Impaired action control in schizophrenia: the role of volitional saccade initiation.

Schizophrenia patients show prefrontal cortex dysfunctions of neurodevelopmental origin, but the cognitive implications of these dysfunctions are not yet understood. This study used experimental variations of oculomotor tasks to evaluate the relative roles of volitional action initiation and the inhibition of reflexive behavior. Thirty schizophrenia patients and 30 control participants performed standard prosaccades (SP), standard antisaccades (SA), delayed prosaccades (DP), and delayed antisaccades (DA). The delayed tasks allowed separating the inhibition of erroneous prosaccades and the initiation of volitional saccades, which coincide in the SA task. Arrow-cued (AC) saccades were used to evaluate initiation without any inhibitory component. Erroneous prosaccades were less frequent in the delayed tasks than in the SA task. Error rates were generally larger in schizophrenia patients than in control participants, but the deficit was smaller in the delayed tasks than in the SA task. Correct saccade latencies of schizophrenia patients were normal in the SP task, but not on conditions of volitional saccade initiation (all other tasks). Volitional saccade latencies were positively correlated with error rates in the schizophrenia group. These results confirm that schizophrenia patients have a specific deficit in initiating volitional action, which may also contribute to the increased error rates.