Preliminary study on subcortical slow potentials related to the readiness potential in monkey.

Two female rhesus monkeys with cortical and subcortical DC-electrodes were studied during self-paced operant responding to determine the feasibility of mapping the intracerebral distribution of readiness potentials (RP). These potentials reflect preparatory aspects of motor activation and may be useful indicators of subcortical areas involved in preparatory set. The monkeys had learned to execute the task appropriately after 17 and 28 sessions respectively; one monkey's performance was very stable, and the other's erratic. However, relatively comparable RPs were recorded from the monkeys when recordings from sessions involving good performance were considered. RPs of relatively large amplitude appeared in electrodes positioned near the substantia nigra and pretectal/collicular region; smaller responses were observed in cortex and midbrain reticulum and, in one monkey, the caudate nucleus. These findings indicate the feasibility of such studies and suggest that, like the contingent negative variation, RPs occur in many subcortical regions.