The relation between antisaccade errors, fixation stability and prosaccade errors in schizophrenia

Whether antisaccade errors in schizophrenia are due to defects in implementing saccadic inhibition or difficulty in generating novel responses is uncertain. We investigated whether antisaccade errors were related to difficulty in inhibiting saccades when subjects were asked to maintain steady fixation, a situation that does not require a novel response. We examined the ocular motor data of 15 schizophrenia subjects and 16 healthy subjects. We assessed fixation in two situations: first, during the period before target onset during each saccadic trial, and second, during fixation trials that were interspersed with saccadic trials. We found that schizophrenia subjects had higher rates of fixation losses than control subjects in both situations. Second, both in healthy and schizophrenia subjects, antisaccade error rate was positively correlated with the frequency of fixation losses in the preparatory period of saccadic trials, but not with the frequency of fixation losses during fixation trials. Third, antisaccade errors were more likely to occur in trials with unstable fixation than in trials with stable fixation. Last, antisaccade error rate was also correlated with prosaccade error rate. We conclude that antisaccade errors are related to difficulties with implementing inhibitory control in the saccadic system. However, the finding of a correlation between the error rates for antisaccades and prosaccades suggests that this is not specifically concerned with inhibiting the automatic prosaccade, but a more general deficit in implementing goal-oriented behavior.