Autism at the beginning: microstructural and growth abnormalities underlying the cognitive and behavioral phenotype of autism

Disentangling the role of gray matter volume and concentration in autism spectrum disorder: A meta-analytic investigation of 25 years of voxel-based morphometry research

Despite over two decades of neuroimaging research, a unanimous definition of the pattern of structural variation associated with autism spectrum disorder (ASD) has yet to be found. One potential impeding issue could be the sometimes ambiguous use of measurements of variations in gray matter volume (GMV) or gray matter concentration (GMC). In fact, while both can be calculated using voxel-based morphometry analysis, these may reflect different underlying pathological mechanisms. We conducted a coordinate-based meta-analysis, keeping apart GMV and GMC studies of subjects with ASD. Results showed distinct and non-overlapping patterns for the two measures. GMV decreases were evident in the cerebellum, while GMC decreases were mainly found in the temporal and frontal regions. GMV increases were found in the parietal, temporal, and frontal brain regions, while GMC increases were observed in the anterior cingulate cortex and middle frontal gyrus. Age-stratified analyses suggested that such variations are dynamic across the ASD lifespan. The present findings emphasize the importance of considering GMV and GMC as distinct yet synergistic indices in autism research.

Why do children with autism spectrum disorder have abnormal visual perception?

Autism spectrum disorder (ASD) is associated with severe impairment in social functioning. Visual information processing provides nonverbal cues that support social interactions. ASD children exhibit abnormalities in visual orientation, continuous visual exploration, and visual-spatial perception, causing social dysfunction, and mechanisms underlying these abnormalities remain unclear. Transmission of visual information depends on the retina-lateral geniculate nucleus-visual cortex pathway. In ASD, developmental abnormalities occur in rapid expansion of the visual cortex surface area with constant thickness during early life, causing abnormal transmission of the peak of the visual evoked potential (P100). We hypothesized that abnormal visual perception in ASD are related to the abnormal visual information transmission and abnormal development of visual cortex in early life, what's more, explored the mechanisms of abnormal visual symptoms to provide suggestions for future research.

Disruption of the gene regulatory programme in neurodevelopmental disorders

Cortical development consists of a series of synchronised events, including fate transition of cortical progenitors, neuronal migration, specification and connectivity. It is becoming clear that gene expression programs governing these events rely on the interplay between signalling molecules, transcription factors and epigenetic mechanisms. When genetic or environmental factors disrupt expression of genes involved in important brain development processes, neurodevelopmental disorders can occur. This review aims to highlight how recent advances in technologies have helped uncover and imitate the gene regulatory mechanisms commonly disrupted in neurodevelopmental disorders.

Impact of brain overgrowth on sensorial learning processing during the first year of life

Macrocephaly is present in about 2–5% of the general population. It can be found as an isolated benign trait or as part of a syndromic condition. Brain overgrowth has been associated with neurodevelopmental disorders such as autism during the first year of life, however, evidence remains inconclusive. Furthermore, most of the studies have involved pathological or high-risk populations, but little is known about the effects of brain overgrowth on neurodevelopment in otherwise neurotypical infants. We investigated the impact of brain overgrowth on basic perceptual learning processes (repetition effects and change detection response) during the first year of life. We recorded high density electroencephalograms (EEG) in 116 full-term healthy infants aged between 3 and 11 months, 35 macrocephalic (14 girls) and 81 normocephalic (39 girls) classified according to the WHO head circumference norms. We used an adapted oddball paradigm, time-frequency analyses, and auditory event-related brain potentials (ERPs) to investigate differences between groups. We show that brain overgrowth has a significant impact on repetition effects and change detection response in the 10–20 Hz frequency band, and in N450 latency, suggesting that these correlates of sensorial learning processes are sensitive to brain overgrowth during the first year of life.

Endoglycan Regulates Purkinje Cell Migration by Balancing Cell-Cell Adhesion

The importance of cell adhesion molecules for the development of the nervous system has been recognized many decades ago. Functional in vitro and in vivo studies demonstrated a role of cell adhesion molecules in cell migration, axon growth and guidance, as well as synaptogenesis. Clearly, cell adhesion molecules have to be more than static glue making cells stick together. During axon guidance, cell adhesion molecules have been shown to act as pathway selectors but also as a means to prevent axons going astray by bundling or fasciculating axons. We identified Endoglycan as a negative regulator of cell-cell adhesion during commissural axon guidance across the midline. The presence of Endoglycan allowed commissural growth cones to smoothly navigate the floor-plate area. In the absence of Endoglycan, axons failed to exit the floor plate and turn rostrally. These observations are in line with the idea of Endoglycan acting as a lubricant, as its presence was important, but it did not matter whether Endoglycan was provided by the growth cone or the floor-plate cells. Here, we expand on these observations by demonstrating a role of Endoglycan during cell migration. In the developing cerebellum, Endoglycan was expressed by Purkinje cells during their migration from the ventricular zone to the periphery. In the absence of Endoglycan, Purkinje cells failed to migrate and, as a consequence, cerebellar morphology was strongly affected. Cerebellar folds failed to form and grow, consistent with earlier observations on a role of Purkinje cells as Shh deliverers to trigger granule cell proliferation.

Increased prefrontal GABA concentrations in adults with autism spectrum disorders

The excitatory-inhibitory imbalance hypothesis postulates dysregulation of the gamma-aminobutyric acid (GABA) and glutamate (Glu) neurotransmitter systems as a common underlying deficit in individuals with autism spectrum disorders (ASD). Previous studies suggest an important role of these systems in the pathophysiology of ASD, including a study of our group reporting decreased glutamate concentrations in the pregenual anterior cingulate cortex (ACC) of adults with ASD. The aim of this study was to replicate our previous findings of impaired glutamate metabolism in ASD in a new sample and to additionally quantify GABA in the ACC and dorsolateral prefrontal cortex (dlPFC). Concentrations of GABA and glutamate-glutamine (Glx; combined glutamate and glutamine signal) were quantified in the ACC and dlPFC of 43 adults with ASD and 43 neurotypical controls (NTC) by magnetic resonance spectroscopy (MRS). The ASD group showed increased absolute GABA concentrations and elevated GABA/creatine ratios in the left dlPFC compared to NTC, while no group differences were detected in the pregenual and dorsal ACC. Previous findings of altered Glx concentration in the pregenual ACC of the ASD group could not be replicated. Regarding Glx concentrations and Glx/creatine ratios, there were no significant differences in the dlPFC and ACC either. The study supports the hypothesis of an altered GABA and glutamate equilibrium, indicating an imbalance between excitatory and inhibitory metabolism in ASD patients. However, inconsistent results across studies and brain regions suggest a complex underlying phenomenon. LAY SUMMARY: Adults of the autism spectrum exhibit elevated levels of the inhibitory neurotransmitter GABA in the left dorsolateral prefrontal cortex. This finding supports the hypothesis of an imbalance between excitatory and inhibitory equilibrium in patients with autism spectrum disorders.

Fragile X Mental Retardation Protein Mediates the Effects of Androgen on Hippocampal PSD95 Expression and Dendritic Spines Density/Morphology and Autism-Like Behaviors Through miR-125a

Dysregulated synaptic plasticity is a key feature of neurodevelopmental disorders, including autism. This study investigated whether Fragile X mental retardation protein (FMRP), a selective RNA-binding protein that regulates synaptic protein expression by interacting with miRNAs, mediates the effects of androgens that play an important role in regulating the synaptic plasticity in the hippocampus. Experiments using mouse hippocampal neuron HT22 cells demonstrated that dihydrotestosterone (DHT) increased the expression of postsynaptic density protein 95 (PSD95) by inhibiting FMRP expression. Administration of miR-125a inhibitor upregulated the PSD95 expression and significantly increased the DHT-induced upregulation of PSD95. FMRP knockdown in HT22 cells reduced the expression of miR-125a. Moreover, miR-125a inhibitor upregulated the PSD95 expression in the DHT-treated HT22 cells with FMRP knockdown. Subsequently, the effects of androgen-mediated via FMRP in regulating neural behaviors and PSD95 expression and dendritic spines density/morphology were investigated using Fmr1 knockout (KO) and wild-type littermate (WT) mice. The castration of WT mice reduced the androgen levels, aggravated anxiety and depression, and impaired learning and memory and sociability of mice. DHT supplementation post-castration reversed the alterations in density and maturity of dendritic spines of hippocampal neurons and behavioral disorders in WT mice; however, it did not reveal such effects in Fmr1 KO mice. Further, immunohistochemical staining and western blotting analyses after knocking down miR-125a revealed similar effects of castration and post-castration DHT supplementation on PSD95 protein expression. These findings clarified that FMRP mediated the effects of DHT through miR-125a in regulating the expression of hippocampal synaptic protein PSD95. This study provides evidence for the neuroprotective mechanism of androgen in PSD95 expression and dendritic spines density/morphology and suggests that treatment interventions with androgen could be helpful for the management of synaptic plasticity disorders.

Lateralized Changes in Language Associated Auditory and Somatosensory Cortices in Autism

Lateralized specialization of the two cerebral hemispheres is a fundamental structural hallmark of the human brain and underlies many cognitive functions and behavioral abilities. In typical developing individuals the influence of handedness on performance of various sensory modalities and the cortical processing has been well recognized. Increasing evidence suggests that several neurodevelopmental and psychiatric disorders such as bipolar disorder, schizophrenia, and autism spectrum disorders (ASD) are associated with abnormal patterns of cerebral lateralization. Individuals with ASD exhibit abnormal structural and functional lateralization of circuits subserving motor, auditory, somatosensory, visual face processing, and language-related functions. Furthermore, a high prevalence of atypical handedness has been reported in ASD individuals. While the hemispheric dominance is also related to functions other than handedness, there is a clear relationship between handedness and language-related cortical dominance. This minireview summarizes these recent findings on asymmetry in somatosensory and auditory cortical structures associated with language processing in ASD. I will also discuss the importance of cortical dominance and interhemispheric disruption of balance between excitatory and inhibitory synapses as pathophysiological mechanisms in ASD.

Endocannabinoid markers in autism spectrum disorder: A scoping review of human studies

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social communication deficits and patterns of restrictive and repetitive behavior. Although the neurological underpinnings of ASD remain elusive, the endocannabinoid system (ECS) may play a role in modulating social behavior in ASD. Preclinical studies have suggested that alterations in the ECS result in ASD-like phenotypes, but currently no reviews have examined ECS abnormalities in human studies. This scoping review investigated any evidence of ECS alterations in humans with ASD. A comprehensive literature search was conducted and five studies were eligible for review. Three studies reported a significant reduction of anandamide in ASD compared to controls. Other alterations included decreased 2-arachidonoylglycerol, oleoylethanolamide, and palmitoylethanolamide and elevated diacylglycerol lipase and monoacylglycerol lipase. Some discrepant findings were also noted, which included elevated or reduced CB2 receptor in three studies and elevated or reduced N-acyl phosphatidylethanolamine phospholipase D and fatty acid amide hydrolase in two studies. We conclude from this preliminary investigation that the ECS may be altered in humans with ASD. Potential limitations of the reviewed studies include medication use and psychiatric comorbidities. Further research, such as positron emission tomography studies, are necessary to fully understand the relationship between ECS markers and ASD.

Collaboration Variability in Autism Spectrum Disorder

This paper addresses how impairments in prediction in young adults with autism spectrum disorder (ASD) relate to their behavior during collaboration. To assess it, we developed a task where participants play in collaboration with a synthetic agent to maximize their score. The agent's behavior changes during the different phases of the game, requiring participants to model the agent's sensorimotor contingencies to play collaboratively. Our results (n = 30, 15 per group) show differences between autistic and neurotypical individuals in their behavioral adaptation to the other partner. Contrarily, there are no differences in the self-reports of that collaboration.

Behaviors Characteristic of Autism Spectrum Disorder in a Geriatric Cohort With Mild Cognitive Impairment or Early Dementia

INTRODUCTION

Autism spectrum disorder (ASD) represents a heterogenous cluster of clinical phenotypes that are classically diagnosed by the time of adolescence. The possibility of late-life emergence of ASD has been poorly explored.

METHODS

To more fully characterize the possibility of late-life emergence of behaviors characteristic of ASD in mild cognitive impairment and AD, we surveyed caregivers of 142 older persons with cognitive impairment from the University of Kentucky Alzheimer's Disease Center Longitudinal Cohort using the Gilliam Autism Rating Scale-2.

RESULTS

Participants with high autism index ratings (autism "possible/very likely," n=23) reported significantly (statistically and clinically) younger age at the onset of cognitive impairment than those who scored in the autism "unlikely" range (n=119): 71.14±10.9 vs. 76.65±8.25 (P=0.034). In addition, those in the autism "possible/very likely" group demonstrated advanced severity of cognitive impairment, indicated by the Clinical Dementia Rating Scale Sum of Boxes scores.

DISCUSSION

Data demonstrate that ASD behaviors may seem de novo of degenerative dementia and such behaviors are more prevalent in those with early onset dementia. Further work elucidating a connection between ASD and dementia could shed light on subclinical forms of ASD, identify areas of shared neuroanatomic involvement between ASD and dementias, and provide valuable insights that might hasten the development of therapeutic strategies.

Microglia Regulate Cell Genesis in a Sex-dependent Manner in the Neonatal Hippocampus

Microglia, the innate immune cells of the brain, regulate brain development through many processes such as synaptic pruning, supporting cell genesis and phagocytosing living and dying cells. There are sex differences in these same developmental processes throughout the brain, thus microglia may contribute to brain sex differences. We examined whether microglia support a known sex difference in neonatal hippocampal neurogenesis and whether juvenile hippocampal neurogenesis was impacted by the loss of neonatal microglia. We used central infusion of liposomal clodronate to selectively deplete microglia and found decreased cell genesis in the male, but not female, dentate gyrus and hippocampus. We found that loss of microglia decreased cell genesis in the cortex and amygdala of both males and females. We assessed the expression of several cytokines and growth factors that have previously been shown to support cell genesis. We found that expression of Il1b and Tnf were decreased in the hippocampus due to microglia depletion however, there were no sex differences in the expression of any immune genes. In adolescence, there was an increase in the number of mitotic cells in the subgranular zone of the dentate gyrus of previously microglia depleted rats however, the number of newly-born neurons was unchanged in the adolescent animals. We also sought to determine whether there was a sex difference in the number of progenitor cells in the dentate gyrus in the neonatal period. We found no sex differences in the number of progenitor cells. Overall, these studies show that microglia are important for regulating region-specific sex differences in cell genesis in the developing brain.

Autism, autistic traits and creativity: a systematic review and meta-analysis

Psychometric, historiometric and psychiatric studies are controversial on a hypothetical link between psychopathology and creativity. In this study, we will try to contribute to this debate by analysing the case of autism. Is there a relationship between autism and creativity? If so, can we find the same relationship in a watered-down form in subjects with autistic traits? In order to answer these questions, we carried out a systematic literature review of the studies on this topic published in the last 10 years. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We also conducted a meta-analysis of data. We found that in the clinical population there are fewer creative performances than in control groups; nonetheless, it is possible to delineate a medium creative profile of subjects with autism. The average creative profile of people with autism shows that they are inhibited in fluency and flexibility, but that they display a high level of detail and a particularly high level of originality in works either generated during tests or created in private time. In particular, the level of detail reached in the latter condition seems to be higher in the autistic population than in the control groups. Better linguistic skills appear to be linked to better creative performances. Linguistic tests, if compared with visual and performative tests, seem to favour the expression of originality in subjects with autism. Although our data on autistic traits are compatible with the hypothesis that a high level of autistic traits is a watered-down replica of the cognitive profile of subjects with autism, we have no sufficient data to support this hypothesis.

Atypical age-related changes in cortical thickness in autism spectrum disorder

Recent longitudinal neuroimaging and neurophysiological studies have shown that tracking relative age-related changes in neural signals, rather than a static snapshot of a neural measure, could offer higher sensitivity for discriminating typically developing (TD) individuals from those with autism spectrum disorder (ASD). It is not clear, however, which aspects of age-related changes (trajectories) would be optimal for identifying atypical brain development in ASD. Using a large cross-sectional data set (Autism Brain Imaging Data Exchange [ABIDE] repository; releases I and II), we aimed to explore age-related changes in cortical thickness (CT) in TD and ASD populations (age range 6–30 years old). Cortical thickness was estimated from T1-weighted MRI images at three scales of spatial coarseness (three parcellations with different numbers of regions of interest). For each parcellation, three polynomial models of age-related changes in CT were tested. Specifically, to characterize alterations in CT trajectories, we compared the linear slope, curvature, and aberrancy of CT trajectories across experimental groups, which was estimated using linear, quadratic, and cubic polynomial models, respectively. Also, we explored associations between age-related changes with ASD symptomatology quantified as the Autism Diagnostic Observation Schedule (ADOS) scores. While no overall group differences in cortical thickness were observed across the entire age range, ASD and TD populations were different in terms of age-related changes, which were located primarily in frontal and tempo-parietal areas. These atypical age-related changes were also associated with ADOS scores in the ASD group and used to predict ASD from TD development. These results indicate that the curvature is the most reliable feature for localizing brain areas developmentally atypical in ASD with a more pronounced effect with symptomatology and is the most sensitive in predicting ASD development.

Autism Spectrum Disorders: Multiple Routes to, and Multiple Consequences of, Abnormal Synaptic Function and Connectivity

Autism spectrum disorders (ASDs) are a heterogeneous group of neurodevelopmental disorders of genetic and environmental etiologies. Some ASD cases are syndromic: associated with clinically defined patterns of somatic abnormalities and a neurobehavioral phenotype (e.g., Fragile X syndrome). Many cases, however, are idiopathic or non-syndromic. Such disorders present themselves during the early postnatal period when language, speech, and personality start to develop. ASDs manifest by deficits in social communication and interaction, restricted and repetitive patterns of behavior across multiple contexts, sensory abnormalities across multiple modalities and comorbidities, such as epilepsy among many others. ASDs are disorders of connectivity, as synaptic dysfunction is common to both syndromic and idiopathic forms. While multiple theories have been proposed, particularly in idiopathic ASDs, none address why certain brain areas (e.g., frontotemporal) appear more vulnerable than others or identify factors that may affect phenotypic specificity. In this hypothesis article, we identify possible routes leading to, and the consequences of, altered connectivity and review the evidence of central and peripheral synaptic dysfunction in ASDs. We postulate that phenotypic specificity could arise from aberrant experience-dependent plasticity mechanisms in frontal brain areas and peripheral sensory networks and propose why the vulnerability of these areas could be part of a model to unify preexisting pathophysiological theories.

A Mouse Mutation That Dysregulates Neighboring Galnt17 and Auts2 Genes Is Associated with Phenotypes Related to the Human AUTS2 Syndrome

AUTS2 was originally discovered as the gene disrupted by a translocation in human twins with Autism spectrum disorder, intellectual disability, and epilepsy. Since that initial finding, AUTS2-linked mutations and variants have been associated with a very broad array of neuropsychiatric disorders, sugg esting that AUTS2 is required for fundamental steps of neurodevelopment. However, genotype-phenotype correlations in this region are complicated, because most mutations could also involve neighboring genes. Of particular interest is the nearest downstream neighbor of AUTS2, GALNT17, which encodes a brain-expressed N-acetylgalactosaminyltransferase of unknown brain function. Here we describe a mouse (Mus musculus) mutation, T(5G2;8A1)GSO (abbreviated 16Gso), a reciprocal translocation that breaks between Auts2 and Galnt17 and dysregulates both genes. Despite this complex regulatory effect, 16Gso homozygotes model certain human AUTS2-linked phenotypes very well. In addition to abnormalities in growth, craniofacial structure, learning and memory, and behavior, 16Gso homozygotes display distinct pathologies of the cerebellum and hippocampus that are similar to those associated with autism and other types of AUTS2-linked neurological disease. Analyzing mutant cerebellar and hippocampal transcriptomes to explain this pathology, we identified disturbances in pathways related to neuron and synapse maturation, neurotransmitter signaling, and cellular stress, suggesting possible cellular mechanisms. These pathways, coupled with the translocation's selective effects on Auts2 isoforms and coordinated dysregulation of Galnt17, suggest novel hypotheses regarding the etiology of the human "AUTS2 syndrome" and the wide array of neurodevelopmental disorders linked to variance in this genomic region.

Functional genomics analysis of Phelan-McDermid syndrome 22q13 region during human neurodevelopment

Phelan-McDermid syndrome (PMS) is a neurodevelopmental disorder characterized by varying degrees of intellectual disability, severely delayed language development and specific facial features, and is caused by a deletion within chromosome 22q13.3. SHANK3, which is located at the terminal end of this region, has been repeatedly implicated in other neurodevelopmental disorders and deletion of this gene specifically is thought to cause much of the neurologic symptoms characteristic of PMS. However, it is still unclear to what extent SHANK3 deletions contribute to the PMS phenotype, and what other genes nearby are causal to the neurologic disease. In an effort to better understand the functional landscape of the PMS region during normal neurodevelopment, we assessed RNA-sequencing (RNA-seq) expression data collected from post-mortem brain tissue from developmentally normal subjects over the course of prenatal to adolescent age and analyzed expression changes of 65 genes on 22q13. We found that the majority of genes within this region were expressed in the brain, with ATNX10, MLC1, MAPK8IP2, and SULT4A1 having the highest overall expression. Analysis of the temporal profiles of the highest expressed genes revealed a trend towards peak expression during the early post-natal period, followed by a drop in expression later in development. Spatial analysis revealed significant region specific differences in the expression of SHANK3, MAPK8IP2, and SULT4A1. Region specific expression over time revealed a consistently unique gene expression profile within the cerebellum, providing evidence for a distinct developmental program within this region. Exon-specific expression of SHANK3 showed higher expression within exons contributing to known brain specific functional isoforms. Overall, we provide an updated roadmap of the PMS region, implicating several genes and time periods as important during neurodevelopment, with the hope that this information can help us better understand the phenotypic heterogeneity of PMS.

Brain region-specific disruption of Shank3 in mice reveals a dissociation for cortical and striatal circuits in autism-related behaviors

We previously reported a new line of Shank3 mutant mice which led to a complete loss of Shank3 by deleting exons 4-22 (Δe4-22) globally. Δe4-22 mice display robust ASD-like behaviors including impaired social interaction and communication, increased stereotypical behavior and excessive grooming, and a profound deficit in instrumental learning. However, the anatomical and neural circuitry underlying these behaviors are unknown. We generated mice with Shank3 selectively deleted in forebrain, striatum, and striatal D1 and D2 cells. These mice were used to interrogate the circuit/brain-region and cell-type specific role of Shank3 in the expression of autism-related behaviors. Whole-cell patch recording and biochemical analyses were used to study the synaptic function and molecular changes in specific brain regions. We found perseverative exploratory behaviors in mice with deletion of Shank3 in striatal inhibitory neurons. Conversely, self-grooming induced lesions were observed in mice with deletion of Shank3 in excitatory neurons of forebrain. However, social, communicative, and instrumental learning behaviors were largely unaffected in these mice, unlike what is seen in global Δe4-22 mice. We discovered unique patterns of change for the biochemical and electrophysiological findings in respective brain regions that reflect the complex nature of transcriptional regulation of Shank3. Reductions in Homer1b/c and membrane hyper-excitability were observed in striatal loss of Shank3. By comparison, Shank3 deletion in hippocampal neurons resulted in increased NMDAR-currents and GluN2B-containing NMDARs. These results together suggest that Shank3 may differentially regulate neural circuits that control behavior. Our study supports a dissociation of Shank3 functions in cortical and striatal neurons in ASD-related behaviors, and it illustrates the complexity of neural circuit mechanisms underlying these behaviors.

NREM sleep EEG activity and procedural memory: A comparison between young neurotypical and autistic adults without sleep complaints

Delta EEG activity (0.75-3.75 Hz) during non-Rapid eye movement (NREM) sleep reflects the thalamo-cortical system contribution to memory consolidation. The functional integrity of this system is thought to be compromised in the Autism spectrum disorder (ASD). This lead us to investigate the topography of NREM sleep Delta EEG activity in young adults with ASD and typically-developed individuals (TYP). The relationship between Delta EEG activity and sensory-motor procedural information was also examined using a rotary pursuit task. Two dependent variables were computed: a learning index (performance increase across trials) and a performance index (average performance for all trials). The ASD group showed less Delta EEG activity during NREM sleep over the parieto-occipital recording sites compared to the TYP group. Delta EEG activity dropped more abruptly from frontal to posterior regions in the ASD group. Both groups of participants learned the task at a similar rate but the ASD group performed less well in terms of contact time with the target. Delta EEG activity during NREM sleep, especially during stage 2, correlated positively with the learning index for electrodes located all over the cortex in the TYP group, but only in the frontal region in the ASD group. Delta EEG activity, especially during stage 2, correlated positively with the performance index, but in the ASD group only. These results reveal an atypical thalamo-cortical functioning over the parieto-occipital region in ASD. They also point toward an atypical relationship between the frontal area and the encoding of sensory-motor procedural memory in ASD. Autism Res 2018, 11: 613-623. © 2018 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Slow EEG waves recorded from the scalp during sleep are thought to facilitate learning and memory during daytime. We compared these EEG waves in young autistic adults to typically-developing young adults. We found less slow EEG waves in the ASD group and the pattern of relationship with memory differed between groups. This suggests atypicalities in the way sleep mechanisms are associated with learning and performance in a sensory-motor procedural memory task in ASD individuals.

Maturation, Refinement, and Serotonergic Modulation of Cerebellar Cortical Circuits in Normal Development and in Murine Models of Autism

The formation of the complex cerebellar cortical circuits follows different phases, with initial synaptogenesis and subsequent processes of refinement guided by a variety of mechanisms. The regularity of the cellular and synaptic organization of the cerebellar cortex allowed detailed studies of the structural plasticity mechanisms underlying the formation of new synapses and retraction of redundant ones. For the attainment of the monoinnervation of the Purkinje cell by a single climbing fiber, several signals are involved, including electrical activity, contact signals, homosynaptic and heterosynaptic interaction, calcium transients, postsynaptic receptors, and transduction pathways. An important role in this developmental program is played by serotonergic projections that, acting on temporally and spatially regulated postsynaptic receptors, induce and modulate the phases of synaptic formation and maturation. In the adult cerebellar cortex, many developmental mechanisms persist but play different roles, such as supporting synaptic plasticity during learning and formation of cerebellar memory traces. A dysfunction at any stage of this process can lead to disorders of cerebellar origin, which include autism spectrum disorders but are not limited to motor deficits. Recent evidence in animal models links impairment of Purkinje cell function with autism-like symptoms including sociability deficits, stereotyped movements, and interspecific communication by vocalization.

Altered proliferation and networks in neural cells derived from idiopathic autistic individuals

Autism spectrum disorders (ASD) are common, complex and heterogeneous neurodevelopmental disorders. Cellular and molecular mechanisms responsible for ASD pathogenesis have been proposed based on genetic studies, brain pathology and imaging, but a major impediment to testing ASD hypotheses is the lack of human cell models. Here, we reprogrammed fibroblasts to generate induced pluripotent stem cells, neural progenitor cells (NPCs) and neurons from ASD individuals with early brain overgrowth and non-ASD controls with normal brain size. ASD-derived NPCs display increased cell proliferation because of dysregulation of a β-catenin/BRN2 transcriptional cascade. ASD-derived neurons display abnormal neurogenesis and reduced synaptogenesis leading to functional defects in neuronal networks. Interestingly, defects in neuronal networks could be rescued by insulin growth factor 1 (IGF-1), a drug that is currently in clinical trials for ASD. This work demonstrates that selection of ASD subjects based on endophenotypes unraveled biologically relevant pathway disruption and revealed a potential cellular mechanism for the therapeutic effect of IGF-1.

Developmental microglial priming in postmortem autism spectrum disorder temporal cortex

Microglia can shift into different complex morphologies depending on the microenvironment of the central nervous system (CNS). The distinct morphologies correlate with specific functions and can indicate the pathophysiological state of the CNS. Previous postmortem studies of autism spectrum disorder (ASD) showed neuroinflammation in ASD indicated by increased microglial density. These changes in the microglia density can be accompanied by changes in microglia phenotype but the individual contribution of different microglia phenotypes to the pathophysiology of ASD remains unclear. Here, we used an unbiased stereological approach to quantify six structurally and functionally distinct microglia phenotypes in postmortem human temporal cortex, which were immuno-stained with Iba1. The total density of all microglia phenotypes did not differ between ASD donors and typically developing individual donors. However, there was a significant decrease in ramified microglia in both gray matter and white matter of ASD, and a significant increase in primed microglia in gray matter of ASD compared to typically developing individuals. This increase in primed microglia showed a positive correlation with donor age in both gray matter and white of ASD, but not in typically developing individuals. Our results provide evidence of a shift in microglial phenotype that may indicate impaired synaptic plasticity and a chronic vulnerability to exaggerated immune responses.

Disrupted development and imbalanced function in the global neuronal workspace: a positive-feedback mechanism for the emergence of ASD in early infancy

Autism spectrum disorder (ASD) is increasingly being conceptualized as a spectrum disorder of connectome development. We review evidence suggesting that ASD is characterized by a positive feedback loop that amplifies small functional variations in early-developing sensory-processing pathways into structural and functional imbalances in the global neuronal workspace. Using vision as an example, we discuss how early functional variants in visual processing may be feedback-amplified to produce variant object categories and disrupted top-down expectations, atypically large expectation-to-perception mismatches, problems re-identifying individual people and objects, socially inappropriate, generally aversive emotional responses and disrupted sensory-motor coordination. Viewing ASD in terms of feedback amplification of small functional variants allows a number of recent models of ASD to be integrated with neuroanatomical, neurofunctional and genetic data.

Vestibulo-ocular reflex function in children with high-functioning autism spectrum disorders

Sensorimotor processing alterations are a growing focus in the assessment and treatment of Autism Spectrum Disorders (ASD). The rotational vestibulo-ocular reflex (rVOR), which functions to maintain stable vision during head movements, is a sensorimotor system that may be useful in understanding such alterations and their underlying neurobiology. In this study, we assessed post-rotary nystagmus elicited by continuous whole body rotation among children with high-functioning ASD and typically developing children. Children with ASD exhibited increased rVOR gain, the ratio of eye velocity to head velocity, indicating a possible lack of cerebellar inhibitory input to brainstem vestibular nuclei in this population. The ASD group also showed less regular or periodic horizontal eye movements as indexed by greater variance accounted for by multiple higher frequency bandwidths as well as greater entropy scores compared to typically developing children. The decreased regularity or dysrhythmia in the temporal structure of nystagmus beats in children with ASD may be due to alterations in cerebellum and brainstem circuitry. These findings could potentially serve as a model to better understand the functional effects of differences in these brain structures in ASD. Autism Res 2017, 10: 251-266. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

The role of heparan sulfate deficiency in autistic phenotype: potential involvement of Slit/Robo/srGAPs-mediated dendritic spine formation

Autism Spectrum Disorders (ASD) are the second most common developmental cause of disability in the United States. ASDs are accompanied with substantial economic and emotional cost. The brains of ASD patients have marked structural abnormalities, in the form of increased dendritic spines and decreased long distance connections. These structural differences may be due to deficiencies in Heparin Sulfate (HS), a proteoglycan involved in a variety of neurodevelopmental processes. Of particular interest is its role in the Slit/Robo pathway. The Slit/Robo pathway is known to be involved in the regulation of axonal guidance and dendritic spine formation. HS mediates the Slit/Robo interaction; without its presence Slit's repulsive activity is abrogated. Slit/Robo regulates dendritic spine formation through its interaction with srGAPs (slit-robo GTPase Activating Proteins), which leads to downstream signaling, actin cytoskeleton depolymerization and dendritic spine collapse. Through interference with this pathway, HS deficiency can lead to excess spine formation.

The Human Model: Changing Focus on Autism Research

The lack of live human brain cells for research has slowed progress toward understanding the mechanisms underlying autism spectrum disorders. A human model using reprogrammed patient somatic cells offers an attractive alternative, as it captures a patient's genome in relevant cell types. Despite the current limitations, the disease-in-a-dish approach allows for progressive time course analyses of target cells, offering a unique opportunity to investigate the cellular and molecular alterations before symptomatic onset. Understanding the current drawbacks of this model is essential for the correct data interpretation and extrapolation of conclusions applicable to the human brain. Innovative strategies for collecting biological material and clinical information from large patient cohorts are important for increasing the statistical power that will allow for the extraction of information from the noise resulting from the variability introduced by reprogramming and differentiation methods. Working with large patient cohorts is also important for understanding how brain cells derived from diverse human genetic backgrounds respond to specific drugs, creating the possibility of personalized medicine for autism spectrum disorders.

Epilepsy and Autism

Epilepsy and autistic spectrum disorder frequently coexist in the same individual. Electroencephalogram (EEG) epileptiform activity is also present at a substantially higher rate in children with autism than normally developing children. As with epilepsy, there are a multitude of genetic and environmental factors that can result in autistic spectrum disorder. There is growing consensus from both animal and clinical studies that autism is a disorder of aberrant connectivity. As measured with functional magnetic resonance imaging (MRI) and EEG, the brain in autistic spectrum disorder may be under- or overconnected or have a mixture of over- and underconnectivity. In the case of comorbid epilepsy and autism, an imbalance of the excitatory/inhibitory (E/I) ratio in selected regions of the brain may drive overconnectivity. Understanding the mechanism by which altered connectivity in individuals with comorbid epilepsy and autistic spectrum disorder results in the behaviors specific to the autistic spectrum disorder remains a challenge.

Cortico-Cerebellar Connectivity in Autism Spectrum Disorder: What Do We Know So Far?

Although the Autism Spectrum Disorder (ASD) is renowned to be a connectivity disorder and a condition characterized by cerebellar involvement, the connectivity between the cerebellum and other cortical brain regions is particularly underexamined. Indeed, converging evidence has recently suggested that the cerebellum could play a key role in the etiopathogenesis of ASD, since cerebellar anomalies have been consistently reported in ASD from the molecular to the behavioral level, and damage to the cerebellum early in development has been linked with signs of autistic features. In addition, current data have shown that the cerebellum is a key structure not only for sensory-motor control, but also for "higher functions," such as social cognition and emotion, through its extensive connections with cortical areas. The disruption of these circuits could be implicated in the wide range of autistic symptoms that the term "spectrum" connotes. In this review, we present and discuss the recent findings from imaging studies that investigated cortico-cerebellar connectivity in people with ASD. The literature is still too limited to allow for definitive conclusions; however, this brief review reveals substantial areas for future studies, underlining currently unmet research perspectives.

Neurodevelopmental sequelae associated with gray and white matter changes and their cellular basis: A comparison between Autism Spectrum Disorder, ADHD and dyslexia

Many psychiatric diseases, such as major depression and schizophrenia, are accompanied by patterns of gray matter and white matter changes in the cortex that may be due to structural pathologies of synapses and their dendrites in the gray matter on the one hand and to pathologies in myelinating oligodendrocytes on the other. Here the possibility has been briefly examined that such a generalization might also hold for Autistic Spectrum Disorders (ASD). Evidence is presented that gray matter changes that accompany ASD may in fact reflect changes in synapses and subsequently of their dendrites, whereas those in the white matter reflect changes in myelination due to pathologies of oligodendrocytes. It is proposed that such structural pathologies during development provide a coherent biological model not only for the onset and course of ASD but also provide the basis for development and systematic evaluation of new treatment strategies.

Eyeblink conditioning: a non-invasive biomarker for neurodevelopmental disorders

Eyeblink conditioning (EBC) is a classical conditioning paradigm typically used to study the underlying neural processes of learning and memory. EBC has a well-defined neural circuitry, is non-invasive, and can be employed in human infants shortly after birth making it an ideal tool to use in both developing and special populations. In addition, abnormalities in the cerebellum, a region of the brain highly involved in EBC, have been implicated in a number of neurodevelopmental disorders including autism spectrum disorders (ASDs). In the current paper, we review studies that have employed EBC as a biomarker for several neurodevelopmental disorders including fetal alcohol syndrome, Down syndrome, fragile X syndrome, attention deficit/hyperactivity disorder, dyslexia, specific language impairment, and schizophrenia. In addition, we discuss the benefits of using such a tool in individuals with ASD.

Altered development and multifaceted band-specific abnormalities of resting state networks in autism

BACKGROUND

Extensive evidence indicates that cortical connectivity patterns are abnormal in autism spectrum disorders (ASD), showing both overconnectivity and underconnectivity. Since, however, studies to date have focused on either spatial or spectral dimensions, but not both simultaneously, much remains unknown about the nature of these abnormalities. In particular, it remains unknown whether abnormal connectivity patterns in ASD are driven by specific frequency bands, by spatial network properties, or by some combination of these factors.

METHODS

Magnetoencephalography recordings (15 ASD, 15 control subjects) mapped back onto cortical space were used to study resting state networks in ASD with both spatial and spectral specificity. The data were quantified using graph theoretic metrics.

RESULTS

The two major factors that drove the nature of connectivity abnormalities in ASD were the mediating frequency band and whether the network included frontal nodes. These factors determined whether clustering and integration were increased or decreased in cortical resting state networks in ASD. These measures also correlated with abnormalities in the developmental trajectory of resting state networks in ASD. Lastly, these measures correlated with ASD severity in some frequency bands and spatially specific subnetworks.

CONCLUSIONS

Our findings suggest that network abnormalities in ASD are widespread, are more likely in subnetworks that include the frontal lobe, and can be opposite in nature depending on the frequency band. These findings thus elucidate seemingly contradictory prior findings of both overconnectivity and underconnectivity in ASD.

Diagnostic classification of intrinsic functional connectivity highlights somatosensory, default mode, and visual regions in autism

Despite consensus on the neurological nature of autism spectrum disorders (ASD), brain biomarkers remain unknown and diagnosis continues to be based on behavioral criteria. Growing evidence suggests that brain abnormalities in ASD occur at the level of interconnected networks; however, previous attempts using functional connectivity data for diagnostic classification have reached only moderate accuracy. We selected 252 low-motion resting-state functional MRI (rs-fMRI) scans from the Autism Brain Imaging Data Exchange (ABIDE) including typically developing (TD) and ASD participants (n = 126 each), matched for age, non-verbal IQ, and head motion. A matrix of functional connectivities between 220 functionally defined regions of interest was used for diagnostic classification, implementing several machine learning tools. While support vector machines in combination with particle swarm optimization and recursive feature elimination performed modestly (with accuracies for validation datasets <70%), diagnostic classification reached a high accuracy of 91% with random forest (RF), a nonparametric ensemble learning method. Among the 100 most informative features (connectivities), for which this peak accuracy was achieved, participation of somatosensory, default mode, visual, and subcortical regions stood out. Whereas some of these findings were expected, given previous findings of default mode abnormalities and atypical visual functioning in ASD, the prominent role of somatosensory regions was remarkable. The finding of peak accuracy for 100 interregional functional connectivities further suggests that brain biomarkers of ASD may be regionally complex and distributed, rather than localized.

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Machine learning of resting fMRI attains high diagnostic accuracy for autism.

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Peak accuracy is seen for a complex pattern of 100 connectivities.

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Somatosensory regions are overall most informative.

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Default mode and visual regions also contribute to diagnostic accuracy.

Gait deviations in children with autism spectrum disorders: a review

In recent years, it has become clear that children with autism spectrum disorders (ASDs) have difficulty with gross motor function and coordination, factors which influence gait. Knowledge of gait abnormalities may be useful for assessment and treatment planning. This paper reviews the literature assessing gait deviations in children with ASD. Five online databases were searched using keywords “gait” and “autism,” and 11 studies were found which examined gait in childhood ASD. Children with ASD tend to augment their walking stability with a reduced stride length, increased step width and therefore wider base of support, and increased time in the stance phase. Children with ASD have reduced range of motion at the ankle and knee during gait, with increased hip flexion. Decreased peak hip flexor and ankle plantar flexor moments in children with ASD may imply weakness around these joints, which is further exhibited by a reduction in ground reaction forces at toe-off in children with ASD. Children with ASD have altered gait patterns to healthy controls, widened base of support, and reduced range of motion. Several studies refer to cerebellar and basal ganglia involvement as the patterns described suggest alterations in those areas of the brain. Further research should compare children with ASD to other clinical groups to improve assessment and treatment planning.

Understanding the brain-behaviour relationship in persons with ASD: implications for PECS as a treatment choice

INTRODUCTION

This article presents emerging neurological findings in Autism Spectrum Disorders (ASD) with particular attention to how this information might inform treatment practices addressing communication impairments.

METHODS

The article begins with a general discussion of the brain-behaviour relationship and moves to the presentation of recent research findings related to ASD. There is particular attention to individuals with autism who are either non-verbal or present emergent verbal abilities.

RESULTS/DISCUSSION

A specific communication treatment, the Picture Exchange Communication System (PECS), is presented as an example of an intervention that addresses the learner needs of many individuals with ASD. The success of PECS is discussed within the context of its fit with brain-based learner characteristics.

Replicated linear association between DUF1220 copy number and severity of social impairment in autism

Sequences encoding DUF1220 protein domains exhibit an exceptional human-specific increase in copy number and have been associated with several phenotypes related to brain size. Autism is a highly heritable and heterogeneous condition characterized behaviorally by social and communicative impairments, and increased repetitive and stereotyped behavior. Given the accelerated brain growth pattern observed in many individuals with autism, and the association between DUF1220 subtype CON1 copy number and brain size, we previously investigated associations between CON1 copy number and autism-related symptoms. We determined that CON1 copy number increase is associated with increasing severity of all three behavioral features of autism. The present study sought to replicate these findings in an independent population (N = 166). Our results demonstrate a replication of the linear relationship between CON1 copy number and the severity of social impairment in individuals with autism as measured by Autism Diagnostic Interview-Revised Social Diagnostic Score, such that with each additional copy of CON1 Social Diagnostic Score increased 0.24 points (SE = 0.11, p = 0.036). We also identified an analogous trend between CON1 copy number and Communicative Diagnostic Score, but did not replicate the relationship between CON1 copy number and Repetitive Behavior Diagnostic Score. Interestingly, these associations appear to be most pronounced in multiplex children. These results, representing the first replication of a gene dosage relationship with the severity of a primary symptom of autism, lend further support to the possibility that the same protein domain family implicated in the evolutionary expansion of the human brain may also be involved in autism severity.

White-matter relaxation time and myelin water fraction differences in young adults with autism

BACKGROUND

Increasing evidence suggests that autism is associated with abnormal white-matter (WM) anatomy and impaired brain 'connectivity'. While myelin plays a critical role in synchronized brain communication, its aetiological role in autistic symptoms has only been indirectly addressed by WM volumetric, relaxometry and diffusion tensor imaging studies. A potentially more specific measure of myelin content, termed myelin water fraction (MWF), could provide improved sensitivity to myelin alteration in autism.

METHOD

We performed a cross-sectional imaging study that compared 14 individuals with autism and 14 age- and IQ-matched controls. T 1 relaxation times (T 1), T 2 relaxation times (T 2) and MWF values were compared between autistic subjects, diagnosed using the Autism Diagnostic Interview - Revised (ADI-R), with current symptoms assessed using the Autism Diagnostic Observation Schedule (ADOS) and typical healthy controls. Correlations between T 1, T 2 and MWF values with clinical measures [ADI-R, ADOS, and the Autism Quotient (AQ)] were also assessed.

RESULTS

Individuals with autism showed widespread WM T 1 and MWF differences compared to typical controls. Within autistic individuals, worse current social interaction skill as measured by the ADOS was related to reduced MWF although not T 1. No significant differences or correlations with symptoms were observed with respect to T 2.

CONCLUSIONS

Autistic individuals have significantly lower global MWF and higher T 1, suggesting widespread alteration in tissue microstructure and biochemistry. Areas of difference, including thalamic projections, cerebellum and cingulum, have previously been implicated in the disorder; however, this is the first study to specifically indicate myelin alteration in these regions.

Oculomotor performance in children with high-functioning Autism Spectrum Disorders

Sensorimotor issues are of increasing focus in the assessment and treatment of Autism Spectrum Disorders (ASD). The oculomotor system is a sensorimotor network that can provide insights into functional neurobiology and has well-established methodologies for investigation. In this study, we assessed oculomotor performance among children with high functioning ASD and typically developing children, ages 6-12 years. Children with ASD exhibited greater horizontal saccade latency and greater phase lag during vertical smooth pursuit. Saccades and smooth pursuit are mediated by spatially distant brain regions and the long-fiber tracts connecting them, many of which are implicated in ASD. Training paradigms for oculomotor deficits have shown positive outcomes in other clinical populations, and deficits described here may provide useful targets for interventions.

Endocasts: possibilities and limitations for the interpretation of human brain evolution

Brains are not preserved in the fossil record but endocranial casts are. These are casts of the internal bony braincase, revealing approximate brain size and shape, and they are also informative about brain surface morphology. Endocasts are the only direct evidence of human brain evolution, but they provide only limited data ('paleoneurology'). This review discusses some new fossil endocasts and recent methodological advances that have allowed novel analyses of old endocasts, leading to intriguing findings and hypotheses. The interpretation of paleoneurological data always relies on comparative information from living species whose brains and behavior can be directly investigated. It is therefore important that future studies attempt to better integrate different approaches. Only then will we be able to gain a better understanding about hominin brain evolution. © 2014 S. Karger AG, Basel.

The cerebellum, sensitive periods, and autism

Cerebellar research has focused principally on adult motor function. However, the cerebellum also maintains abundant connections with nonmotor brain regions throughout postnatal life. Here we review evidence that the cerebellum may guide the maturation of remote nonmotor neural circuitry and influence cognitive development, with a focus on its relationship with autism. Specific cerebellar zones influence neocortical substrates for social interaction, and we propose that sensitive-period disruption of such internal brain communication can account for autism's key features.

Deficits in motor abilities and developmental fractionation of imitation performance in high-functioning autism spectrum disorders

The co-occurrence of motor and imitation disabilities often characterises the spectrum of deficits seen in patients with autism spectrum disorders (ASD). Whether these seemingly separate deficits are inter-related and whether, in particular, motor deficits contribute to the expression of imitation deficits is the topic of the present study and was investigated by comparing these deficits' cross-sectional developmental trajectories. To that end, different components of motor performance assessed in the Zurich Neuromotor Assessment and imitation abilities for facial movements and non-meaningful gestures were tested in 70 subjects (aged 6-29 years), including 36 patients with high-functioning ASD and 34 age-matched typically developed (TD) participants. The results show robust deficits in probands with ASD in timed motor performance and in the quality of movement, which are all independent of age, with one exception. Only diadochokinesis improves moderately with increasing age in ASD probands. Imitation of facial movements and of non-meaningful hand, finger, hand finger gestures not related to social context or tool use is also impaired in ASD subjects, but in contrast to motor performance this deficit overall improves with age. A general imitation factor, extracted from the highly inter-correlated imitation tests, is differentially correlated with components of neuromotor performance in ASD and TD participants. By developmentally fractionating developmentally stable motor deficits from developmentally dynamic imitation deficits, we infer that imitation deficits are primarily cognitive in nature.

Multimodal brain imaging in autism spectrum disorder and the promise of twin research

Current evidence suggests the phenotype of autism spectrum disorder to be driven by a complex interaction of genetic and environmental factors impacting onto brain maturation, synaptic function, and cortical networks. However, findings are heterogeneous, and the exact neurobiological pathways of autism spectrum disorder still remain poorly understood. The co-twin control or twin-difference design is a potentially powerful tool to disentangle causal genetic and environmental contributions on neurodevelopment in autism spectrum disorder. To this end, monozygotic twins discordant for this condition provide unique means for the maximum control of potentially confounding factors. Unfortunately, only few studies of a rather narrow scope, and limited sample size, have been conducted. In an attempt to highlight the great potential of combining the brain connectome approach with monozygotic twin design, we first give an overview of the existing neurobiological evidence for autism spectrum disorder and its cognitive correlates. Then, a special focus is made onto the brain imaging findings reported within populations of monozygotic twins phenotypically discordant for autism spectrum disorder. Finally, we introduce the brain connectome model and describe an ongoing project using this approach among the largest cohort of monozygotic twins discordant for autism spectrum disorder ever recruited.

Altered expression of Alzheimer's disease-related genes in the cerebellum of autistic patients: a model for disrupted brain connectome and therapy

Autism and Alzheimer's disease (AD) are, respectively, neurodevelopmental and degenerative diseases with an increasing epidemiological burden. The AD-associated amyloid-β precursor protein-α has been shown to be elevated in severe autism, leading to the 'anabolic hypothesis' of its etiology. Here we performed a focused microarray analysis of genes belonging to NOTCH and WNT signaling cascades, as well as genes related to AD and apoptosis pathways in cerebellar samples from autistic individuals, to provide further evidence for pathological relevance of these cascades for autism. By using the limma package from R and false discovery rate, we demonstrated that 31% (116 out of 374) of the genes belonging to these pathways displayed significant changes in expression (corrected P-values <0.05), with mitochondria-related genes being the most downregulated. We also found upregulation of GRIN1, the channel-forming subunit of NMDA glutamate receptors, and MAP3K1, known activator of the JNK and ERK pathways with anti-apoptotic effect. Expression of PSEN2 (presinilin 2) and APBB1 (or F65) were significantly lower when compared with control samples. Based on these results, we propose a model of NMDA glutamate receptor-mediated ERK activation of α-secretase activity and mitochondrial adaptation to apoptosis that may explain the early brain overgrowth and disruption of synaptic plasticity and connectome in autism. Finally, systems pharmacology analyses of the model that integrates all these genes together (NOWADA) highlighted magnesium (Mg(2+)) and rapamycin as most efficient drugs to target this network model in silico. Their potential therapeutic application, in the context of autism, is therefore discussed.

Prenatal ethanol exposure disrupts intraneocortical circuitry, cortical gene expression, and behavior in a mouse model of FASD

In utero ethanol exposure from a mother's consumption of alcoholic beverages impacts brain and cognitive development, creating a range of deficits in the child (Levitt, 1998; Lebel et al., 2012). Children diagnosed with fetal alcohol spectrum disorders (FASD) are often born with facial dysmorphology and may exhibit cognitive, behavioral, and motor deficits from ethanol-related neurobiological damage in early development. Prenatal ethanol exposure (PrEE) is the number one cause of preventable mental and intellectual dysfunction globally, therefore the neurobiological underpinnings warrant systematic research. We document novel anatomical and gene expression abnormalities in the neocortex of newborn mice exposed to ethanol in utero. This is the first study to demonstrate large-scale changes in intraneocortical connections and disruption of normal patterns of neocortical gene expression in any prenatal ethanol exposure animal model. Neuroanatomical defects and abnormal neocortical RZRβ, Id2, and Cadherin8 expression patterns are observed in PrEE newborns, and abnormal behavior is present in 20-d-old PrEE mice. The vast network of neocortical connections is responsible for high-level sensory and motor processing as well as complex cognitive thought and behavior in humans. Disruptions to this network from PrEE-related changes in gene expression may underlie some of the cognitive-behavioral phenotypes observed in children with FASD.

Independently outgrowing neurons and geometry-based synapse formation produce networks with realistic synaptic connectivity

Neuronal signal integration and information processing in cortical networks critically depend on the organization of synaptic connectivity. During development, neurons can form synaptic connections when their axonal and dendritic arborizations come within close proximity of each other. Although many signaling cues are thought to be involved in guiding neuronal extensions, the extent to which accidental appositions between axons and dendrites can already account for synaptic connectivity remains unclear. To investigate this, we generated a local network of cortical L2/3 neurons that grew out independently of each other and that were not guided by any extracellular cues. Synapses were formed when axonal and dendritic branches came by chance within a threshold distance of each other. Despite the absence of guidance cues, we found that the emerging synaptic connectivity showed a good agreement with available experimental data on spatial locations of synapses on dendrites and axons, number of synapses by which neurons are connected, connection probability between neurons, distance between connected neurons, and pattern of synaptic connectivity. The connectivity pattern had a small-world topology but was not scale free. Together, our results suggest that baseline synaptic connectivity in local cortical circuits may largely result from accidentally overlapping axonal and dendritic branches of independently outgrowing neurons.