Deficient inhibition of return in chronic but not first-episode patients with schizophrenia

Background: Inhibition of return (IOR) has been tested in patients with schizophrenia with contradictory results. Some studies indicated that patients with schizophrenia have normal levels of IOR; however, other studies reported delayed or blunted IOR. Inconsistency in findings might be due to differences across studies in relevant aspects associated with disease, such as heterogeneity of the disorder, different medications, onset and severity of the illness. The present study was to explore different patterns of IOR in antipsychotic medication free first-episode schizophrenia and chronic schizophrenia. Methods: Forty two patients with first-episode schizophrenia, 44 patients with chronic schizophrenia, and 38 healthy controls were included in the study. All subjects went through a covert orienting of attention task with seven stimulus onset asynchrony (SOA) intervals (400. ms, 500. ms, 600. ms, 700. ms, 800. ms, 1200. ms and 1500. ms). Results: Compared with healthy controls, the magnitude and onset of IOR in first-episode patients with schizophrenia were intact. However, in patients with chronic schizophrenia, there was an attenuated cuing effect especially at SOA 700. ms; in addition, there was a robust IOR until at SOAs 800. ms or above. Moreover, the illness duration and the number of psychotic episodes were significantly correlated with the validity effect at SOAs 400. ms and 600. ms. Conclusion: Our study suggests that deficient IOR presents in chronic but not in first-episode patients with schizophrenia. IOR deficit in schizophrenia may begin during the course of illness and deteriorate over the course of illness. Our findings are consistent with the neurodegenerative model of schizophrenia.