Workplace stress is a complex phenomenon that may often be dynamic and evolving over time. Traditional linear modeling does not allow representation of recursive feedback loops among the implicated factors. The objective of this study was to develop a multidimensional system dynamics model (SDM) of workplace stress among nursing aides and conduct simulations to illustrate how changes in psychosocial perceptions and workplace factors might influence workplace stress over time.Eight key informants with prior experience in a large study of US nursing home workers participated in model building. Participants brainstormed the range of components related to workplace stress. Components were grouped together based on common themes and translated into feedback loops. The SDM was parameterized through key informant insight on the shape and magnitude of the relationship between model components. Model construction was also supported utilizing survey data collected as part of the larger study. All data was entered into the software program, Vensim. Simulations were conducted to examine how adaptations to model components would influence workplace stress.The SDM included perceptions of organizational conditions , workplace social support , workplace safety, and demands outside of work (i.e. work-family conflict). Each component was part of a reinforcing feedback loop. Simulations exhibited that scenarios with increasing job control and decreasing job demands led to a decline in workplace stress. Within the context of the system, the effects of workplace social support, workplace safety, and work-family conflict were relatively minor.SDM methodology offers a unique perspective for researchers and practitioners to view workplace stress as a dynamic process. The portrayal of multiple recursive feedback loops can guide the development of policies and programs within complex organizational contexts with attention both to interactions among causes and avoidance of adverse unintended consequences. While additional research is needed to further test the modeling approach, findings might underscore the need to direct workplace interventions towards changing organizational conditions for nursing aides. Workplace stress is a complex and dynamic experience often reported by workers in health care settings. Nursing aides, in particular, report a number of interrelated psychological and physical workplace and non-workplace factors that may contribute to variable stress responses , 2. To dWorkplace stress can be operationalized as both an outcome of factors inside and outside of work, and can be a determinant to health and quality of life and performance of work roles. This may be especially the case for nursing aides who report challenging working conditions that may include little assistance with job tasks, high psychological and emotional demands, few opportunities for decision-making, and poor safety climate –5. WhileThe predominant model examining and measuring workplace stress is the Job Demand-Control model (JDC) , 23, 24.A sociotechnical perspective considers organizations as adaptive systems made up of interdependent personal, social, technical, and organizational components that interact with one another in non-linear ways , 32. SysA multi-staged model building methodology based on key informant insights was conducted . Model dEight key informants were recruited to participate in model building. Key informants were chosen because of their exposure to the personal, psychosocial, and organizational conditions of nursing aides. Each were members of the Pro-Care investigative team for an average of 6 years and conducted field work directly with nursing aides in nursing home facilities. To participate, all key informants had to have in-depth knowledge of health, workplace, and personal experiences of nursing aides that they were willing to share with others. Prior to model building, each participant was given a short tutorial on sociotechnical systems to facilitate broader thinking regarding workplace stress. All key informants then engaged in four model-building sessions that lasted 60 to 90 minutes and consented to having their insights incorporated into the model. An external model builder facilitated discussions to elicit the structure and process of the workplace stress system, while concurrently translating conversations into visual mapping of the SDM .In the first session, key informants discussed the scope of the model and established model boundaries at the organizational level. As part of this initial conversation, informants talked about workplace stress broadly as a major determinant of health and well-being of nursing aides. The second model building session involved brainstorming the range of influential components within an organizational system boundary. The model boundary was set at the organizational level to focus sessions, and allow for comparisons between nursing home sites in different community contexts . When paFollowing the first two key informant sessions, construction of the model began with an examination of the relationship between components identified by the key informants using Pro-Care data. Further model building was conducted with a subgroup of three key informants. These subgroup sessions aimed at critically discussing and confirming the structure of each feedback loop. The refined SDM generated through the subgroup sessions was shared with the larger group of key informants who were asked for their level of agreement regarding model accuracy in representing the factors associated with workplace stress. In cases where there was disagreement, further discussions were conducted among the subgroup, and the structure of the model was refined and fed back to the larger group. This iterative process continued until agreement on the description of each feedback loop was reached. After several critical discussions, a final feedback structure of the model was generated and entered into the system dynamics modeling software program, Vensim .n = 950). The Pro-Care survey was administered biannually to nursing home staff and measures a range of concepts including individual characteristics, psychosocial perceptions, and workplace conditions. In our model, job strain was utilized as a proxy for perceived workplace stress [After determining the feedback structure, the SDM was parameterized. First, baseline mean values for each component were entered into Vensim as parameter values that reflected initial model conditions. These values were extracted from a Pro-Care survey administered to nursing aides in 24 sites from 2012 to 2013  in the model influenced workplace stress over time. Using the simulation model, model sensitivity tests were also conducted. First, component values were set to extreme conditions to determine if changes to workplace stress occurred as expected . Second,The SDM presented in Fig. As exhibited in the SDM, workplace stress was the primary stock (level of outcome) and flow (rate of change of outcome). Aligning with previous workplace stress models, key informants indicated that job demands and job control represented two secondary stocks and flows that impacted workplace stress. Indicated by the positive polarity ‘+’, an increase in job demands led to an increase in the flow of workplace stress. As discussed in model building, several components amplified the stock and flow of job demands including psychological demands  (+), workplace safety (+), and work-family conflict (+). Participants reported that job control was the second stock and flow that impacted workplace stress. Findings from model building showed that job control had an opposing effect. An increase in job control would dampen workplace stress (−). In the model building process, key informants discussed several components that impacted job control including skill discretion , decision authority  (+), and workplace support (+).Interestingly, through model building, three reinforcing feedback loops that generated action in the workplace stress system were described. In the first reinforcing feedback loop (R1), workplace social support was positively linked with job control (+); job control was negatively linked with workplace stress (−); and a negative link existed between workplace stress and workplace social support (−). The second reinforcing feedback loop involved workplace safety (R2). Greater workplace safety was related to lower job demands (−); job demands were positively linked with workplace stress (+); and workplace stress was negatively linked with workplace safety (−). As reflected in the last reinforcing feedback loop (R3), greater conflict between work and family contributed to more job demands (+); job demands were positively linked with workplace stress (+); and workplace stress was positively linked with work-family conflict (+).Using the key informant-designed SDM, simulation scenarios were conducted to determine how changes to perceptions of organizational conditions, organizational social support, workplace safety, and work-family conflict could impact workplace stress within the nursing homes in which the model was based. System behavior was simulated over the 10-week time horizon set by participants. Simulations provide important practice-based insight into how adapting model components could impact workplace stress and uncover potential points of intervention . For intNext, simulations were conducted to examine how changes to model components impacted workplace stress. First, simulations were conducted to compare job control base case simulation to increased (25% increase) and decreased (25% decrease) scenarios. As reflected in Fig. The next set of simulations examined how changes to the remaining system components  would impact workplace stress. The base case was compared to an increased workplace social support scenario , and a decreased workplace social support scenario . Interestingly, both simulation scenarios followed a similar declining trajectory  as important components in the model, along with workplace social support and workplace safety, and demands outside of work . Feedback loops consisting of model components were developed that had distinct amplifying effects on workplace stress. Feedback loops illustrate the cyclical nature of workplace stress, which is conceptualized as both an outcome and determinant of conditions both inside and outside of the workplace. Based on the perspective provided by our model, workplace stress may be addressed by designing workplace interventions that account for the multiple factors within an organizational system, and programs that may disrupt reinforcing feedback relationships between model components.By building a systems-based simulation model, this study aimed to expand on classic workplace stress models. Interestingly, the base case scenario suggested that over the 10-week period workplace stress was relatively constant, and underscores the need to develop primary and secondary workplace interventions for nursing aides. As shown in the subsequent simulation scenarios, improvement in the organizational conditions will help to treat workplace stress. Small organizational changes that could enable nursing aides to have more control and experience fewer demands were related to a decline in workplace stress over the simulation period. Conversely, policy changes that may increase demands or reduce control can have an opposing effect, and result in a reinforcement of workplace stress over time. It is important to acknowledge that organizational policies, low institutional resources, restrictions to the number and type of tasks a nursing aide performs can limit significant changes in the clinical workplace settings. At the same time, our study suggests that potentially minor changes to perceptions of organizational conditions can generate conditions that weaken the stock and flow of workplace stress.Within the context of the nursing homes and nursing aides in which key informants had insights, workplace social support, workplace safety and demands outside of work  were important components in the SDM. In contrast to findings from previous studies , 43–45, There were several benefits related to the model building methodology. By participating in model building sessions, participants were able to gain a greater awareness of the complexity of stress within the organizations with which they were working and develop an understanding of how to devise and implement changes within the dynamic system. Through model simulations, decision-makers can also test hypotheses, examine how various interventions impact workplace stress, and better understand why interventions may not have intended outcomes. Based on the model we produced, findings point towards changing organizational conditions rather than on workplace social support, workplace safety, and work-family balance to improve perception of workplace stress. Ultimately, insights gained from the model building process can be valuable to engage workplace health promoters and nursing home administrators with ways that they can direct scarce resources to have the greatest impact on minimizing workplace stress.There are methodological strengths and weaknesses worth noting. Our model was built using insights from key informants who had in-depth observational knowledge of the nursing aides’ personal and work-related experiences and were able to think about various components from a sociotechnical systems perspective. This knowledge was incorporated into the feedback loops that made up the model and enabled us to test the feasibility of SDM in examining workplace stress among key informants. Additionally, our model of workplace stress was data-driven and incorporated parameter values from a large survey of nursing home staff. We utilized results from a multi-center longitudinal study of nursing homes to establish initial model conditions, and as a way to examine preliminary model validity. Although our model was developed within the context of specific US nursing homes, it may have some applicability to other settings. While specific physical and psychological exposures of nursing aides in nursing homes might differ from other clinical settings, features of the job and perceptions of workplace stress may be similar to other allied health professionals. Moving forward, it is suggested that additional research applying the model building methodology to workplace stress among a broader range of healthcare workplaces is required to understand the generalizability and the reliability of the approach.There are also several limitations. First, learning to view and express workplace stress as a system of interrelated components can be challenging. Through a series of probing questions, the model-builder encouraged team members to think more holistically about workplace stress . While wWorkplace stress reported by nursing aides occurs within the context of a dynamic and complex organizational system. Through the application of system dynamics modeling methodology, key informants identified a range of interrelated variables associated with workplace stress among nursing aides. The constructed model depicted the perceived importance of job control and job demands to long-term workplace stress. Model simulations suggested that workplace social support, workplace safety, and work-family conflict appeared to be less integral within the context of the broader system. Based on the model designed in this study, there is a need to direct workplace interventions towards changing organizational conditions. Findings underscore the importance of conceptualizing the system as a whole when designing policies and programs to reduce stress in the workplace. The SDM model can be a valuable educational tool for managers by illustrating dynamics over time and enabling assessment of “what if” scenarios from changes in programs and policies; the results of this work will be used to inform future dissemination products and strategies.


Soft-tissue sarcomas (STS) are a rare group of malignant tumors which can affect any age group. For the majority of patients who present with a localized STS, treatment involves a multidisciplinary team decision-making approach ultimately relying on surgical resection with or without adjuvant radiation for successful limb salvage. The goals of treatment are to provide the patient with a functional extremity without local tumor relapse. The purpose of this article is to review the treatment of extremity STS, with a focus on staging, treatment options, and outcomes. Soft-tissue sarcomas (STS) are a diverse group of rare malignant tumors which arise from mesenchymal tissue. Approximately 11,000 new cases of STS are diagnosed each year in the United States, accounting for <1% of all cancers . STS canThe etiology of most STS remains unknown; however, there are certain environmental factors and genetic predispositions which have been associated with the development of some types of STS, including neurofibromatosis and Li-Fraumeni syndrome. The initial signs and symptoms of a STS may vary depending on the tumor site, subtype, and grade. Most commonly patients present with an enlarging painless mass, however tumor growth can cause pain via a mass effect on nearby neurovascular structures.Certain tumors have a tendency to appear at a certain age (e.g. liposarcoma in adults and rhabdomyosarcoma in children). Likewise, certain STS are more common in specific anatomic locations: liposarcoma is more common in the lower extremity, whereas synovial sarcoma, epithelioid sarcoma, and fibrosarcoma are encountered more often in the upper extremity . Rapid gThere are three factors which need to be evaluated as part of the investigation of a patient with a STS: (1) local extension, (2) histological diagnosis, and (3) staging of metastases. Each of these pieces of information plays an important role in developing a patient-specific treatment plan , 9.STS generally spread along tissue planes, compressing the surrounding tissues and typically do not violate anatomic barriers such as fascia or bone. It is unusual for a STS to invade bone, but when it occurs, bone invasion is associated with a significant reduction in overall survival . LikewisImaging evaluation is best performed by MRI of the extremity. Plain radiographs are rarely required but can help identify bone remodeling, bone invasion, and soft-tissue calcification or ossification . MRI is Pathological assessment is necessary to define the histologic subtype and grade and should be obtained prior to definitive treatment if there is concern for a STS. Different subtypes can vary in their clinical behavior and response to treatment and histologic grade has been identified as one of the strongest predictors of metastatic risk and disease-free survival , 16–19.In the case of a suspected STS, biopsy should be performed prior to excision in order to avoid inadequate surgery. Two types of biopsies are commonly used today: needle (fine-needle aspiration (FNA), core needle biopsy (CNB)) and open biopsy . Needle biopsies are less time consuming, relatively inexpensive, cause minimal morbidity, limited soft-tissue contamination, and can be performed in an outpatient clinic setting –23. FNA Incisional biopsy provides a larger amount of tissue for histologic assessment and grading and thereby provides a better estimate of prognosis . An operThe diagnostic workup is completed by staging investigations for regional and distant metastases. The two most commonly used staging systems are the American Joint Committee on Cancer (AJCC) staging system and the Musculoskeletal Tumor Society (MSTS) staging system . Both ofExtremity STS most commonly metastasize hematogenously with a strong predilection for the lungs and 10% of patients will have detectable pulmonary disease at the time of initial presentation . The iniEvery patient with a soft-tissue sarcoma in the upper or lower extremity will require an individualized treatment plan. Various patient, tumor, and anatomic characteristics need to be evaluated in a multidisciplinary setting in order to generate the optimal treatment plan.Most localized extremity STS are best treated surgically with or without radiation therapy. Chemotherapy is usually reserved for management of patients with metastatic disease either at presentation or following resection of the primary tumor, or less commonly for attempting to facilitate local tumor down-staging for very extensive lesions which might not otherwise be amenable to limb sparing surgery. Isolated lymph node metastases are somewhat of an exception however as long-term survival is still possible following surgical resection . The oveThe term “oncologic control” refers to minimizing each patient’s risk of local and systemic recurrence with current treatment modalities. Historically, many soft-tissue sarcomas of the extremity were treated with amputation or radical resection alone. Although this approach provided a high degree of local tumor control, it was at the expense of residual limb function and yet still left patients at risk for developing metastatic disease. The introduction of adjuvant radiotherapy and developments in cross-sectional imaging, particularly MRI, has allowed more conservative resection margins to be considered safe, thereby extending the indications for limb salvage. In general, modern limb-salvage techniques can achieve comparable oncologic control with superior functional outcomes compared to amputation. As a result, primary amputation for management of extremity STS is rarely indicated except for situations with very extensive and locally invasive disease  27]..27].Radiation therapy is recommended for all STS where surgery will provide less than a wide negative resection margin. Adjuvant radiation can be given preoperatively or postoperatively and this was the subject of a randomized clinical trial (RCT) . PreoperIn the above RCT, patients who received 50 Gy preoperatively and had positive resection margins were treated with an additional 16 Gy radiation boost following surgery. Two subsequent studies showed that this postoperative radiation boost increased the total dose of radiation without offering any detectable advantage in local control so this practice has since been abandoned at our institution, as well as many others in North America, but has yet to become a widely accepted treatment policy , 34. In Image-guided intensity-modulated radiation therapy (IMRT) is becoming the standard of care for sarcoma patients at our institution and can be provided in either the preoperative or postoperative setting . The potSurgical margin has an important impact on outcome because it may be the only independent risk factor under the surgeon’s control in the treatment of an extremity STS , 40, 41.Other studies have assessed the safety and efficacy of close dissection along bone or critical neurovascular structures to facilitate limb salvage combined with radiation therapy . ClarksoFractures in the radiation field can be particularly problematic because radiated bone does not reliably heal. Radiation-related fractures most commonly affect the femur and are significantly more frequent following postoperative radiation, likely due to the combination of higher radiation dose and larger treatment field –49. HighThe primary goal of oncologic surgery is to achieve negative surgical margins, and this often means that large soft-tissue defects are left following resection which are not amenable to primary wound closure . Soft-tiFollowing primary wound closure; skin grafting is the first rung of the reconstructive ladder. Split thickness skin grafting (STSG) can be used in a well-vascularized wound to cover muscle and tendons with paratenon. A historic contraindication to STSG was a radiated wound bed; however, recent studies have shown that a STSG can provide durable coverage of a radiated wound, and healing may be enhanced with a negative pressure wound dressing .If the soft-tissue defect following STS resection precludes primary wound closure, and/or there are exposed nerves, vessels, bone, tendon without paratenon or hardware, the wound will need flap coverage as opposed to skin grafting. Flaps can be either local pedicled flaps or free flaps depending on the anatomic location and size of the defect requiring coverage . RotatioFollowing limb-salvage surgery or amputation, patients may be left with significant physical and emotional disability and reduced overall quality of life (QOL). In order to evaluate the impact of these procedures on patients, various functional assessments have been utilized. The most commonly used outcome measures are the Toronto Extremity Salvage Score (TESS) and the Musculoskeletal Tumor Society (MSTS) scoring system –57. The Resection of extremity STS is frequently a very invasive procedure, which can significantly impact a patient’s life; however, a majority of patients are left with moderate-to-high function following limb salvage , 58 Tab. PredictThe majority of local recurrences as well as lung metastases will become evident within the first two years following treatment. As a result, high-risk patients are seen in follow-up every three months for the first two years for clinical examination and a chest x-ray or CT-scan. We only perform MRI of the surgical site or lymph nodes as part of regular follow-up if there is clinical concern for local or regional recurrence, based on physical examination in the clinic or changes noted by the patient. After the first two years high-risk patients are reviewed every six months until five years and then annually until 10 years.Extremity STS are aggressive and rare malignant tumors with several factors such as size, depth, grade, and tumor location which influence outcome. Following a tissue diagnosis and staging, the treatment of patients with STS involves a multidisciplinary team approach and most patients are eligible for limb-salvage surgery, usually combined with radiation. Following treatment the majority of patients can expect a painless and functional extremity.No conflicts of interest are declared by any author on this study.


One of the oldest and most influential theories of psychosis formation states that delusions arise in an attempt to explain unusual experiences, including perceptual aberrations. The White Noise Task by Galdos et al (2011) was developed as an experimental task to assess the tendency to attribute meaning to random perceptual stimuli: speech illusions in white noise. Studies to date have demonstrated that speech illusions as assessed with the White Noise Task are associated with a composite measure of positive symptoms in patients with psychotic disorders . However, findings in non-clinical samples have been inconsistent: one study found an association with a composite measure of subclinical positive symptoms, including support for a relation with familial psychosis liability , whereas other studies did not find any association in non-clinical samples or only partly . The current study aims to further examine whether speech illusions as assessed with the White Noise Task are indicative of psychosis liability and to explore specific symptomatic pathways.www.eu-gei.eu). Psychotic symptoms were assessed with the Brief Psychiatric Rating Scale (BPRS). Transition to clinical psychosis was assessed with the Comprehensive Assessment of At Risk Mental State (CAARMS). We used a conservative measure of speech illusions, as described in Catalan et al (2014).We conducted symptom-based network analyses in Ultra-High Risk (UHR) subjects participating in the European network of national networks studying gene-environment interactions in schizophrenia project  experienced speech illusions. Preliminary network analyses in cross-sectional baseline data showed potential pathways from speech illusions to delusional ideation, through hallucinatory experiences. We also found evidence of prospective relations between speech illusions at baseline and transition to clinical psychosis. Pathways ran via baseline psychotic symptoms and affective symptoms, as well as a ‘direct’ pathway.As far as we are aware, this is the first study combining an experimental measure of aberrant experiences with symptom-based network analysis. Although the current reported findings are preliminary and exploratory, they tentatively support a relation between speech illusions as assessed with the White Noise Task and psychosis liability. This relation may be dependent on sample composition, and not generalizable to the general population as a whole. Future studies may benefit from focusing on more detailed trajectories of both susceptibility to speech illusions and course of (sub)clinical psychotic symptom severity in subjects with increased risk for psychosis, with use of more frequent, short assessment periods and inclusion of environmental risk factors for transition to clinical disorder.


Comparative genomics has revealed a class of non-protein-coding genomic sequences that display an extraordinary degree of conservation between two or more organisms, regularly exceeding that found within protein-coding exons. These elements, collectively referred to as conserved non-coding elements (CNEs), are non-randomly distributed across chromosomes and tend to cluster in the vicinity of genes with regulatory roles in multicellular development and differentiation. CNEs are organized into functional ensembles called genomic regulatory blocks–dense clusters of elements that collectively coordinate the expression of shared target genes, and whose span in many cases coincides with topologically associated domains. CNEs display sequence properties that set them apart from other sequences under constraint, and have recently been proposed as useful markers for the reconstruction of the evolutionary history of organisms. Disruption of several of these elements is known to contribute to diseases linked with development, and cancer. The emergence, evolutionary dynamics and functions of CNEs still remain poorly understood, and new approaches are required to enable comprehensive CNE identification and characterization. Here, we review current knowledge and identify challenges that need to be tackled to resolve the impasse in understanding extreme non-coding conservation. Extremely conserved sequences within the non-coding portion of metazoan genomes were initially identified more than three decades ago by comparing the introns and UTRs of mammalian and avian mRNAs –5. TheseSince then, numerous studies have defined sets of evolutionarily conserved CNEs, each using different conservation criteria, species comparisons and nomenclature  and, in addition to the array of CNEs, always contain a target gene regulated by the CNEs. Some, but not all, GRBs also contain bystander genes. Bystander genes frequently contain CNEs within their introns; however, they are unresponsive to CNE regulation due to differences in their promoter architecture  for homeodomain DNA-binding factors  N-gram graphs which combine neighborhood information (co-occurrence of substrings) with sequence compositional motifs  and (ii)et al. recovered the established primate phylogeny , revealed a high degree of CNE loss compared to other teleost fish. Many of these CNEs cluster around key retained developmental genes, and may have contributed to the extensive morphological changes in seahorses  for CNEs in the folding, establishment or maintenance of TADs? TAD structures are lost during mitosis, indicating that TADs must consistently refold after each cell division. The principles that guide TAD folding and maintenance are still largely unknown. Given the correspondence between GRBs and TADs, it would be tempting to investigate the possible role of CNEs in TAD formation.What is the role of CNEs in disease pathogenesis? Recent studies have demonstrated that when elements that define TAD boundaries are disrupted, distinct developmental disorders and cancer arise (er arise –173. GivWe conclude by outlining questions, the answers to which may further our understanding of CNEs and their function:Supplementary DataClick here for additional data file.


The musculoskeletal system is acutely sensitive to changes in the biomechanical environment and prolonged exposure to microgravity causes bones to demineralize, and skeletal muscles to lose mass and strength.5 The lost tissue appears to be restored following return to normal gravity, although long-term studies have identified incomplete recovery of bone mineral density and architecture and permanent damage to bone remains a concern.2From the early days of spaceflight when humans first escaped the gravitational pull of Earth, it became clear that the unloading environment of microgravity .12 Together, the joint trauma and unloading studies support the notion that a normal range of mechanical forces are critical for maintaining healthy joints. Interestingly, consistent with this hypothesis is the finding that active exercise prevented cartilage degradation in rats subjected to HLU13 suggesting that exercise may be useful as a countermeasure to minimize joint pathology in microgravity. With the goal of minimizing long-term musculoskeletal problems, pre-flight and post-flight physiotherapy and conditioning regimes to complement mid-flight exercise are being considered.14Is there evidence that biomechanical unloading impacts the joint? Data from terrestrial hind-limb unloading (HLU) animal experiments and human bed-rest studies demonstrate that reduced mechanical forces associated with joint unloading and immobilization leads to the proteoglycan loss in articular cartilage.15 More recently, experiments using simulated microgravity,17 and on parabolic flights, where repeated but short duration periods of microgravity are possible, have been conducted.19 In studies on cultured human chondrocytes, parabolic flight resulted in upregulation of cytoskeletal network genes and proteins suggesting even with short duration microgravity, cells respond by reorganizing the cytoskeleton.18 Cytoskeletal reorganization were also reported in simulated microgravity experiments17 as was reduction in extracellular matrix production and mineralization.21 Our studies indicate that extended exposure to microgravity results in articular cartilage proteoglycan loss in mice (m/s in preparation). What about in humans? Cartilage degradation products would be present in synovial fluid, urine and blood of flight personnel. While elevated levels of bone resorption markers and calcium metabolism in body fluids of flight personnel have been reported,22 there are no studies that focused on cartilage breakdown products released by damaged joints, such as carboxy-terminal telopeptides of Type II Collagen. This deficiency can be addressed by sampling the stored fluids of astronauts for cartilage biomarkers.If biomechanical unloading on Earth leads to cartilage breakdown, is there evidence that exposure to microgravity causes joint degradation? An early microgravity study reported smaller chondrogenic pellets, less proteoglycan synthesis and reduced dynamic stiffness of three-dimensional engineered cartilage constructs grown for 4 months on the Russian MIR craft.Degradation mechanisms—trauma vs. HLU vs. microgravity: Does the microgravity-induced cartilage breakdown occur via the same mechanisms as in the HLU model? If so, then HLU can be used to simulate the effects of microgravity. However, the possibility of a compounding effect of microgravity in addition to the unloading cannot be discounted. Similarly, are there common mechanistic steps between unloading and trauma that lead to cartilage destruction? The existence of a common response would suggest that findings from microgravity studies could inform mechanisms of OA with the potential to reveal new therapies.Biochemical threshold for tissue restoration: Are there specific biochemical or molecular thresholds that need to be breached for tissue restoration to fail? Our studies suggest that microgravity is sufficient for reversible proteoglycan loss in mouse femoral cartilage. In these studies, the lack of surface fibrillation and damage suggests that the collagen network is intact and that the point-of-no-return has not yet been reached. Microgravity studies on joint tissues could be used to determine the relationship between cellular and molecular events and the potential for restorative tissue repair.Gravitational threshold for tissue restoration: What is the minimal amount of gravity required to maintain healthy cartilage? If microgravity is detrimental to cartilage, would gravity at the surface of the moon (0.16 G), or Mars (0.38 G), be sufficient to maintain tissue regeneration pathways and prevent uncontrolled cartilage destruction? Efforts are underway to explore the use of fractional gravity generated by centrifugal forces to counteract the detrimental effects of microgravity. The application of partial gravity on long duration spaceflight may be the best countermeasure for a host of microgravity-induced pathologies.10Radiation and tissue regeneration: Does the increased radiation exposure of spaceflight affect tissue healing? The Earth’s magnetic field shields craft in low earth orbit (LEO) from significant radiation. However, beyond LEO and protection from radiation, the effects of radiation on biological systems may be significant. A recent report suggesting that radiation worsens cartilage loss caused by HLU suggests that radiation has a compounding effect on cartilage destruction.If cartilage loss in microgravity does occur, as seems likely based on unloading studies on Earth and our mouse findings, several fascinating questions arise.23 to include cartilage. Understanding mechanisms of joint tissue damage in microgravity and the limitations governing consequent tissue repair on return to 1 G will provide insights into repair and regeneration processes for OA here on Earth.If the goal of long duration spaceflight is to be achieved then more research is needed into the effects of microgravity on cells, tissue explants, and whole animals on orbiting platform both in LEO, and beyond. Monitoring of joint health on the ISS can be achieved by fluid biomarker analysis and the expansion of existing imaging technologies


Muscle degeneration has been consistently identified as an independent risk factor for high mortality in both aging populations and individuals suffering from neuromuscular pathology or injury. While there is much extant literature on its quantification and correlation to comorbidities, a quantitative gold standard for analyses in this regard remains undefined. Herein, we hypothesize that rigorously quantifying entire radiodensitometric distributions elicits more muscle quality information than average values reported in extant methods. This study reports the development and utility of a nonlinear trimodal regression analysis method utilized on radiodensitometric distributions of upper leg muscles from CT scans of a healthy young adult, a healthy elderly subject, and a spinal cord injury patient. The method was then employed with a THA cohort to assess pre- and postsurgical differences in their healthy and operative legs. Results from the initial representative models elicited high degrees of correlation to HU distributions, and regression parameters highlighted physiologically evident differences between subjects. Furthermore, results from the THA cohort echoed physiological justification and indicated significant improvements in muscle quality in both legs following surgery. Altogether, these results highlight the utility of novel parameters from entire HU distributions that could provide insight into the optimal quantification of muscle degeneration. Muscle degeneration, characterized by the progressive loss of muscle mass, strength, and function, has been consistently identified as an independent risk factor for high mortality in both aging populations and individuals suffering from neuromuscular pathology or injury –7. When The potential mechanisms that govern muscle degeneration in sarcopenia have likewise been identified within the context of neuromuscular pathology or injury. Indeed, the dramatic deleterious changes in muscle composition and function exhibited in these patients have been implicated as accelerated analogues to the changes evidenced in sarcopenia. This notion is especially evident in patients with spinal cord injury (SCI), as paralysis from lower motor neuron denervation drastically reduces skeletal muscle mass and increases local muscle adiposity and fibrosis . In addiIdentifying a quantitative gold standard for myological assessment would allow for the generalizability of translational myology studies to clinical practice, thereby supporting the indication of compensatory targets for clinical intervention. Indeed, there is much extant literature regarding the investigation of muscle quality and implicating its use as a comorbidity index , 31–40, As of yet, the use of entire radiodensitometric distribution to assess muscle quality remains unreported. The increasing prevalence of sarcopenic and cachexic muscle degeneration necessitates the establishment of a gold standard for quantitative myological assessment. This was the prime motive for this study, which herein reports the development of a novel nonlinear trimodal regression analysis methodology utilized with radiodensitometric distributions from CT scans of defined upper leg volumes of a healthy young adult, a healthy elderly subject, and an SCI patient with complete lower motor neuron denervation. This method is further tested with a cohort of total hip arthroplasty (THA) patients, whose operative and healthy legs were assessed both before and one year following surgery. Results from these assessments highlight the utility of utilizing entire HU attenuation value distributions and identify novel parameters that could provide further insight into how muscle degeneration can be optimally quantified. tibialis anterior and severe, partial denervation of the glutei and posterior muscles of the thigh was confirmed one year after surgery. CT images at this time were obtained via academic collaboration with the RISE2-Italy project for the purposes of this study  as performed in literature , 42–45: Gaussian probability density function (φ):  N is the amplitude, μ is the location, σ is the width, and α is the skewness of each distribution, all of which are iteratively evaluated at each CT bin, which is herein defined as the dependent variable, x. This definition is resultant from the hypothesis that each HU distribution is trimodal, in which they consist of three separate tissue types whose linear attenuation coefficients occupy distinct HU domains, namely, fat [−200 to −10 HU], loose connective tissue and atrophic muscle [−9 to 40], and normal muscle [41 to 200]. Additionally, we hypothesized that the inwardly sloping asymmetries within the fat and muscle peaks could be described by skewness  of their probability density functions, whereas the central connective tissue distribution was assumed to be a normal, nonskewed Gaussian distribution. Utilizing this definition, a theoretical curve was generated by employing an iterative generalized reduced gradient algorithm via minimization of the sum of standard errors at each CT bin value, x, thereby generating an 11-parameter matrix of probability density function variables. This algorithm iterates each function variable according to the computed variance of each step, and the selection of new trial values is guided by computing the rates of change of this variance as new inputs are generated. The minimization of the sum of standard errors at each point, and thereby the maximization of the coefficient of determination, R2, was computed according to standard definitions [The method utilized to computationally define each HU distribution was a modified methodology for nonlinear regression analysis. First, the general equation for each distribution was defined as a quasi-probability density function by summing two skewed and one standard  in the pathological subject. Interestingly, muscle skewness was zero in the elderly and control subjects and nonzero but very small (0.07) in the pathological subject. These data suggest that the fat peak's positive asymmetry could likewise be due to the progressive infiltration of fatty tissue into the much higher HU value muscle tissue. However, as this skewness relationship is not commensurate in the muscle peak, it remains unclear whether skewness as a variable can completely describe muscle degeneration.The location parameter is almost identical between subjects' fat distributions, but the muscle peak location was singularly high in the elderly subject. Likewise, the control subject had a singularly positive connective tissue HU location, whereas the other subjects' values were negative. While less significant, perhaps, these results are still intriguing, showing that the central connective tissue regime of the HU distribution shifted towards more negative, “fatter” HU values in the elderly and pathological subjects. However, the fat peaks remained unshifted, and, unexpectedly, the muscle peak was higher in HU value in the elderly subject and nearly identical in the control and pathological subjects.Finally, the width parameter exhibited noticeable differences between subjects. The control subject had the widest fat distribution, but the control muscle width was at least twofold lower than the other subjects. Likewise, while the elderly and pathological subjects had similar fat and muscle widths, the elderly subject elicited a comparatively much higher connective tissue distribution width. The physiological interpretation of width as a parameter is somewhat obscure, but one could argue that a sharply defined muscle and/or fat peak might suggest a comparative reduction in muscle degeneration. This notion is supported by the control subject's muscle peak being remarkably lower in width compared to the other subjects', but this is unsupported by the fat peak results.As previously mentioned, the potential utility of the reported method was further tested with a cohort of 15 THA patients to assess changes in their upper leg muscle following surgery. To do this, HU distributions from each patient were acquired from both presurgical and one-year postoperative CT scans. Each distribution parameter was analyzed for both healthy and operative legs, and differences were assessed for statistical significance.As is evident in Regarding the location parameter, there were minimal shifts evident in muscle and fat peaks, but commensurate with previous observation, there were notable increases in connective tissue location values in both the healthy and operative legs one year after surgery. This suggests the notion that connective tissue distributions may shift towards healthy muscle following one year of corrective ambulation and normative use. Indeed, once again, this was most evident and singularly significant in the operative leg.The width parameter elicited no significant or meaningful changes in either leg, but in accordance with previous observation, the connective tissue peak widths were significantly larger than either the muscle or fat peaks, which were both nearly identical in magnitude in both legs. While not apparently useful, it still remains intriguing that each distribution parameter seems to have its own sensitivity with respect to the population.Finally, the skewness parameter decreased in magnitude in both the healthy and operative fat peaks but remained relatively constant and small (less than one) in the muscle peak, with one exception: the preoperative muscle peak was significantly higher than each of the others. We previously saw that the pathological subject had a much more extreme (more negative) fat skewness than the other two initial subjects, suggesting the infiltration and/or buildup of intramuscular fat in his degenerating muscle. This was once again similarly evident here, as the operative legs of the THA cohort elicited significantly more extreme, negative skewness than the rest of the fat peak values.Altogether, these results indicate significant improvement in muscle quality in both legs following surgery, a notion which is most evident in patient operative legs. These data further support the notion that each HU distribution parameter may have a particular range of specificity when it comes to muscle assessment, thereby suggesting the method's utility as a straightforward indicator for muscle degeneration.One of the more commonly discussed topics regarding tissue segmentation from medical images is that of the Partial Volume Effect (PVE). This phenomenon may be defined as the loss of fidelity in small regions or morphologies from limitations in spatial resolution of a particular imaging modality, and PVE is of particular relevance in positron emission tomography (PET) and dissemination of intracranial tissues using magnetic resonance imaging (MRI) . In regaTo test this notion, we took the control subject's HU CT scan and segmented a two-pixel wide boundary layer between fat and muscle tissues. These pixels were then subtracted from the distribution at their given HU values and redistributed to either the fat or muscle mean HU value based on their respective proximities to either tissue. The results from this analysis are shown in It is likewise useful to assess these subjects according to their average HU value, which is the oft-cited method for CT analysis, as previously mentioned. As is evident in While there is much extant literature reporting the use of average HU values to investigate muscle quality and its utility as a comorbidity index, no studies have yet to utilize the entire radiodensitometric distribution. The increasing prevalence of sarcopenic and cachexic muscle degeneration necessitates the establishment of a robust quantitative myological assessment methodology. Herein, we hypothesize that rigorously quantifying entire HU distributions can elicit much more information regarding muscle quality than extant methods. This study reports the development and use of this method, wherein we assess upper leg muscle quality utilizing nonlinear trimodal regression analysis with radiodensitometric distributions from computed tomography (CT) scans of a healthy young adult, a healthy elderly subject, and a spinal cord injury patient exhibiting complete lower motor neuron denervation. We show that physiological justification for these initial results is yet again evidenced by the use of a cohort of total hip arthroplasty (THA) subjects. While the use of more subjects will be essential to reinforcing the physiological claims reported here, these results altogether highlight the potential utility of our method and the importance of utilizing entire HU attenuation value distributions. We have likewise identified a host of novel regression parameters from these analyses that could provide further insight into how muscle degeneration can be optimally quantified. These notions support the conclusion that our method may be a pivotal first step in the development of a new gold standard for the analysis of muscle.


Detection of iatrogenic root perforation during post-space preparation especially in labiolingual plane can be challenging due to the two-dimensional nature of conventional radiography; this can be even more challenging if the cemented post is radiolucent. Cone-beam computed tomography (CBCT) scans were shown to be a valuable diagnostic aid in diagnosis of such cases. However, in this case, the application of CBCT did not help in diagnosis of a labial fiber post perforation in a maxillary central incisor which was finally detected through exploratory surgery. Root perforation refers to creation of an artificial and unwanted communication between the root canal system and the periodontal ligament (PDL); at the site of root perforation, an inflammatory reaction in PDL occurs and leads to the formation of a primary endodontic lesion . PerforaAccidental and unnoticed lateral root perforations during post-space preparation, show lateral bone defects on radiographies and cause formation of a sinus tract or periodontal pocket . OccasioHappening for any reason, this unwanted communication leads to destruction of the adjacent periodontal tissues . The surCalcium-enriched mixture (CEM) cement is a tooth-colored cement with clinical applications similar to MTA. It offers proper sealing ability, biocompatibility, antimicrobial properties, hard tissue induction properties and shorter setting time, greater flowability and lower film thickness than MTA -13.The pA young women in her early twenties was referred by a dentist, complaining of localized discomfort in the anterior maxillary vestibule subsequent to endodontic treatment and restoration of the left maxillary central incisor. Her medical history was noncontributory. Upon clinical assessment the buccal gingiva of the maxillary left central incisor had a sinus tract in the mid root area which according to the patient was occasionally formed after RCT. In the referral letter, the dentist had mentioned RCT was indicated after detection of pulp necrosis of the incisor which had a class three cavity. The tooth was not sensitive to percussion. A parallel periapical radiography was taken that indicated perfect RCT and restoration . Due to As the CBCT findings were not suggestive of the lesion origin , exploraInterestingly, after curettage of the granular tissue surrounding the fenestration, a fiber-reinforced lucent prefabricated post became visible that had perforated the root and bone just under the gingival soft tissues . That seThe present report reviewed successful surgical management of a mid-root perforation during post space preparation in an upper left central incisor that was left undetected by the dentist. The post lucency prevented its emergence in radiographies and contrary to our perception, CBCT was not much helpful in detection of the lesion origin. Thus, exploratory surgery was indicated which uncovered the cause of patient’s problem; labial mid-root perforation during post space preparation where the radiolucent fiber post was cemented. The perforation site was prepared/sealed using CEM cement. After one year, the tooth was symptomless and functional.et al. observed that more than half of the perforations in their cases of root perforation occurred during post-preparation procedures [Root perforation often happens iatrogenically as a result of misaligned application of burs during endodontic access preparation and search for root canal orifices, and during efforts to negotiate calcified and curved canals , 4. Inapocedures . In some cases of endodontic practice, conventional intraoral radiography does not provide adequate information on pathologic conditions and positional relationships. Three-dimensional images have become possible with introduction of CBCT technology to dentistry. The imaged area can be arbitrarily sliced and observed from three different directions . Althouget al. [Many important factors that are all related to infection control at the perforation site, influence the survival prognosis of the tooth , 20: theet al.  perforatCEM cement has been recommended as an appropriate endodontic biomaterial for repair of lateral root perforations , 9, 11. In conclusion, the present case report showed that a surgical approach may be effective for treating a combined endodontic-periodontal lesion originating from a root perforation in the middle third of a maxillary central incisor with a cement lucent post, which was treated with a surgical approach using CEM cement. The presented case demonstrates that CBCT imaging technology is not always useful in detection of lesions that are not clinically and radiographically diagnosable. Endodontic surgical flaps for diagnostic purposes and management of complex endodontic problems cannot be overlooked.


Children with autism spectrum disorders (ASD), characterized by a range of behavioral abnormalities and social deficits, display high incidence of gastrointestinal (GI) co-morbidities including chronic constipation and diarrhea. Research is now increasingly able to characterize the “fragile gut” in these children and understand the role that impairment of specific GI functions plays in the GI symptoms associated with ASD. This mechanistic understanding is extending to the interactions between diet and ASD, including food structure and protein digestive capacity in exacerbating autistic symptoms. Children with ASD and gut co-morbidities exhibit low digestive enzyme activity, impaired gut barrier integrity and the presence of antibodies specific for dietary proteins in the peripheral circulation. These findings support the hypothesis that entry of dietary peptides from the gut lumen into the vasculature are associated with an aberrant immune response. Furthermore, a subset of children with ASD exhibit high concentrations of metabolites originating from microbial activity on proteinaceous substrates. Taken together, the combination of specific protein intakes poor digestion, gut barrier integrity, microbiota composition and function all on a background of ASD represents a phenotypic pattern. A potential consequence of this pattern of conditions is that the fragile gut of some children with ASD is at risk for GI symptoms that may be amenable to improvement with specific dietary changes. There is growing evidence that shows an association between gut dysfunction and dysbiosis and ASD symptoms. It is therefore urgent to perform more experimental and clinical research on the “fragile gut” in children with ASD in order to move toward advancements in clinical practice. Identifying those factors that are of clinical value will provide an evidence-based path to individual management and targeted solutions; from real time sensing to the design of diets with personalized protein source/processing, all to improve GI function in children with ASD. Autism spectrum disorder (ASD) is characterized by varying degrees of neural dysfunction that lead to behavioral abnormalities including: stereotyped/repetitive behaviors, impairments in social interaction, lack of verbal and nonverbal language skills, insistence on routines and intense or idiosyncratic interests –3. ASD iThere is active research into the mechanisms that cause different autism phenotypes, including studies of genetic markers, structural, and functional brain abnormalities, immune dysfunction, gut microbial dysbiosis, sensitivity to environmental toxin exposure, and oxidative stress –13. HoweThe concept of the “fragile gut” is proposed to be involved in a subset of children with ASD and that impaired gastrointestinal (GI) function, including deficiency in protein digestive capacity, is central to the GI symptoms associated with ASD and may exacerbate behavioral symptoms in ASD.Gastrointestinal co-morbidities are common in children with ASD and have been reported to affect 9–91% of patients –21 with + T cells with associated epithelial damage  are elevated in the duodenal mucosa while IL-4 is elevated in the colon (+TNFα+) compared to children on unrestricted diets  resulted in elevated pro-inflammatory cytokine production when compared to healthy controls as well as non-ASD controls with non-allergic food hypersensitivity  or pancreatic insufficiency have little or no undigested or unabsorbed nutrients in the feces. The gastrointestinal tract digests and absorbs nutrients from consumed food matrices while excluding harmful bacteria and toxins. Pancreatic enzymes are produced in amounts that exceed substrate requirements allowing for complete digestion. Brush border enzymes and transporters have expression levels and activities capable of ensuring total absorption of nutrients in the small intestine . HoweverThe gut is the largest immune organ and the main site of immune system development . ConsideFor the purposes of this review a “healthy gut” is one that is able to (1) effectively extract and absorb nutrients from complex food matrices; (2) properly identify foreign materials as benign  or harmful ; (3) support the colonization of the gut by commensal organisms while eliminating pathogens; (4) restrict uptake or passage of potentially damaging substances out of the gut lumen through maintenance of gut barrier integrity; and (5) provide appropriate nutrient and energy status signals to other organ systems . All of In this review, we will define the term “fragile gut” as a gastrointestinal tract that is basically “healthy” , but is not robust to stressors, challenges, or microbial insults. Stressors include diets containing indigestible or toxic components or infectious agents. The concept is that a fragile gut influences a variety of clinical and non-clinical situations where gut dysfunction is not the explicit disease state or site, but rather a secondary problem. Examples of populations with a fragile gut include premature infants, the elderly, patients undergoing chemotherapy and children with ASD and gastrointestinal symptoms. The fragile gut phenotype in children with ASD includes a distribution of dysbiotic and pathological states. While a subset has been diagnosed as exhibiting explicit immunopathologies, others are asymptomic normally, but become symptomatic when confronted with challenges from poorly digested diets. Transient blooms of detrimental bacteria  and “pulses” of microbial metabolites have been observed, as discussed below Tables , 2. The We propose that the fragile gut is influenced by dietary protein digestion. Incomplete digestion increases microbial protein fermentation (putrefaction) and inflammatory putrefactive metabolites, which can result in decreased gut barrier integrity, increased gut-associated immune responses, and microbial population shifts. In some children with ASD, reduced proteolytic capacity and colonic putrefaction may cause gastrointestinal problems and also exacerbate ASD symptoms Figure . IdentifIt is important to note that most of the available evidence linking gut dysfunction and dysbiosis to ASD is at this point based on associations and not causal relationships. Therefore, we are calling for future experimental and clinical studies designed to specifically address the potential causal relationship between these factors, including the gold standard of dietary intervention trials in children with ASD and GI symptoms.Protein digestive capacity may be impaired in some children with ASD, which would contribute to the abnormal immune activation and gastrointestinal symptoms observed in these populations Figure . HoweverLater studies investigated brush border enzyme function in children with ASD further. One study found significantly decreased levels of ileal sucrose isomaltase, maltase glucoamylase, and lactase mRNA in children with ASD and gastrointestinal symptoms when compared to typically developing children who also had similar gastrointestinal symptoms ; therefoChildren with ASD who have shown elevated levels of urinary peptides of dietary origin  provide Plasma amino acid profiles tend to be altered in children with ASD, although studies have reported mixed results. While some studies have shown elevated levels of certain plasma amino acids, such as glutamic acid, aspartic acid , 63 and Low proteolytic enzyme activity in the gut would lead to increased levels of undigested peptides in the gut lumen, resulting in increased plasma and urinary concentrations of these peptides. High levels of foreign peptides in the systemic circulation can induce an adaptive immune response that leads to autoantibody  production Figure . TherefoChlamydia pneumoniae peptide Streptococcus M protein   . These fin vitro models and have been shown to increase intestinal permeability  to be decreased in ASD, and again intermediate in siblings, as well as elevated relative numbers of “B. fragilis” in children with ASD and gastrointestinal symptoms vs. children with ASD without gastrointestinal symptoms. It was hypothesized that lower levels of A. muciniphila indicate a thinner gastrointestinal mucus barrier, since this species is mucolytic and may be reduced due to lack of substrate  are easily hydrolyzed into amino acids in the small intestine, whereas others  are highly resistant to proteolysis . ProteinBeyond protein structure, dietary protein digestibility can be reduced by anti-nutritional factors that reduce protein bioavailability. These factors include protease inhibitors, tannins and phytates  that arein vitro  is an indirect measure of pancreatic exocrine function . One stuIt is now recognized that there is a connection between the health of the gut and the presence of psychiatric symptoms. For example, irritable bowel syndrome is associated with a high prevalence of depression, panic disorder, generalized anxiety and post-traumatic stress disorder . ExploraGiven the general detrimental effect that consumption of proteins with low digestibility could have in children with ASD, examination of studies that consider diets where several of these proteins are eliminated can provide insight into the hypothesis of impaired protein digestive capacity in this cohort even when specific mechanisms of action have not been determined. Several observational and clinical studies looking at the effect of specific protein-free diets, such as GFCF, have reported mixed results in regard to benefit in reduction of gastrointestinal symptoms and behavioral problems . MultiplThere are important limitations to all dietary intervention studies conducted in this field, such as short duration of treatment (<1 year), heterogeneous sampling , lack of reporting of changes in gastrointestinal symptoms, and lack of testing for compliance, which is important considering that these proteins are ubiquitous in the modern diet. Indeed, strict implementation of the diet has resulted in substantially greater improvement ASD behaviors, physiological symptoms, and social behaviors . In addiChildren with ASD are notoriously “picky eaters”; they have particularly strong food aversions and can be ultrasensitive to food context, especially texture –186. SpeAlong with an oral sensitivity, children with ASD have lower facial feedback when performing pleasurable tasks that induce laughter or other positive reactions normally seen in typically developing children . This deSensorial properties of foods are important, especially in children with ASD, since proteins affect food texture and are not homogenous in the diet. Different food commodities provide various types of proteins with varying configurations, including differences in amino acid composition as well as secondary and tertiary structure. Some dietary proteins are easily broken down completely into their constitutive amino acids during digestion in the small intestine, whereas others are more resistant to digestion . These pPalatability varies and is dependent upon food processing methods that alter protein texture and structure. For instance, there are many industrial meat processing techniques that change the texture and the palatability of the meat such as, the use of a pulsed electric field that perturbs cellular architecture , the prep = 0.001) and protein (p = 0.001) categories than typically developing children  . While ochildren . In addichildren . In viewchildren . If indilactobacilli, lactococci, and bifidobacteria, or yeasts such as “saccharomyces boulardii”  significantly reduced a marker of invasive pathogenic candidiasis in children with ASD and gastrointestinal symptoms (Bacteroides fragilis” (“B. fragilis”) not only increased gut barrier integrity and reversed some microbial alterations, but also ameliorated certain behavioral deficits. Defects in communicative, stereotypic, anxiety-like and sensorimotor behaviors were significantly improved with probiotic administration. Therefore, further investigation into the role of probiotic supplementation in children with ASD and gastrointestinal symptoms via properly designed randomized controlled trials that correlate behavioral and physiological outcomes is warranted.Probiotics, as defined by the WHO in 2001  have shown some efficacy in reducing ASD associated gastrointestinal co-morbidities, as previously mentioned, the effect is often marginal with some studies showing greater benefit than others , 178–183If digestive capacity is impaired in a subset of children with ASD, another potential treatment option is digestive enzyme supplementation, specifically with a full panel of proteases. A limited number of studies have been conducted to test the efficacy of digestive enzyme supplementation on gastrointestinal and behavioral outcomes in children with ASD. One study  utilizedIn conclusion, impaired gut immune and digestive function, high levels of circulating dietary peptides, presence of autoantibodies that cross react with dietary proteins, increased levels of putrefactive metabolites with potent actions on gut and behavior, and the microbial patterns associated with ASD, such as high prevalence of clostridial species and high ratios of Firmicutes to Bacteroidetes, suggest that protein-driven microbial dysbiosis exacerbates both gastrointestinal and ASD symptoms. In general, saccharolytic microbes that thrive off of dietary glycans (such as fermentable fibers) tend to produce short chain fatty acids, lower the pH of the intestine, lower pathogens and promote the maturation and metabolism of gut epithelial cells. In contrast, proteolytic microbes that thrive off of incompletely digested dietary proteins produce byproducts such as ammonia, amines, phenols, and sulfides that have a negative effect on gut health  and braiUnderstanding the gut etiology of disease has been hindered by technological and clinical limitations that have inhibited advancements in the field of dietary protein digestion. The application of peptidomics will allow for characterization of protein digestion site, specifically within the gastrointestinal tract. Currently, protein digestion is viewed as a single event definable in very narrow terms when, in fact, digestion is a very broad process varying in multiple aspects of space and time. Recent technological advancements in the area of proteomics and peptidomics now provide the capabilities to perform extensive characterization of digestive processes occurring continually along the length of the small intestine –212. LikFurther research in this area should expand on the current body of literature that has focused on determining associations between gut function and ASD symptoms to include experimental and clinical studies designed to determine causal relationships between these factors. These studies will have broad implications to many diseases associated with gastrointestinal function, and knowledge gained will play a crucial role in the design of personalized diets with protein sources tailored to individuals with a fragile gut.MS wrote the manuscript based on her original ideas and designed the figure. JK wrote sections of the manuscript and created the figure. KA contributed to the overall concept of the manuscript and provided content expertise on ASD and behavioral symptoms, and JG revised the work critically for important intellectual content and provided approval for publication of the content. All authors have read and approved the final version of the manuscript.JB German is a cofounder of Evolve Biosystems a commercial entity providing products for breast fed infants. The other 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.


Sounds in everyday life seldom appear in isolation. Both humans and machines are constantly flooded with a cacophony of sounds that need to be sorted through and scoured for relevant information—a phenomenon referred to as the ‘cocktail party problem’. A key component in parsing acoustic scenes is the role of attention, which mediates perception and behaviour by focusing both sensory and cognitive resources on pertinent information in the stimulus space. The current article provides a review of modelling studies of auditory attention. The review highlights how the term attention refers to a multitude of behavioural and cognitive processes that can shape sensory processing. Attention can be modulated by ‘bottom-up’ sensory-driven factors, as well as ‘top-down’ task-specific goals, expectations and learned schemas. Essentially, it acts as a selection process or processes that focus both sensory and cognitive resources on the most relevant events in the soundscape; with relevance being dictated by the stimulus itself (e.g. a loud explosion) or by a task at hand (e.g. listen to announcements in a busy airport). Recent computational models of auditory attention provide key insights into its role in facilitating perception in cluttered auditory scenes.This article is part of the themed issue ‘Auditory and visual scene analysis’. The challenge of directing our attention despite numerous prominent distractors, referred to as the ‘cocktail party problem’ ,2, engagAttention is not a single, unidirectional process ,6. It caWhile attention has started to garner increasing interest from the auditory research community –10, therAlthough research on the neural underpinnings of these networks is thriving, our understanding of the exact role of adaptive stimulus- or task-directed processing remains in its infancy. The field is particularly challenged by the lack of theories that integrate our knowledge of cortical circuitry in the auditory pathway with adaptive and cognitive processes that shape behaviour and perception of complex acoustic scenes. By contrast, active and adaptive processing has more commonly been explored in models of the visual system. These implementations typically model predictive coding in the visual thalamus (LGN), contextual modulation in primary visual cortex (V1), attentional modulation in higher cortical areas  and decision-making in parietal and frontal cortex ,16. ThatA number of perspectives have emerged about conceptual frameworks for understanding the role of attention in auditory perception. Much of this work closely parallels theories from vision in which attention is viewed as a multifaceted phenomenon that encompasses mechanisms of selection, integration and sampling . In one The present review aims to provide a synopsis of current computational efforts in modelling attention in the context of auditory scene analysis. 2.(a)Models of bottom-up attention remain very scarce in the auditory literature. The limited efforts in this direction have greatly benefited from the very prolific research on bottom-up attention  in vision. Indeed, visual salience is a thriving research field that has resulted in a rich body of work examining the perceptual attributes underlying visual salience , as wellet al. presented one of the early efforts in this direction [Building on this tradition in the visual modality, early models of auditory bottom-up attention adapted popular visual salience models to the domain of sound. Kayser irection . This woirection . The bacThis initial effort was later expanded to incorporate more intricate analyses of auditory features. Work by Kalinli & Narayanan  operatedT)–frequency (F) spectrogram as an auditory image, these models treated the T–F dimensions as spatial X–Y axes, failing to process the time axis as a special dimension. Effectively, the auditory image approach ignores temporal build-up and short- and long-term dependencies, and results in non-causal analyses of current events based on future information. Consider for instance a musical scene such as Haydn's Surprise Symphony  a temporal analysis of sound features operating on different components derived from mel-frequency cepstral coefficients [et al. [Two trends emerged from this work that are reflected in most current auditory attention models: building probabilistic expectations of sound to derive salience, and employing behavioural responses from perceptual experiments with human listeners to learn properties of acoustic features relevant for salience perception. The idea that salience is derived from statistics gathered over the scene was further explored in the work of Wang et al. . This stficients , an alte [et al. . This coet al. [et al. [et al. used no prior knowledge of acoustical features to guide their feature estimation, Tordini et al. tested the contribution of acoustic features in defining auditory salience. Features such as temporal centroid, spectral centroid, harmonicity, effective duration and tempo were all found to correlate with salience ratings. The results also revealed interactions between some of these features in line with observations from Kaya & Elhilali [In contrast with more theoretical approaches to auditory salience, Kim et al.  took a m [et al. ,48 approElhilali .It is worth highlighting that one of the challenges of studies of auditory salience is the open interpretation of what auditory salience refers to. Visual salience has historically relied on measures of eye gaze despite their shortcomings ,49,50. I(b)et al.'s early findings in the late 1950s [In contrast with bottom-up attention, top-down models of auditory selective attention build on a richer body of work investigating the neural underpinnings of task-driven attention in the auditory system. It is well established that neural activity across the auditory cortex is heavily modulated by directed attention ,13,51. Hte 1950s  showed mCharacterization of the tuning properties of cortical neurons using computational techniques has played a major role in investigating adaptive effects of attention on cortical activity. Specifically, spectro-temporal receptive fields (STRFs) are mathematical descriptions of the selectivity of individual neurons in response to sound events . The STRBeyond findings at the single-neuron level in animal models, various non-invasive techniques have been used to investigate the extent of attentional modulation across auditory cortex for more complex auditory scenes in human listeners. Results using functional magnetic resonance imaging and electroencephalogram (EEG) have confirmed attention-driven increase of neural activity in the auditory cortex ,62. Neuret al. [Despite the growing body of work supporting evidence that responses across auditory cortex are modulated by attention, translating such knowledge into computational models has been slow. One avenue in modelling has been to explicitly characterize the adaptation mechanism of STRFs. Mesgarani et al.  hypothesRecognizing these limitations, Carlin & Elhilali  proposedAnother body of work modelled selective attention in a more abstract way by incorporating the attentional gains observed in neurons across physiological experiments into computational models implementing various components of auditory scene analysis. Kalinli & Narayanan  extracteThe studies described thus far have taken a forward approach to modelling attention: given the sound input, they predict neural responses and compare the model output with brain responses. Some recent studies have taken a reverse approach to characterizing attention by reconstructing the sound input from recorded neural signals and comparing the reconstructed acoustic waveform with the input to illuminate the aspects of the soundscape that are most prominently represented in the recorded cortical area. While employing regression methods to reconstruct the sensory input from neural recordings is not new, the potential of this paradigm to study the effects of attention has only recently been used to demonstrate exciting results. Mesgarani & Chang  reconstr3.While eye-tracking data provides objective evaluation metrics for vision models, attention models in audition have suffered from a lack of clear salience metrics. Most attention models mentioned in this review use their own validation data and metrics, ranging in scope from single-neuron activity to human responses or carefully selected sound events or scenes with attended or salient ‘ground-truth’ determined conceptually by the experimenter. Unfortunately, there is so far little consensus on the best way to probe effects of attention on auditory perception, whether it is task-directed or purely based on salience.With the first auditory salience models, behavioural experimentation was employed merely to illustrate that the model could detect objectively salient events, such as an animal call amidst pure noise. These studies had subjects choose the more salient of two presented scenes ,35,38, aOn the neural front, single-unit recordings from cats, monkeys and ferrets provide the most direct access to effects of attention on neural activity in the auditory system. While very informative about neural correlates of attentional modulation on brain networks, they are costly to perform, too invasive for human research and are limited in the amount of information that can be extracted about the intricate cortical networks engaged in auditory perception. They are also restricted to relatively simple or constrained behavioural paradigms that can be used to train animals in a laboratory setting.The closest correlate to single-unit recordings for humans is electrocorticography (ECoG). Though highly invasive and applicable only to neurosurgery patients, this technique uses electrode grids placed on the exposed brain to investigate attentional modulation of cerebral cortex using rich and complex stimuli. By contrast, MEG and EEG offer non-invasive alternatives that are applicable to a more general population, even though they lack the spatial resolution of EcoG, and are more susceptible to artefacts. Unlike other behavioural measures, MEG and EEG also allow direct insights into neural processes without engaging explicit perceptual decision. However, analytic techniques need to be improved to balance the elimination of noise and preservation of neural information about attentional and perceptual states of subjects, especially in complex sound environments . Further4.Aside from providing important contributions to theoretical neuroscience, models of attention play a significant role in a large variety of engineering applications. Particularly, performance on tasks for which humans effortlessly outperform computers could be improved with attention mechanisms, where the attention component would act as a filter to guide computational resources to areas of maximum information, effectively reducing system noise by ignoring irrelevant parts of the scene. One such task is speech and sound recognition: although a trivial task to perform for humans, automatic recognition suffers from significant performance degradation in noisy environments. Some of the surveyed modelling studies have demonstrated various ways in which attentional mechanisms could work to improve existing recognition technologies. Feature-based approaches make use of the feature-extraction schemes of salience models as a way to get a perceptually informative representation of sound input. This representation can be used to detect prominent syllables from speech  or as anThe beneficial effect of attention has also been incorporated into numerous computational auditory models; we give some illustrative examples here. One computational system incorporated both bottom-up and top-down components to mimic human attentional orienting in a busy acoustic environment, allowing a soundscape designer to evaluate how the sound in planned urban environments might affect people . A bottoFinally, auditory attention models are an important component of audio–visual models and applications. In recent years, the necessity of incorporating auditory salience information in visual attention models is becoming increasingly recognized. This has led to the emergence of models using auditory salience direction to guide visual attention –90, alonMechanisms of multimodal attention are especially crucial in efficient designs of robotic systems  and brai