Confirmation for a delayed inhibition of return by systematic sampling in schizophrenia

Inhibition of return (IOR) is a phenomenon thought to reflect a mechanism to protect the organism from redirecting attention to previously scanned insignificant locations. A number of studies reported altered IOR in schizophrenia patients with a reduction of its amplitude. However, incomplete sampling of stimulus onset asynchronies (SOAs) makes data on IOR time course incomplete. We examined 14 stabilized young patients with recent onset schizophrenia and 16 healthy controls matched for gender, age, and years of education. Schizophrenia patients (13 males, 1 female) had a mean age of 26.3+/-5.8 years and a mean number of years of study of 9.6+/-3.6. Their illness had a mean duration of 147 weeks. Patients displayed moderate overall slow reaction times (387 ms) in comparison with controls (322 ms). Onset of IOR was found to be delayed in schizophrenia patients appearing between 700 and 800 ms following the cue onset while it appeared at 300 ms in controls. In patients, IOR was constant up to 1100 ms; however, its amplitude was weak with an average of 6 ms. Validity effects (overall and at each SOA value) were uncorrelated to age, years of study, duration of illness, or total or subscale scores on the Positive and Negative Syndrome Scale.