Effect of pain and pain expectation on primary motor cortex excitability

Abstract

Objective: The study aimed to test whether pain and pain expectation affect corticospinal excitability.

Methods: Transcranial magnetic stimulation was used to measure corticospinal excitability among 15 subjects in five experimental conditions in which thermic stimulations were applied to the hand: (1) neutral stimulus; (2) actual heat; (3) actual pain; (4) expected heat; and (5) expected pain. Motor-evoked potentials were recorded in two intrinsic hand muscles.

Results: A significant difference was found between experimental conditions for both muscles (p<0.005). Contrast analysis showed that actual pain led to a significant corticospinal inhibition compared with both neutral and actual heat conditions, whereas no effect was observed during pain expectation.

Conclusions: Our results suggest that acute pain (low-to-moderate intensity (∼3/10)) does elicit motor inhibition but that its expectation does not.

Significance: The fact that low and short-lasting pain can induce motor inhibition suggests that even moderate pain might interfere with optimal motor function in patients with both pain and motor deficits.