Rates of preterm birth (<37 weeks of gestation) are increasing worldwide. Improved perinatal care has markedly increased survival of very (<32 weeks gestation) and extremely (<28 weeks gestation) preterm infants, however, long term respiratory sequalae are common among survivors. Importantly, individual's lung function trajectories are determined early in life and tend to track over the life course. Preterm infants are impacted by antenatal, postnatal and early life perturbations to normal lung growth and development, potentially resulting in significant shifts from the “normal” lung function trajectory. This review summarizes what is currently known about the long-term lung function trajectories in survivors of preterm birth. Further, this review highlights how antenatal, perinatal and early life factors are likely to contribute to individual lung health trajectories across the life course. Rates of preterm birth are increasing. Currently, around 11% (~15 million) of global births are preterm (<37 weeks of gestation) and over 2 million of these annual births are very preterm (<32 weeks gestation) , a debilitating and life threatening lung disease with few effective treatments –4. Given2)  of 34 weeks and prolonged exposures to mechanical ventilation and high concentrations of oxygen (O2) , with se2) . Consequ2) . Very pr2) . This buIn healthy individuals, lung growth and development, measured by lung function, follows a distinct pattern (or trajectory) over the life course , green. in-utero environment of preterm infants is often compromised prior to a preterm delivery (Preterm birth (<37 weeks of gestation) represents a significant perturbation to lung development. Further, the delivery , 11  have been reported in a few studies , orange.Maternally administered corticosteroids have a well-established role in reducing the rates of many adverse outcomes associated with preterm birth including perinatal death, RDS, need for mechanical ventilation, intraventricular hemorrhage, necrotizing enterocolitis, and systemic infections in the first 48 h of life , 21. WheDespite much literature on the short-term benefits of antenatal corticosteroids, there is limited evidence on their long-term impact on lung health. Doyle et al.  followedAcute and chronic chorioamnionitis are commonly reported lesions in the placenta after spontaneous preterm birth , 26. It A recent meta-analysis by Sarno et al.  exploredThere is limited evidence on how chorioamnionitis affects long-term lung function. Chorioamnionitis has been directly associated with reduced long term lung function a study of preterm infants (<37 weeks gestation) by Jones et al.  who founMaternal smoking during pregnancy is a significant modifiable risk factor associated with substantial pregnancy related morbidity and mortality, and has been identified as a direct risk factor for inducing preterm birth . AntenatAnimal models may provide some indication as to the underlying mechanisms of the harmful effects of antenatal nicotine exposure. Rodent studies have shown that nicotine exposure can decrease maximal expiratory flow by stimulating epithelial cell growth and lung branching, resulting in more tortuous airways  and a re1/FVC and FEV25−75 in children and adolescents aged from 7 to 18 years. Reductions in FEV1 and FEV25−75 appear to persist into early adulthood in a study by Hayatbakhsh et al.  occurs early in the lungs of preterm infants as a result of damage to the airway epithelium caused by a lack of surfactant production in an immature airway, resulting in the activation of inflammatory processes . A conseAnimal models provide evidence on the longitudinal effects of oxygen exposure in prematurity which is not yet available in humans. In mouse studies performed by Yee et al. , newborn1), forced vital capacity (FVC), forced expiratory flow at 25–75% of FVC , and the elastic properties of the lung (respiratory system reactance at 8 Hz) in survivors of preterm birth at 9 to 11 years of age, indicating there may be ongoing damage to the airways and peripheral lung  and heated humidified high flow nasal cannula (HFNC) . This moImprovements in ventilator technology have allowed for a shift from traditional pressure limited ventilation (PLV) to volume-targeted ventilation (VTV) strategies with the aim of reducing volutrauma to the lungs caused by inconsistent tidal volumes being delivered to the lungs . The curThere has been interest in HFNC as an alternative form of non-invasive respiratory to CPAP over the last two decades, predominantly because it is easier to set up and maintain, is more comfortable for infants, and is preferred by nurses and parents –79. InitOver the last two decades there has been increased uptake of high frequency oscillatory ventilation (HFOV) techniques to minimize the effects of barotrauma caused by conventional mechanical ventilation (CMV), though evidence in this field is extremely limited. HFOV delivers small tidal volumes at rapid rates, usually between 10 and 15 Hz . HFOV haThe use of postnatal corticosteroids in the management of preterm infants with BPD has varied significantly over the last several decades . InitialThe long-term respiratory outcomes associated with postnatal corticosteroids have not been well defined, with few studies specifically commenting on this area. Some evidence exists from Nixon et al.  who follThere is emerging evidence that early administration of inhaled corticosteroids may reduce the risk of chronic lung disease in children, without many of the significant side effects of systemic corticosteroids. A Cochrane review by Shah et al.  suggesteLike antenatal steroids, surfactant administration to preterm infants revolutionized neonatal care due to its ability to prevent and treat respiratory distress syndrome by improving pulmonary compliance and reducing surface tension in newborns with immature type II pneumocytes , 98. UnfThe current evidence does appear to support the notion that childhood lung function in survivors of preterm birth in the post-surfactant era has improved when compared with survivors of the pre-surfactant era. A small study by Pelkonen et al.  followedAn area which warrants monitoring moving into the future is how the long-term outcomes of preterm infants who less invasive surfactant administration (LISA) compare with those who receive surfactant delivered via an endotracheal tube. In this technique, surfactant is delivered to the trachea by a thin catheter, then dispersed to the lungs using nasal CPAP without the need to perform endotracheal intubation . There hCaffeine, a methylxanthine, has become a commonly administered medication for preterm neonates over the last two decades. The Caffeine for Apnea of Prematurity (CAP) trial identified the benefits of caffeine, showing that neonates who were given caffeine between days 3 and 10 of life for apnoea of prematurity had reduced rates of BPD, decreased duration of mechanical ventilation, and improved survival without neurodevelopmental disability at between 18 and 21 months , 105. MoTiming of caffeine administration has also been an area of recent interest, with evidence suggesting that early caffeine administration (within 2 days of birth) may provide more neurodevelopmental benefits and reduced rates of BPD compared with late caffeine administration –110. A cChildren born preterm, particularly very low birth weight infants, are at a significantly increased risk of neonatal sepsis due to immature innate and adaptive immune systems . PostnatThe previously mentioned study by Lahra et al.  which shThe long-term impact of postnatal sepsis as a risk factor for altered lung function trajectories throughout life has yet to be determined. Significant advances have been made over the last two decades in the identification of infants at risk of sepsis, early diagnosis, and management strategies . It woulExposure to viral infections in early life has been shown to have the potential to have significant impact on lung function trajectories in healthy individuals, and those with asthma –119. As Exposure to respiratory syncytial virus (RSV) early in life has also been identified as a significant factor in the developmental of suboptimal lung health and lung function in both term and preterm children. Studies have shown that children exposed to RSV have an increased risk of: late-onset or persistent wheezing phenotypes; a diagnosis of asthma; and impairments in lung function during adolescent or young adult life , 123–125Ongoing improvements in prevention and treatment of viral infections in this population is needed to minimize the impact that they have on lung health, with potential interventions like an RSV vaccine offering promising views for the future .Maternal smoking and personal smoking have been established as risk factors toward the development of chronic obstructive pulmonary disease (COPD) as an adult, and more rapid declines in lung function trajectories , 131. ItAt present, no study appears to compare lung function in adults who smoke between those born at term and those born preterm to further explore this. There is evidence, however, that survivors of preterm birth exposed to passive smoke during childhood   and thosVery limited evidence exists investigating the use of corticosteroids beyond the neonatal period, with even fewer investigating the effects of inhaled corticosteroids. Yuksel et al.  found a While we have considered each of the identified risk factors for reduced lung function in relative isolation during this review, it is important to consider how these factors will interact with each other to have a potentially cumulative impact on lung health. For instance, a child born at 24 weeks gestation is much more likely to require intensive treatment with antenatal and possibly postnatal steroids, surfactant administration, respiratory support with ventilation, and a longer duration of oxygen exposure than a child born at 32 weeks gestation who may require relatively minimal therapy.The studies tracking lung function over time imply ongoing and potentially progressive chronic lung disease throughout life. However, they do not elucidate if poor long-term lung health outcomes are linked to specific, remediable risk factors and do not allow at-risk individuals to be identified. A sophisticated life-course approach would be beneficial to understand the impact of preterm birth and try an elucidate how each risk factor directly impacts on long term lung health to ensure that neonatal care and ongoing follow up is further optimized and appropriately targeted , 136.Much of this review focuses on the effects of very and extremely preterm infants, however there is growing interest in the long term respiratory outcomes of moderate preterm (32–33 weeks gestation), late preterm (34–36 weeks gestation), and early term born children (37–38 weeks gestation) in the current era of neonatal care. Late preterm and early term births account for between 3 to 6% and 15 to 30% respectively across different countries, with higher rates in high income countries . It has There is increasing evidence that children and young people born pre-term may follow a number of different postnatal lung function trajectories. In addition, there are numerous factors which have the potential to modify which trajectory is followed. There are many antenatal, neonatal, and postnatal factors which may influence lung function trajectory, however more research is required to determine how these interact, and whether there are interventions that may improve outcomes.All authors contributed to the literature review, intellectual input, drafting and final review of the manuscript.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.


This shape change is accompanied by changes in mechanical properties. Multiple studies using different measurement methods have revealed that cell surface tension, intracellular pressure and cortical stiffness increase upon entry into mitosis. These cell-scale, biophysical changes are driven by alterations in the composition and architecture of the contractile acto-myosin cortex together with osmotic swelling and enable a mitotic cell to exert force against the environment. When the ability of cells to round is limited, for example by physical confinement, cells suffer severe defects in spindle assembly and cell division. The requirement to push against the environment to create space for spindle formation is especially important for cells dividing in tissues. Here we summarize the evidence and the tools used to show that cells exert rounding forces in mitosis  Cell division requires the separation and equal partition of DNA and cellular contents into two daughter cells. To achieve this, animal cells undergo a remarkable series of structural changes when they enter mitosis, which impact every cellular compartment. Chromosomes condense and enter the cytoplasm following loss of nuclear envelope integrity. Centrosomes separate, and microtubules form a bipolar spindle to array chromosomes at metaphase before pulling them apart to segregate the genetic material at anaphase. However, mitosis is accompanied by an equally dramatic series of morphological changes  are disassembled at mitotic entry  and cellatomic force microscopy (AFM)  , which hpy (AFM) . In the py (AFM) , surfacepy (AFM) , a poroepy (AFM) , and shepy (AFM) . Moreovepy (AFM)  or micropy (AFM)  cantilevpy (AFM) . To obtapy (AFM) .micropipette aspiration . Thereby a micropipette is brought into contact with individual cells and a suction pressure is applied that draws the cell partly into the pipette as observed by light microscopy  . Using RT-DC, rates of higher than 100 cells/sec can be reached  ultra high-frequency sound waves (MHz-GHz range) passing through cells and tissues are analyzed and parameters such as sound velocity and attenuation and sample thickness are measured. The obtained sound velocity can be related to the compression modulus and thereby reflects on the cell mechanical properties  relies on the effect of Brillouin scattering, which occurs due to the interaction of incident laser light with acoustic phonons, causing a frequency shift that can be related to the longitudinal modulus and therefore sample compressibility . Here a flat cantilever is positioned above a cell in prophase. As the cell rounds and comes into contact with the cantilever, the forces exerted onto the cantilever can be read out . As a result, an increase in cortical contraction will raise intracellular pressure causing water efflux. This in turn will cause an increase in the osmotic pressure difference between the inside and outside. Nevertheless, because the osmotic forces involved are orders of magnitude higher than those generated by cortex contractility, the volume changes involved are expected to be negligible . This is+H+ ion exchange was seen when single cells were weighed in medium using a suspended microchannel resonator , the ezrin/radixin/moesin (ERM) family of proteins is likely to be critical in mitosis. Members of this family are widely expressed at high levels, bind both the actin cortex and transmembrane proteins within the plasma membrane, and are activated by phosphorylation and specifically recruited to the cell cortex in mitosis in both fly and human cells . In fly The acto-myosin cortex is key to generating mitotic cortical tension. However, two recent studies revealed the involvement of a second network of the intermediate filament protein, vimentin, which lies just beneath the actin cortex in mitotic cells. Serres and colleagues compared the proteins bound to actin in interphase and mitosis using mass spectroscopy and found that vimentin was specifically enriched in mitosis in HeLa cells . Duarte The mechanical changes associated with mitosis are striking in that they occur over a rapid timescale (10 min) and reverse just as quickly at mitotic exit . IncreasOnce cells reach anaphase, cyclin B degradation and the resulting decline in Cdk1 activity coincide with the reverse process as rounding pressure drops . In prep+H+ antiporter required for mitotic swelling may be regulated by RhoA  identified several ion channels that when knocked down decreased cell rounding force . This st by RhoA . Howeverin vivo where cells divide surrounded by other cells and extracellular matrix (ECM)?The mechanical changes in early mitosis allow cells to exert force on their environment. In single adherent cells, this can be measured as force on an AFM cantilever . Cells confined under soft polyacrylamide gels (∼ 5 kPa) are able to generate forces to deform the gel and create the space needed for spindle assembly . Howeverin vivo during development and in many different adult tissues , or use direct contact with the cell surface  see . Thus, m tissues . A drop  tissues ; Box 1.  tissues , 2012. TDrosophila neural stem cells was found to be generated by an unequal re-distribution of force-generating molecules at anaphase: the larger daughter cell had increased hydrostatic pressure, while the smaller had increased myosin localization and contractility , a phenotypic transformation commonly found in many epithelial-derived cancers and frequently associated with invasion and metastasis  alters tMost cancers are driven by mutations in a handful of oncogenes, and we recently addressed the role of one such oncogene, Ras, in regulating mitotic mechanics . We founFinally, as well as promoting faithful spindle formation in mitosis, there may be mechanisms whereby mitotic rounding and stiffening in cancer contributes to disease progression. There have been several reports of mitotic rounding driving changes in tissue structure. Mitotic rounding of individual cells within a monolayer of breast cancer cells triggers a 2D to 3D tissue transformation . Individin vivo, nor how acto-myosin contractility is regulated in a co-ordinated way to allow mitotic rounding while ensuring tissue integrity by maintaining cell/cell adhesion. Finally, several recent studies have revealed that changes associated with cancer, such as oncogene activation or EMT, can directly impact mitotic mechanics hinting at a role for mitotic rounding in facilitating cell division in tumors. Studying this further will rely on non-invasive techniques that allow the mechanical properties of living tissues under normal and diseased conditions to be interrogated.A wealth of work using different techniques has demonstrated that cells change their mechanical properties when they enter mitosis. In recent years, we are beginning to form an understanding of how this happens in single cells, downstream of mitotic kinases, through the formation of a high tension acto-myosin cortex and an increase in intracellular pressure. However, there remain many unanswered questions about the molecular regulation of mitotic rounding. For example, how molecular changes to the architecture of actin networks result in a mitotic cortex, which is both stiffer and thinner than in interphase. Although there is clear evidence that water enters the cell to increase intracellular pressure, the mechanisms that control the underlying changes in osmolarity are as yet unknown. The function of mitotic stiffening has been revealed by confinement studies using single cells. By exerting pressure against their environment, cells create space for spindle formation and faithful cell division. However, mitotic stiffening is likely to be of greater importance for cells dividing in tissues, but little is known about the extent of mechanical changes during mitosis AT, BB, and HM conceived the ideas, discussed, and edited the manuscript. AT and HM wrote the manuscript and made the figures. All authors contributed to the article 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.


Transfer learning plays a major role in medical image analyses; however, obtaining adequate training image datasets for machine learning algorithms can be challenging. Although many studies have attempted to employ transfer learning in medical image analyses, thus far, only a few review articles regarding the application of transfer learning to medical image analyses have been published. Moreover, reviews on the application of transfer learning in ultrasound breast imaging are rare. This work reviews previous studies that focused on detecting breast cancer from ultrasound images by using transfer learning, in order to summarize existing methods and identify their advantages and shortcomings. Additionally, this review presents potential future research directions for applying transfer learning in ultrasound imaging for the purposes of breast cancer detection and diagnoses. This review is expected to be significantly helpful in guiding researchers to identify potential improved methods and areas that can be improved through further research on transfer learning-based ultrasound breast imaging.Transfer learning is a machine learning approach that reuses a learning method developed for a task as the starting point for a model on a target task. The goal of transfer learning is to improve performance of target learners by transferring the knowledge contained in other (but related) source domains. As a result, the need for large numbers of target-domain data is lowered for constructing target learners. Due to this immense property, transfer learning techniques are frequently used in ultrasound breast cancer image analyses. In this review, we focus on transfer learning methods applied on ultrasound breast image classification and detection from the perspective of transfer learning approaches, pre-processing, pre-training models, and convolutional neural network (CNN) models. Finally, comparison of different works is carried out, and challenges—as well as outlooks—are discussed. Breast cancer is the second leading cause of death in women; 12.5% of women from different societies worldwide are diagnosed with breast cancer . CurrentTransfer learning is based on the principle that previously learned knowledge can be exceptionally implemented to solve new problems in a more efficient and effective manner ,18. ThusThis work reviews articles that focus on breast cancer imaging using transfer learning to summarize existing methods and identify their strengths and weaknesses. Further, it presents potential future research directions for transfer learning in breast cancer imaging using ultrasound. The review will be instrumental in guiding researchers to identify potential improved methods as well as areas that would benefit from future research on transfer learning-based ultrasound breast imaging.Transfer learning is a popular approach for building machine learning models without concerns about the amount of available data . Traininn layers from a pre-trained model to a target network and randomly initialize the rest 27], the It is customary that achieving better accuracy machine learning greatly depends on large training sample datasets. Nevertheless, compared with the available datasets in natural image domain, publicly available datasets in the field of medical ultrasound is still limited. The limited training data is a bottleneck for the further application of machine learning methods in medical ultrasound image analyses. To address the issue of small sample datasets, the commonly used method is transfer learning.Effectiveness of a particular transfer learning algorithm for a given target task highly depends on two issues: source task as well as relation to the target. Generally, transfer learning would produce a sound learning between adequately related tasks while preventing negative transfer. However, achieving this is practically challenging. In order to overcome negative transfer, considering recognizing and rejecting detrimental source task knowledge, selecting the adequate source task from a set of potential source tasks, and designing the task similarity between multiple candidate sources tasks could be sound solutions. Furthermore, mapping is important for translating between task representations if the source and target tasks are different. Other challenges related to the use of transfer learning in machine learning include architecture selection, number of instances adequate to fine-tune besides the numbers of layers used in addition to the pre-trained model. Moreover, the effectiveness of transfer learning decreases when the target task (ultrasonic diagnosis) mismatches the source task (pre-trained network’s task).Several directions are available for future research in the transfer learning area. First, transfer learning techniques can be further explored and applied to a wider range of applications in ultrasound image analysis. Second, how to measure the transferability across domains and avoid negative transfer is also an important issue. Although there have been some improvements on negative transfer, negative transfer still needs further systematic analyses. Third, the interpretability of transfer learning also needs to be investigated further. Finally, theoretical studies can be further conducted to provide theoretical support for the effectiveness and applicability of transfer learning. As a popular and promising area in machine learning, transfer learning shows some advantages over traditional machine learning, such as less data dependence and less label dependence in breast ultrasound imaging.Transfer learning has facilitated the development of breast cancer diagnoses using ultrasound imaging, by overcoming the general challenge of obtaining a large set of training data using models that are pre-trained on a larger dataset of natural images, specifically, ImageNet. However, there remain issues that need to be addressed in order to achieve superior performance in terms of the pre-processing algorithms used and the dataset types for both the target and training tasks. Pre-processing techniques, such as color conversion, matching layer, and augmentation play a significant role in improving the performance of transfer learning; therefore, further research in this area should be the focus of future studies. Furthermore, most of the previous research on breast cancer diagnosis via ultrasound imaging has focused mainly on cross-domain transfer learning, although a few studies report the superiority of the cross-modal transfer learning method. Therefore, future studies should focus on applying cross-modal transfer learning and evaluate the performance under different applications of breast cancer diagnosis, including detection, classification, and segmentation.


Diabetes mellitus is characterized by the body’s inability to control blood glucose levels within a physiological range due to loss and/or dysfunction of insulin producing beta cells. Progressive beta cell loss leads to hyperglycemia and if untreated can lead to severe complications and/or death. Treatments at this time are limited to pharmacologic therapies, including exogenous insulin or oral/injectable agents that improve insulin sensitivity or augment endogenous insulin secretion. Cell transplantation can restore physiologic endogenous insulin production and minimize hyper- and hypoglycemic excursions. Islet isolation procedures and management of transplant recipients have advanced over the last several decades; both tight glycemic control and insulin independence are achievable. Research has been conducted in isolating islets, monitoring islet function, and mitigating the immune response. However, this procedure is still only performed in a small minority of patients. One major barrier is the scarcity of human pancreatic islet donors, variation in donor pancreas quality, and variability in islet isolation success. Advances have been made in generation of glucose responsive human stem cell derived beta cells (sBCs) and islets from human pluripotent stem cells using directed differentiation. This is an emerging promising treatment for patients with diabetes because they could potentially serve as an unlimited source of functional, glucose-responsive beta cells. Challenges exist in their generation including long term survival of grafts, safety of transplantation, and protection from the immune response. This review focuses on the progress made in islet allo- and auto transplantation and how these advances may be extrapolated to the sBC context. Diabetes is characterized by the body’s inability to control blood glucose within a tight physiological range, due to insulin deficiency from beta cell loss or dysfunction and/or insulin resistance. Prolonged or recurrent hyperglycemia can lead to macro and microvascular complications, associated with substantial morbidity and early mortality , 2.Type 1 diabetes is an autoimmune attack on a patient’s own insulin producing beta cells. If left untreated, severe insulin deficiency leads to hyperglycemia, diabetic ketoacidosis and potentially death. Treatment options at this time are limited to exogenous insulin; although progress has been made in the precision of delivery of insulin and blood glucose monitoring , patientIn contrast, type 2 diabetes is a condition of insulin resistance and progressive beta cell decline . PatientWhile type 1 and 2 diabetes are the more common causes of glucose dysfunction, beta cell loss and dysfunction can also occur in the setting of persistent inflammation and stress within the pancreas due to chronic pancreatitis . This isIn these etiologies of dysglycemia, replacement of beta cell function is a potential treatment to alleviate glycemic variability and reduce risk for the complications associated with long term hyperglycemia. A common challenge is obtaining a sufficient number of islets to successfully treat individual patients and offer cell therapy to a larger number of patients with diabetes. Here we review the uses of allo- and auto- islet transplantation and how stem cell derived beta cells (sBCs) or islets may overcome barriers and limitations currently inherent in islet transplantation Table 1.Allogenic transplantation of cadaveric islets as a functional source of beta cells has become a treatment for patients with type 1 diabetes, particularly those with either life-threatening hypoglycemia or diabetes-related kidney failure requiring kidney transplantation. Although whole organ pancreas transplants can also be performed for these individuals –10, the Even when insulin independence is not achieved, islet transplantation is highly successful in preventing severe hypoglycemia, if islet graft function is maintained , 14, 15.Despite improving long-term outcomes after islet allotransplantation, challenges remain around the longevity of insulin independence. Transplanted islets are subjected to non-immune attrition, and at risk for alloimmune rejection and recurrent autoimmunity –20. Immuin vivo to augment the immune response to evaluate immune interactions and perhaps protect transplanted beta cells from immune destruction  is nearly universal when a minimum threshold of 5,000 IEQ/kg is transplanted in the autograft setting, suggesting this may be an appropriate minimum “dose” target for a stem cell-derived therapy [particularly if immune barriers are fully addressed ]. Islet in vivo in rodents  are a potential future treatment for those with diabetes. Both human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) are potential sources of hPSCs from which sBCs can be generated. hESCs are have been derived from blastocysts , 54. iPS rodents . Further rodents . While i rodents .While great progress has been made in the development of these sBCs, there are several challenges and factors to consider. One factor to consider is the presence of off-target or undifferentiated cells that could interfere with the functional sBCs or be tumorigenic. Current and future clinical approaches using partially mature (pancreatic endoderm) or fully mature islets for implantation may reduce this risk, but close clinical follow up will be needed.A second consideration is the role of immunogenicity of the sBCs or stem-cell derived islets. hESC derived cells, in the absence of genome editing, are subject to risk for alloimmune rejection which may require immunosuppression or encapsulation. Using iPSCs subverts this risk of alloimmunity and would be ideal for a cell source in TPIAT. Autologous sBCs have been successfully derived from patients with type 1 diabetes , but in in vivo . The contents of this Article are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.MB discloses the following potential conflicts: Research grant support from Viacyte and Dexcom. Medical advisory role (DSMB) for Insulet.The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Sensory substitution techniques are perceptual and cognitive phenomena used to represent one sensory form with an alternative. Current applications of sensory substitution techniques are typically focused on the development of assistive technologies whereby visually impaired users can acquire visual information via auditory and tactile cross-modal feedback. But despite their evident success in scientific research and furthering theory development in cognition, sensory substitution techniques have not yet gained widespread adoption within sensory-impaired populations. Here we argue that shifting the focus from assistive to mainstream applications may resolve some of the current issues regarding the use of sensory substitution devices to improve outcomes for those with disabilities. This article provides a tutorial guide on how to use research into multisensory processing and sensory substitution techniques from the cognitive sciences to design new inclusive cross-modal displays. A greater focus on developing inclusive mainstream applications could lead to innovative technologies that could be enjoyed by every person. Sensory substitution devices transform the representation of one sensory input into a new representation with a different sensory form. For example, a visual feed from a camera can be turned into sound to be heard or into tactile stimuli that can be felt. The most common applications of this to date are in developing assistive technologies which aid vestibular problems, visual impairments and hearing impairments. State-of-the-art sensory substitution techniques can contribute significantly to our understanding of how the brain processes and represents sensory information. This progressively advances cognitive theories with respect to multisensory perception and cognition, attention, mental imagery and brain plasticity. Sensory substitution techniques provide a novel opportunity to dissociate the stimulus, the task and the sensory modality, and thus offer a unique way to explore the level of representation that is most crucial for cognition. Due to their versatility, sensory substitution phenomena have the potential to help translate the principles underpinning cognitive theories of multisensory perception into other interdisciplinary research areas, such as human-computer interaction and artificial intelligence. In this review, we provide a novel framework which has two main aims: (i) to explain how applying sensory substitution techniques in a multisensory context for inclusive design can have a wide benefit to society beyond individuals with disabilities and (ii) to explain how inclusive cross-modal displays which utilise sensory substitution techniques will contribute to future cognitive theories of sensory processing.Disability has previously been regarded as something which professionals should seek to cure and attempt to provide rehabilitation for, enabling individuals to make strides towards a more ‘normal’ existence  studies to investigate the margins between congruent and incongruent cross-modal cues for improving user experience and performance. For example, congruent visual and audio/tactile stimuli can be used to increase the perceived quality of buttons on touch-screen devices  via tactile cues presented in a two-dimensional circular pattern. To enhance navigation, tactile sensory substitution techniques have been used to represent magnetic North or to provide positional information using a tactile belt or vest  could be utilised interchangeably to have access to the same sensory information (see Table As sensory substitution stands between perception and cognition (Arnold, Pesnot-Lerousseau, & Auvray, Developing a single product or service that appeals to a great number of people is challenging. Inclusive design does not claim to provide omnipotent and omnipresent solutions to address every barrier to usability and accessibility. Instead, the inclusive designer aims to develop flexible and adjustable technologies that appeal to all of us. We suggest this can be done by considering our shared perceptual and/or cognitive capabilities. While individuals vary in terms of their sensory experiences, with some individuals experiencing impairments, more individuals will be similar in their cognitive processing of sensory information. Rather than aim to compensate for impaired sensory forms using specialist devices built for sub-populations, technologies which take advantage of the metamodal organisation of the brain could be used by all individuals.Sensory substitution techniques have the potential to enable users to alternate between different cross-modal display modes which would allow a wide range of users to access the same device. A simple example could be the way that pedestrians use navigation applications which require frequent screen-dependent feedback. This means of human-computer interaction is more difficult for a pedestrian with a visual impairment, resulting in the development of multiple specialist solutions. While specialist solutions are helpful, an inclusive alternative could co-exist, which would benefit all parties. A navigation application which utilises cross-modal display modes would enable users to switch between auditory and tactile sensory channels as required. The same information will be provided in each of the sensory channels. A visually impaired pedestrian would benefit from this technology since they could receive information about the environment via auditory and/or tactile display modes. Meanwhile, the use of auditory and/or tactile display modes would allow a sighted pedestrian to navigate their environment without relying on visual feedback from a screen, allowing for greater enjoyment of their surroundings. In this way, both users benefit from the use of the same cross-modal displays.Other future cross-modal displays using sensory substitution techniques could include artistic applications; games; extended reality environments; portable and intuitive systems; and mobility, communication or education platforms (Lenay et al., These examples are all hypothetical. To our knowledge, no such mainstream technologies currently exist which make use of sensory substitution techniques. However, enormous potential exists to develop such cross-modal devices in the future. The scientific literature offers a vast amount of sensory substitution techniques with distinct methods of transforming sensory signals. Investigating their information capacity and perceived resolutions (e.g., Richardson et al., In recent years, the concepts of cross-modal cognition have spread into multiple disciplines, and examples of their applications can be found in neural networks, artificial intelligence and cognitive robotics (Corradi, Hall, & Iravani, Inclusion is as much about technology, art, policies, social institutions, and commercial models as it is about how one accepts and tolerates others in society. It is a mindset that can be applied in thinking, designing and creating, thereby encouraging all individuals to exist in equilibrium with one another. Overall, these premises offer an inclusive alternative to the usability and accessibility perspectives that are built on a legacy of traditional frameworks, commercial models, and social and academic conversations which view disability as something which accompanies individuals, rather than something which is created by environmental barriers. Human-technology interactions can take advantage of the information processing capability of the metamodal brain in a multisensory context. Rather than creating tools which are merely assistive to compensate for sensory impairments, research and development into sensory substitution techniques could be unified by a motivation for inclusion. New technologies which benefit all individuals could be developed. Accumulated knowledge might then be transferred laterally in a multidisciplinary context, and practically applied to inclusive innovations that appeal to us all.


Spatial disorientation is one of the earliest symptoms in Alzheimer's disease (AD)  or via an immersive head-mounted display, has offered many advantages for navigation testing. As VR navigation correlates highly with RW navigation . This strategy is associated with a brain network centered around the parietal lobe and subcortical structures . This strategy is associated with a brain network centered around the medial temporal lobe, particularly the hippocampus . This lack of control makes it challenging to keep environments consistent over time for repeated navigation testing , when they are temporarily left alone on purpose, or during the night when the caregiver is sleeping are key contextual factors , studies show that AD patients exhibit impairments in egocentric navigation, which was associated with decreased volumes of the right posterior hippocampus/parietal cortex, landmark recognition/recall, and allocentric processes   associated with missing incidents in AD patients. However, most RW studies do not link to the underlying spatial navigation brain changes or pathophysiology in AD. Although some studies attempted to relate the external factors to neurocognitive findings in patients, these findings were mostly based on neuropsychological tests which do not measure spatial navigation With current VR and RW studies shedding light on neurocognitive/external factors, respectively, an approach combining VR with RW navigation would offer the best chance to study interactions between these types of factors and investigate how their alterations could lead to spatial disorientation in AD. We suggest a potential experimental model using navigation tests in naturalistic RW settings, like familiar neighborhoods used in previous studies (Sheehan et al., In conclusion, in our opinion it is important that future studies relate VR navigation results to RW factors to gain a more holistic view of factors contributing to spatial disorientation in AD. Theoretically, this would allow greater ecological validity of VR tasks and might inform future VR task designs. Clinically, this approach could help enhance our understanding of getting lost events in AD patients, which in turn would allow use of VR for predicting patients at higher risk for these events before they actually occur. This could then be used to inform and implement much-needed, effective safeguarding strategies to prevent AD patients from getting lost in future, which currently are very limited (Emrich-Mills et al., VP and MH designed the manuscript. VP, LE-M, EL, MP, and MH wrote the manuscript. All authors contributed to the article 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. The reviewer LS declared a past co-authorship with one of the authors MH to the handling editor.


Specifically, we assessed differences in connectivity between core olfactory processing regions as well as differences in regional homogeneity and homotopic connectivity within the primary olfactory cortex. In contrast to congenital blindness, none of the analyses indicated atypical connectivity in individuals with congenital anosmia. In fact, post-hoc Bayesian analysis provided support for an absence of group differences. These results suggest that a lifelong absence of olfactory experience has a limited impact on the functional connectivity in the olfactory cortex, a finding that indicates a clear difference between sensory modalities in how sensory cortical regions develop.Congenital blindness is associated with atypical morphology and functional connectivity within and from visual cortical regions; changes that are hypothesized to originate from a lifelong absence of visual input and could be regarded as a general (re) organization principle of sensory cortices. Challenging this is the fact that individuals with congenital anosmia (lifelong olfactory sensory loss) display little to no morphological changes in the primary olfactory cortex. To determine whether olfactory input from birth is essential to establish and maintain normal functional connectivity in olfactory processing regions, akin to the visual system, we assessed differences in functional connectivity within the olfactory cortex between individuals with congenital anosmia ( Absence of input from a sensory modality has been linked to notable alterations in the human brain . These aAssessing functional activity within a sensory neural network without presenting the associated sensory stimuli is not trivial. However, fluctuations in the blood-oxygen-level dependent (BOLD) signal at rest, measured by resting-state functional magnetic resonance imaging (fMRI), have been linked to intrinsic functional networks in the adult brain . Hence, To determine whether olfactory experience is critical to develop normal functional connectivity within the olfactory system, we assess what effects a lifelong absence of olfactory input has on the functional connectivity within and between core olfactory regions by comparing individuals with isolated congenital anosmia (ICA)  to age, sex, and education matched individuals with established functional olfactory abilities. First, we will determine potential ICA-dependent differences in functional connectivity within the olfactory network by comparing resting-state functional connectivity between regions important for olfactory processing. Here, we hypothesize that the lifelong absence of olfactory input in individuals with ICA is associated with a lower functional connectivity between said regions. Second, based on the unexpected display of typical morphology in the primary olfactory cortex in individuals with ICA , we willA total of 68 individuals participated: 34 individuals with ICA and 34 controls matched in terms of age, sex and educational level . One indDiagnosing ICA is a nontrivial problem due to the difficulty of dissociating a congenital cause from a very early onset of anosmia. We took a number of precautions to decrease the risk of incorrectly including an individual in the ICA group. All participants labeled as ICA reported a lifelong absence of olfactory perception and, based on questionnaires, absence of potential noncongenital causes of their anosmia  orother congenital disorders . Additionally, 24 of the individuals with ICA had previously sought medical care for their inability to smell odors and received the clinical diagnose anosmia. Finally, all participants were tested to establish normal sense of smell (controls) or functional anosmia (ICA). Due to the rareness of ICA, participants were recruited and tested at two different sites: 46 individuals (23 ICA) in Stockholm, Sweden, and 22 individuals (11 ICA) in Wageningen, the Netherlands; a matched control was always scanned at the same site as an individual with ICA. The study was approved by the ethical review boards in both Sweden and the Netherlands and all participants provided written informed consent prior to study participation.Participants’ olfactory ability was assessed using the full Sniffin’ Sticks olfactory test battery . The test consists of three subtests assessing odor detection threshold (T), odor quality discrimination (D), and cued odor quality identification (I), each rendering a maximum score of 16. The combined score of the subtests (TDI) was used to assess individual olfactory ability compared to normative data from over 3000 individuals , correspImaging data were acquired on two 3 T Siemens Magnetom MR scanners : a Prisma scanner using a 20-channel head coil (Sweden) and a Verio scanner using a 32-channel head coil (the Netherlands). Both sites used identical scanning sequence protocols and participant instructions.3, 41 slices, FOV = 228 mm, interleaved acquisition). To reduce the risk of participants falling asleep, participants were instructed to keep their eyes open and look at a fixation cross. A structural T1-weighted image was acquired for each individual using an MP-RAGE sequence . Results from structural image analysis are reported elsewhere  running in MATLAB 2019b . The preprocessing pipeline included slice timing correction, image realigning using a six parameter rigid body transformation model, coregistering the structural image to the mean functional image using affine transformation, 1 using functions based on the “unified segmentation” approach , and no group differences in individual number of time-points with frame-wise displacement > 0.5 mm were demonstrated , a threshold above which notable correlation changes have been observed  thought to play a key role in olfactory processing. All regions were chosen based on a previously published activation likelihood estimation analysis  of olfactory processing : the bilP < 0.05 family wise error (FWE) corrected within the ROI was used for all analyses; if no voxel reached significance, a threshold of P < 0.01 was implemented to assess potential differences at a more liberal statistical threshold.We here use the primary olfactory cortex ROI according to the definition by Two different measures were used to assess the quality of our data. First and foremost, the amplitude and variability of BOLD-signal in our ROIs were assessed given that the OFC lies in close proximity to the sinuses and is therefore commonly affected by macroscopic susceptibility artifacts . In addi3 smoothing kernel and conducted a seed-to-voxel analysis. Based on visual comparison of the resulting connectivity maps with those presented by Tobia and colleagues, and inclusion of the regions mentioned in their paper, such as thalamus and hippocampus, our results match those previously presented  were computed for each individual and compared between groups . Within t-tests were conducted for the 15 connections using JASP . All tests yielded anecdotal to moderate evidence for the null hypothesis .To better assess whether these results could be interpreted in favor of the null hypothesis, that is, no difference in connectivity between the two groups, Bayesian independent samples P < 0.05, FWE corrected within the ROI . Because no significant group differences in either regional homogeneity or voxel-mirrored homotopic connectivity were demonstrated, further group comparisons using Bayesian independent samples t-tests were done, analogous with the analysis of the connectivity between the core olfactory regions. Specifically, for each individual, the mean homogeneity and homotopic connectivity were extracted from each of the eight primary olfactory subregions and compared between groups. All comparisons yielded anecdotal to moderate support for the null hypothesis .To assess ICA-related functional deviations within the primary olfactory cortex, regional homogeneity and voxel-mirrored homotopic connectivity were compared between ICA and control groups. Neither regional homogeneity A nor vox the ROI B. At theWe investigated whether a lifelong absence of olfactory input is linked to altered function of core olfactory processing regions by comparing resting-state functional connectivity between individuals with ICA and matched controls. Specifically, the functional connectivity between core olfactory regions as well as the regional homogeneity and homotopic connectivity within primary olfactory cortex were assessed. In stark contrast to our hypotheses, none of our results support the notion that ICA is linked to atypical functional connectivity in the olfactory cortex. This implies that, unlike visual and auditory sensory deprivation, a lifelong absence of olfactory sensations has a limited effect on the functional connectivity of the core processing regions of the deprived sensory modality.We found no difference between individuals with ICA and matched healthy individuals in resting-state functional connectivity within the predefined olfactory network. Albeit a decrease in functional connectivity for ICA individuals was hypothesized, we suggest that the demonstrated lack of group differences are an indication of group similarity rather than an indication of inability to find existing differences due to, for example, low power. We argue this based on the additional Bayesian analyses that showed support for the null hypotheses (no group differences). The fact that individuals with ICA, that have had a lifelong absence of olfactory input, did not demonstrate atypical connectivity raises interesting questions about the development of olfactory connectivity and, specifically, the influence of early olfactory input on the olfactory processing network.Results from developmental studies  and studIn rodent models, experimental olfactory bulb ablation has different effects on the development of the piriform cortex depending on at what age the ablation occurs. Removal of the olfactory bulb right after birth, thus removing afferent input to the piriform (primary olfactory) cortex and mimicking congenital or very early olfactory sensory deprivation, has little to no effect on the cortical thickness of the piriform cortex, whereas a later removal leads to a definitive thinning of the piriform cortex . The corResting-state fMRI has led to a greater understanding of the functional organization of the human brain ; howeverAlthough none of the group comparisons of functional connectivity indicated differences between individuals with ICA and controls, it seems unlikely that a lifelong lack of olfactory input has absolutely no effect on the connectivity of core olfactory processing regions, even during rest. Needless to say, we are inherently limited by the spatial and temporal resolution of the methods we use and are thereby unable to draw conclusions regarding potential alterations in connectivity occurring at spatial or temporal scales not investigated here. Although we do not claim that a lifelong lack of olfactory input has absolutely no effect on the connectivity of the olfactory cortex, our results do imply that even if atypical connectivity (between or within olfactory regions) not detectable here exists in individuals with ICA, these potential alterations are far from the magnitude of those demonstrated in visual cortex of blind individuals where connectivity alterations are clearly detectable using ROI-to-ROI functional connectivity , regionaThe lack of group differences, supported by post-hoc Bayesian analysis, in resting-state functional connectivity between the core olfactory processing regions could be interpreted as a preserved functional olfactory network displayed by individuals with ICA despite a lifelong absence of olfactory input. However, although these core olfactory processing regions were chosen based on their known involvement in olfactory processing  and prevTo enable the inclusion of a greater number of individuals with the rare condition ICA, data were collected at two different locations. The use of multiple sites has been reported to have minimal effects on the reliability of functional connectivity, but uncontrolled differences across sites may potentially introduce bias . Thus, eIn summary, our data indicate that individuals with ICA demonstrate typical resting-state functional connectivity between core olfactory processing regions as well as within primary olfactory cortex despite a lifelong lack of olfactory experience. This suggests that, in sharp contrast to the visual cortex, the olfactory cortex does not require early sensory input to develop and maintain functional connectivity. These results call for further studies on the basis of this suggested developmental difference between sensory processing regions in general, and the development of olfactory cortical regions in particular.Peter_Supplementary_bhaa217Click here for additional data file.


Tools for medical image analysis have been developed to reduce the time needed to detect abnormalities and to provide more accurate results. Particularly, tools based on artificial intelligence and machine learning techniques have led to significant improvements in medical imaging interpretation in the last decade. Automatic evaluation of acute ischemic stroke in medical imaging is one of the fields that witnessed a major development. Commercially available products so far aim to identify (and quantify) the ischemic core, the ischemic penumbra, the site of arterial occlusion and the collateral flow but they are not (yet) intended as standalone diagnostic tools. Their use can be complementary; they are intended to support physicians’ interpretation of medical images and hence standardise selection of patients for acute treatment. This review provides an introduction into the field of computer-aided diagnosis and focuses on the automatic analysis of non-contrast-enhanced computed tomography, computed tomography angiography and perfusion imaging. Future studies are necessary that allow the evaluation and comparison of different imaging strategies and post-processing algorithms during the diagnosis process in patients with suspected acute ischemic stroke; which may further facilitate the standardisation of treatment and stroke management.The online version of this article (10.1186/s42466-019-0028-y) contains supplementary material, which is available to authorized users. The diagnosis of stroke is based on the clinical examination and also on different imaging technics. The differentiation between haemorrhagic and ischemic stroke and the detection of large vessel occlusions (LVO) represent key steps in determining the optimal therapy regimen for the individual patient. Time is essential: the faster the diagnosis is made, and the appropriate therapy is initiated, the better the outcome of patients . Many toIn the 1980s, a concept called computer-aided diagnosis (CAD) was introduced. Its primary intent was to provide radiologists with a second opinion while reading their cases . CAD hasCAD is strongly related to Artificial intelligence (AI), a branch of computer science that has witnessed an incredible development in the last few years. CAD and automated computer diagnosis (ACD) are two concepts with similar names but different meanings.CAD usually relies on a combination of interpretation of medical images through computational algorithms and the physicians’ evaluation of the medical images. In this case, medical physicians are not replaced by an algorithm, but they use algorithms’ output as a second opinion. The diagnosis and the final decision are made at the end of the process by the physicians . This coACD is based on computer algorithms only, and the diagnosis is made directly by the algorithm. In this case, the algorithm’s performance in a clinical routine must be at least equal or better than the performance of an average physician. Although computer algorithms may easily exceed human performance in many fields, developing such tools for the usage in medical imaging remains a difficult task. More difficult is even the adequate assessment and validation of CAD or ACD based algorithms.In 2011 Goldenberg et al. presented another concept of CAD for the usage in emergency medicine called computer-aided simple triage (CAST), which performs an analysis of medical images and sorts them into different prioritisation’s categories. CAST systems should attract the radiologists’ attention to acute and time-sensitive critical cases .Physicians use CAD systems as a support for their decision-making process aiming to get better results in the detection and interpretation of pathologies in medical images. Evaluating the performance of CAD schemes against a gold standard is usually not sufficient; measuring the influence of CAD systems on the decisions made by the physicians and on the general workflow in a clinical setting is also crucial. This influence may be positive, and this could be mirrored by a decrease of time need to diagnosis establishment or an increase in the detection rate of true subtle anomalies due to CAD support. A negative influence may be marked by an increase in false positive results due to the confusion generated by the bias effect. Therefore, although not easy, it is essential to study the effect of CAD systems on their users. For such studies, a large number of physicians or radiologists is needed, and a comparison between final results obtained by the physicians with or without getting CAD support in different settings is helpful to determine the impact of these tools on the performance of the physicians, which is related to the outcome of patients.CAD algorithms are developed to perform tasks that usually require human intelligence and aim at extracting patterns from medical images and using these patterns to perform a specific task like suggesting a diagnosis.Pattern recognition and extraction requires prior identification of relevant image features. Classical multistep CAD systems are based on conventional machine learning algorithms in which human-experts hand-engineer these features. Classical CADs process data in multi-steps (at least two: hand-encoded features extraction and classification) .Unlike these, modern CAD systems use representation learning (RL) based algorithms, in which no manual feature encoding is necessary . RL scheDeep learning (DL) is a subfield of RL, in which algorithms get from simple features, like edges or textures, to more complex features such as shapes or organs in their learning process Fig. a and b , 9. ThroClassical and modern CAD systems alike are usually trained by using labelled data; this method is called supervised learning. The labelling is commonly done by a human expert; the algorithm’s possible output-results in this model are well defined. It is worth noting that this is a crucial step in developing e.g. deep learning-based algorithms. It can generally be said, that a larger dataset for training should lead to a more robust algorithm that would be less prone to overfitting and should be able to perform better on previously unseen external data. However, large datasets are not easy to obtain, and labelling large datasets is time-consuming if done by hand, but prone to errors if done automatically. On the other hand, unsupervised learning algorithms try to discover previously unknown patterns and structures in the unlabelled input data without previous labelling. The algorithm decides by itself how to cluster the data into different subgroups. A combination of these two methods is called semi-supervised learning, in which a large amount of unlabelled data in conjunction with a usually small quantity of labelled data are used ; this me(i)Preprocessing of medical images is essential to simplify interpretation and the subsequent processes. Different technics can be used, such as image resizing and application of smoothing filters for noise reduction.(ii)During the feature extraction stage, the algorithms determine the characteristic of objects or ROIs, which can then be used in the classification step. There are many feature extractors and they differ in their processing method, time to extract features and also their computational methods.(iii)For the final classification task, the CAD system can either perform simple two-class categorisations or more refined multi-class categorisations. The first one would only classify features in the medical images in two categories, for example normal and abnormal. The second one could classify the obtained features into various categories and thus provide differential diagnosis to some extent.Pattern recognition process in classical and modern CAD medical algorithms usually follows three main steps; however, getting through all these steps is not mandatory. These main steps are: (i) preprocessing of medical images – including segmentation and designation of regions of interest (ROI), (ii) extracting automatically generated or hand-engineered features that are predefined from human experts and finally (iii) data classification based on these features Fig. . Modern Especially since the advent of deep learning, medical image analysis using AI is a worldwide rapidly growing market . SeveralMany methods have been applicated to evaluate the performance of CAD systems for commercialization. Some examples of these methods are leave-one-out, cross-validation, hold-out, and resubstitution. However there is until now no standardized approach; trying to solve this issue, the Computer Aided Detection in Diagnostic Imaging Subcommittee (CADSC) which is a committee initiated by the American Association of Physicists in Medicine (AAPM) proposed some recommendations on the methodology applicated in the evaluation of CAD system performance.Health authorities firmly regulate the commercialisation of medical devices and drugs. Medical softwares are usually included under the medical devices category. Software as a Medical Device (SaMD) is a new term defined by the International Medical Device Regulators Forum (IMDRF) for applications that are used without being a part of a hardware medical device. These SaMD have special regulations and validation processes, which are adopted by the American Food and Drug Administration (FDA). Within the European Economic Area, medical softwares must obtain a certification mark (CE Marking) demonstrating conformity with medical devices regulations (MDR) approved by the European Parliament and Council before free commercialization. Of note, some of these certification processes do not require the presentation of clinical validation data.A non-contrast-enhanced computed tomography (NCCT) brain scan is still the most widely available tool in acute stroke imaging because it is easily accessible, inexpensive, efficient, fast and reliably rules out haemorrhage. The most accurate assessment of the early infarction is obtained by diffusion-weighted magnetic resonance imaging (DWI) . HoweverThe probably first semi-automated approach to identify putative hypodensity within the middle cerebral artery (MCA) territory was published in 2001. In the following years, several other different computer-aided detection schemes for cerebral ischemia on CT were published. However, all of these papers described different approaches and focused on the methodology of the algorithms used; sample sizes were rather small and rigorous comparisons against the current gold standard, the interpretation of the scan by a neuroradiologist or against DWI were missing , which is not yet certified for clinical application but has undergone comparison to the e-ASPECTS software . Here the-ASPECTS, RAPID ASPECTS, as well as Frontier-ASPECTS, are based on quantitative evaluation of early focal ischemic damage by the Alberta Stroke Programme Early CT Score (ASPECTS), which is a topographic scoring system that divides the MCA territory into ten areas of interest. Originally ASPECTS was calculated within two prespecified slices through the level of the basal ganglia and the level of supra-ganglionic structures , while sWhile so far only one study on the performance of RAPID ASPECTS has been published , there aHyperdense vessel sign (HDVS) on NCCT represents an early marker of acute ischemic stroke caused by intracranial arterial occlusion. HDVS is a radiological phenomenon marked by an increase of vessel radiodensity on NCCT after an acute occlusion. HDVS can be seen in various vascular diseases, including acute arterial occlusion, acute arterial dissection, aneurysm rupture, and acute venous thrombosis .HDVS is most commonly reported in the MCA region; this is because MCA territory is usually the most affected cerebral region by ischemic stroke . Also, tHDVS is highly specific (95%) and moderately sensitive (55%) for arterial obstruction in acute ischemic stroke; usage of thin-slicing improves the sensitivity significantly . HoweverThrough its early visibility, already after vessel occlusion and before upcoming pathological parenchymal ischemic changes, it represents a perfect diagnostic aid in time crucial acute stroke cases. Automating the process of MCA or intracranial HDVS sign detection in emergency imaging may accelerate the identification of positive cases, especially in spoke centers without regular access to CTA. This could improve referral logistics and reduce the time to acute treatment, e. g. mechanical recanalization or systemic thrombolysis. Important success elements of CAD of HDVS are: Acquisition of high-quality cranial native CT, application of new reconstruction methods like iterative model reconstruction to reduce noise and improve diagnostic performance  and usinRecent trials have demonstrated the therapeutic potential of thrombectomy even in an extended time window , 38. PatAs an alternative, validation can be done indirectly by investigating the ability of a particular score to predict the clinical outcome of the patient, appropriate therapy  provided. Consequently, CTA-based scoring of collaterals has proven to be predictive not only for the success of recanalization but also for clinical outcome in several MT studies –46. DiffIt was also demonstrated that the timing of the CTA is crucial for the assessment of collateral flow and that acquisition in the late arterial or early venous phase increases the specificity . This isThe numerous different scores and the dependence on acquisition techniques as well as individual parameters such as blood pressure or cardiac ejection fraction all can lead to considerable interrater variability in assessing collateral flow on CTA images and standardisation would be beneficial . So far,There is a commercial software available from Brainomix called e-CTA® which is embedded in the company’s e-Stroke Suite platform. It determines the Tan score and also gives a percentage of vasculature detected in the affected MCA territory as compared to the contralateral side, similar to the aforementioned approach . It has Another application of machine learning algorithms to acute LVO CTA is automated detection of the occlusion. In contrast to CS, where automatization can overcome interrater variability, the advantage is different from LVO detection, since experts are not really challenged. However, less experienced physicians in primary care institutions will depend on the correct detection of an LVO when deciding to refer a patient to a comprehensive stroke centre or not. Technically, such an approach is straight forward as algorithms such as the “region growing” approach can be employed here. There are two reports on this issue so far. In the ALADIN study, Barreira and colleagues used a commercial software employing an AI-based algorithm , in 875 patients with 46% LVO and compared the results against an expert-based ground truth , 52. TheAutomated analysis of CTA using AI-based algorithms can have several advantages in acute stroke imaging: i) interrater variability can be reduced to increase objectivity, ii) less experienced physicians can get support in diagnosing LVO and collateral flow and iii) decision making in stroke treatment can be accelerated. As with human reading, however, timing of the arrival of contrast is pivotal here, too.Perfusion imaging can be performed with either CT or MRI. Whereas NCCT can only identify early ischemic changes, which – if present – are generally not reversible and turn into final infarction, perfusion imaging, like DWI has the chance to estimate the ischemic core even before ischemic changes can be seen on NCCT, in the very early time window. Furthermore perfusion imaging can visualize tissue at risk that might be rescuable. Perfusion imaging is a depiction of the passage of blood or fluids through the vessels of an organ or tissue to allow quantification. It enables visualisation of regions of abnormal cerebral hemodynamics and quantifies the effect of interfering situations, such as a preceding stenosis or an occlusion. The main principle of contrast-enhanced perfusion imaging is to monitor the first pass of a bolus of contrast agent through the cerebral circulation.In order to derive information from perfusion maps, it is important to define specific imaging parameters. Cerebral blood volume (CBV) is commonly referred to a volume of blood in a given region of brain tissue as per millilitres per 100 g of brain tissue . CerebraMean transit time (MTT) is the average time (in seconds) a certain volume of blood takes to pass through a given volume of brain . MTT is (i)The bolus needs to be recorded during the whole passage through the brain including the arterial, parenchymal and venous phase. As perfusion imaging acquisition usually takes only 40 to 60 s, a common pitfall occurs, for example, in patients with decreased cardiac output which leads to a delayed or slow increase in arterial input shifting the bolus curve to the end of imaging acquisition.(ii)By placing the intravenous access very peripherally, for example in the back of the hand or foot of the patient, the contrast agent takes more time to reach the brain for imaging acquisition (see paragraph above) and the bolus gets diluted until it reaches the brain vessels. Therefore the increase in contrast agent is diminished, which leads to inaccurate perfusion maps, specifically to underestimated CBF and overestimated MTT, mimicking hypoperfusion.Physicians need to be aware of major pitfalls that could lead to a falsified or useless perfusion imaging:In order to evaluate the quality of the perfusion data and to assess the reliability of the post-processing results, both situations need to be taken account for using the arterial input function (AIF) and venous output function (VOF) profiles during imaging post-processing. Computer-assisted imaging algorithms usually provide AIF and VOF profiles automatically. Moreover, “head shaking” head movement can be corrected for by using the midline of the brain. If, however, the patient moves his head within the longitudinal axis , the sections of the brain change the level or imaging slice and voxels usually cannot be reassigned properly during imaging postprocessing.Over the years, there have been several different approaches to distinguish normal tissue from hypoperfused, viable tissue (‘tissue at risk’) from nonviable tissue (‘ischemic core’) using CT- and MR-perfusion imaging. Correspondingly, numerous thresholds have been advocated . Using CThe amount of absolute (ml) or relative mismatch between ischemic core and tissue at risk varies within studies , 62, butPost-processing software estimates perfusion parameters based on above mentioned brain perfusion principles using deconvolution of tissue and arterial signals  deconvolution method, methods using Bayes theorem) in perfusion imaging (incl. co-registration with DWI images in MRI) with specified thresholds for an automated segmentation and quantification of the infarct core and the tissue at risk , 67. ForBecause of different post-processing algorithms and thresholds – results differ among commercially available fully automated software even when using identical source data , 70. PhyRecently, a different approach has been used to either improve or replace previous software solutions. By using machine learning methods, i.e. deep learning techniques using neural networks, the infarct core volume and tissue at risk can be predicted directly from the CTP or MRP source images. Additional metadata – such as the time parameters and treatment – could further increase prediction accuracy and might even predict infarct growth over time or depending on treatment modality  – a commercial software solution – has been used and is currently used in a number of large stroke trials  treatments.Future clinical studies are necessary for proper validation, evaluation and comparison of the different available software solutions in order to broaden and generalise treatment selection criteria for patients with acute ischemic stroke. Furthermore, future studies may focus on the integration of CAD algorithms within the workflow of stroke referral networks.Additional file 1:Supplementary Appendix. (DOCX 102 kb)


The paraventricular thalamic nucleus (PVT) is highly interconnected with brain areas that control reward-seeking behavior. Despite this known connectivity, broad manipulations of PVT often lead to mixed, and even opposing, behavioral effects, clouding our understanding of how PVT precisely contributes to reward processing. Although the function of PVT in influencing reward-seeking is poorly understood, recent studies show that forebrain and hypothalamic inputs to, and nucleus accumbens (NAc) and amygdalar outputs from, PVT are strongly implicated in PVT responses to conditioned and appetitive or aversive stimuli that determine whether an animal will approach or avoid specific rewards. These studies, which have used an array of chemogenetic, optogenetic, and calcium imaging technologies, have shown that activity in PVT input and output circuits is highly heterogeneous, with mixed activity patterns that contribute to behavior in highly distinct manners. Thus, it is important to perform experiments in precisely defined cell types to elucidate how the PVT network contributes to reward-seeking behaviors. In this review, we describe the complex heterogeneity within PVT circuitry that appears to influence the decision to seek or avoid a reward and point out gaps in our understanding that should be investigated in future studies. Several recent reviews have comprehensively summarized the literature on the role of the paraventricular nucleus of the thalamus (PVT) in reward-seeking  vs. risk (STOP) in foraging for food. Substance use disorders also can be characterized as an approach (GO)-avoidance (STOP) problem. The transition to addiction evolves from the initial euphoric responses to addictive drugs to repeated drug use and maladaptive behaviors aimed to relieve the dysphoria associated with drug abstinence. The compulsion to seek and take drugs eventually overwhelms the motivation to abstain despite negative consequences. Recent evidence has implicated posterior PVT in this motivation PVT has been linked to appetitive/approach behaviors and posterior (p)PVT to aversive/avoidance behaviors  hypothalamic area, and zona incerta (ZI) neurons dorsal to LHA send GABAergic projections to PVT  suppressed the expression of conditioned sucrose seeking and cue discrimination. The PFC→PVT role in conditioned cue-induced behavior is reinforced by a report that photoinhibition of PFC→PVT (or PVT→CeA) neurons decreased retrieval of a fear-conditioned memory from 24 h to 7 days after experiencing a foot shock paired with a tone CS+ . Thus, here we discuss the cellular diversity found in PVT and highlight approaches that could be particularly useful for targeting and dissociating distinct PVT cell types.The PVT consists of strikingly unique cell populations based on its anterior-posterior, medial-lateral, and dorsal-ventral axes. Although PVT consists of glutamatergic excitatory projection neurons that bifurcate to several downstream targets, aPVT projection neurons are thought to provide stronger innervation of PFC and ventral subiculum, whereas pPVT projection neurons provide stronger input to the BNST and CeA , and these neurons also project to the NAc . Despite this knowledge, no studies to date have measured the activity of neuropeptide-specific inputs to PVT Due to the multi-faceted heterogeneity among neurons that comprise the PVT , unraveling the mystery of PVT function for motivated behaviors has remained difficult. Several new approaches could help us untangle, particularly those that emphasize dissection, recording, and perturbation of single neurons. Most importantly, we need a greater resolution for defining unique cell types in PVT, a feat that has been difficult to achieve when evaluating cell populations based on axon projection (due to widespread bifurcation), anatomical location (due to the undefinable gradient that separates each axis of PVT), and activity (due to heterogeneous activity patterns in defined cell populations). Thus, here we propose that scientists prioritize dissection of PVT neurons based on gene expression, as some cell types seem to express completely unique genes and thus are completely isolatable through cre-driver mouse lines and viruses. One approach that would be particularly useful for the field is high-throughput, single-cell mRNA sequencing . Single-cell sequencing could isolate cell-types that express unique genes and/or enriched gene sets , providing unprecedented insight into the cell populations that make up PVT.c-fos), used in an attempt to show that a particular behavioral event or context activates PVT neurons. Considering that inhibitory rather than excitatory activity dynamics often drive behavior through PVT (see above), conclusions made from such studies should be made with significant caution as such neuronal dynamics could be completely missed by c-fos (or Fos) labeling. Another commonly used approach is calcium photometry, used to determine if the bulk cellular dynamics in a single cell population changes over time. This approach is also limiting and possibly misleading, as calcium sensor fluorescence dynamics bias detection of excitatory responses in neurons due to the rapid on but slow off kinetics. As such, in a scenario wherein one cell is inhibited and another cell is excited, bulk photometry is likely to indicate an excitatory response overall. This problem is highly relevant for PVT studies due to heterogeneous activity dynamics found in PVT cell types. Considering this heterogeneity, it is important to perform recordings with single-cell resolution and in identified cell types . Calcium imaging or optogenetic photo-tagging with in vivo electrophysiology provide the best means to monitor activity in single, genetically-defined neurons  inhibitory dynamics in PVT change the nature of “sufficiency” and “necessity” experiments and (2) heterogeneity in PVT makes it difficult to completely dissect the function of discrete neuronal ensembles.Considering the inhibitory dynamics that often arise during reward consumption and seeking in PVT cell populations (Do-Monte et al., in vivo activity patterns. Such experiments would be transformative in that the range of activity dynamics in PVT that contribute to behavior could be resolved.The heterogeneous nature of PVT neuronal dynamics has made it difficult to dissect the function of that activity for behavior. For example, recently we found that neurons in the PVT→NAc pathway can be split into two basic categories, neurons that are inhibited and neurons that are excited during the presentation of a sucrose-predictive cue. This heterogeneity, as discussed above, is not unique when studying PVT and should thus be considered for all functional experiments and conclusions. Novel experimental approaches that would be particularly useful involve those that target single neuronal ensembles defined based on activity. This has traditionally been performed through genetic mouse lines that allow “trapping” of activated neuronal ensembles based on immediate-early gene expression (Guenthner et al., in vivo activity dynamics—none of which seem to be mutually exclusive. In addition to such heterogeneity, PVT responses during reward-seeking and consumption tend to be inhibitory, making it difficult not only to characterize that activity but also to identify the function of such dynamics for behavior. We propose the use of single-cell transcriptional profiling strategies for defining precise cell types in PVT, as well as excitatory optogenetics to identify how inhibitory activity patterns in these cell types are functionally necessary for controlling behavior. Altogether, studies thus far suggest that PVT influences reward-seeking and consummatory behavior based on a variety of environmental and physiological conditions that amalgamate into multiple PVT output channels to provide integrated decisions over motivated behaviors (Choi et al., Studies described herein reveal the inherent complexity of PVT that seems to be organized as a variety of cell types based on anatomical location, gene expression, connectivity, and JM and JO contributed equally to the writing of this review article.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.


Integrating neural cultures developed through synthetic biology methods with digital computing has enabled the early development of Synthetic Biological Intelligence (SBI). Recently, key studies have emphasized the advantages of biological neural systems in some information processing tasks. However, neither the technology behind this early development, nor the potential ethical opportunities or challenges, have been explored in detail yet. Here, we review the key aspects that facilitate the development of SBI and explore potential applications. Considering these foreseeable use cases, various ethical implications are proposed. Ultimately, this work aims to provide a robust framework to structure ethical considerations to ensure that SBI technology can be both researched and applied responsibly. The most advanced of these have sought to embody these neural systems into simulated environments to elicit dynamic goal-directed behavior, referred to as Synthetic Biological Intelligence (SBI) and similar approaches as it does not involve whole organisms, using only specific biological material, usually neural tissue derived typically through synthetic biology processes, as a biomimetic material within the larger system.Advancements in hardware, software, and synthetic biology (wetware) have resulted in new methods for interacting with nce (SBI). SBI sysIt is only relatively recent that the ethics of experimenting with brain tissue has been seriously considered, with the overwhelming focus on cells from a human origin. The majin vitro neurons – whereby activity from a neural system is measured, applied to an environment, and updated environmental information communicated back to the neural system – has received relatively limited exploration. Early work supported the proposition that in vitro neurons would respond to incoming stimulation adaptively or engage in behaviors consistent with blind-source separation phenomena . Yet keew  the scalable and diverse opportunities that arise from modern stem cell technology and synthetic biological methods; 2) the hardware and software applications which enable the interaction with the biological tissue; 3) the neurocomputational theories and subsequent inferences for eliciting behavior from the system and to better understand what the implications of this may be.Building on this work, recent research has shown that ironments. Importa1)Perhaps the largest advancement in experimental neurobiology related to SBI has occurred with the generation of renewable pluripotent stem cell cultures that can be differentiated to neural cells. Early wFirstly, primary cell culture is, at best, linearly scalable, which means to scale up systems would require a growing number of animals to be killed for tissue harvesting – an ethically fraught prospect . SecondlIn contrast, the use of iPSCs removes all these concerns while providing new opportunities. Techniques to exponentially scale up the production of iPSCs are well established. Neural 2)SBI technology must be able to record activity from living biological neurons, transmit this information to a virtual or physical system to allow action, and then provide information back to the biological neural network that can be altered according to the action performed. Ideally this closed loop occurs in real-time, so that the neural system is able to dynamically adapt to the effect of its actions on the environment. Improvements in hardware and software allow for more advanced and nuanced interactions with neural systems.The most prevalent method of interaction remains through electrophysiological recording and stimulation via multielectrode arrays (MEA). HoweverFurther, while passive MEA are capable of being used in sophisticated approaches, the dev3)While the ability to generate neural tissue and interact with it via hardware and software is necessary for SBI, it is not sufficient. It is also critical to be able to understand mechanisms by which neural systems engage in intelligent and/or goal-directed behavior in order to elicit these functions in a meaningful way. Other works cover the myriad of theories postulated in greater detail (e.g. ), so herin vivo. The lain vivo. Therefoin vivo. In turnThe Mind in Vitro project, for which The National Science Foundation awarded a 7-year, $15 million project grant to the multi-university team led by the University of Illinois Urbana-Champaign (UIUC); the EU-funded NEU-ChiP project which received €3.5 million in funding from the European Commission; and the John Hopkins University-led Organoid Intelligence research focus group, althouSome ethical and regulatory issues raised by the development of SBIs will mirror those raised by brain organoids. This includes concerns around obtaining informed consent from donors, ensurinHowever, these ethical restrictions should not be a barrier to research with SBIs, especially in the early stages. The non-invasive nature of donating skin/saliva cells or the minimal risk of donating small amounts of blood, along with the potential to use a small number of donors to generate a large number of SBIs, should mean there is an adequate supply of samples. Yet other issues, such as the legal status of these devices, that are also currently under discussion for brain organoid research will still need to be considered Rather than looking deeper at the donor issues raised by SBIs, we will focus on other issues which have received less attention. These can be broadly broken down into two key subsets: 1) concerns about applications of SBI technology; 2) uncertainty around the potential of SBI technology to give rise to ‘conscious’ systems that may be worthy of special moral consideration. We discuss both below.in vitro preclinical drug screening and modeling of brain-related diseases or disorders. Recently, in vitro testing drug targets has become increasingly more common, especially with the advent of organoids are alsDeveloping SBI also offers the potential to better understand how computation or intelligence arises in neural systems. This exploration offers both short- and long-term applications. Shorter term SBIs offer the chance to explore how neural systems process information and provide the potential to refine existing, or develop new, theories. Being able to better understand how neural systems display traits such as ‘intelligence’ also means that such traits could be leveraged in wider applications in the future. Such applications could focus on improving drug discovery, better understandings of neural function, or even advanced iterations of SBI technology, perhaps being leveraged for real-time autonomous tasks in robotics.in press;in vitro (or other) systems as similar mathematical criteria could be established in non-conscious systems , neuro-representationalism, active inference, global workspace theories (GWTs), et cetera., offer avenues to establish useful correlates of potential states . Moreovein vitro, previously a contentious question. Not only would this inform fundamental mechanisms underpinning intelligence and related states, it may provide insight into more efficient or powerful algorithms for machine learning and artificial intelligence research – consistent with calls from the research community(Further applications of SBI research are aimed at developing approaches to integrate broader theories of population dynamics with more reductive single cell processes, to allow a better understanding of neurobiology. For exacommunity.A potential longer-term benefit of SBI research is more sustainable computer systems which are less dependent on the availability of large amounts of power to operate. Climate change, driven by increasing carbon emissions, has been described as the greatest moral challenge of our time. It resu3 of terms, constructive discourse will be greatly hampered. Previously, key terminology has been imprecise, with signifiers used interchangeably to represent one or another concept that are themselves seldom formally defined. Even in cases where a term may be defined in one paper, the lack of coherence in the field can give rise to semantic disagreements that may distract from underlying scientific efforts(Foremost, it is imperative that a broadly agreed upon nomenclature for this field is adopted. We usedc efforts. Terms rSecondly, identifying reliable objective metrics which can track phenomena of ethical relevance should remain a focus of research going forward. These cThirdly, once these understandings have been obtained, it will become crucial to identify areas and approaches that maximize benefits and minimize risks. Anticipatory approaches to the ethics and governance of emerging science and technologies could be useful here . Anticipin vitro systems. This inherent uncertainty further highlights the need for an approach that can reasonably anticipate morally significant properties and guide an ethical response as new evidence and knowledge emerges over obstructive precautionary measures that pay insufficient attention to the potential for beneficial outcomes. To manage the uncertainties and avoid polarizing the discussions, anticipatory approaches apply deliberative methods for engaging stakeholders and wider publics, as recently demonstrated with organoid research (For example, when considering what metrics may identify features worthy of moral consideration, it is likely that only through further development of SBI technology will the necessary knowledge to even identify these metrics be obtained. As described above, while currently some measures used in humans such as the PCI may have some merit, there is no evidence they are appropriate for research and humanresearch .Elucidating the full range of applications and associated ethical or moral issues raised by SBIs exceeds the scope of this work. Therefore, here we have proposed key steps to building a viable framework to explore these issues in a constructive manner. Researchers should engage with broader publics and stakeholders to generate meaningful dialogue on the moral boundaries and shape SBI applications towards achieving socially and ethically desired outcomes.142 Following this perspective, even if SBIs produce human-like intelligence, this does not inherently imply they have moral status. Despite this, it is possible that the more sophisticated neural architecture required for human-like intelligence may facilitate more complex – and more morally valuable – conscious experiences and/or cognitive mental states. Determining measures that can help researchers infer when systems are likely to possess evaluative sophistication should be a goal of on-going research.Going forward, one key question will be: What, if anything, can we deduce about the moral status of these entities? For example, it has been argued that the most important feature of conscious systems that gives rise to moral status is not general, or domain specific, intelligence, but rather evaluative sophistication – the capacity to have a wide range of valanced subjective experiences. This bu