Negative emotion can enhance human motor cortical plasticity.

Although emotion often primes us for action, its effects on the human motor system are not well understood. The relationship between emotion and motor plasticity also remains unclear, despite the close link between emotion and memory formation. Here, we tested the hypothesis that emotion modulates the plasticity of the human primary motor cortex, using the International Affective Picture System and transcranial magnetic stimulation. Intermittent theta-burst stimulation was applied to the primary motor cortex to produce long-term potentiation-like changes in normal volunteers experimentally. Primary motor cortex plasticity was enhanced and sustained in both excitatory and inhibitory systems only when intermittent theta-burst stimulation was combined with the presentation of pictures that induced negative, but not positive or neutral, emotion. Moreover, negative emotion was found to enhance the inhibitory networks within the primary motor cortex, and to improve motor behavior during the choice reaction-time task. Our findings indicate that negative emotion can increase primary motor cortex plasticity by modulating the intracortical GABAergic system, as well as N-methyl-d-aspartic acid receptor-dependent changes. These findings could help to explain the physiological basis of abnormal motor symptoms in psychogenic movement disorders following emotional events.