title: Transcranial magnetic stimulation reveals dissociable mechanisms for global versus selective corticomotor suppression underlying the stopping of action.
abstract: Stopping an initiated response is an essential function, investigated in many studies with go/no-go and stop-signal paradigms. These standard tests require rapid action cancellation. This appears to be achieved by a suppression mechanism that has "global" effects on corticomotor excitability (i.e., affecting task-irrelevant muscles). By contrast, stopping action in everyday life may require selectivity (i.e., targeting a specific response tendency without affecting concurrent action). We hypothesized that while standard stopping engages global suppression, behaviorally selective stopping engages a selective suppression mechanism. Accordingly, we measured corticomotor excitability of the task-irrelevant leg using transcranial magnetic stimulation while subjects stopped the hand. Experiment 1 showed that for standard (i.e., nonselective) stopping, the task-irrelevant leg was suppressed. Experiment 2 showed that for behaviorally selective stopping, there was no mean leg suppression. Experiment 3 directly compared behaviorally nonselective and selective stopping. Leg suppression occurred only in the behaviorally nonselective condition. These results argue that global and selective suppression mechanisms are dissociable. Participants may use a global suppression mechanism when speed is stressed; however, they may recruit a more selective suppression mechanism when selective stopping is behaviorally necessary and preparatory information is available. We predict that different fronto-basal-ganglia pathways underpin these different suppression mechanisms.
authors.affiliation: Department of Psychology, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: D S Adnan
authors.initials: DS
authors.lastname: Majid
authors.forename: Weidong
authors.initials: W
authors.lastname: Cai
authors.forename: Jobi S
authors.initials: JS
authors.lastname: George
authors.forename: Frederick
authors.initials: F
authors.lastname: Verbruggen
authors.forename: Adam R
authors.initials: AR
authors.lastname: Aron
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D003657:Decision Making; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology; D012094:Repression, Psychology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult