Neurologic abnormalities in infantile autism

Clinical characteristics of children affected by autism spectrum disorder with and without generalized hypotonia

In this cross-sectional study, we aimed to evaluate the association between generalized hypotonia (GH) and demographic features and clinical characteristics in toddlers (2 to 5 years) with autism spectrum disorder (ASD). Among 93 children, 32 (34.4%) had GH. These patients had a later onset of independent walking (17 vs. 15 months, p < 0.01), a higher proportion of motor stereotypies (65.6 vs. 27.9%, p < 0.01), a lower mean total score in the parental-reported Generic Core Scale of Pediatric Quality of Life Inventory 4.0 (71 vs. 76 points, p 0.03), and a higher mean total score in the Calibrated Severity Score of Autism Diagnostic Observation Schedule version 2 at diagnosis (6 vs. 5 points, p 0.02) compared to the group without GH.Conclusion: Hypotonia is associated with other motor abnormalities and could be an early marker for higher autistic symptom severity and lower quality of life in young children with ASD. What is Known: • Motor function is closely related to autism spectrum disorder (ASD) • Muscle hypotonia is present in 15% to 67% of children with ASD What is New: • Muscle hypotonia is associated with higher autistic symptom severity and lower quality of life in children with ASD • Children with ASD and muscle hypotonia have more commonly motor stereotypies and a later onset of independent walking.

Anxious attachment is associated with heightened responsivity of a parietofrontal cortical network that monitors peri-personal space

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A parietofrontal cortical network is more active when stimuli are near the body.

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Responses of this network were positively correlated with “attachment anxiety”.

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No other types of attachment or symptoms accounted for this association.

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Connectivity strength within this network was not linked with attachment anxiety.

Background

Attachment, or affiliative bonding among conspecifics, is thought to involve neural mechanisms underlying behavioral responses to threat and reward-related social signals. However, attachment-oriented responses may also rely on basic sensorimotor processes. One sensorimotor system that may play a role in attachment is the parietofrontal cortical network that responds to stimuli that are near or approaching the body, the peripersonal space (PPS) monitoring system. We hypothesized that this network may vary in responsivity to such potentially harmful stimuli, particularly those with social salience, based on individual differences in attachment styles.

Methods

Young adults viewed images of human faces or cars that appeared to move towards or away from them, while functional magnetic resonance imaging data were collected. Correlations between each of four adult attachment styles, measured using the Relationship Questionnaire, and responses of the PPS network to approaching (versus withdrawing) stimuli were measured.

Results

A region-of-interest (ROI) analysis, focused on six cortical regions of the PPS network that showed significant responses to approaching versus withdrawing face stimuli in an independent sample (n = 80), revealed that anxious attachment style (but not the other 3 attachment styles) was significantly positively correlated with responses to faces (but not to cars) in all six ROIs (r = 0.33–0.49, p = 0.01–0.0001, n = 50).

Conclusions

These findings suggest that anxious attachment is associated with over-responsivity of a sensorimotor network involved in attending to social stimuli near the body.

Brain Disorders and Chemical Pollutants: A Gap Junction Link?

The incidence of brain pathologies has increased during last decades. Better diagnosis (autism spectrum disorders) and longer life expectancy (Parkinson's disease, Alzheimer's disease) partly explain this increase, while emerging data suggest pollutant exposures as a possible but still underestimated cause of major brain disorders. Taking into account that the brain parenchyma is rich in gap junctions and that most pollutants inhibit their function; brain disorders might be the consequence of gap-junctional alterations due to long-term exposures to pollutants. In this article, this hypothesis is addressed through three complementary aspects: (1) the gap-junctional organization and connexin expression in brain parenchyma and their function; (2) the effect of major pollutants (pesticides, bisphenol A, phthalates, heavy metals, airborne particles, etc.) on gap-junctional and connexin functions; (3) a description of the major brain disorders categorized as neurodevelopmental (autism spectrum disorders, attention deficit hyperactivity disorders, epilepsy), neurobehavioral (migraines, major depressive disorders), neurodegenerative (Parkinson's and Alzheimer's diseases) and cancers (glioma), in which both connexin dysfunction and pollutant involvement have been described. Based on these different aspects, the possible involvement of pollutant-inhibited gap junctions in brain disorders is discussed for prenatal and postnatal exposures.

Lower-extremity rotational profile and toe-walking in preschool children with autism spectrum disorder

The aim of this study was to establish the torsional and toe-walking profiles of children with autism spectrum disorder (ASD), and to analyze the correlations between torsion, toe-walking, autism severity score, and age. In total, 79 consecutive children with autism were examined to determine their hip rotations, thigh-foot angle, degree of toe-walking, and autism severity. Femoral and tibial torsion values, of the preschool patients, were compared statistically with age-matched controls. The hip rotation profile of the patients was similar to the normal group. Nearly a half of the patients with ASD present excessive external tibial torsion. The difference in the tibial torsion between patients and normal children was statistically significant. A weak correlation was found only between tibial torsion and the autism severity score, but no correlation was found between the other parameters. External tibial torsion is the cardinal and persistent orthopedic manifestation among patients with ASD. Toe-walking is the second most common such manifestation and is an independent orthopedic feature in these patients. External tibial torsion may potentially contribute toward the described gait abnormalities in patients with ASD.

Minor Neurological Dysfunctions (MNDs) in Autistic Children without Intellectual Disability

Background: Children with autism spectrum disorder (ASD) require neurological evaluation to detect sensory-motor impairment. This will improve understanding of brain function in children with ASD, in terms of minor neurological dysfunctions (MNDs). Methods: We compared 32 ASD children without intellectual disability (IQ ≥ 70) with 32 healthy controls. A standardized and age-specific neurological examination according to Touwen was used to detect the presence of MNDs. Particular attention was paid to severity and type of MNDs. Results: Children with ASD had significantly higher rates of MNDs compared to controls (96.9% versus 15.6%): 81.3% had simple MNDs (p < 0.0001) and 15.6% had complex MNDs (p = 0.053). The prevalence of MNDs in the ASD group was significantly higher (p < 0.0001) than controls. With respect to specific types of MNDs, children with ASD showed a wide range of fine manipulative disability, sensory deficits and choreiform dyskinesia. We also found an excess of associated movements and anomalies in coordination and balance. Conclusions: Results replicate previous findings which found delays in sensory-motor behavior in ASD pointing towards a role for prenatal, natal and neonatal risk factors in the neurodevelopmental theory of autism.

Evaluation of neuromuscular tone phenotypes in children with autism spectrum disorder: An exploratory study

OBJECTIVE

Motor disorders are known in autism spectrum disorder (ASD), but muscle tone assessments are rarely performed. Muscle tone underpins movement. We investigated muscle tone in 34 ASD children using a standardized neuro-developmental battery, which uses the French norms for muscular tone in children.

METHODS

Dangling and extensibility were used to examine passive muscle tone in the upper and lower limbs and the body axis. A comparison between muscles of the right and left sides enabled the determination of tonic laterality.

RESULTS

We found a disharmonious tonic typology, with a tonic component for the muscles of the trunk and the proximal muscles of the lower limbs and a laxity component for the ankles and the proximal and distal muscles of the upper limbs (wrists and shoulders). No establishment of tonic laterality was found in the upper limbs in 61% of ASD children (P<0.001).

CONCLUSION

The disturbed tonic organization influenced by subcortical structures, such as the cerebellum, may partially explain the motor disorders, and indefinite tonic laterality may also be linked to low hemispheric brain dominance described in autism. This preliminary examination is necessary before any gross motor assessments to understand the nature of movement disorders, explore typologies and highlight possible soft neuro-motor signs.

Decreased parvalbumin mRNA levels in cerebellar Purkinje cells in autism

Recent neuropathology studies in human brains indicate that several areas of the prefrontal cortex have decreased numbers of parvalbumin interneurons or decreased parvalbumin expression in Autism Spectrum disorders (ASD) [Hashemi, Ariza, Rogers, Noctor, & Martinez-Cerdeno, 2017; Zikopoulos & Barbas, ]. These data suggest that a deficit in parvalbumin may be a key neuropathology of ASD and contribute to altered GABAergic inhibition. However, it is unclear if a deficit in parvalbumin is a phenomenon that occurs in regions other than the cerebral cortex. The cerebellum is a major region where neuropathology was first detected in ASD over three decades ago [Bauman & Kemper, ]. In view of the documented association between parvalbumin-expressing neurons and autism, the objective of the present study was to determine if parvalbumin gene expression is also altered in Purkinje neurons of the cerebellum. Radioisotopic in situ hybridization histochemistry was used on human tissue sections from control and ASD brains in order to detect and measure parvalbumin mRNA levels at the single cell level in Purkinje cells of Crus II of the lateral cerebellar hemispheres. Results indicate that parvalbumin mRNA levels are significantly lower in Purkinje cells in ASD compared to control brains. This decrease was not influenced by post-mortem interval or age at death. This result indicates that decreased parvalbumin expression is a more widespread feature of ASD. We discuss how this decrease may be implicated in altered cerebellar output to the cerebral cortex and in key ASD symptoms. Autism Res 2017, 10: 1787-1796. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

The cerebellum of the brain controls movement and cognition, including memory and language. This study investigated mechanisms of cerebellar function in Autism. Our hypothesis is that parvalbumin, a molecule that controls and coordinate many cellular brain functions, contributes to the excitatory/inhibitory imbalance in Autism. We report that parvalbumin expression is depressed in Purkinje cells of the cerebellum in autism. This finding contributes to elucidate the cellular and molecular underpinings of autism and should provide a direction for future therapies.

Annual Research Review: Understudied populations within the autism spectrum - current trends and future directions in neuroimaging research

BACKGROUND

Autism spectrum disorders (ASDs) are a heterogeneous group of neurodevelopmental conditions that vary in both etiology and phenotypic expression. Expressions of ASD characterized by a more severe phenotype, including autism with intellectual disability (ASD + ID), autism with a history of developmental regression (ASD + R), and minimally verbal autism (ASD + MV) are understudied generally, and especially in the domain of neuroimaging. However, neuroimaging methods are a potentially powerful tool for understanding the etiology of these ASD subtypes.

SCOPE AND METHODOLOGY

This review evaluates existing neuroimaging research on ASD + MV, ASD + ID, and ASD + R, identified by a search of the literature using the PubMed database, and discusses methodological, theoretical, and practical considerations for future research involving neuroimaging assessment of these populations.

FINDINGS

There is a paucity of neuroimaging research on ASD + ID, ASD + MV, and ASD + R, and what findings do exist are often contradictory, or so sparse as to be ungeneralizable. We suggest that while greater sample sizes and more studies are necessary, more important would be a paradigm shift toward multimodal (e.g. imaging genetics) approaches that allow for the characterization of heterogeneity within etiologically diverse samples.

Neuron density is decreased in the prefrontal cortex in Williams syndrome

Williams Syndrome (WS) is a rare neurodevelopmental disorder associated with a hemideletion in chromosome 7, which manifests a distinct behavioral phenotype characterized by a hyperaffiliative social drive, in striking contrast to the social avoidance behaviors that are common in Autism Spectrum Disorder (ASD). MRI studies have observed structural and functional abnormalities in WS cortex, including the prefrontal cortex (PFC), a region implicated in social cognition. This study utilizes the Bellugi Williams Syndrome Brain Collection, a unique resource that comprises the largest WS postmortem brain collection in existence, and is the first to quantitatively examine WS PFC cytoarchitecture. We measured neuron density in layers II/III and V/VI of five cortical areas: PFC areas BA 10 and BA 11, primary motor BA 4, primary somatosensory BA 3, and visual area BA 18 in six matched pairs of WS and typically developing (TD) controls. Neuron density in PFC was lower in WS relative to TD, with layers V/VI demonstrating the largest decrease in density, reaching statistical significance in BA 10. In contrast, BA 3 and BA 18 demonstrated a higher density in WS compared to TD, although this difference was not statistically significant. Neuron density in BA 4 was similar in WS and TD. While other cortical areas were altered in WS, prefrontal areas appeared to be most affected. Neuron density is also altered in the PFC of individuals with ASD. Together these findings suggest that the PFC is targeted in neurodevelopmental disorders associated with sociobehavioral alterations. Autism Res 2017, 10: 99-112. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Neuromotor Assessment and Autistic Disorder

Autistic disorder presents in early childhood with marked deviations in social interactions and communication and with a restricted and peculiar range of interests and activities. Although probably a heterogeneous condition, autistic disorder includes a class of individuals who also have subtle neurological impediments manifested as disturbances of movement, balance, posture and gait. We review neuromotor and neurobehavioral assessments for persons with autistic disorder and related conditions to improve the classification of the impairments and to facilitate the utilization of therapies specific for each class.

Failure in pantomime action execution correlates with the severity of social behavior deficits in children with autism: a praxis study

Here we describe the performance of children with autism, their siblings, and typically developing children using the Florida Apraxia Battery. Children with autism showed the lowest performance in all sections of the test. They were mostly impaired in pantomime actions execution on imitation and on verbal command, and in imitation of meaningless gestures. Interestingly, a correlation was found between performance in pantomime actions and the severity of social behavior deficits. We conclude that the presence of a rigid internal model prevents the execution of an exact copy of the observed pantomime actions and that the deficit in imitation of meaningless gestures is most likely due to a deficit in the mechanisms responsible for visuomotor transformations.

[Formula: see text]Current knowledge on motor disorders in children with autism spectrum disorder (ASD)

Motor symptomatology in autism is currently poorly understood, and still not included in the autism spectrum disorder (ASD) diagnostic criteria, although some studies suggest the presence of motor disturbances in this syndrome. We provide here a literature review on early motor symptoms in autism, focusing on studies on psychomotor issues (tone, postural control, manual dexterity, handedness, praxis). The approach adopted in research to study altered motor behaviors is generally global and there is no detailed semiology of the motor or neuromotor disorders observed in people with ASD. This global approach does not enable understanding of the neuro-developmental mechanisms involved in ASD. Identification of clinical neuro-psychomotor profiles in reference to a standard would help to better understand the origin and the nature of the disorders encountered in ASD, and would thus give new directions for treatment.

Variants of the CNTNAP2 5' promoter as risk factors for autism spectrum disorders: a genetic and functional approach

Contactin-associated protein-like 2 gene (CNTNAP2), a member of the Neurexin gene superfamily, is one of the best-replicated risk genes for autism spectrum disorders (ASD). ASD are predominately genetically determined neurodevelopmental disorders characterized by impairments of language development, social interaction and communication, as well as stereotyped behavior and interests. Although CNTNAP2 expression levels were proposed to alter ASD risk, no study to date has focused on its 5' promoter. Here, we directly sequenced the CNTNAP2 5' promoter region of 236 German families with one child with ASD and detected four novel variants. Furthermore, we genotyped the three most frequent variants (rs150447075, rs34712024, rs71781329) in an additional sample of 356 families and found nominal association of rs34712024G with ASD and rs71781329GCG[7] with language development. The four novel and the three known minor alleles of the identified variants were predicted to alter transcription factor binding sites (TFBS). At the functional level, the respective sequences spanning these seven variants were bound by nuclear factors. In a luciferase promoter assay, the respective minor alleles showed cell line-specific and differentiation stage-dependent effects at the level of promoter activation. The novel potential rare risk-variant M2, a G>A mutation -215 base pairs 5' of the transcriptional start site, significantly reduced promoter efficiency in HEK293T and in undifferentiated and differentiated neuroblastoid SH-SY5Y cells. This variant was transmitted to a patient with autistic disorder. The under-transmitted, protective minor G allele of the common variant rs34712024, in contrast, increased transcriptional activity. These results lead to the conclusion that the pathomechanism of CNTNAP2 promoter variants on ASD risk is mediated by their effect on TFBSs, and thus confirm the hypothesis that a reduced CNTNAP2 level during neuronal development increases liability for ASD.

Dyspraxia, motor function and visual-motor integration in autism

This project assessed dyspraxia in high-functioning school aged children with autism with a focus on Ideational Praxis. We examined the association of specific underlying motor function including eye movement with ideational dyspraxia (sequences of skilled movements) as well as the possible role of visual-motor integration in dyspraxia. We found that compared to IQ-, sex- and age-matched typically developing children, the children with autism performed significantly worse on: Ideational and Buccofacial praxis; a broad range of motor tests, including measures of simple motor skill, timing and accuracy of saccadic eye movements and motor coordination; and tests of visual-motor integration. Impairments in individual children with autism were heterogeneous in nature, although when we examined the praxis data as a function of a qualitative measure representing motor timing, we found that children with poor motor timing performed worse on all praxis categories and had slower and less accurate eye movements while those with regular timing performed as well as typical children on those same tasks. Our data provide evidence that both motor function and visual-motor integration contribute to dyspraxia. We suggest that dyspraxia in autism involves cerebellar mechanisms of movement control and the integration of these mechanisms with cortical networks implicated in praxis.

Restricted and repetitive behaviors in autism spectrum disorders: the relationship of attention and motor deficits

Restricted and repetitive behaviors (RRBs) are hallmark symptoms of autism spectrum disorders (ASDs); however, it has proven difficult to understand the mechanisms underlying these behaviors. One hypothesis suggests that RRBs are the result of a core deficit in attention. Alternatively, abnormalities of the motor system may constitute the central mechanism underlying RRBs, given motor deficits observed in ASDs. In this experiment, we investigated the etiology of RRBs and the relationship between attention and motor deficits. Movement impairments (a) may be indirectly related to attention deficits, (b) may result from a shared compromised process, or (c) may be independent. Twenty-two adolescents with ASD and 20 typically developing participants performed a spatial attention task. Movement impairments were assessed with a rhythmic tapping task. Attentional orienting and motor control were found to be related and supported the hypothesis that these impairments in ASD arise from a shared process. In contrast, measures of attention switching and motor control were found to be independent. Stereotyped behaviors, as assessed by parental ratings, were related more to the degree of motor impairment than to deficits of attention. These results suggest that both attentional orienting deficits and stereotyped RRBs are related to a compromised motor system.

Abnormalities of joint mobility and gait in children with autism spectrum disorders

AIMS

Abnormalities of gross motor function in children with autism are well known to clinicians but have not received much empirical documentation and, with the exception of stereotypies, are not among its diagnostic criteria. We recorded the characteristics of gait and prevalence of toe walking, the range of passive joint mobility, and age at walking in children with DSM IV autism spectrum disorders (ASDs) and in age- and gender-matched typically developing peers (mean age 4years 6months, range 22months-10years 9months).

METHODS

We evaluated maximum range of mobility at the elbow, wrist, metacarpo-phalangeal, and ankle joints and videoed children walking and running. Two neurologists blind to diagnosis independently scored features of gait clinically.

RESULTS

Children with ASDs had significantly greater joint mobility (p<.002), more gait abnormalities (p<.0001), and on average walked 1.6months later than their non-autistic peers.

INTERPRETATION

This study indicates that attention should be directed to motor abnormalities as well as sociability, communication, and restricted and repetitive behaviors in individuals with ASDs. Motor deficits add to children's other handicaps. They indicate that ASDs affect a broader range of central nervous system circuitry than often appreciated.

Saccade adaptation abnormalities implicate dysfunction of cerebellar-dependent learning mechanisms in Autism Spectrum Disorders (ASD)

The cerebellar vermis (lobules VI-VII) has been implicated in both postmortem and neuroimaging studies of autism spectrum disorders (ASD). This region maintains the consistent accuracy of saccadic eye movements and plays an especially important role in correcting systematic errors in saccade amplitudes such as those induced by adaptation paradigms. Saccade adaptation paradigms have not yet been used to study ASD. Fifty-six individuals with ASD and 53 age-matched healthy controls performed an intrasaccadic target displacement task known to elicit saccadic adaptation reflected in an amplitude reduction. The rate of amplitude reduction and the variability of saccade amplitude across 180 adaptation trials were examined. Individuals with ASD adapted slower than healthy controls, and demonstrated more variability of their saccade amplitudes across trials prior to, during and after adaptation. Thirty percent of individuals with ASD did not significantly adapt, whereas only 6% of healthy controls failed to adapt. Adaptation rate and amplitude variability impairments were related to performance on a traditional neuropsychological test of manual motor control. The profile of impaired adaptation and reduced consistency of saccade accuracy indicates reduced neural plasticity within learning circuits of the oculomotor vermis that impedes the fine-tuning of motor behavior in ASD. These data provide functional evidence of abnormality in the cerebellar vermis that converges with previous reports of cellular and gross anatomic dysmorphology of this brain region in ASD.

Embodiment and sense-making in autism

In this article, I sketch an enactive account of autism. For the enactive approach to cognition, embodiment, experience, and social interaction are fundamental to understanding mind and subjectivity. Enaction defines cognition as sense-making: the way cognitive agents meaningfully connect with their world, based on their needs and goals as self-organizing, self-maintaining, embodied agents. In the social realm, the interactive coordination of embodied sense-making activities with others lets us participate in each other's sense-making (social understanding = participatory sense-making). The enactive approach provides new concepts to overcome the problems of traditional functionalist accounts of autism, which can only give a piecemeal and disintegrated view because they consider cognition, communication, and perception separately, do not take embodied into account, and are methodologically individualistic. Applying the concepts of enaction to autism, I show: How embodiment and sense-making connect, i.e., how autistic particularities of moving, perceiving, and emoting relate to how people with autism make sense of their world. For instance, restricted interests or preference for detail will have certain sensorimotor correlates, as well as specific meaning for autistic people.That reduced flexibility in interactional coordination correlates with difficulties in participatory sense-making. At the same time, seemingly irrelevant "autistic behaviors" can be quite attuned to the interactive context. I illustrate this complexity in the case of echolalia. An enactive account of autism starts from the embodiment, experience, and social interactions of autistic people. Enaction brings together the sensorimotor, cognitive, social, experiential, and affective aspects of autism in a coherent framework based on a complex non-linear multi-causality. This foundation allows to build new bridges between autistic people and their often non-autistic context, and to improve quality of life prospects.

Perception-action in children with ASD

How do disturbances to perception and action relate to the deficiencies expressed by children with autism? The ability to predict what is going to happen next is crucial for the construction of all actions and children develop these predictive abilities early in development. Children with autism, however, are deficient in the ability to foresee future events and to plan movements and movement sequences. They are also deficient in the understanding of other people's actions. This includes communicative actions as they are ultimately based on movements. Today there are two promising neurobiological interpretation of Autism Spectrum Disorder (ASD). First, there is strong evidence that the Mirror Neuron System (MNS) is impaired. As stated by this hypothesis, action production and action understanding are intimately related. Both these functions rely on predictive models of the sensory consequences of actions and depend on connectivity between the parietal and premotor areas. Secondly, action prediction is accomplished through a system that includes a loop from the posterior parietal cortex (PPC) through the cerebellum and back to the premotor and motor areas of the brain. Impairment of this loop is probably also part of the explanation of the prediction problems in children with ASD. Both the cortico-cerebellar loop and the MNS rely on distant neural connections. There are multiple evidence that such connections are weak in children with autism.

Mitochondrial and ion channel gene alterations in autism

To evaluate the potential importance in autistic subjects of copy number variants (CNVs) that alter genes of relevance to bioenergetics, ionic metabolism, and synaptic function, we conducted a detailed microarray analysis of 69 autism probands and 35 parents, compared to 89 CEU HapMap controls. This revealed that the frequency CNVs of≥100kb and CNVs of≥10 Kb were markedly increased in probands over parents and in probands and parents over controls. Evaluation of CNVs≥1Mb by chromosomal FISH confirmed the molecular identity of a subset of the CNVs, some of which were associated with chromosomal rearrangements. In a number of the cases, CNVs were found to alter the copy number of genes that are important in mitochondrial oxidative phosphorylation (OXPHOS), ion and especially calcium transport, and synaptic structure. Hence, autism might result from alterations in multiple bioenergetic and metabolic genes required for mental function. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

Specificity of dyspraxia in children with autism

OBJECTIVE

To explore the specificity of impaired praxis and postural knowledge to autism by examining three samples of children, including those with autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), and typically developing (TD) children.

METHOD

Twenty-four children with ASD, 24 children with ADHD, and 24 TD children, ages 8-13, completed measures assessing basic motor control (the Physical and Neurological Exam for Subtle Signs; PANESS), praxis (performance of skilled gestures to command, with imitation, and tool use) and the ability to recognize correct hand postures necessary to perform skilled gestures (the Postural Knowledge Test; PKT).

RESULTS

Children with ASD performed significantly worse than TD children on all three assessments. In contrast, children with ADHD performed significantly worse than TD controls on PANESS but not on the praxis examination or PKT. Furthermore, children with ASD performed significantly worse than children with ADHD on both the praxis examination and PKT, but not on the PANESS.

CONCLUSIONS

Whereas both children with ADHD and children with ASD show impairments in basic motor control, impairments in performance and recognition of skilled motor gestures, consistent with dyspraxia, appear to be specific to autism. The findings suggest that impaired formation of perceptual-motor action models necessary to development of skilled gestures and other goal directed behavior is specific to autism; whereas, impaired basic motor control may be a more generalized finding.

Minor neurological dysfunction in children with autism spectrum disorder

AIM

The aim of this study was to improve the understanding of brain function in children with autism spectrum disorder (ASD) in relation to minor neurological dysfunctions (MNDs).

METHOD

We studied MNDs in 122 children (93 males, 29 females; mean age 8 y 1 mo, SD 2 y 6 mo) who, among a total cohort of 705 children (513 males, 192 females; mean age 9 y, SD 2 y 0.5 mo) referred to a regional outpatient non-academic psychiatric centre in the Netherlands, were diagnosed with ASD after an extensive multidisciplinary psychiatric assessment. Children with clear neurological abnormalities (e.g. cerebral palsy or spina bifida) were excluded from the study. MNDs were assessed in all 705 children using the Touwen examination method. Special attention was paid to the severity and type of MND. Data of the children with ASD were compared with neurological morbidity data of children with other psychiatric disorders and with children in the general population, who were born at Groningen University Hospital between 1975 and 1978.

RESULTS

Seventy-four percent of the children with ASD showed complex MNDs compared with 52% of the children with other psychiatric disorders and 6% of the reference group (χ(2) =18.0, p<0.001; χ(2) =937.5, p<0.001 respectively). Specific dysfunctions frequently encountered in ASD were dysfunctional posture and muscle tone, fine manipulative disability, dyscoordination, and excessive associated movements.

CONCLUSION

These findings suggest a contribution of dysfunctional supraspinal networks involving multiple parts of the brain in the pathogenesis of ASD. This is consistent with findings from neuroimaging studies, and highlights the importance of neurological examinations in paediatric psychiatric assessments.

Developmental malformation of the corpus callosum: a review of typical callosal development and examples of developmental disorders with callosal involvement

This review provides an overview of the involvement of the corpus callosum (CC) in a variety of developmental disorders that are currently defined exclusively by genetics, developmental insult, and/or behavior. I begin with a general review of CC development, connectivity, and function, followed by discussion of the research methods typically utilized to study the callosum. The bulk of the review concentrates on specific developmental disorders, beginning with agenesis of the corpus callosum (AgCC)-the only condition diagnosed exclusively by callosal anatomy. This is followed by a review of several genetic disorders that commonly result in social impairments and/or psychopathology similar to AgCC (neurofibromatosis-1, Turner syndrome, 22q11.2 deletion syndrome, Williams yndrome, and fragile X) and two forms of prenatal injury (premature birth, fetal alcohol syndrome) known to impact callosal development. Finally, I examine callosal involvement in several common developmental disorders defined exclusively by behavioral patterns (developmental language delay, dyslexia, attention-deficit hyperactive disorder, autism spectrum disorders, and Tourette syndrome).

White matter compromise of callosal and subcortical fiber tracts in children with autism spectrum disorder: a diffusion tensor imaging study

OBJECTIVE

Autism spectrum disorder (ASD) is increasingly viewed as a disorder of functional networks, highlighting the importance of investigating white matter and interregional connectivity. We used diffusion tensor imaging (DTI) to examine white matter integrity for the whole brain and for corpus callosum, internal capsule, and middle cerebellar peduncle in children with ASD and typically developing (TD) children.

METHOD

DTI data were obtained from 26 children with ASD and 24 matched TD children. Fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusion were calculated for the whole brain, the genu, body, and splenium of the corpus callosum, the genu and anterior and posterior limbs of the internal capsule, and the middle cerebellar peduncle.

RESULTS

Children with ASD had reduced FA and increased radial diffusion for whole-brain white matter and all three segments of the corpus callosum and internal capsule, compared with those in TD children. Increased MD was found for the whole brain and for anterior and posterior limbs of the internal capsule. Reduced axial diffusion was found for the body of corpus callosum. Reduced FA was also found for the middle cerebellar peduncle.

CONCLUSIONS

Our findings suggest widespread white matter compromise in children with ASD. Abnormalities in the corpus callosum indicate impaired interhemispheric transfer. Results for the internal capsule and middle cerebellar peduncle add to the currently limited DTI evidence on subcortico-cortical tracts in ASD. The robust impairment found in all three segments of the internal capsule is consistent with studies documenting impairment of elementary sensorimotor function in ASD.

Mapping brain abnormalities in boys with autism

Children with autism spectrum disorder (ASD) exhibit characteristic cognitive and behavioral differences, but no systematic pattern of neuroanatomical differences has been consistently found. Recent neurodevelopmental models posit an abnormal early surge in subcortical white matter growth in at least some autistic children, perhaps normalizing by adulthood, but other studies report subcortical white matter deficits. To investigate the profile of these alterations in 3D, we mapped brain volumetric differences using a relatively new method, tensor-based morphometry. 3D T1-weighted brain MRIs of 24 male children with ASD (age: 9.5 years +/- 3.2 SD) and 26 age-matched healthy controls (age: 10.3 +/- 2.4 SD) were fluidly registered to match a common anatomical template. Autistic children had significantly enlarged frontal lobes (by 3.6% on the left and 5.1% on the right), and all other lobes of the brain were enlarged significantly, or at trend level. By analyzing the applied deformations statistically point-by-point, we detected significant gray matter volume deficits in bilateral parietal, left temporal and left occipital lobes (P = 0.038, corrected), trend-level cerebral white matter volume excesses, and volume deficits in the cerebellar vermis, adjacent to volume excesses in other cerebellar regions. This profile of excesses and deficits in adjacent regions may (1) indicate impaired neuronal connectivity, resulting from aberrant myelination and/or an inflammatory process, and (2) help to understand inconsistent findings of regional brain tissue excesses and deficits in autism.

Energetics, epigenetics, mitochondrial genetics

The epigenome has been hypothesized to provide the interface between the environment and the nuclear DNA (nDNA) genes. Key factors in the environment are the availability of calories and demands on the organism's energetic capacity. Energy is funneled through glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), the cellular bioenergetic systems. Since there are thousands of bioenergetic genes dispersed across the chromosomes and mitochondrial DNA (mtDNA), both cis and trans regulation of the nDNA genes is required. The bioenergetic systems convert environmental calories into ATP, acetyl-Coenzyme A (acetyl-CoA), s-adenosyl-methionine (SAM), and reduced NAD(+). When calories are abundant, ATP and acetyl-CoA phosphorylate and acetylate chromatin, opening the nDNA for transcription and replication. When calories are limiting, chromatin phosphorylation and acetylation are lost and gene expression is suppressed. DNA methylation via SAM can also be modulated by mitochondrial function. Phosphorylation and acetylation are also pivotal to regulating cellular signal transduction pathways. Therefore, bioenergetics provides the interface between the environment and the epigenome. Consistent with this conclusion, the clinical phenotypes of bioenergetic diseases are strikingly similar to those observed in epigenetic diseases (Angelman, Rett, Fragile X Syndromes, the laminopathies, cancer, etc.), and an increasing number of epigenetic diseases are being associated with mitochondrial dysfunction. This bioenergetic-epigenomic hypothesis has broad implications for the etiology, pathophysiology, and treatment of a wide range of common diseases.

Converging evidence for abnormalities of the prefrontal cortex and evaluation of midsagittal structures in pediatric posttraumatic stress disorder: an MRI study

Volumetric imaging research has shown abnormal brain morphology in posttraumatic stress disorder (PTSD) when compared with control subjects. We present results on a study of brain morphology in the prefrontal cortex (PFC) and midline structures, via indices of gray matter volume and density, in pediatric PTSD. We hypothesized that both methods would demonstrate aberrant morphology in the PFC. Further, we hypothesized aberrant brainstem anatomy and reduced corpus callosum volume in children with PTSD. Twenty-four children (aged 7-14) with history of interpersonal trauma and 24 age- and gender-matched controls underwent structural magnetic resonance imaging (sMRI). Images of the PFC and midline brain structures were first analyzed using volumetric image analysis. The PFC data were then compared with whole brain voxel-based techniques using statistical parametric mapping (SPM). The PTSD group showed significantly increased gray matter volume in the right and left inferior and superior quadrants of the PFC and smaller gray matter volume in the pons and posterior vermis areas by volumetric image analysis. The voxel-by-voxel group comparisons demonstrated increased gray matter density mostly localized to ventral PFC as compared with the control group. Abnormal frontal lobe morphology, as revealed by separate-complementary image analysis methods, and reduced pons and posterior vermis areas are associated with pediatric PTSD. Voxel-based morphometry may help to corroborate and further localize data obtained by volume of interest methods in PTSD.

Slowed orienting of covert visual-spatial attention in autism: Specific deficits associated with cerebellar and parietal abnormality

The most commonly reported finding from structural brain studies in autism is abnormality of the cerebellum. Autopsy and magnetic resonance imaging (MR) studies from nine independent research groups have found developmental abnormality of the cerebellar vermis or hemispheres in the majority of the more than 240 subjects with autism who were studied. We reported previously that patients with autism and those with acquired damage to the cerebellum were slow to shift attention between and within sensory modalities. In this study, we found that patients with autism who come from a group with significant cerebellar abnormality were also slow to orient attention in space.

A subgroup of these patients who have additional or corollary parietal abnormality, like previously studied patients with acquired parietal damage, were also slow to detect and respond to information outside an attended location. Posner, Walker, Friedrich, and Rafal (1984) showed that patients with parietal lesions were slow to respond to contralesional information if they were attending an ipsilesional location. This study has replicated that finding in patients with autism who have developmental bilateral parietal abnormality, and found a strong correlation between the attentional deficits and the amount of neuroanatomic parietal abnormality in these patients. This is the first time in the study of autism that there is evidence for a statistically significant association of the size of a specific brain structural abnormality with a specific behavioral deficit.

These findings illustrate that in autism different patterns of underlying brain pathology may result in different patterns of functional deficits. In conjunction with previous studies of patients with acquired lesions, these data have implications for the brain bases of normal attention. The cerebellum may affect the speed with which attentional resources can be activated, while the parietal cortex affects the ability to use those resources for efficient information processing at locations outside an attended focus. Deficits in the speed and efficiency with which neural activity can be modulated to facilitate processing can clearly influence cognitive function. Such deficits may contribute to the behavioral disabilities that characterize autism.

GABA(A) receptor downregulation in brains of subjects with autism

Gamma-aminobutyric acid A (GABA(A)) receptors are ligand-gated ion channels responsible for mediation of fast inhibitory action of GABA in the brain. Preliminary reports have demonstrated altered expression of GABA receptors in the brains of subjects with autism suggesting GABA/glutamate system dysregulation. We investigated the expression of four GABA(A) receptor subunits and observed significant reductions in GABRA1, GABRA2, GABRA3, and GABRB3 in parietal cortex (Brodmann's Area 40 (BA40)), while GABRA1 and GABRB3 were significantly altered in cerebellum, and GABRA1 was significantly altered in superior frontal cortex (BA9). The presence of seizure disorder did not have a significant impact on GABA(A) receptor subunit expression in the three brain areas. Our results demonstrate that GABA(A) receptors are reduced in three brain regions that have previously been implicated in the pathogenesis of autism, suggesting widespread GABAergic dysfunction in the brains of subjects with autism.

Expression of astrocytic markers aquaporin 4 and connexin 43 is altered in brains of subjects with autism

Neuroanatomical studies have revealed extensive structural brain abnormalities in subjects with autism. Recently, studies have provided evidence of neuroglial responses and neuroinflammation in autism. The current study investigated whether two astrocytic markers, aquaporin 4 and connexin 43, are altered in brains from subjects with autism. Postmortem brain tissues from Brodmann's Area 40 (BA40, parietal cortex), Brodmann's Area 9 (BA9, superior frontal cortex), and cerebella of subjects with autism and matched controls were subject to SDS-PAGE and western blotting. Connexin 43 expression was increased significantly in BA9. Aquaporin 4 expression was decreased significantly in cerebellum. These data suggest that changes are apparent in markers for abnormal glial-neuronal communication (connexin 43 and aquaporin 4) in brains of subjects with autism.

Abnormalities on the neurological examination and EEG in young children with pervasive developmental disorders

This study examined the nature and frequency of neurological and EEG abnormalities in 60 young children (ages 2-6 years) with pervasive developmental disorders. A number of standard neurological functions could not be adequately assessed due to the young age of the children and/or limited comprehension and cooperation. The most common neurological deficits were hyporeflexia, stereotypies, and hypotonia. EEG abnormalities were identified in 32% of the children while only two children were known to have clinical seizures. The frequency of cases with hypotonia or hyporeflexia was more common than in older children with this diagnosis. Results also indicate that EEG abnormalities are common in this young population but clinical seizures are rare, confirming other studies.

Exogenous and endogenous attention orienting in autism spectrum disorders

Fifteen children with high-functioning Autism Spectrum Disorder (ASD) and 15 children with typical development completed an attentional cuing task using peripheral cues (exogenous orienting) and central cues (endogenous orienting). Results showed that participants with ASD had impaired exogenous and intact endogenous orienting. The pattern of exogenous orienting was related to motor functioning. Individuals with ASD who had poor motor functioning displayed slowed exogenous orienting. However, individuals with ASD who had relatively good motor functioning showed typical levels of exogenous orienting when given a short time but decreased orienting when given a longer amount of time. These results suggest attention impairments in ASD may not be specific to social orienting and instead may represent a more general orienting impairment.

Mapping corpus callosum deficits in autism: an index of aberrant cortical connectivity

BACKGROUND

Volumetric studies have reported reductions in the size of the corpus callosum (CC) in autism, but the callosal regions contributing to this deficit have differed among studies. In this study, a computational method was used to detect and map the spatial pattern of CC abnormalities in male patients with autism.

METHODS

Twenty-four boys with autism (aged 10.0 +/- 3.3 years) and 26 control boys (aged 11.0 +/- 2.5 years) underwent a magnetic resonance imaging (MRI) scan at 3 Tesla. Total and regional areas of the CC were determined using traditional morphometric methods. Three-dimensional (3D) surface models of the CC were also created from the MRI scans. Statistical maps were created to visualize morphologic variability of the CC and to localize regions of callosal thinning in autism.

RESULTS

Traditional morphometric methods detected a significant reduction in the total callosal area and in the anterior third of the CC in patients with autism; however, 3D maps revealed significant reductions in both the splenium and genu of the CC in patients.

CONCLUSIONS

Statistical maps of the CC revealed callosal deficits in autism with greater precision than traditional morphometric methods. These abnormalities suggest aberrant connections between cortical regions, which is consistent with the hypothesis of abnormal cortical connectivity in autism.

Developmental dyspraxia is not limited to imitation in children with autism spectrum disorders

Impaired imitation of skilled gestures is commonly reported in autism. Questions, however, remain as to whether impaired imitation is associated with a more generalized deficit in performance of gestures consistent with a dyspraxia and whether the pattern of errors differs from that observed in typically developing children. To address these questions, praxis in 21 high-functioning children with autism spectrum disorders (ASD) was compared with 24 typically developing controls using a traditional approach in which performance was evaluated through detailed examination of error types. Children with ASD produced significantly fewer correct responses not only during Gesture to Imitation, but also during Gesture to Command and with Tool Use. The pattern of errors in ASD was similar to that of controls with spatial errors being most common in both groups; however, body-part-for-tool errors were more common in children with ASD, suggesting dyspraxia is not entirely attributable to motor deficits. The findings suggest that autism is associated with a generalized praxis deficit, rather than a deficit specific to imitation. In a developmental disorder such as autism, the findings may reflect abnormalities in frontal/parietal-subcortical circuits important for acquisition (i.e., learning) of sensory representations of movement and/or the motor sequence programs necessary to execute them.

Subjective Perceptual Distortions and Visual Dysfunction in Children with Autism

Case reports and sensory inventories suggest that autism involves sensory processing anomalies. Behavioral tests indicate impaired motion and normal form perception in autism. The present study used first-person accounts to investigate perceptual anomalies and related subjective to psychophysical measures. Nine high-functioning children with autism and nine typically-developing children were given a questionnaire to assess the frequency of sensory anomalies, as well as psychophysical tests of visual perception. Results indicated that children with autism experience increased perceptual anomalies, deficits in trajectory discrimination consistent with dysfunction in the cortical dorsal pathway or in cerebellar midsagittal vermis, and high spatial frequency contrast impairments consistent with dysfunctional parvocellular processing. Subjective visual hypersensitivity was significantly related to greater deficits across vision tests.

Reduced functional connectivity between V1 and inferior frontal cortex associated with visuomotor performance in autism

Some recent evidence has suggested abnormalities of the dorsal stream and possibly the mirror neuron system in autism, which may be responsible for impairments of joint attention, imitation, and secondarily for language delays. The current study investigates functional connectivity along the dorsal stream in autism, examining interregional blood oxygenation level dependent (BOLD) signal cross-correlation during visuomotor coordination. Eight high-functioning autistic men and eight handedness and age-matched controls were included. Visually prompted button presses were performed with the preferred hand. For each subject, functional connectivity was computed in terms of BOLD signal correlation with the mean time series in bilateral visual area 17. Our hypothesis of reduced dorsal stream connectivity in autism was only in part confirmed. Functional connectivity with superior parietal areas was not significantly reduced. However, the autism group showed significantly reduced connectivity with bilateral inferior frontal area 44, which is compatible with the hypothesis of mirror neuron defects in autism. More generally, our findings suggest that dorsal stream connectivity in autism may not be fully functional.

Cerebellar function in autism: functional magnetic resonance image activation during a simple motor task

BACKGROUND

The cerebellum is one of the most consistent sites of neuroanatomic abnormality in autism, yet it is still unclear how such pathology impacts cerebellar function. In normal subjects, we previously demonstrated with functional magnetic resonance imaging (fMRI) a dissociation between cerebellar regions involved in attention and those involved in a simple motor task, with motor activation localized to the anterior cerebellum ipsilateral to the moving hand. The purpose of the present investigation was to examine activation in the cerebella of autistic patients and normal control subjects performing this motor task.

METHODS

We studied eight autistic patients and eight matched normal subjects, using fMRI. An anatomic region-of-interest approach was used, allowing a detailed examination of cerebellar function.

RESULTS

Autistic individuals showed significantly increased motor activation in the ipsilateral anterior cerebellar hemisphere relative to normal subjects, in addition to atypical activation in contralateral and posterior cerebellar regions. Moreover, increased activation was correlated with the degree of cerebellar structural abnormality.

CONCLUSIONS

These findings strongly suggest dysfunction of the autistic cerebellum that is a reflection of cerebellar anatomic abnormality. This neurofunctional deficit might be a key contributor to the development of certain diagnostic features of autism (e.g., impaired communication and social interaction, restricted interests, and stereotyped behaviors).

Autism clinical trials: biological and medical issues in patient selection and treatment response

Biomedical measures are critical in the initial patient-screening and -selection phases of a clinical trial in autism and related disorders. These measures can also play an important role in the assessment and characterization of response and can provide an opportunity to study underlying etiologic and pathophysiologic processes. Thus, biomedical measures, including clinical laboratory analyses, metabolic screening, and chromosomal analysis, are used to screen for potential safety-related problems, to decrease biological and genetic heterogeneity, and to define subgroups. Neurobiological measures can be examined as possible predictors, modifiers or surrogates of therapeutic response, and adverse effects. Neurobiological research measures can also be used to study mechanisms and extent of drug action and to perform baseline and longitudinal investigations of possible pathophysiologic alterations. The potential utility and desirability of specific measures are considered and the general approach to choosing measures for incorporation is discussed.

Alterações anátomo-funcionais do sistema nervoso central no transtorno autístico: um estudo com RNM e SPECT

Apresentamos um estudo das alterações anátomo-funcionais do sistema nervoso central (SNC) de pacientes com transtorno autístico (TA), através da ressonância nuclear magnética (RNM) e da tomografia computadorizada por emissão de fóton único (SPECT). Foram estudados 24 pacientes, sendo 15 (62,5%) do sexo masculino e 9 (17,5%) do feminino, com idade média de 9 anos. Todos os pacientes foram submetidos à RNM e apenas em 19 foi realizado o SPECT. Dos pacientes que realizaram RNM, 75% apresentaram alterações anatômicas e dos que realizaram o SPECT todos apresentaram alterações funcionais. As alterações anatômicas estavam preferencialmente localizadas no corpo caloso (25%), septo pelúcido (15,63%), ventrículos cerebrais (12,55%), cerebelo (9,38%), lobo temporal (6,25%), lobo occipital (6,25%) e hipocampo (6,25%). As alterações funcionais predominaram no lobo frontal (53,13%), lobo temporal (28,13%) , lobo parietal (15,63%) e nos núcleos da base (3,13%). A presença de alterações anátomo-funcionais do SNC não são prioritárias para o diagnóstico, o qual deve ter sempre uma validação clínica.

The cerebellum and spatial ability: dissection of motor and cognitive components with a mouse model system

The cerebellum has recently been linked to spatial navigation, as indicated by the inferior performance of cerebellar mutant or cerebellar lesioned animals in the water maze. The inability to dissociate motor from cognitive deficits in the impaired water maze performance has been a confounding variable in previous studies, however. In this study, we sought to define clearly the role of the cerebellar system in spatial navigation outside of motor control by creating a mouse model of Purkinje cell loss with intact motor ability, and testing these mice in the water maze. To this end, we made aggregation chimeras between Lc/+ mice, which lose all Purkinje cells postnatally, and +/+ control mice. Lc/+ mice are ataxic and show impaired rotor-rod performance. By contrast, we show that Lc/+ left arrow over right arrow +/+ chimeras above a threshold of Purkinje cell loss show no outward signs of motor impairment and demonstrated normal rotor-rod ability. In the water maze, we found that Lc/+ mice showed impaired performance in the place, cue and platform removal tasks, whereas Lc/+ left arrow over right arrow +/+ chimeras performed similarly to controls in all tasks. We found that the impaired performance in the water maze of Lc/+ mice resulted from both motor as well as cognitive impairment that could be separated from one another by statistical means. In addition, through the analysis of individual chimeric mice, the relationships between these deficits and the total number of Purkinje cells were determined and a specific role for Purkinje cells in search strategy was identified.

Childhood autism: a circuit syndrome?

BACKGROUND

Autism is a disorder that can lead to life-long disability. Currently, the etiology of autism is unknown, and although there are treatments for some of the behavioral abnormalities, there is no cure.

REVIEW SUMMARY

While this article will review the clinical, anatomic, and pathologic features seen in autism, the primary focus will be to present a new and provocative unifying theory regarding the underlying mechanisms causing this disorder. Current research advances, some controversial, will be discussed, and a novel definition of autism as a "circuit syndrome" will be presented. The work elaborated here will tie many of the disparate findings together, based on the idea that autism arises from abnormalities of the cerebellolimbic circuitry. Some of the more alternative theories of autism, such as mercury toxicity, linkage to the measles, mumps, and rubella vaccine, and the use of secretin will be discussed. Finally, pharmacologic treatment options will be reviewed.

CONCLUSIONS

Autism is not single disorder but represents dysfunction of the cerebellolimbic circuitry that can arise from many different etiologies.

Glutamic acid decarboxylase 65 and 67 kDa proteins are reduced in autistic parietal and cerebellar cortices

BACKGROUND

A limited number of reports have demonstrated abnormalities involving the glutamate and gamma amino butyric acid systems in blood and platelets of subjects with autism. To further investigate these studies, brain levels of rate limiting enzyme, glutamic acid decarboxylase, which is responsible for normal conversion of glutamate to gamma amino butyric acid in the brain, were investigated.

METHODS

Postmortem cerebellar and parietal cortices of age (mean +/- SD for controls 23 +/- 4.2, autistic 25.2 +/- 5.2 cerebellum; controls 23.5 +/- 4.8, autistic 21.6 +/- 3.8 parietal cortex), gender and postmortem interval-matched autistic and control subjects (n = 8 control, n = 5 autism, cerebellum; n = 4 control, n = 5 autism, parietal cortex) were subjected to SDS-PAGE and western blotting. Brain levels of glutamic acid decarboxylase proteins of 65 and 67 kDa and beta-actin were determined.

RESULTS

Glutamic acid decarboxylase protein of 65 kDa was reduced by 48% and 50% in parietal and cerebellar (p <.02) areas of autistic brains versus controls respectively. By the same token, glutamic acid decarboxylase protein of 67 kDa was reduced by 61% and 51% in parietal (p <.03) and cerebellar areas of autistic brains versus controls respectively. Brain levels of beta-actin were essentially similar in both groups.

CONCLUSIONS

The observed reductions in glutamic acid decarboxylase 65 and 67 kDa levels may account for reported increases of glutamate in blood and platelets of autistic subjects. Glutamic acid decarboxylase deficiency may be due to or associated with abnormalities in levels of glutamate/gamma amino butyric acid, or transporter/receptor density in autistic brain.