| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2004: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
In contrast to the well-known involvement of cerebral cortex, the functions of spinal cord neurons for controlling voluntary movements has never been examined. To address this issue, we recorded activities of spinal neurons from a monkey performing a precision grip task and wrist flexion and extension tasks. We implanted the nerve cuff electrodes to the superficial radial (SR) and median (M) nerves at the level of forearm and an oval chamber implanted over vertebrae in two monkey. Spinal cord neurons [C6-T1] were identified by applying electrical shock to each nerve cuffs. Extracellular recordings from 110 spinal neurons were obtained through a chamber implanted over the lower cervical spinal cord (C6-T1). 64/110 neurons (58%) showed movement-related modulations of firing rate (FR ; p<0.05) during the grip (34/64,53%), hold (43/64,67%), and/or release period (31/64,48%). For some neurons showing the static firing pattern during the hold period (6/19,32%), the mean FR was correlated wit
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h the magnitude of gripping force during this period (p<0.05). Some FR modulations during the grip period showed a significant correlation between their peak FR and the peak rate-of-change of gripping force (6/30,20%; p<0.05). Spike-triggered averaging of electromyographic (EMG) signals from hand muscles revealed that 3 of 8 tested neurons (38%) have a post-spike facilitation in one or more muscles and, therefore, identified as premotor interneurons (PreM-INs). All of these PreM-INs showed movement-related modulations during the grip- and hold period and the onset of the modulation preceded the onset of EMG burst of their target muscles by 20±106(SD) ms. The mean FR during hold period was positively correlated with the mean EMG activity of their target muscles (p<0.05). In some neurons (25/110,23%), the modulation of FRs started before (715±353ms) the appearance of the visual targets signaling the monkey to start gripping. Equivalent recording have also made during wrist flexion and extension task, and their result is now analyzing. Overall, we conclude that the method we develop to record and identify spinal neuron is capable to be applied in awake, behaving monkey. Less
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