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Stimulus-locked responses on human arm muscles reveal a rapid neural pathway linking visual input to arm motor output

Authors

  • J. Andrew Pruszynski,

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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    • J.A.P. and G.L.K. contributed equally to this work.

  • Geoffrey L. King,

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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    • J.A.P. and G.L.K. contributed equally to this work.

  • Lysa Boisse,

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    2. Department of Medicine, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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  • Stephen H. Scott,

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    2. Department of Medicine, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    3. Department of Anatomy and Cell Biology, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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  • J. Randall Flanagan,

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    2. Department of Physiology, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    3. Department of Psychology, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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  • Douglas P. Munoz

    1. Centre for Neuroscience Studies, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    2. Department of Medicine, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    3. Department of Physiology, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
    4. Department of Psychology, Botterell Hall, Queen’s University, Kingston, ON K7L 3N6, Canada
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J. Andrew Pruszynski, as above.
E-mail: andrewp@biomed.queensu.ca

Abstract

Previous studies have demonstrated that humans are sometimes capable of initiating arm movements towards visual stimuli at extremely short latencies, implying the presence of a short-latency neural pathway linking visual input to limb motor output. However, little is known about the neural mechanisms that underlie such hastened arm responses. One clue may come from recent demonstrations that the appearance of a visual target can elicit a rapid response in neck muscles that is time-locked to target appearance and functionally relevant for orienting gaze (head and eye) towards the target. Because oculomotor structures thought to contribute to ‘visual responses’ on neck muscles also target some arm muscles via a tecto-reticulo-spinal pathway, we hypothesized that a similar visual response would be present in arm muscles. Our results were consistent with this hypothesis as we observed the presence of rapid arm muscle activity (< 100 ms latency) that was time-locked to target appearance and not movement onset. We further found that the visual response in arm muscles: (i) was present only when an immediate reach towards the target was required; (ii) had a magnitude that was predictive of reaction time; (iii) was tuned to target location in a manner appropriate for moving the arm towards the target; and (iv) was more prevalent in shoulder muscles than elbow muscles. These results provide evidence for a rapid neural pathway linking visual input to arm motor output and suggest the presence of a common neural mechanism for hastening eye, head and arm movements.

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