Search

Background Increased total brain volume (TBV) has been reported for children with autism spectrum disorder (ASD) but studies in older ASD subjects have been contradictory. Similarly, studies of corpus callosum (CC) area in ASD differ with regard to inclusion criteria, age, and IQ. Methods In the present study, TBV, gray matter (GM), and white matter (WM) volume as well as midsagittal CC area were compared between 15 medication-naive, high-functioning adolescent and young adult ASD subjects and 15 healthy control individuals, and correlations with visuomotor coordination and imitation abilities were explored. In addition, computational surface-based methods were implemented to encode callosal thickness at high spatial resolution. Results Total brain volume, GM, and WM were increased and CC area was decreased in ASD subjects, a finding that was predominantly due to ASD subjects with lower IQ. Positive correlations of IQ with volume measures were observed only in control subjects. Autism spectrum disorder subjects showed reduced thickness in the posterior part of the CC. White matter volume showed a trend for negative correlation with dynamic balance and imitation abilities across groups. Conclusions This study replicates previous structural magnetic resonance imaging (MRI) findings in ASD, emphasizes the role of IQ differences, and adds some evidence for functional implications of structural findings.

Background Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have revealed structural abnormalities in the brains of affected individuals. One of the most replicated alterations is a significantly smaller corpus callosum (CC), for which conflicting reports exist with respect to the affected callosal segments. Methods We applied novel surface-based geometrical modeling methods to establish the presence, direction, and exact location of callosal alterations in ADHD at high spatial resolution. For this purpose, we calculated the thickness of the CC at 100 equidistant midsagittal points in an age-matched male sample of 19 individuals with ADHD and 19 typically developing control subjects. Results In close agreement with many prior observations, the CC was shown to be significantly thinner in ADHD subjects in anterior and, particularly, posterior callosal sections. Covarying for intelligence did not significantly alter the observed ADHD effects. However, group differences were no longer present in anterior sections when covarying for brain volume and after excluding ADHD subjects comorbid for oppositional defiant disorder. Conclusions Decreased callosal thickness may be associated with fewer fibers or a decrease in the myelination of fibers connecting the parietal and prefrontal cortices. This might affect interhemispheric communication channels that are necessary to sustain attention or motor control, thus contributing to symptoms of hyperactivity and impulsivity, or inattention, observed in ADHD. Future studies are necessary to determine whether callosal abnormalities reflect maturational delays or persist into adulthood.

Background Abnormalities in the patterns and frequency of cortical folding might help identify temporal and regionally specific disturbances in normal neurodevelopmental processes that occur in association with schizophrenia. Few studies, however, have investigated gyral complexity in schizophrenia. Methods High-resolution magnetic resonance images were used to examine differences in gyral complexity, measured three-dimensionally in five separate hemispheric regions covering the entire cortical surface, in patients with first-episode schizophrenia ( n = 50) compared with demographically matched healthy comparison subjects ( n = 50). The modulating effects of gender and hemisphere were also examined. Results Significant increases in cortical folding were observed in the right superior frontal cortex in male schizophrenic patients compared with male control subjects, but not between female diagnostic groups. Significant main effects of hemisphere were found in frontal, parietal, and occipital regions in directions complementary to cerebral torques. Conclusions Results support previous findings of right frontal hypergyria in male schizophrenic patients and suggest that these abnormalities predate illness onset and are of neurodevelopmental origin. Therefore, in schizophrenia, sexually dimorphic developmental processes and differences in hemispheric connectivity, which have been shown to influence the organization and/or frequency of cortical folding, seem to be disturbed during gyral formation in utero.