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Motor-related functional subdivisions of human lateral premotor cortex: epicortical recording in conditional
Riki Matsumoto1, Akio Ikeda, Shinji Ohara
1Human Brain Research Center, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo, 606-8507, Kyoto, Japan
Objective:
To clarify the functional subdivisions of the human lateral premotor cortex (PM) in the visuomotor control.
Methods:
Event-related potentials (ERPs) were epicortically recorded from PM in 5 epilepsy patients. S1-Go/NoGo choice delayed reaction time (RT), S1-warned S2-Go simple RT and control fixation paradigms were compared using paired visual stimuli (S1, S2).
Results:
Signal-related activity peaked at 176-194 ms after S1 in the ventrorostral PM (PMvr) in all 3 paradigms, indicating its role in signal perception. Early set-related activity was recorded with its peak <810 ms after S1 in the dorsorostral PM (PMdr) and was larger in the choice than in the simple RT paradigm, suggesting its role in signal selection. Its cognitive component was recorded as surface-positive transients at PMdr, while its motoric aspect, seen as negative transients, extended to the caudal PM. Late sustained set-related activity was observed in preparation for hand movement in the caudal PM at the hand and face positive motor areas. After presentation of S2, movement-related activity was observed at the hand sensorimotor area for motor execution, following the signal-related activity at PMvr.
Conclusions:
The present ERP study suggests the temporally sequential representation of predominantly 'cognitive' function in the rostral PM and 'motor' function in the caudal PM.
Significance:
The rostrocaudal cognitive-motor gradient was demonstrated in the lateral premotor cortex in humans by means of an epicortical ERP approach.