Cortical activation during somatosensory stimulation and voluntary movement in man: A regional cerebral blood flow study

Abstract

Regional cerebral blood flow (rCBF) changes were measured by a 254-channel dynamic gamma camera in 7 human subjects during peripheral nerve stimulation and during voluntary movement. Normal somatosensory evoked potentials (SEPs) were recorded simultaneously from the scalp over the primary cortical projection areas when contralateral digital or ipsi- or contralateral median nerve was stimulated electrically. The voluntary movement was an imitation of the passive thumb twitch which occurred during median nerve stimulation. Focal rCBF increases were observed during nerve stimulation and during voluntary movement in the same area within the middle part of the contralateral central region. This area of cortical activation was localized over the sensory and motor projection areas of the hand and thus involved both the precentral and postcentral gyri. During voluntary movement additional focal increases of rCBF were observed in the upper premotor region, including the supplementary motor area. This area was also activated during contralateral median nerve stimulation. Focal rCBF increases were also observed during contralateral nerve stimulation in the lower central region, just anterior to the primary auditory cortex. This area appears to correspond to the second sensory area (SII) in man. During ipsilateral median nerve stimulation no focal increases of rCBF were observed and also no SEPs were recorded within the analysis time of 200 msec. It is concluded that activation of the contralateral primary cortical sensory and motor areas, as well as the SII area, as shown by focal rCBF increases, reflects generation of the early components of the SEP. The activation of the upper premotor region during median nerve stimulation and during voluntary movement is more likely to be involved in the generation of the later components of the evoked potential and the electrical activity preceding voluntary movement. The same extents of the focal rCBF activation in the contralateral sensorimotor area during peripheral nerve stimulation and during voluntary movements confirm that the precentral gyrus is involved in sensory perception and, similarly, that sensory feedback to the post-central gyrus is a normal component of the execution of voluntary movement.