Abstract
Human psychophysical studies proposed that the control system of convergence eye movement included both feedback and open-loop controllers. The neuronal basis of this hypothesis was sought in the lateral suprasylvian cortex (LS), one of the extrastriate visual cortex of cat where microstimulation evoked convergence eye movement. Cats (n=5) were trained by a set of stimuli: an alarm signal (blinks of an LED, and buzz sound) preceding the target movement by 4 sec. After training, open-loop convergence (convergence eye movement elicited after buzz sound but before the target onset) was found in 60% of trials. Then GABAA agonist, muscimol (4μg/μl,0.5μl x 3) injected locally into their LS. Amplitudes of ordinary convergence were significantly reduced by muscimol injection, while neither those nor probabilities occurence of open-loop convergence were changed significantly. We also employed buzzer only or LED only alarm signal instead of visuo-audio combined alarm signal. Cat (n=2) could learn to evoke open-loop convergence as well as training with combined alarm signal. These results suggest that GABAA inhibition plays a different influence on the neuronal circuits in the LS, controlling the ordinary and open-loop convergence in response to multimodal alarm signal. [Jpn J Physiol 55 Suppl:S175 (2005)]
