No evidence for preferential involvement of medial temporal lobe structures in high-functioning autism

Background. Autism is a neurodevelopmental disorder associated with slight increases in brain volume. There has been some suggestion that medial temporal lobe structures may be preferentially involved in this disorder, although results have not always been consistent. Here, we investigate amygdala and hippocampus volumes in medication-naive subjects with high-functioning autism. Method. Whole-brain magnetic resonance imaging scans were acquired from 42 patients and 42 closely matched, healthy control subjects. Results. Amygdala volume did not differ significantly between patients and controls. A significant increase in hippocampal volume was proportional to an increase in overall brain volume. Conclusions. These results argue against preferential involvement of medial temporal lobe structures in autism, at least in high-functioning medication-naive individuals.