Alcohol affects eye movements essential for visually guided stepping.

BACKGROUND: To understand how and why alcohol intoxication affects visually guided stepping, the eye movements and performance of 6 subjects (aged 22-35 years) were monitored as they progressed along a pathway of 18 irregularly placed stepping stones before and after consumption of an acute oral dose of alcohol.

METHODS: Horizontal eye movements were measured with infrared reflectometry; footfall on or off target was monitored via copper fabric soles stuck to subjects' footwear. Breath alcohol concentration was monitored with an Alco-Sensor III breathalyzer.

RESULTS: After alcohol loading, both locomotor and oculomotor deficits were evident. All subjects increased their step cycle duration-with prolonged stance, swing, and double support phases-and occasionally missed footfall targets. A large proportion of saccades made to fixate successive stepping stones were inaccurate and were accompanied by one or more corrective saccades. These problems with looking and stepping to footfall targets tended to occur together and were comparable to those seen previously in cerebellar patients undertaking the same task.

CONCLUSIONS: The fact that healthy subjects acutely intoxicated by alcohol show symptoms of cerebellar dysfunction suggests that alcohol acutely and adversely affects the cerebellar contribution to performance of visually guided movements.