Differential effects of cigarette smoking on performance of a smooth pursuit and a saccadic eye movement task in schizophrenia

Schizophrenic patients demonstrate a number of physiological defects including smooth pursuit, eye movement dysfunction (SPEM), involuntary reflexive saccades to a prepotent stimulus during saccadie tasks, and increased response to the second of two identical auditory stimuli, the P50 evoked potential response. The P50 deficit appears to be mediated by the alpha7 nicotinic cholinergic receptor. This study compared the failure of saccadic inhibition demonstrated in two different eye movement tasks, to see if either deficit, like the P50 inhibitory deficit, was normalized by nicotine. Fifteen smoking schizophrenic patients and 15 smoking non-schizophrenic subjects were compared on the percentage of premature saccades in a memory-guided saccadic task, and the frequency of intrusive small and large anticipatory saccades during a SPEM task. No significant effects or interactions of smoking, group or time on premature or large anticipatory saccades were detected. However, leading saccades demonstrated a significant group X time X smoking interaction. Leading saccades may therefore be a measure of cholinergic inactivity and thus part of the alpha7 nicotinic receptor dysfunction observed in schizophrenia. However, premature saccades and large anticipatory saccades, although measures of inhibitory dysfunction in schizophrenia, appear to be unrelated to the nicotinic system. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.