Impaired saccadic adaptation in schizophrenic patients with high neurological soft sign scores

Many motor and cognitive alterations in schizophrenia suggest the involvement of the cerebellum. Neurological soft signs (NSS) are frequent in patients with schizophrenia and reductions in cerebellar volume have been associated with high NSS scores. In this study, we tested saccadic adaptation, a well-characterised oculomotor paradigm involving the cerebellum, in schizophrenic patients with high NSS scores. We used a backward reactive saccade adaptation task, in which the target moves intrasaccadically toward initial fixation, causing the saccade to complete with an endpoint error. A group of 12 schizophrenic patients (SZ; DSM IV) with high NSS scores was compared to a group of 13 matched healthy controls (HC). SZ patients showed lower saccade adaptation than HC. Nevertheless, the time course of adaptation was similar for both groups. This study indicates cerebellar dysfunction in patients with schizophrenia and high NSS scores. Part of the deficit seen in schizophrenia may have a cerebellar origin.