Bilateral Somatosensory Responses of Pallidal Neurons in Humans Studied with Microrecording

Abstract

In the previous IBAGS Meeting and on other occasions, we reported several behaviours of neuronal activities of the globus pallidus (GP) in relation to active and passive limb movement, especially in the internal segment of GP (GPi), in Parkinson’s disease during the course of stereotactic pallidotomy (Ohye, 1995; Ohye et al., 1994, 1996). It was revealed that although most of them were related to active movement of limbs, often activated bilaterally, some of them responded to passive movement. Interested in such somatosensory responses of the GPi neuron to the natural somatosensory stimuli, we had one parkinsonian case of thalamotomy with microrecording. In this particular case, the recording electrode incidentally passed through a part of GPi prior to come in the thalamic ventralis intermedius (Vim) nucleus, the somatosensory responses were found both in GPi and Vim by the similar natural stimuli. In this case, at the level of GPi, we found an isolated spike(s) responding to bilateral passive movement of elbow, wrist and ankle joint, and also other response to tapping on the contralateral forearm. Further advancing the recording electrode into the Vim nucleus, we found again the kinesthetic response as usually the case, and a response to tapping on the similar contralateral part of forearm. Therefore, taking this rare opportunity, we tried later to compare some aspects of these sensory responses in GPi and Vim by the response pattern and latency, our special attention being focused on bilateral response and the tap response.