Positron emission tomography studies of the somatosensory system in man.

Activity in the human somatosensory system was measured by regional cerebral blood flow (rCBF) and by the binding of [11C]nimodipine to L-type Ca2+ channels. These physiological variables were considered to be indicators of neuronal and synaptic activity. In general, structures in the cerebellum, thalamus and the somatosensory cortices which increased their rCBF in response to somatosensory stimulation also showed high binding of [11C]nimodipine. Voluntary movements carried out largely independently of sensory feedback, natural somatosensory stimulation and passive stimulation of the somatosensory system all activate the somatosensory system. However, it is possible by subtraction techniques to show that differences in activations between these conditions exist in the cerebellum and the somatosensory cortices in the anterior part of the parietal lobe.