Semantic fluency deficits and reduced grey matter before transition to psychosis: a voxelwise correlational analysis

Early identification of subjects with an increased risk of psychosis is necessary to develop interventions to delay or prevent disease onset. We recently reported that decreased semantic verbal fluency performance in ultra high risk (UHR) subjects predicts the development of psychosis (Becker et al., 2010). The present study investigated whether semantic and verbal fluency scores correlate with grey matter density in UHR subjects. Thirty-seven UHR subjects underwent structural MRI scanning and verbal fluency assessment after which they were followed up for 2 years. Using voxel-based morphometry, we investigated whether grey matter density correlated with verbal fluency scores in 10 UHR subjects who developed psychosis during follow-up and 27 UHR subjects who did not develop psychosis. In UHR subjects developing psychosis, lower semantic fluency scores correlated significantly with reduced grey matter density in the right superior and middle temporal gyrus, the right insula, and the left anterior cingulate cortex. This study shows that a correlation between semantic fluency performance and grey matter density in task-related areas can differentiate between UHR subjects who subsequently will develop psychosis and those who will not. Combining these two measures could improve psychosis prediction in UHR subjects.