that the majority of cell death during Using neuronal cells from chicks, investigators first documented embryonic cell death resulting from prenatal alcohol exposure in the late 1960’s . More thMore recent studies have provided support that apoptosis is indeed the type of cell death at work in embryos exposed to alcohol. Alcohol-exposed cells within the embryo have several structural and biochemical features that are unique to apoptosis. For example, Realizing that the cells of the neural crest are particularly vulnerable to alcohol-induced death, researchers have focused on this cell population. Analysis of alcohol-induced facial defects revealed certain commonalities among the affected structures. Many of these structures  are derived from the same cellular ancestors in the embryo , a subset of the neural crest population called the cranial neural crest. This lineage originates within the primitive neural tube   originates from the primitive spinal cord and contributes to other body structures see . Unlike The mouse studies of Recent advances in developmental biology have made this question approachable at the molecular level, because much is now known about the mechanisms involved in neural crest development. Several clues have come from research zeroing in on the role played by the precise timing of alcohol exposure in relation to the embryo’s developmental stage. Researchers have made progress in identifying the critical sensitivity window for neural crest apoptosis, when and where cell death actually occurs, and how alcohol-induced and “natural”  apoptosis interact.To investigate the mechanism of neural crest cell death, some researchers have turned to the chick embryo, which has long been a model of choice for neural crest studies.  Chicks offer several advantages to investigators studying embryo development. Because the chick develops in an egg outside the mother’s body, studies can avoid potential complicating factors arising from maternal and placental metabolism and nutrition. Moreover, researchers can cut a small window in the eggshell and directly view and manipulate the embryo. Resealing the window with tape or wax provides sufficient protection to allow the chick embryo’s development to continue.As with mouse embryos, chick embryos exposed to alcohol levels greater than 0.15 percent exhibit significant cell death within regions enriched with cranial neural crest cells and distinct sections of the primitive brain  . Using sStudies using mouse embryos pinpointed the critical sensitivity window for facial defects to the short time during the creation of the embryo’s three basic cell layers  and the first organization of the primitive nervous system  . ResearcThe ability to precisely identify the developmental stage of chick embryos allowed even more refined investigation of the window’s extent with further studies. These studies uncovered a curious finding about alcohol-induced cell death in chick embryos: Alcohol exposure caused cell death only if the alcohol was administered before the neural crest cells emigrated from their birthplace in the neurectoderm. Once the cells began migrating toward the site where the chick’s face would develop, the neural crest cells were resistant to alcohol-induced death; moreover, alcohol exposure after the start of neural crest cell migration no longer resulted in facial defects. Thus, at least for chicks, the critical sensitivity window for producing facial malformations is extremely narrow, lasting only from gastrulation to cranial neural crest migration, or from 18 to 36 hours of egg incubation after laying.Determining the critical sensitivity window for facial malformations in people is not possible, but because mice and chicks represent such diverse species sharing a similarly narrow window, these findings strongly suggest that a comparable window exists for humans. If so, then the appearance of facial defects in FAS may reflect peak blood alcohol concentration in early gestation more strongly than previously suspected.Recent studies demonstrate that the regulation of apoptosis depends on the embryo’s developmental stage. In chick embryos, initial alcohol exposure and peak alcohol concentration achieved any time before neural crest cell migration do not actually result in cell death until later, specifically at 46 to 48 hours of incubation . Thus, aCloser examination of where apoptosis is occurring in the embryo at a given timepoint further supports this theory. Because embryos develop in a head-to-tail  sequence, the neural folds do not meet along their entire length simultaneously, but are “zipped” together to form the neural tube. Thus, the neural crest cells arising from the foremost part of the neural tube are created and mature first, whereas those cells toward the opposite end of the tube are progressively less mature at any given timepoint. Likewise, exposure to alcohol at an early point in embryo development produces maximal cell death in the more rostral neural crest cell populations , whereas later exposure shifts the majority of cell death to more caudal populations  . This fiMouse studies by The coincidence of alcohol-induced and normal neural crest death prompted the hypothesis that alcohol exposure aberrantly activates the apoptotic machinery in cranial neural crest cells. This hypothesis predicts that the prevalence or activity of substances involved in endogenous apoptosis would increase during concurrent alcohol-induced death. Molecular analysis did not support this prediction, however: A study by Understanding the molecular regulation of apoptosis will help explain how alcohol initiates the apoptotic pathway and results in the death of some, but not all, cell populations. In pursuit of this goal, current research efforts focus on identifying the mechanism that activates the cell-death pathway following alcohol exposure. In all likelihood, the trigger for alcohol-induced apoptosis lies within the target cell population itself, because many other cell populations do not apoptose, despite equivalent alcohol exposures. Investigators have presented several hypotheses to explain alcohol’s activation of apoptosis, each with strong supporting evidence. The following sections explore these hypotheses and the evidence to support them.Retinoic acid (RA), an active form of vitamin A, is essential for neural crest survival and is a key regulator of body form and structure development . RA affects the positional identity of cells according to the structure that they will form within diverse embryonic regions, including the cranial neural crest, face, central nervous system, limbs, and urogenital tract. In addition, RA is a potent mediator of differentiation in many cell lineages. Alcohol exposure is associated with localized RA deficiencies in embryos, however . BecauseStudies of a class IV alcohol dehydrogenase enzyme found in embryos further supports this hypothesis. This enzyme is involved in the synthesis of retinal, an immediate precursor of RA. Although frank deficiency of vitamin A compounds  is seldom observed in Western populations, a recent study in Iowa  found thAn alternative hypothesis on the mechanism behind neural crest apoptosis is based on alcohol’s known ability to cause cell injury during its metabolism. Alcohol exposure can increase the levels of highly reactive oxygen molecules known as free radicals as well as deplete cells of the protective compounds  that normally scavenge these toxic molecules. Under such conditions , vital components of the cell may begin to combine with free radicals and result in injury. In particular, free radicals can damage cell membranes through a process called lipid peroxidation. This process may interfere with many important cell regulatory processes, including control over substances entering and leaving the cell, intercellular communication, and protein synthesis. Damage from such interference could be fatal to cells.Approaches using whole embryo and cell cultures, particularly the research conducted by Chen and colleagues  have beeSupplementation with gangliosides, a type of lipid compound usually found abundantly in nerve cell membranes, also decreases the death of alcohol-exposed neural crest cells , and proFurther research will prove informative in understanding free radical damage and how alcohol-induced oxidative stress contributes to alcohol’s injury to the embryo. Alcohol exposure may result in free radical production from several sources. For example, free radicals could be formed as a consequence of alcohol’s oxidation itself ; its alteration of the cell’s potential for chemical reactions or the chemical chain of events involved in generating cell energy ; or the action of other agents, such as nitric oxide. The sensitive intracellular probes that are now available for detecting free radicals and their sources will enable researchers to test these mechanisms directly.A third mechanism proposed for alcohol-induced apoptosis involves alcohol’s ability to perturb the function of cell membrane-associated proteins. These proteins function as channels or receptors that transfer critical chemical signals from the cell surface to its interior . Interference with this process, perhaps through direct alcohol-protein interactions, could cause aberrant activation or inhibition of the communication pathways vital to cell survival.Studies using various cultured cell lines have documented alcohol’s ability to alter intracellular communication through a variety of mechanisms , depending on the target cell . Thus, oAgain, recent advances in deciphering the molecular signals that govern development will greatly facilitate further exploration of altered cellular communication as a potential mechanism of apoptosis. Quite likely, a combination of RA deficiency, free radical damage, and interference with cellular communication, as well as other mechanisms, all contribute to alcohol’s toxicity and subsequent pathologies.Advances in molecular and cellular biology have opened multiple avenues for exploring alcohol’s impact on prenatal development. Many of alcohol’s target tissues, including face, nervous system, limb, and urogenital tract tissues, employ a common set of genes that are responsible for coordinating tissue growth . SeveralNew approaches also are available to study alcohol’s effects on the cell’s normal metabolic processes and communication. For example, highly sensitive intracellular reagents and probes allow scientists to monitor the various metabolic pathways that link events in the cell membrane to changes within the cell. Combining these techniques with specialized computer-driven detection equipment, such as laser-driven microscopy , will enable investigators to monitor alcohol’s short-term effects on single cells as they occur.Finally, although the cranial neural crest contributes to many tissues, alcohol-related research on these cells predominantly focuses on facial bone and cartilage. Examination of other tissues arising from the cranial neural crest could uncover less recognized targets of prenatal alcohol exposure. Approaches similar to those undertaken by researchers studying facial defects also will benefit studies of brain, heart, urogenital tract, and limb development.Taken together, recent discoveries in cellular and molecular embryology will greatly advance our understanding of alcohol’s impact on prenatal development. Moreover, understanding the limited circumstances that create alcohol-induced facial defects may bolster the recognition that children who demonstrate alcohol-related neurodevelopmental deficits but lack overt facial defects represent a syndrome that can equal FAS in severity and long-term prognosis.


Non-alcoholic steatohepatitis morbidity and mortality is on the rise due to the obesity pandemic. Its pathophysiology is not well understood and implies complex interactions between local hepatic cells populations, adipocytes, immune effectors that lead to hepatic lipid excess, lipotoxicity, cellular stress and inflammation, as well as programmed cell death. A better understanding of these pathogenic interactions would allow better identification of therapeutic targets in a disease that has no known pharmacological therapy until now. Non-alcoholic steatohepatitis (NASH) became the leading cause of liver transplantation in a world afflicted by obesity epidemics. It is a component of the metabolic syndrome  and, alongside simple steatosis, is one of the faces of non-alcoholic fatty liver disease (NAFLD).If steatosis is the most widely met manifestation of NAFLD and represents a benign excess of fat within the hepatocyte that seldom leads to complications, NASH implies not only steatosis but also inflammation that in some patients is associated with progressive fibrosis, cirrhosis and occasionally hepatocellular carcinoma. This process seems to be driven by lipotoxicity and cellular metabolism dysfunctions caused by insulin resistance and eventually advances to chronic apoptosis, fibrosis, and cirrhosis. From hepatocytes and immune cells to adipose tissue and endothelium, multiple cellular actors are involved in NASH progression. Their action is modulated by genetic predisposition and environmental factors like diet and intestinal microbiota.A better understanding of these pathogenic interactions would allow better identification of therapeutic targets in a disease that, until now, has no known pharmacological therapy. This review focuses on how different cells interact and mediate NASH progression.Excess fat, especially triglycerides, stored as droplets within the hepatocytes, seems to be continuously found in both steatosis and NASH. Since triglycerides are probably not hepatotoxic and even protective for the hepatocyte , the simThese hepatic fat stores originate either from dietary esterified chylomicrons or, more often, from free fatty acids (FFA). These FFAs can be either the results of a spillover mechanism where they are synthesized from lipolysis of chylomicrons by lipoprotein lipase activation or from a de novo hepatic non-lipid source production mechanisms ,8. They At some point, the liver fatty acids excess seems to overcome the protective mitochondrial beta-oxidation and triglyceride production mechanisms from the endoplasmic reticulum and induces a lipotoxic state through metabolic stress with progressive mitochondrial dysfunction  and the Other mitochondrial and nonmitochondrial  enzymatic processes, both toxic and protective, are impaired through long-chain saturated fatty acids like palmitate and stearate excess and seem to participate in this cellular stress state -14.Reactive oxygen species and excess lipotoxins within the hepatocyte lead to the saturation of the endoplasmic reticulum, which responds through a stress state of unfolded protein response (UPR) . This stAutophagy is upregulated in NASH by an excess of unfolded proteins and excess lipid droplets through the mTOR and PI3K pathways, but clearance of the substrate is insufficient. Defective autophagy could explain the persistence of lipotoxic moieties and inflammation within the hepatocyte, which finally leads to programmed cell death and increased hepatic insulin resistance . InsulinPyroptosis, another type of programmed cell death tied to NF-kB activation, is excessive in individuals with NASH via an excess of gasdermin D signaling that correlates linearly with NAFLD activity and induces a pro-inflammatory environment within the liver . These lSince lipid storage alone does not always lead to steatohepatitis, factors like genetics , microbiAnother target that could explain phenotypic differences in the fatty liver is the host-microbiota interaction. Disturbance of the gut–liver axis by inflammation or bile acid signaling could initiate or aggravate NASH, maybe through excess bacterial lipopolysaccharides within the portal vein. Lipopolysaccharides exposition induces inflammation and autophagy within the healthy liver, but the causal association with NASH is still to be determined.Until this point, steatohepatitis is mainly confined to the hepatocyte cytoplasm. Once the endoplasmic reticulum is overwhelmed by lipotoxic by-products and UPR is initiated, and mitochondrial dysfunction with reactive oxygen species formation alongside insulin resistance activates inflammation and programmed death, the process spreads to the nucleus and outside the hepatocyte. Inflammation is initiated by Fas, NF-Kb and TNF receptors, as well as TNF-related apoptosis-inducing ligand receptor . HepatocThis inflammatory process leads to the activation of the main effector of fibrosis progression, the hepatic stellate cells. They represent less than 5% of the healthy liver population that are generally found in the space of Disse and have a role in the storage of lipids and fat-soluble vitamins . Their aSteatohepatitis is a complex and heterogeneous syndrome in which insulin resistance and impaired lipid metabolism seem to induce a constant state of hepatic inflammation that leads to hepatocyte programmed death and activation of tissue repair mechanisms that will eventually conduct to fibrosis and cirrhosis.The authors confirm that there are no conflicts of interest.