Neuronal activity preceding directional and nondirectional cues in the premotor cortex of rhesus monkeys.
Pre-cue activity, the neuronal modulation that precedes a predictable stimulus, was studied in the premotor cortex of three rhesus monkeys. In one condition, a directional cue dictated the timing and target of a forelimb movement. In another condition, a nondirectional cue provided identical timing information but did not indicate the target. Of 501 task-related neurons recorded in premotor cortex, 168 showed pre-cue activity. The onset time of pre-cue activity varied markedly from trial to trial and cell to cell, ranging from trial initiation to 4.8 sec later. No pre-cue activity reflected the direction of limb movement; thus, the data argue against the hypothesis that pre-cue activity reflects preparation for specific limb movements. A small number of cells showed greater pre-cue activity before directional than before nondirectional cues, and this difference may reflect anticipation of the cue's directional information. However, the vast majority (84%) of neurons lacked such differences. We therefore hypothesize that most pre-cue activity reflects or contributes to a facet of behavior common to the two conditions: anticipation of the time and/or nature of events.
Vaadia
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Laboratory of Neurophysiology, National Institute of Mental Health, Poolesville, Maryland 20837.
Kurata
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Wise
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D000818:Animals; D001931:Brain Mapping; D003463:Cues; D005552:Forelimb / Q000294:innervation; D005625:Frontal Lobe / Q000502:physiology; D008253:Macaca mulatta; D009044:Motor Cortex / Q000502:physiology*; D009132:Muscles / Q000294:innervation; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology