The purpose of this study was to investigate the connectivity from the negative motor area and to elucidate the mechanism of negative motor phenomena. We report the results of cortico-cortical evoked potentials (CCEPs) by electrical stimulation of the primary motor area (MI), primary sensory area (SI), primary (PNMA) and supplementary negative motor area (SNMA) in eight epilepsy patients who underwent intracranial electrode placement. Alternating 1-Hz electrical stimuli were delivered to MI (six patients), SI (five), PNMA (six) and SNMA (two). CCEPs were recorded by averaging electrocorticograms time-locked to the stimuli. Stimulation of MI, SI and PNMA induced CCEP responses in the premotor area (PM), pre- and postcentral gyri, posterior parietal cortex and the temporo-parietal junction. Upon SNMA stimulation, CCEP responses were detected in the prefrontal cortex, PM, pre- and postcentral gyri, supplementary motor area (SMA) and preSMA. Compared with stimulation of SI and MI, PNMA stimulation revealed a broader distribution of CCEP responses in the frontal or parietal association cortex, indicating the importance of the fronto-parietal network associated with a higher level of motor control. We concluded that these connections are associated with motor control and that the negative motor phenomenon results from impairment of the organization of movements.
Keywords: Cortical stimulation; Cortico-cortical evoked potential; Electrocorticogram; Negative motor area; Sensorimotor area.
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