Corticospinal excitability is enhanced while preparing for complex movements

  • Michael Kennefick
  • Joel S. Burma
  • Paul van Donkelaar
  • Chris J. McNeilEmail author
Research Article


Movement complexity is known to increase reaction time (RT). More recently, transcranial magnetic stimulation (TMS) of the motor cortex has revealed that movement complexity can alter corticospinal excitability. However, the impact of a sequential addition of movement components on corticospinal excitability during the preparatory phase of a simple RT task is unknown. Thus, the purpose of this study was to examine how motor evoked potentials (MEPs) in the premotor period were affected by the complexity of a movement in a simple RT paradigm. Participants (n = 12) completed ballistic movements with their dominant arm, in which they directed a robotic handle to one, two or three targets (32 trials per condition). TMS was delivered prior to movement at 0, 70, 80 or 90% of each participant’s mean premotor RT, at the stimulator intensity which yielded a triceps brachii MEP of ~ 10% the maximal M-wave. As expected, premotor RT slowed with increasing task complexity. Although background electromyographic activity (EMG) of the triceps brachii during the preparation phase did not differ among conditions, MEP amplitude increased with movement complexity (i.e., MEPs were greater for the 2- and 3-movement conditions, compared to the 1-movement condition at 80% of premotor RT). We propose the lengthened RTs could be due in part to less suppression of particular motor circuits, while other circuitry is responsible for the increased MEPs. This study demonstrates that, prior to movement, corticospinal excitability increases as a consequence of movement complexity.


Motor evoked potential (MEP) Movement complexity Movement preparation Reaction time 



This work was supported by the Natural Sciences and Engineering Research Council of Canada (DG 04412-2017 and DG 435912-2013) and the Canada Foundation for Innovation/British Columbia Knowledge Development Fund (30979 and 32260).

Compliance with ethical standards

Conflict of interest

All the authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Michael Kennefick
    • 1
  • Joel S. Burma
    • 1
  • Paul van Donkelaar
    • 1
  • Chris J. McNeil
    • 1
    Email author
  1. 1.School of Health and Exercise SciencesUniversity of British Columbia -OkanaganKelownaCanada

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