Abnormal microglial-neuronal spatial organization in the dorsolateral prefrontal cortex in autism

Microglial activation and alterations in neuron number have been reported in autism. However, it is unknown whether microglial activation in the disorder includes a neuron-directed microglial response that might reflect neuronal dysfunction, or instead indicates a non-directed, pro-activation brain environment. To address this question, we examined microglial and neuronal organization in the dorsolateral prefrontal cortex, a region of pronounced early brain overgrowth in autism, via spatial pattern analysis of 13 male postmortem autism subjects and 9 controls. We report that microglia are more frequently present near neurons in the autism cases at a distance interval of 25 μm, as well as 75 and 100 μm. Many interactions are observed between near-distance microglia and neurons that appear to involve encirclement of the neurons by microglial processes. Analysis of a young subject subgroup preliminarily suggests that this alteration may be present from an early age in autism. We additionally observed that neuron-neuron clustering, although normal in cases with autism as a whole, increases with advancing age in autism, suggesting a gradual loss of normal neuronal organization in the disorder. Microglia-microglia organization is normal in autism at all ages, indicating that aberrantly close microglia-neuron association in the disorder is not a result of altered microglial distribution. Our findings confirm that at least some microglial activation in the dorsolateral prefrontal cortex in autism is associated with a neuron-specific reaction, and suggest that neuronal organization may degrade later in life in the disorder.

Age-dependent brain gene expression and copy number anomalies in autism suggest distinct pathological processes at young versus mature ages

Autism is a highly heritable neurodevelopmental disorder, yet the genetic underpinnings of the disorder are largely unknown. Aberrant brain overgrowth is a well-replicated observation in the autism literature; but association, linkage, and expression studies have not identified genetic factors that explain this trajectory. Few studies have had sufficient statistical power to investigate whole-genome gene expression and genotypic variation in the autistic brain, especially in regions that display the greatest growth abnormality. Previous functional genomic studies have identified possible alterations in transcript levels of genes related to neurodevelopment and immune function. Thus, there is a need for genetic studies involving key brain regions to replicate these findings and solidify the role of particular functional pathways in autism pathogenesis. We therefore sought to identify abnormal brain gene expression patterns via whole-genome analysis of mRNA levels and copy number variations (CNVs) in autistic and control postmortem brain samples. We focused on prefrontal cortex tissue where excess neuron numbers and cortical overgrowth are pronounced in the majority of autism cases. We found evidence for dysregulation in pathways governing cell number, cortical patterning, and differentiation in young autistic prefrontal cortex. In contrast, adult autistic prefrontal cortex showed dysregulation of signaling and repair pathways. Genes regulating cell cycle also exhibited autism-specific CNVs in DNA derived from prefrontal cortex, and these genes were significantly associated with autism in genome-wide association study datasets. Our results suggest that CNVs and age-dependent gene expression changes in autism may reflect distinct pathological processes in the developing versus the mature autistic prefrontal cortex. Our results raise the hypothesis that genetic dysregulation in the developing brain leads to abnormal regional patterning, excess prefrontal neurons, cortical overgrowth, and neural dysfunction in autism.

Autism is a disorder characterized by aberrant social, communication, and restricted and repetitive behaviors. It develops clinically in the first years of life. Toddlers and children with autism often exhibit early brain enlargement and excess neuron numbers in the prefrontal cortex. Adults with autism generally do not display enlargement but instead may have a smaller brain size. Thus, we investigated DNA and mRNA patterns in prefrontal cortex from young versus adult postmortem individuals with autism to identify age-related gene expression differences as well as possible genetic correlates of abnormal brain enlargement, excess neuron numbers, and abnormal functioning in this disorder. We found abnormalities in genetic pathways governing cell number, neurodevelopment, and cortical lateralization in autism. We also found that the key pathways associated with autism are different between younger and older autistic individuals. These findings suggest that dysregulated gene pathways in the early stages of neurodevelopment could lead to later behavioral and cognitive deficits associated with autism.

Preprocessing and Quality Control Strategies for Illumina DASL Assay-Based Brain Gene Expression Studies with Semi-Degraded Samples

Available statistical preprocessing or quality control analysis tools for gene expression microarray datasets are known to greatly affect downstream data analysis, especially when degraded samples, unique tissue samples, or novel expression assays are used. It is therefore important to assess the validity and impact of the assumptions built in to preprocessing schemes for a dataset. We developed and assessed a data preprocessing strategy for use with the Illumina DASL-based gene expression assay with partially degraded postmortem prefrontal cortex samples. The samples were obtained from individuals with autism as part of an investigation of the pathogenic factors contributing to autism. Using statistical analysis methods and metrics such as those associated with multivariate distance matrix regression and mean inter-array correlation, we developed a DASL-based assay gene expression preprocessing pipeline to accommodate and detect problems with microarray-based gene expression values obtained with degraded brain samples. Key steps in the pipeline included outlier exclusion, data transformation and normalization, and batch effect and covariate corrections. Our goal was to produce a clean dataset for subsequent downstream differential expression analysis. We ultimately settled on available transformation and normalization algorithms in the R/Bioconductor package lumi based on an assessment of their use in various combinations. A log2-transformed, quantile-normalized, and batch and seizure-corrected procedure was likely the most appropriate for our data. We empirically tested different components of our proposed preprocessing strategy and believe that our results suggest that a preprocessing strategy that effectively identifies outliers, normalizes the data, and corrects for batch effects can be applied to all studies, even those pursued with degraded samples.

A failure of left temporal cortex to specialize for language is an early emerging and fundamental property of autism

Failure to develop normal language comprehension is an early warning sign of autism, but the neural mechanisms underlying this signature deficit are unknown. This is because of an almost complete absence of functional studies of the autistic brain during early development. Using functional magnetic resonance imaging, we previously observed a trend for abnormally lateralized temporal responses to language (i.e. greater activation on the right, rather than the expected left) in a small sample (n = 12) of sleeping 2-3 year olds with autism in contrast to typically developing children, a finding also reported in autistic adults and adolescents. It was unclear, however, if findings of atypical laterality would be observed in a larger sample, and at even earlier ages in autism, such as around the first birthday. Answers to these questions would provide the foundation for understanding how neurofunctional defects of autism unfold, and provide a foundation for studies using patterns of brain activation as a functional early biomarker of autism. To begin to examine these issues, a prospective, cross-sectional design was used in which brain activity was measured in a large sample of toddlers (n = 80) during the presentation of a bedtime story during natural sleep. Forty toddlers with autism spectrum disorder and 40 typically developing toddlers ranging in age between 12-48 months participated. Any toddler with autism who participated in the imaging experiment prior to final diagnosis was tracked and diagnoses confirmed at a later age. Results indicated that at-risk toddlers later diagnosed as autistic display deficient left hemisphere response to speech sounds and have abnormally right-lateralized temporal cortex response to language; this defect worsens with age, becoming most severe in autistic 3- and 4-year-olds. Typically developing children show opposite developmental trends with a tendency towards greater temporal cortex response with increasing age and maintenance of left-lateralized activation with age. We have now demonstrated lateralized abnormalities of temporal cortex processing of language in autism across two separate samples, including a large sample of young infants who later are diagnosed with autism, suggesting that this pattern may reflect a fundamental early neural developmental pathology in autism.

Neuron number and size in prefrontal cortex of children with autism

CONTEXT

Autism often involves early brain overgrowth, including the prefrontal cortex (PFC). Although prefrontal abnormality has been theorized to underlie some autistic symptoms, the cellular defects that cause abnormal overgrowth remain unknown.

OBJECTIVE

To investigate whether early brain overgrowth in children with autism involves excess neuron numbers in the PFC. DESIGN, SETTING, AND CASES: Postmortem prefrontal tissue from 7 autistic and 6 control male children aged 2 to 16 years was examined by expert anatomists who were blinded to diagnostic status. Number and size of neurons were quantified using stereological methods within the dorsolateral (DL-PFC) and mesial (M-PFC) subdivisions of the PFC. Cases were from the eastern and southeastern United States and died between 2000 and 2006.

MAIN OUTCOME MEASURES

Mean neuron number and size in the DL-PFC and M-PFC were compared between autistic and control postmortem cases. Correlations of neuron number with deviation in brain weight from normative values for age were also performed.

RESULTS

Children with autism had 67% more neurons in the PFC (mean, 1.94 billion; 95% CI, 1.57-2.31) compared with control children (1.16 billion; 95% CI, 0.90-1.42; P = .002), including 79% more in DL-PFC (1.57 billion; 95% CI, 1.20-1.94 in autism cases vs 0.88 billion; 95% CI, 0.66-1.10 in controls; P = .003) and 29% more in M-PFC (0.36 billion; 95% CI, 0.33-0.40 in autism cases vs 0.28 billion; 95% CI, 0.23-0.34 in controls; P = .009). Brain weight in the autistic cases differed from normative mean weight for age by a mean of 17.6% (95% CI, 10.2%-25.0%; P = .001), while brains in controls differed by a mean of 0.2% (95% CI, -8.7% to 9.1%; P = .96). Plots of counts by weight showed autistic children had both greater total prefrontal neuron counts and brain weight for age than control children.

CONCLUSION

In this small preliminary study, brain overgrowth in males with autism involved an abnormal excess number of neurons in the PFC.

Genome-wide expression assay comparison across frozen and fixed postmortem brain tissue samples

Background

Gene expression assays have been shown to yield high quality genome-wide data from partially degraded RNA samples. However, these methods have not yet been applied to postmortem human brain tissue, despite their potential to overcome poor RNA quality and other technical limitations inherent in many assays. We compared cDNA-mediated annealing, selection, and ligation (DASL)- and in vitro transcription (IVT)-based genome-wide expression profiling assays on RNA samples from artificially degraded reference pools, frozen brain tissue, and formalin-fixed brain tissue.

Results

The DASL-based platform produced expression results of greater reliability than the IVT-based platform in artificially degraded reference brain RNA and RNA from frozen tissue-based samples. Although data associated with a small sample of formalin-fixed RNA samples were poor when obtained from both assays, the DASL-based platform exhibited greater reliability in a subset of probes and samples.

Conclusions

Our results suggest that the DASL-based gene expression-profiling platform may confer some advantages on mRNA assays of the brain over traditional IVT-based methods. We ultimately consider the implications of these results on investigations of neuropsychiatric disorders.

Disrupted neural synchronization in toddlers with autism

Autism is often described as a disorder of neural synchronization. However, it is unknown how early in development synchronization abnormalities emerge and whether they are related to the development of early autistic behavioral symptoms. Here, we show that disrupted synchronization is evident in the spontaneous cortical activity of naturally sleeping toddlers with autism, but not in toddlers with language delay or typical development. Toddlers with autism exhibited significantly weaker interhemispheric synchronization (i.e., weak "functional connectivity" across the two hemispheres) in putative language areas. The strength of synchronization was positively correlated with verbal ability and negatively correlated with autism severity, and it enabled identification of the majority of autistic toddlers (72%) with high accuracy (84%). Disrupted cortical synchronization, therefore, appears to be a notable characteristic of autism neurophysiology that is evident at very early stages of autism development.

Brain growth across the life span in autism: age-specific changes in anatomical pathology

Autism is marked by overgrowth of the brain at the earliest ages but not at older ages when decreases in structural volumes and neuron numbers are observed instead. This has led to the theory of age-specific anatomic abnormalities in autism. Here we report age-related changes in brain size in autistic and typical subjects from 12 months to 50 years of age based on analyses of 586 longitudinal and cross-sectional MRI scans. This dataset is several times larger than the largest autism study to date. Results demonstrate early brain overgrowth during infancy and the toddler years in autistic boys and girls, followed by an accelerated rate of decline in size and perhaps degeneration from adolescence to late middle age in this disorder. We theorize that underlying these age-specific changes in anatomic abnormalities in autism, there may also be age-specific changes in gene expression, molecular, synaptic, cellular, and circuit abnormalities. A peak age for detecting and studying the earliest fundamental biological underpinnings of autism is prenatal life and the first three postnatal years. Studies of the older autistic brain may not address original causes but are essential to discovering how best to help the older aging autistic person. Lastly, the theory of age-specific anatomic abnormalities in autism has broad implications for a wide range of work on the disorder including the design, validation, and interpretation of animal model, lymphocyte gene expression, brain gene expression, and genotype/CNV-anatomic phenotype studies.

Maternal transmission of a rare GABRB3 signal peptide variant is associated with autism

Maternal 15q11-q13 duplication is the most common copy number variant in autism, accounting for ∼1-3% of cases. The 15q11-q13 region is subject to epigenetic regulation, and genomic copy number losses and gains cause genomic disorders in a parent-of-origin-specific manner. One 15q11-q13 locus encodes the GABA(A) receptor β3 subunit gene (GABRB3), which has been implicated by several studies in both autism and absence epilepsy, and the co-morbidity of epilepsy in autism is well established. We report that maternal transmission of a GABRB3 signal peptide variant (P11S), previously implicated in childhood absence epilepsy, is associated with autism. An analysis of wild-type and mutant β3 subunit-containing α1β3γ2 or α3β3γ2 GABA(A) receptors shows reduced whole-cell current and decreased β3 subunit protein on the cell surface due to impaired intracellular β3 subunit processing. We thus provide the first evidence of an association between a specific GABA(A) receptor defect and autism, direct evidence that this defect causes synaptic dysfunction that is autism relevant and the first maternal risk effect in the 15q11-q13 autism duplication region that is linked to a coding variant.

Amygdala enlargement in toddlers with autism related to severity of social and communication impairments

BACKGROUND

Autism is a heterogeneous neurodevelopmental disorder of unknown etiology. The amygdala has long been a site of intense interest in the search for neuropathology in autism, given its role in emotional and social behavior. An interesting hypothesis has emerged that the amygdala undergoes an abnormal developmental trajectory with a period of early overgrowth in autism; however this finding has not been well established at young ages nor analyzed with boys and girls independently.

METHODS

We measured amygdala volumes on magnetic resonance imaging scans from 89 toddlers at 1-5 years of age (mean = 3 years). Each child returned at approximately 5 years of age for final clinical evaluation.

RESULTS

Toddlers who later received a confirmed autism diagnosis (32 boys, 9 girls) had a larger right (p < .01) and left (p < .05) amygdala compared with typically developing toddlers (28 boys, 11 girls) with and without covarying for total cerebral volume. Amygdala size in toddlers with autism spectrum disorder correlated with the severity of their social and communication impairments as measured on the Autism Diagnostic Interview and Vineland scale. Strikingly, girls differed more robustly from typical in amygdala volume, whereas boys accounted for the significant relationship of amygdala size with severity of clinical impairment.

CONCLUSIONS

This study provides evidence that the amygdala is enlarged in young children with autism; the overgrowth must begin before 3 years of age and is associated with the severity of clinical impairments. However, neuroanatomic phenotypic profiles differ between males and females, which critically affects future studies on the genetics and etiology of autism.

Family-Based Association Testing of OCD-associated SNPs of SLC1A1 in an autism sample

Reports identified the neuronal glutamate transporter gene, SLC1A1 (OMIM 133550, chromosome 9p24), as a positional and functional candidate gene for obsessive-compulsive disorder (OCD). The presence of obsessions and compulsions similar to OCD in autism, the identification of this region in a genome-wide linkage analysis of individuals with autism spectrum disorders (ASDs), and the hypothesized role of glutamate in ASDs make SLC1A1 a candidate gene for ASD as well. To test for association between SLC1A1 and autism, we typed three single nucleotide polymorphisms (SNPs, rs301430, rs301979, rs301434) previously associated with OCD in 86 strictly defined trios with autism. Family-Based Association Tests (FBAT) with additive and recessive models were used to check for association. Additionally, an rs301430-rs301979 haplotype identified for OCD was investigated. FBAT revealed nominally significant association between autism and one SNP under a recessive model. The G allele of rs301979 was undertransmitted (equivalent to overtransmission of the C allele under a dominant model) to individuals with autism (Z=-2.47, P=0.01). The G allele was also undertransmitted in the T-G haplotype under the recessive model (Z=-2.41, P=0.02). Both findings were also observed in the male-only sample. However, they did not withstand correction for multiple comparisons.

Deviant functional magnetic resonance imaging patterns of brain activity to speech in 2-3-year-old children with autism spectrum disorder

BACKGROUND

A failure to develop normal language is one of the most common first signs that a toddler might be at risk for autism. Currently the neural bases underlying this failure to develop language are unknown.

METHODS

In this study, functional magnetic resonance imaging (fMRI) was used to identify the brain regions involved in speech perception in 12 2-3-year-old children with autism spectrum disorder (ASD) during natural sleep. We also recorded fMRI data from two typically developing control groups: a mental age-matched (MA) (n = 11) and a chronological age-matched (CA) (n = 12) group. During fMRI data acquisition, forward and backward speech stimuli were presented with intervening periods of no sound presentation.

RESULTS

Direct statistical comparison between groups revealed significant differences in regions recruited to process speech. In comparison with their MA-matched control subjects, the ASD group showed reduced activity in an extended network of brain regions, which are recruited in typical early language acquisition. In comparison with their CA-matched control subjects, ASD participants showed greater activation primarily within right and medial frontal regions. Laterality analyses revealed a trend toward greater recruitment of right hemisphere regions in the ASD group and left hemisphere regions in the CA group during the forward speech condition. Furthermore, correlation analyses revealed a significant positive relationship between right hemisphere frontal and temporal activity to forward speech and receptive language skill.

CONCLUSIONS

These findings suggest that at 2-3 years, children with ASD might be on a deviant developmental trajectory characterized by a greater recruitment of right hemisphere regions during speech perception.

Functional abnormalities of the default network during self- and other-reflection in autism

Recent studies of autism have identified functional abnormalities of the default network during a passive resting state. Since the default network is also typically engaged during social, emotional and introspective processing, dysfunction of this network may underlie some of the difficulties individuals with autism exhibit in these broad domains. In the present experiment, we attempted to further delineate the nature of default network abnormality in autism using experimentally constrained social and introspective tasks. Thirteen autism and 12 control participants were scanned while making true/false judgments for various statements about themselves (SELF condition) or a close other person (OTHER), and pertaining to either psychological personality traits (INTERNAL) or observable characteristics and behaviors (EXTERNAL). In the ventral medial prefrontal cortex/ventral anterior cingulate cortex, activity was reduced in the autism group across all judgment conditions and also during a resting condition, suggestive of task-independent dysfunction of this region. In other default network regions, overall levels of activity were not different between groups. Furthermore, in several of these regions, we found group by condition interactions only for INTERNAL/EXTERNAL judgments, and not SELF/OTHER judgments, suggestive of task-specific dysfunction. Overall, these results provide a more detailed view of default network functionality and abnormality in autism.

Functional neuroimaging of speech perception during a pivotal period in language acquisition

A pivotal period in the development of language occurs in the second year of life, when language comprehension undergoes rapid acceleration. However, the brain bases of these advances remain speculative as there is currently no functional magnetic resonance imaging (fMRI) data from healthy, typically developing toddlers at this age. We investigated the neural basis of speech comprehension in this critical age period by measuring fMRI activity during passive speech comprehension in 10 toddlers (mean +/- SD; 21 +/- 4 mo) and 10 3-year-old children (39 +/- 3 mo) during natural sleep. During sleep, the children were presented passages of forward and backward speech in 20-second blocks separated by 20-second periods of no sound presentation. Toddlers produced significantly greater activation in frontal, occipital, and cerebellar regions than 3-year-old children in response to forward speech. Our results suggest that rapid language acquisition during the second year of life may require the utilization of frontal, cerebellar, and occipital regions in addition to classical superior temporal language areas. These findings are consistent with the interactive specialization hypothesis, which proposes that cognitive abilities develop from the interaction of brain regions that include and extend beyond those used in the adult brain.

fMRI during natural sleep as a method to study brain function during early childhood

Many techniques to study early functional brain development lack the whole-brain spatial resolution that is available with fMRI. We utilized a relatively novel method in which fMRI data were collected from children during natural sleep. Stimulus-evoked responses to auditory and visual stimuli as well as stimulus-independent functional networks were examined in typically developing 2-4-year-old children. Reliable fMRI data were collected from 13 children during presentation of auditory stimuli (tones, vocal sounds, and nonvocal sounds) in a block design. Twelve children were presented with visual flashing lights at 2.5 Hz. When analyses combined all three types of auditory stimulus conditions as compared to rest, activation included bilateral superior temporal gyri/sulci (STG/S) and right cerebellum. Direct comparisons between conditions revealed significantly greater responses to nonvocal sounds and tones than to vocal sounds in a number of brain regions including superior temporal gyrus/sulcus, medial frontal cortex and right lateral cerebellum. The response to visual stimuli was localized to occipital cortex. Furthermore, stimulus-independent functional connectivity MRI analyses (fcMRI) revealed functional connectivity between STG and other temporal regions (including contralateral STG) and medial and lateral prefrontal regions. Functional connectivity with an occipital seed was localized to occipital and parietal cortex. In sum, 2-4 year olds showed a differential fMRI response both between stimulus modalities and between stimuli in the auditory modality. Furthermore, superior temporal regions showed functional connectivity with numerous higher-order regions during sleep. We conclude that the use of sleep fMRI may be a valuable tool for examining functional brain organization in young children.

No reduction of spindle neuron number in frontoinsular cortex in autism

It has been suggested that spindle neurons, an evolutionarily unique type of neuron, might be involved in higher-order social, emotional, and cognitive functions. As such, it was hypothesized that these neurons may be particularly important to the pathophysiology of autism, a disease characterized in part by disruption of higher-order social and emotional processing. Therefore, we conducted the first stereological investigation of the number of spindle neurons in autism, using the optical fractionator technique. Our results did not provide evidence of a reduction in spindle neuron number in frontoinsular cortex in autism. However, this study provides the first quantitative stereological data on spindle neuron number in autism. Future postmortem studies with larger sample sizes will likely be critical in elucidating the spared and defective neural systems underlying the autistic phenotype.

N-acetyl aspartate in autism spectrum disorders: regional effects and relationship to fMRI activation

Rapid progress in our understanding of macrostructural abnormalities in autism spectrum disorders (ASD) has occurred in recent years. However, the relationship between the integrity of neural tissue and neural function has not been previously investigated. Single-voxel proton magnetic resonance spectroscopy and functional magnetic resonance imaging of an executive functioning task was obtained in 13 high functioning adolescents and adults with ASD and 13 age-matched controls. The ASD group showed significant reductions in N-acetyl aspartate (NAA) in all brain regions combined and a specific reduction in left frontal cortex compared to controls. Regression analyses revealed a significant group interaction effect between frontal and cerebellar NAA. In addition, a significant positive semi-partial correlation between left frontal lobe NAA and frontal lobe functional activation was found in the ASD group. These findings suggest that widespread neuronal dysfunction is present in high functioning individuals with ASD. Hypothesized developmental links between frontal and cerebellar vermis neural abnormalities were supported, in that impaired neuronal functioning in the vermis was associated with impaired neuronal functioning in the frontal lobes in the ASD group. Furthermore, this study provided the first direct evidence of the relationship between abnormal functional activation in prefrontal cortex and neuronal dysfunction in ASD.

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.

MRI neuroanatomy in young girls with autism: a preliminary study

OBJECTIVE

To test the hypothesis that young girls and boys with autism exhibit different profiles of neuroanatomical abnormality relative to each other and relative to typically developing children.

METHOD

Structural magnetic resonance imaging was used to measure gray and white matter volumes (whole cerebrum, cerebral lobes, and cerebellum) and total brain volume in nine girls (ages 2.29-5.16) and 27 boys (ages 1.96-5.33) with autism and 14 girls (ages 2.17-5.71) and 13 boys (ages 1.72-5.50) with typical development. Structure size and the relationship between size and age were examined. Diagnostic and cognitive outcome data were obtained after the children reached 4 to 5 years of age.

RESULTS

Girls with autism exhibited nearly every size-related abnormality exhibited by boys with autism. Furthermore, additional sites of abnormality were observed in girls, including enlargement in temporal white and gray matter volumes and reduction in cerebellar gray matter volume. Significant correlations were observed between age and white matter volumes (e.g., cerebral white matter rs = 0.950) for the girls with autism, whereas no significant age-structure size relationships were observed for the boys with autism.

CONCLUSIONS

Results suggest sex differences in etiological factors and the biological time course of the disorder.

Offering to share: how to put heads together in autism neuroimaging

Data sharing in autism neuroimaging presents scientific, technical, and social obstacles. We outline the desiderata for a data-sharing scheme that combines imaging with other measures of phenotype and with genetics, defines requirements for comparability of derived data and recommendations for raw data, outlines a core protocol including multispectral structural and diffusion-tensor imaging and optional extensions, provides for the collection of prospective, confound-free normative data, and extends sharing and collaborative development not only to data but to the analytical tools and methods applied to these data. A theme in these requirements is the need to preserve creative approaches and risk-taking within individual laboratories at the same time as common standards are provided for these laboratories to build on.

Atypical [corrected] participation of visual cortex during word processing in autism: an fMRI study of semantic decision

Language delay and impairment are salient features of autism. More specifically, there is evidence of atypical semantic organization in autism, but the functional brain correlates are not well understood. The current study used functional MRI to examine activation associated with semantic category decision. Ten high-functioning men with autism spectrum disorder and 10 healthy control subjects matched for gender, handedness, age, and nonverbal IQ were studied. Participants indicated via button press response whether visually presented words belonged to a target category (tools, colors, feelings). The control condition required target letter detection in unpronounceable letter strings. Significant activation for semantic decision in the left inferior frontal gyrus (Brodmann areas 44 and 45) was found in the control group. Corresponding activation in the autism group was more limited, with smaller clusters in left inferior frontal areas 45 and 47. Autistic participants, however, showed significantly greater activation compared to controls in extrastriate visual cortex bilaterally (areas 18 and 19), which correlated with greater number of errors on the semantic task. Our findings suggest an important role of perceptual components (possibly visual imagery) during semantic decision, consistent with previous evidence of atypical lexicosemantic performance in autism. In the context of similar findings from younger typically developing children, our results suggest an immature pattern associated with inefficient processing, presumably due to atypical experiential embedding of word acquisition in autism.

Reduced minicolumns in the frontal cortex of patients with autism

Cell minicolumns were shown to be narrower in frontal regions in brains of autistic patients compared with controls. This was not found in primary visual cortex. Within the frontal cortex, dorsal and orbital regions displayed the greatest differences while the mesial region showed the least change. We also found that minicolumns in the brain of a 3-year-old autistic child were indistinguishable from those of the autistic adult in two of three frontal regions, in contrast to the control brains. This may have been due to the small size of the columns in the adult autistic brain rather than to an accelerated development. The presence of narrower minicolumns supports the theory that there is an abnormal increase in the number of ontogenetic column units produced in some regions of the autistic brain during corticoneurogenesis.