Non-selective inhibition of the motor system following unexpected and expected infrequent events
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RESEARCH ARTICLE
Non‑selective inhibition of the motor system following unexpected and expected infrequent events Carly Iacullo1 · Darcy A. Diesburg1 · Jan R. Wessel1,2 Received: 25 March 2020 / Accepted: 2 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Motor inhibition is a key control mechanism that allows humans to rapidly adapt their actions in response to environmental events. One of the hallmark signatures of rapidly exerted, reactive motor inhibition is the non-selective suppression of corticospinal excitability (CSE): unexpected sensory stimuli lead to a suppression of CSE across the entire motor system, even in muscles that are inactive. Theories suggest that this reflects a fast, automatic, and broad engagement of inhibitory control, which facilitates behavioral adaptations to unexpected changes in the sensory environment. However, it is an open question whether such non-selective CSE suppression is truly due to the unexpected nature of the sensory event, or whether it is sufficient for an event to be merely infrequent (but not unexpected). Here, we report data from two experiments in which human subjects experienced both unexpected and expected infrequent events during a two-alternative forced-choice reaction time task while CSE was measured from a task-unrelated muscle. We found that expected infrequent events can indeed produce non-selective CSE suppression—but only when they occur during movement initiation. In contrast, unexpected infrequent events produce non-selective CSE suppression relative to frequent, expected events even in the absence of movement initiation. Moreover, CSE suppression due to unexpected events occurs at shorter latencies compared to expected infrequent events. These findings demonstrate that unexpectedness and stimulus infrequency have qualitatively different suppressive effects on the motor system. They also have key implications for studies that seek to disentangle neural and psychological processes related to motor inhibition and stimulus detection. Keywords Motor inhibition · Motor evoked potentials · Cortico-motor excitability · Surprise · Oddball
Introduction
Communicated by Winston D Byblow. Carly Iacullo and Darcy A. Diesburg have equally contributed to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00221-020-05919-3) contains supplementary material, which is available to authorized users. * Jan R. Wessel Jan‑[email protected] http://www.wessellab.org 1
Department of Psychological and Brain Sciences, University of Iowa, 376 Psychological and Brain Sciences Building, 340 Iowa Avenue, Iowa City, IA 52240, USA
Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
2
Motor inhibition is a core component of controlled and flexible human behavior. The rapid interruption of active motor representations allows humans to momentarily cancel ongoing movements and movement plans, which in turn allows them to reevaluate whether those move
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