Responses in the motor cortex time-locked to the sensory stimuli conditioning target-reaching in the cat.
Single unit activity in the forelimb area of the sensorimotor cortex (area 4gamma) was investigated in unrestrained cats during target-reaching with the contralateral limb to a morsel of food. An acoustic stimulus (tone) was used as a cue for movement initiation. A total of 159 cells which modulated their activity in relation to the task were investigated and the responses were analysed with respect to the onset of the stimulus and the movement, respectively. Eighteen per cent of the recorded cells showed responses to the conditional signal with a latency ranging from 20 to 100 ms. The response pattern of these neurones always had a second component coupled to the movement. Correlation between timing of neuronal responses and movement onset revealed that the short latency responses were strongly time-locked to the sensory cue but not to the movement. A Go/No-go discrimination task in which the animal was required to initiate or withhold the movement depending on the frequency of the tone showed that the short latency responses were selective to the cue relevant for initiation of the movement and were substantially decreased or absent when a No-go cue was presented. It was also shown that these neurones did not respond to an indifferent cue, but acquired short-latency responses when it was repeatedly rewarded. The results indicate that some motor cortical neurones are recruited in the early stages of sensory-to-motor transformation related to the processing of the conditional signal. It is suggested that these cells may be involved in identifying a cue as relevant for initiation of a goal-directed movement.
Perfiliev
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Department of Physiology, Göteborg University. sergei.perfiliev@physiol.gu.se
D000818:Animals; D002415:Cats; D003213:Conditioning, Psychological / Q000502:physiology*; D004594:Electrophysiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*