Object versus spatial visual mental imagery in patients with schizophrenia

Objective: Recent research has revealed a larger impairment of object perceptual discrimination than of spatial perceptual discrimination in patients with schizophrenia. It has been suggested that mental imagery may share processing systems with perception. We investigated whether patients with schizophrenia would show greater impairment regarding object imagery than spatial imagery. Methods: Forty-four patients with schizophrenia and 20 healthy control subjects were tested on a task of object visual mental imagery and on a task of spatial visual mental imagery. Both tasks included a condition in which no imagery was needed for adequate performance, but which was in other respects identical to the imagery condition. This allowed us to adjust for nonspecific differences in individual performance. Results: The results revealed a significant difference between patients and controls on the object imagery task (F-1,F-63 = 11.8, p = 0.001) but not on the spatial imagery task (F-1,F-63 = 0.14, p = 0.71). To test for a differential effect, we conducted a 2 (patients v. controls) x 2 (object task v. spatial task) analysis of variance. The interaction term was statistically significant (F-1,F-62 = 5.2, p = 0.026). Conclusions: Our findings suggest a differential dysfunction of systems mediating object and spatial visual mental imagery in schizophrenia.