Dynamic changes in area 1 somatosensory cortex during transient sensory deprivation: a preliminary study.

To investigate the neural plasticity in the somatosensory cortex, changes in somatosensory evoked potentials (SSEPs) during finger ischemia were evaluated and compared with those affected by touch or movement interference. Somatosensory evoked potentials were recorded in the vicinity of the central sulcus in four patients with intractable epilepsy. During electrical stimulation to a selected finger, ischemic anesthesia was induced in another finger. Effects of tactile or movement interference were examined during electrical stimulation to the selected finger by applying tactile stimulation to or inducing voluntary movement of the other finger. Dynamic SSEPs were recorded during varying levels of sensory deprivation and different types of interference, and the dynamic nature of the SSEP changes within an individual was studied in detail. Somatosensory evoked potential changes appeared during finger ischemia and tended to persist during the postischemic stage, which is indicative of sensory plasticity and the maintenance of new conditioning. Amplitudes of the early and late cortical components increased when complete finger anesthesia was induced-a sign of the unmasking phenomenon. Amplitudes of early cortical SSEPs decreased when ischemic anesthesia was incomplete, similar to the findings when tactile or movement interference was applied. Surrounding inhibition, therefore, may become dominant before the unmasking phenomenon appears in early cortical SSEPs.