Emotional stimuli modulate readiness for action: a transcranial magnetic stimulation study.

Emotional stimuli may prime the motor system and facilitate action readiness. Direct evidence for this effect has been shown by recent studies using transcranial magnetic stimulation (TMS). When administered over the primary motor cortex involved in responding, TMS pulses elicit motor-evoked potentials (MEPs) in the represented muscles. The amplitudes of these MEPs reflect the state of corticospinal excitability. Here, we investigated the dynamic effects of induced emotions on action readiness, as reflected by corticospinal excitability. Subjects performed a choice task while viewing task-irrelevant emotional and neutral pictures. The pattern of MEP amplitudes showed a typical increase as the TMS pulse was presented closer in time to the imminent response. This dynamic pattern was amplified by both pleasant and unpleasant emotional stimuli, but more so when unpleasant pictures were viewed. These patterns present novel evidence in support of the notion that emotional stimuli modulate action readiness.