The autism brain imaging data exchange: towards a large-scale evaluation of the intrinsic brain architecture in autism.

Autism spectrum disorders (ASDs) represent a formidable challenge for psychiatry and neuroscience because of their high prevalence, lifelong nature, complexity and substantial heterogeneity. Facing these obstacles requires large-scale multidisciplinary efforts. Although the field of genetics has pioneered data sharing for these reasons, neuroimaging had not kept pace. In response, we introduce the Autism Brain Imaging Data Exchange (ABIDE)-a grassroots consortium aggregating and openly sharing 1112 existing resting-state functional magnetic resonance imaging (R-fMRI) data sets with corresponding structural MRI and phenotypic information from 539 individuals with ASDs and 573 age-matched typical controls (TCs; 7-64 years) (http://fcon_1000.projects.nitrc.org/indi/abide/). Here, we present this resource and demonstrate its suitability for advancing knowledge of ASD neurobiology based on analyses of 360 male subjects with ASDs and 403 male age-matched TCs. We focused on whole-brain intrinsic functional connectivity and also survey a range of voxel-wise measures of intrinsic functional brain architecture. Whole-brain analyses reconciled seemingly disparate themes of both hypo- and hyperconnectivity in the ASD literature; both were detected, although hypoconnectivity dominated, particularly for corticocortical and interhemispheric functional connectivity. Exploratory analyses using an array of regional metrics of intrinsic brain function converged on common loci of dysfunction in ASDs (mid- and posterior insula and posterior cingulate cortex), and highlighted less commonly explored regions such as the thalamus. The survey of the ABIDE R-fMRI data sets provides unprecedented demonstrations of both replication and novel discovery. By pooling multiple international data sets, ABIDE is expected to accelerate the pace of discovery setting the stage for the next generation of ASD studies.

Mechanisms of postnatal neurobiological development: implications for human development.

This review focuses on the postnatal neuroanatomical changes that arise during the first years of human life. Development is characterized by 2 major organizational periods. The first period begins at conception and includes the major histogenetic events such as neurulation, proliferation, migration, and differentiation. It has been proposed that these events may be controlled by genetic and epigenetic events, which give rise to neural structures that are amenable to external influence. The second period is a time of reorganization in the human cortex. These events occur during gestation and continue postnatally, possibly through the 2nd decade of life. This stage is characterized by dendritic and axonal growth, synapse production, neuronal and synaptic pruning, and changes in neurotransmitter sensitivity. Although the initiation of these events is influenced by endogenous signals, further neural maturation is primarily influenced by exogenous signals. To illustrate both the progressive and regressive events during the postnatal period, we use examples from the development of the human cortex.

Prenatal neurobiological development: molecular mechanisms and anatomical change.

During prenatal development, the central nervous system is transformed from a thin layer of unspecified tissue into a complex system that can process information and organize actions. There are 8 general mechanisms that permit this transformation: neural induction, neurulation, proliferation, migration, axonal outgrowth, synaptogenesis, differentiation, and apoptosis. These processes as well as the anatomical changes they cause are described. Future research with humans, such as in utero MRI as well as behavioral and electrophysiological testing of infants following specific prenatal perturbations, is suggested to link the findings from molecular approaches to developmental neuropsychology.

Functional neuroanatomy of spatial working memory in children.

Functional magnetic resonance imaging (fMRI) was used to examine spatial working memory in 8- to 11-year-old children tested under three conditions. In the visual condition, children were asked to examine the location of a dot on a screen. In the motor condition, children were instructed to push a button that corresponded to the location of a dot presented on a screen. In the memory condition, children were asked to remember the location of a dot presented 1 or 2 trials previously. Subtracting the activation of the motor condition from the memory condition revealed activity in the dorsal aspects of the prefrontal cortex and in the posterior parietal and anterior cingulate cortex. These findings were also obtained in the analysis of the memory minus visual conditions except that motor cortex activation was also observed. These findings parallel those reported in comparable studies of adults and suggest that fMRI may be a useful means of examining function-structure relations in developmental populations.