Associatively-Mediated Suppression of Corticospinal Excitability: A Transcranial Magnetic Stimulation (TMS) Study. (15th September 2019)

• Record Type: Journal Article
• Authors: Seet, Manuel S.; Livesey, Evan J.; Harris, Justin A.
• Is Part Of: Neuroscience. Volume 416(2019)
• Page Start: 1
• Page End: 8
• Publication Date: 2019-09-15
• Subjects: M1 Primary Motor Cortex -- SICI Short-Interval Intracortical Inhibition -- GABA Gamma-Aminobutyric Acid -- RT Reaction Time -- FDI First Dorsal Interosseous -- MEP Motor Evoked Potential -- TMS Transcranial Magnetic Stimulation -- spTMS Single-pulse TMS -- ppTMS Paired-pulse TMS -- EMG Electromyography -- rmsEMG root-mean-squared EMG -- SEM Standard Error of the Mean -- rIFC Right Inferior Frontal Cortex -- PMd Dorsal Premotor Area; stop signal task -- motor-evoked potential -- short-interval intra-cortical inhibition -- inhibitory conditioning; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2019.07.038
• Languages: English
• ISSNs: 0306-4522

Abstract

Abstract: Response inhibition – the suppression of prepotent behaviours when they are inappropriate – has been thought to rely on executive control. Against this received wisdom, it has been argued that external cues repeatedly associated with response inhibition can come to trigger response inhibition automatically without top-down command. The current project endeavoured to provide evidence for associatively-mediated motor inhibition. We tested the hypothesis that stop-associated stimuli can, in a bottom-up fashion, directly activate inhibitory mechanisms in the motor cortex. Human subjects were first trained on a stop-signal task. Once trained, the subjects received transcranial magnetic stimulation applied over their primary motor cortex during passive observation of either the stop signal (i.e. without any need to stop a response) or an equally familiar control stimulus never associated with stopping. Analysis of motor-evoked potentials showed that corticospinal excitability was reduced during exposure to the stop signal, which likely involved stimulus-driven activation of intracortical GABAergic interneurons. This result provides evidence that, through associative learning, stop-associated stimuli can engage local inhibitory processes at the level of the motor cortex. Highlights: We examined activity in the motor cortex during exposure to a visual stimulus associated with stopping a motor response. Subjects were first trained on a stop-signal task, in which they countermanded go-responses in presence of a stop-signal. Single- and paired-pulse transcranial magnetic stimulation were then used to probe motor cortical activity. Corticospinal excitability was reduced when subjects viewed the stop-signal without needing to stop a response. Automatic activation of inhibitory interneurons likely produced the observed reduction in corticospinal excitability.