Ricerc@Sapienza

An increasing number of evidence suggests the existence of a Tactile Mirror System in the human brain: the same cortical network implicated in tactile perception, which comprises the primary somatosensory cortex (S1), also responds to the mere observation of tactile events. It has been suggested that such cross-modal, mirror-like, responses of S1 may arise from Hebbian associative plasticity: the contingency of seeing a touch and the feeling of a tactile sensation on one’s own body may reinforce synapses between visual and somatosensory neurons.

We developed and assessed the effects of a novel cross-modal protocol aimed at inducing associative (Hebbian-like) plasticity in the somatosensory cortical system through vision. Associative long-term potentiation can be induced in the primary somatosensory cortex (S1) by means of paired associative stimulation (PAS), in which a peripheral electrical stimulation of the median nerve is repeatedly paired with a transcranial magnetic stimulation (TMS) pulse over S1.

Paired associative stimulation (PAS) protocols can be used to induce Hebbian plasticity in the human brain. A modified, cross-modal version, of the PAS (cross-modal PAS, cm-PAS) has been recently developed. The cm-PAS consists in the repetitive pairings of a transcranial magnetic