Alcohol and visually guided saccades: gap effect and predictability of target location

Rationale: Alcohol is known to affect most parameters of visually guided sa ccades, but it is unclear whether intoxicated subjects are able to utilize temporal or spatial pre-cues to compensate for their alcohol-related slowin g of saccades. Objectives: We examined the effects of both temporal and spa tial predictability on gain, latency, and peak velocity in sober and intoxi cated subjects, e.g. by employing a temporal gap condition. Methods: Saccad es were recorded with subjects once sober and once intoxicated (0.8 g ethan ol per kg body weight). Unpredictable and predictable target locations alte rnated in both the classical (no gap) and temporal gap condition (extinctio n of fixation point 200 ms before target onset). Results: The gain was only slightly affected by alcohol, but increased for predictable target locatio ns. After alcohol consumption, latencies increased, even in the gap conditi on and for predictable targets. However, intoxicated subjects took relative ly more benefit from the gap than sober subjects did. In addition, they sho wed a "pretrial effect", i.e. their latencies depended on the condition for the previous saccade. For predictable target locations, latencies decrease d and peak velocities increased both in sober rind intoxicated subjects. Th us, intoxicated subjects were able to utilize both the spatial predictabili ty and the temporal gap to speed up their saccades. Conclusions: These resu lts lead to suggest that as far as the saccadic system is concerned alcohol predominantly affects the function of the superior colliculus (SC) and/or the oculomotor regions in the brain stem, either directly or indirectly. On the other hand, cortical areas assumed to mediate prediction and the gap e ffect seem to be less affected by alcohol intoxication.