Saccadic eye movements in tracking, fixation, and rest in schizophrenic and normal subjects

Horizontal eye movements were recorded electrooculographically during two different eye fixation tasks, during an eyes-closed waking state, and during eye tracking on a sinusoidally moving target in 16 chronic schizophrenics and in 12 normal subjects. The relationship between saccadic eye movements during tracking and in the other experimental situations was investigated. The intensities of eye fixation were successively decreased from Experiment I (eye fixation on a stationary target) through Experiment II (eye fixation on an imagined spot in the dark) to Experiment III (eyes closed in the dark, no cue for eye fixation), in that order. The frequency of saccades increased as the intensities of fixation decreased from Experiment I to Experiment III in both schizophrenic and normal groups. It was demonstrated that the frequency of saccades was higher in schizophrenics than in normal subjects in all of the experimental conditions. Some correlations were found between the increased frequency of saccades seen during eye tracking and the similar increases seen in eyes-fixated or eyes-closed states in schizophrenic subjects. It is suggested that the increased saccades seen during eye tracking and in other experimental conditions in schizophrenics are related to a deficit of nonvoluntary attention, due to a failure of an inhibitory mechanism.