抄録
To examine functional roles of primary motor cortex (M1) in the control of primate locomotion, we recorded activity of M1 neurons during quadrupedal locomotion in a freely-moving monkey using a custom-made electromotive micromanipulator. To date, 20 neurons recorded in M1 trunk/hindlimb region were analyzed. During locomotion, almost all neurons (19/20) exhibited task-related modulation. Of these, 18 neurons modulated their discharge phasically time-locked to the step cycle and the rest modulated tonically. Mean firing frequency of task-related neurons during locomotion (15.6±1.7 spikes/s) was higher than that during standing (5.6±1.5 spikes/s). For neurons showing phasic modulation, the peak activity occurred at widely different times during the step cycle in different cells. Thirteen cells peaked once (mono-phasic) and 5 peaked twice per step (bi-phasic). Frequency of the peak activity ranged from 16.2 to 98.4 spikes/s (mean 40.2±4.6 spikes/s). Of the task-related neurons, 8 were tested for the effects of treadmill speed on their discharge patterns and all increased their discharge frequency as the speed increased. Four out of them clearly showed linear relationship between mean and/or peak discharge frequency and the speed. All these results suggest the possibility that output from M1 in macaque monkeys directly and/or indirectly acts on spinal circuitries generating a basic pattern of rhythmic activity during simple locomotion in a manner different from that in subprimates. [J Physiol Sci. 2007;57 Suppl:S158]
