Reward-related activity in the human motor cortex.
The human primary motor cortex (M1) participates in motor learning and response selection, functions that rely on feedback on the success of behavior (i.e. reward). To investigate the possibility that behavioral contingencies alter M1 activity in humans, we tested intracortical inhibition with single and paired (subthreshold/suprathreshold) transcranial magnetic stimulation during a slot machine simulation that delivered variable money rewards for three-way matches and required no movement. A two-way match before the third barrel had stopped (increased reward expectation) was associated with more paired-pulse inhibition than no match. Receiving a large reward on the preceding trial augmented this effect. A control task that manipulated attention to the same stimuli produced no changes in excitability. The origin of this reward-related activity is not clear, although dopaminergic ventral tegmental area neurons project to M1, where they are thought to inhibit output neurons and could be the source of the finding. Transcranial magnetic stimulation of M1 may be useful as a quantitative measure of reward-related activity.
Kapogiannis
Dimitrios
D
Brain Stimulation Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, MSC 1440, 10 Center Drive, Bethesda, MD 20892-1440, USA.
Campion
Paul
P
Grafman
Jordan
J
Wassermann
Eric M
EM
D000328:Adult; D006801:Humans; D007858:Learning / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012201:Reward; D050781:Transcranial Magnetic Stimulation / Q000379:methods