Abnormal timing of visual feedback processing in young adults with schizophrenia

Background: Recent studies have shown that schizophrenia is characterized by visual perceptual deficits, especially in the ability to integrate stimulus details into a global percept. Also, several studies have found amplitude attenuation of the visual P1 component of the event-related brain potential (ERP), probably indicating impaired visual feedforward processing in schizophrenia. However, there is little knowledge on the role of feedbackward processing in this group. This question is of importance, as recent studies indicate that feedback processing is critical in stimulus integration. Methods: In the present study we tested whether there is evidence for atypical recurrent processing in a group of 14 young adults with recent-onset schizophrenia (mean age 21.7 years, mean TIQ 92.7) and 17 age and IQ matched control subjects, all males. To achieve this aim, we used a texture segregation task and measured ERP activity concurrently. Results: We found normal amplitudes, but longer latencies of activity related to feedbackward processing in the schizophrenia group. In addition, we found enhanced occipito-temporal activity around 160 ms that is probably the reflection of increased detail processing. Discussion: We show for the first time evidence for abnormal timing in feedback activity related to visual perception in subjects with schizophrenia. It is hypothesized that this latency effect is the functional reflection of abnormal structural connectivity in this group, and might result in increased processing of stimulus detail.