Symmetric abnormalities in sulcal patterning in schizophrenia

Abstract

To compare the morphology of the cerebral cortex and its characteristic pattern of gyri and sulci in individuals with and without schizophrenia, T1-weighted magnetic resonance scans were collected, along with clinical and cognitive information, from 33 individuals with schizophrenia and 30 healthy individuals group-matched for age, gender, race and parental socioeconomic status. Sulcal depth was measured across the entire cerebral cortex by reconstructing surfaces of cortical mid-thickness (layer 4) in each hemisphere and registering them to the human PALS cortical atlas. Group differences in sulcal depth were tested using methods for cluster size analysis and interhemispheric symmetry analysis. A significant group difference was found bilaterally in the parietal operculum, where the average sulcal depth was shallower in individuals with schizophrenia. In addition, group differences in sulcal depth showed significant bilateral symmetry across much of the occipital, parietal, and temporal cortices. In individuals with schizophrenia, sulcal depth in the left hemisphere was correlated with the severity of impaired performance on tests of working memory and executive function.

Figure 1

Lateral (first and second rows) and medial (third and fourth rows) views of the average fiducial cortical surfaces of schizophrenia subjects (second and fourth rows) and healthy individuals (first and third rows). Arrows point to the dorsal ramus of the Sylvian Fissure, where the two surfaces differ in shape. These and other subtle differences were studied by sulcal depth analyses in subsequent figures.

Figure 2

Lateral and medial views of t-statistic maps of group differences in sulcal depth, displayed on very inflated lateral views and on inflated lateral and medial views of the PALS atlas surface (left and middle columns). Control-deeper regions are indicated in yellow and red; schizophrenia-deeper regions are shown in green and blue. Far right panels display interhemispheric correlation maps on the very inflated lateral view and inflated medial view. See text for statistical results.

Figure 3

A significant group difference in sulcal depth observed as a cluster of nodes in the parietal operculum. This cluster is displayed on the average fiducial cortical surface of the healthy individuals (top row); the average fiducial cortical surface of the schizophrenia subjects (second row); and the inflated PALS-B12 surface (third row). The significant sulcal depth abnormality is shaded blue; the associated gyral region is shaded yellow. In the bottom panels, average fiducial cortical contours from the subjects with schizophrenia subjects (red) and healthy individuals (black) are shown superimposed on the 711-2Y atlas target volume. The average fiducial surface is visibly more lateral (closer to the cerebral hull) near the lip of the Sylvian fissure (yellow arrow) on the left and in the insula on both sides (green arrow). The depth difference was highly significant along a bilateral swath of operculum (black arrows).

Figure 4

Scattergrams of correlations between sulcal depth within the cluster of nodes where a significant group difference was found and measures of neurocognitive function (panel a – executive function; panel b – working memory) and psychopathology (panel c – thought disorganization; panel d – negative symptoms). Less negative depth values (i.e, more shallow sulcal depth) were more disparate from the average depth value of the healthy comparison group. The correlations noted in panels c and d were found post-hoc, and the statistical significance of these correlations did not survive correction for multiple comparisons.