Neurocorrelates of Thought Disorder in Schizophrenia: An Event-related Fmri Study of Semantic Processing.

Abstract:
We aimed to identify specific cognitive impairments in Thought Disorder (TD) and their neurocorrelates. In an event-related FMRI study, semantic processing (SP) was examined in 11 schizophrenic patients with TD, 8 schizophrenic patients without TD and 10 healthy controls, by measuring the effect of sentence constraint (SC) in a semantic decision task. Reaction times (RT) and error scores (ES) were measured on-line. Factorial analysis of the behavioural data showed robust main effects of SC for both RT and ES. Post-hoc analysis showed that RT was significantly different in each of the 3 groups. TD patients made significantly more errors than controls, whereas NON-TD patients were not different from the other groups. Higher constraint sentences were processed more efficiently in all groups (facilitation effect-FE). Post-hoc analysis of FE only showed differences between the 2 patient groups. TD patients had a smaller FE. Positive TD score across all subjects (n=29) was significantly correlated with the number of errors in the task. FE was associated with activation in the left inferior frontal cortex, with a distinct pattern in each group. Our findings suggest that TD is associated with specific impairments in sentence processing and with distinct activity in the left inferior frontal cortex.