Two modes of central gaze fixation maintenance and oculomotor distractibility in schizophrenics

Distractibility defined operationally as a lack of stability in central-gaze fixation has been studied using two different oculomotor tasks that require the suppression of reflexive saccades triggered by the sudden appearance of novel, peripheral visual stimuli. In the first task ('Instructed'), maintenance of central gaze fixation was based on verbal instruction, whereas, in the second task ('Non-Instructed'), it was based upon a foveating mechanism maintained by sensory stimulation during the performance of a categorization task. 15 schizophrenics and 20 healthy control subjects were tested in the two tasks. Schizophrenics made more saccades than control subjects in the Instructed task only. The Instructed task saccade rate correlated significantly with scores on neuropsychological tests sensitive to frontal lobe dysfunction. Because the type of deficit observed in schizophrenics resembled that previously seen in patients with unilateral lesions of the ventrolateral convexity of frontal lobe, frontal lobe dysfunction was proposed as underlying the high task-specific distractibility of schizophrenics.