Investigating inhibition deficit in schizophrenia using task-modulated brain networks.

Schizophrenia subjects have shown deficits of inhibition in conditions such as a stop signal task. The stop signal response time (SSRT) is consistently longer compared with healthy controls, and is accompanied by decreased brain activations in the right inferior frontal gyrus. However, as to how the response inhibition function is supported by distributed brain networks, and whether such networks are altered in schizophrenia are largely unknown. We analyzed functional MRI data of a stop signal task from 44 schizophrenia patients and 44 matched controls, and performed whole-brain psychophysiological interaction analysis to obtain task-modulated connectivity (TMC). Support vector classification was used to classify schizophrenia, and support vector regression was applied to explore the relationships between TMC and behavior indexes, such as SSRT. Schizophrenia group showed a decreased TMC pattern which mainly involved the fronto-parietal network, and increased TMC related to the sensorimotor network. Moreover, TMC could only successfully predict SSRT in the control group, further suggesting an abnormal task modulation in schizophrenia. Lastly, we compared the classification and prediction results from different types of measures, i.e., TMC, task-independent connectivity (TIC), task-functional connectivity (TFC), and resting-state functional connectivity (RSFC). TMC performed better in the behavior predictions, while TIC performed better in the classification. TFC and RSFC had similar classification and prediction performance as TIC. The current results provide new insights into the altered brain functional integration underlying response inhibition in schizophrenia, and suggest that different types of connectivity measures are complementary for a better understanding of brain networks and their alterations.