Stimulating plastic change

Abstract

The plastic changes in brain organization that are thought to underlie learning can be studied in the relatively well-mapped areas of the primary sensory and motor cortices. There are now several demonstrations of sensory and motor representations changing over periods of minutes to months in response to peripheral injury or simply the learning of a behavioural task. Ziemann et al. have recently demonstrated that a transcranial magnetic stimulation technique involving a train of repeated pulses (rTMS) can be used to modulate neuroplasticity in human subjects[1]. They used a second TMS technique, involving just paired pulses, to examine intracortical facilitation and inhibition in the motor cortex. The application of rTMS to the motor cortex had no measurable effect but when it was combined with ischaemic nerve block of the hand, however, Ziemann et al. observed changes in intracortical facilitation and inhibition. Ischaemic nerve block applied alone for a similar period did not have such profound reorganizing effects. These results suggest a way of directly, but non-invasively, modulating human cortical plasticity.