Three-dimensional variability in cortical sulci between the patient and control groups. C, central sulcus; L, lateral sulcus. Courtesy of Jennifer G. Levitt, University of California, Los Angeles.

Neuroanatomical abnormalities that accompany autism include widespread deviations in cortical surface anatomy, a new study published in Cerebral Cortex indicates. Examining the differences between autistic and normal subjects in the pattern of cortical gyri and sulci could provide clues to the developmental pathology of the disorder.

Previous studies have described limbic and cerebellar pathology in autism, and evidence is accumulating for an involvement of neocortical regions. However, there is no clear consensus on the neural basis of this condition. In an attempt to home in on affected areas of the cortex, Levitt and co-workers carried out the first three-dimensional mapping of cortical sulcal patterns in autistic disorder.

Using MRI (magnetic resonance imaging) scans of the brains of autistic and normal children, Levitt et al. generated a high-resolution model of the cortex for each subject, and built average sulcal maps for the two groups. A comparison of these maps revealed displacements of several major sulci in patients with autism, primarily in frontal and temporal regions. For example, anterior and superior shifting of the superior frontal sulcus was detected bilaterally, and the left and right superior temporal sulci, the left inferior frontal gyrus and the right lateral sulcus were found to be shifted anteriorly in the patient group.

In view of developmental data that point to a posterior shifting with age of the inferior frontal gyrus, Levitt et al. speculate that anterior displacements in autism could reflect delayed or incomplete maturation, at least in the frontal lobe. Further studies will be required to identify the root of sulcal displacements in autism, and to establish whether such changes represent causes or consequences of the disorder.