Associative pairing of tactile stimulation induces somatosensory cortical reorganization in rats and humans.

We used a protocol of associative (Hebbian) pairing of tactile stimulation (APTS) to evoke cortical plastic changes. Reversible reorganization of the adult rat paw representations in somatosensory cortex (SI) induced by a few hours of APTS included selective enlargement of the areas of cortical neurones representing the stimulated skin fields and of the corresponding receptive fields (RFs). Late, presumably NMDA receptor-mediated response components were enhanced, indicating an involvement of glutamatergic synapses. A control protocol of identical stimulus pattern applied to only a single skin site revealed no changes of RFs, indicating that co-activation is crucial for induction. Using an analogous APTS protocol in humans revealed an increase of spatial discrimination performance indicating that fast plastic processes based on co-activation patterns act on a cortical and perceptual level.