Neuronal activity of oculomotor cortical areas during sequential saccade task

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We compared the effects of intracortical microstimulation (ICMS) of the lateral wall of the intraparietal sulcus (LIP) with those of ICMS of the frontal eye field (FEF) on monkeys performing oculomotor tasks. Our results suggests that, shortly before initiation of voluntary saccades, a dynamic process occurs in the LIP so that the reference point for calculating the saccade target shifts from the fixation point to the target of a voluntary saccade. Such predictive updating of reference points seems useful for immediate reprogramming of upcoming saccades that can occur in rapid succession.We explored the ventral part of the premotor cortex (PMV) and the dorsal part of the premotor area (PMd) with intracortical microstimulation (ICMS) while monkeys performed a visual fixation task, to see whether the PM is involved in oculomotor control. ICMS evoked saccades from a small-restricted region in the PMV, without evoking movements in the limbs, neck, or body. We also found saccades were evoked from the rostral part (PMdr), whereas in the caudal part (PMdc) forelimb or body movements were the predominant positive effects.These findings suggested that saccadic eye movements were controlled by multiple oculomotor areas. Furthermore, each area can be distinguished from other areas based on effects of ICMS and neuronal activities during oculomotor tasks.