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Updated: Jun 16, 2026
Online Transcranial Magnetic Stimulation Protocol for Measuring Cortical Physiology Associated with Response Inhibition
Published on: February 8, 2018
Somatosensory effects of action inhibition: a study with the stop-signal paradigm
Eamonn Walsh1, Patrick Haggard
1Department of Psychology, Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London, WC1N 3AR, UK. eamonn.walsh@ucl.ac.uk
Abstract:
When a weak shock is delivered to the finger immediately before a voluntary movement, or during a delay interval where subjects are prepared to make the movement, shock detection rates worsen progressively as the movement approaches. Further, we previously showed that shock detection improves again if a NoGo signal produces inhibition of a prepared response. Here, we used a somatosensory version of the stop-signal paradigm to investigate inhibitory processing during the 'horserace' period when motor excitation and inhibition processes may be simultaneously active. When subjects made a rapid keypress response to a go-signal, shock detection deteriorated in a time-dependent manner, replicating sensory suppression. However, when go-signals were followed by adaptively delayed stop-signals so that subjects could not inhibit the prepared movement, and made errors of commission, we found a paradoxical brief increase in shock detection performance just after the stop-signal, as if in a NoGo trial. During this brief window, the somatosensory system showed a pattern consistent with motor inhibition, even though the motor system itself was too far advanced in movement execution for action to be inhibited. Most models of stop-signal processing propose a two-horse race between excitation and inhibition, with a winner-takes-all solution. We show that there may be distinct motor and somatosensory races. Moreover, inhibitory processes may lead in the somatosensory race, at least briefly, even when excitatory processes win the motor race.
Insights
Inhibitory processes in the brain may operate in parallel motor and sensory systems. This study reveals distinct
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Motor Control
Background:
- Shock detection performance worsens as voluntary movement approaches, a phenomenon known as sensory suppression.
- Previous research indicated that shock detection improves with response inhibition following a NoGo signal.
- The 'horserace' model describes the competition between motor excitation and inhibition during response control.
Purpose of the Study:
- To investigate inhibitory processing during the motor 'horserace' period using a somatosensory stop-signal paradigm.
- To explore the interplay between motor excitation and inhibition when response execution is advanced.
Main Methods:
- Utilized a somatosensory stop-signal paradigm with a keypress response task.
- Manipulated go-signals and adaptively delayed stop-signals to probe inhibitory control.
- Measured shock detection rates as an indicator of sensory processing during motor preparation and execution.
Main Results:
- Replicated sensory suppression, showing time-dependent deterioration of shock detection with movement approach.
- Observed a paradoxical, brief increase in shock detection after a stop-signal when commission errors occurred.
- This sensory enhancement coincided with motor inhibition patterns, despite failed motor response inhibition.
Conclusions:
- Suggests distinct 'horserace' dynamics for motor and somatosensory systems during response control.
- Demonstrates that somatosensory inhibition can transiently lead the 'race' even when motor execution is committed.
- Challenges winner-takes-all models by highlighting parallel inhibitory processes in distinct neural systems.
