2002 Abstract

THE TIME COURSE OF COMPENSATION FOR ANTICIPATORY SMOOTH EYE MOVEMENTS IN A TARGET LOCALIZATION TASK

G. Blohm^1,2; M. Crommelinck^2*; M. Missal²; P. Lefèvre^1,2

1. CESAME, Univ. catholique de Louvain, Louvain-la-Neuve, Belgium

2. Lab. Neurophysiol., Univ. catholique de Louvain, Brussels, Belgium

A target briefly flashed during smooth pursuit eye movements evokes localization saccades that do not compensate for the ongoing smooth eye movement (McKenzie and Lisberger 1986). In this study, we use a flash localization task to investigate the compensation mechanism of anticipatory smooth eye movements.
After a fixation (800ms) and a gap period (300ms), 7 human subjects were required to pursue a moving target (40deg/s). Repetitive presentation of this stimulus led to robust anticipatory smooth eye movements (10deg/s). In 30% of the trials, instead of the ramp, a peripheral 10ms flash appeared +/-15deg around the current eye position. Subjects were instructed to make saccades to the remembered location of the flash in darkness.
We found that, on average, the smooth eye movement lasted until 540ms after the flash. The capture of the target typically required 2 to 4 saccades because the smooth eye displacement (SED) perturbed the orientation to the flash. The compensation of this perturbation was a dynamical process that, on average, started only ~300ms after the flash. At the end of the orientation process (on average 849 ms after the flash), the oculomotor system compensated for 70% of the SED (43%-92% across subjects).
We conclude that the compensation of the SED must be based on an efference copy of the smooth anticipatory motor command that updates the spatial localization of the flashed target. In addition, there is a 300ms delay in this compensation that includes the time necessary to program and execute saccades but also for the integration of anticipatory motion.
Supported by: FNRS, SSTC and FSR (Belgium)

Citation:
G. Blohm, M. Crommelinck, M. Missal, P. Lefèvre. THE TIME COURSE OF COMPENSATION FOR ANTICIPATORY SMOOTH EYE MOVEMENTS IN A TARGET LOCALIZATION TASK Program No. 364.3. 2002 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2002. Online.