TARGET LOCALIZATION DURING ANTICIPATORY SMOOTH EYE MOVEMENTS G. Blohm1; M. Missal2*; P. Lefèvre1 1. CESAME and Lab. Neurophysiol., Universite catholique de Louvain, Louvain-la-Neuve, Belgium 2. Smith-Kettlewell Eye Res. Inst., San Francisco, CA, USA Expectation of future target motion leads to anticipatory smooth eye movements that are reinforced by repetitive and predictable visual stimuli (Kowler et al., 1984). We investigated the influence of anticipatory smooth eye movements on saccades in a target localization task. Anticipatory smooth eye movements (mean 12deg/s) were obtained with a repetitive ramp target stimulus (40deg/s, 300ms gap). In 30% of trials, a peripheral target appeared ±15deg around the eye position for 10ms (transient condition) or 1000ms (sustained condition) and remained stationary. The human subjects typically made 2-3 saccades to the target and we measured the amplitude of the first saccade and the final eye position (after the last saccade). Firstly, we compared the main sequence of saccades during anticipatory smooth eye movements with control saccades and found that there is a linear addition of saccadic and smooth motor commands. Secondly, the amplitude of the first saccade was only correlated with position error at the flash offset (transient condition), whereas it was correlated with both position error and smooth eye movement velocity (or retinal slip) in the sustained condition. Thirdly, in the transient condition, final eye position was accurate because it accounted for the smooth eye displacement. We conclude that, in the transient condition, the oculomotor system probably uses the memorized position of the target. However, the poor precision of the first saccade indicates that the smooth movement was not compensated for at the time that saccade was planned, but only later during the orientation process. Supported by: FNRS, SSTC and FSR (Belgium)