The effect of distraction on smooth pursuit eye movements: comparison of normal subjects with schizophrenic patients

Abstract

Smooth pursuit eye movements (SPEM) made in response to 15°/s and 30°/s targets were studied in schizophrenic patients (DSM III-R and ICD 10 criteria) and normal controls using infrared photo-electric techniques. Tracking of the target was carried out without competing stimuli and while acoustic (click-noises, 80 dB, delivered binaural through headphones with 5 Hz) and visual (Manhattan at night background) distractions were presented. As previously described, gain values of SPEM of schizophrenic patients were significantly reduced when compared to those of the control group. Smooth pursuit in both groups was impaired when tracking the target against a background as well as when an auditory distraction was present. In all distraction paradigms, gain was reduced to a similar extent in the schizophrenic group and normal controls. In addition, schizophrenic patients performed as well as normal controls on tests of sustained attention (continuous performance test, CPT). In conclusion, these results suggest that smooth pursuit dysfunction in schizophrenia may not be due to an increase in distractibility or a general deficit in sustained attention.