Neurophysiological markers discriminate different forms of motor imagery during action observation

Adam Bruton, Zoë C. Franklin, Paul Holmes, Daniel L. Eaves, David J. Wright

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The dual-action simulation hypothesis proposes thatboth an observed and an imagined action can be represented simultaneously inthe observer’s brain. These two sensorimotor streams would either merge orcompete depending on their relative suitability for action planning. To testthis hypothesis, three forms of combined action observation and motor imagery(AO+MI) instructions were used in this repeated-measures experiment.Participants observed index finger abduction-adduction movements whileimagining the same action (congruentAO+MI), little finger abduction-adduction (coordinative AO+MI), ora static hand (conflicting AO+MI). Single-pulsetranscranial magnetic stimulation was applied to the left primary motor cortex.The amplitude of motor evoked potential responses were recorded from both thefirst dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles of theright-hand while eye movements were tracked. When controlling for the influenceof relevant eye movements, corticospinalexcitability was facilitated relative to control conditions in the concurrentlyobserved and imagined muscles for both congruentand coordinative AO+MI conditions.Eye-movement metrics and social validation data from post-experiment interviewsprovided insight into the cognitive mechanisms underlying these effects. Thefindings provide empirical support for the dual-action simulation hypothesis,indicating for the first time that it is possible to co-represent observed andimagined actions simultaneously.

© 2019, The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See

Original languageEnglish
Pages (from-to)119-136
Early online date16 Nov 2019
Publication statusPublished - 1 Mar 2020


  • motor imagery during action observation
  • dual-action simulation
  • Transcranial Magnetic Stimulation
  • eye-tracking

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