Exploration of Corticospinal Excitability During Movement Preparation
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Date
2024-03-25
Authors
Gomez, Isaac
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Publisher
University of Oregon
Abstract
Action preparation is a vital component of healthy goal-directed movement. While several studies have found evidence of transient inhibition of the motor system prior to simple finger movements, the functional role and putative source of this inhibition is not well understood. We explored corticospinal activity during the preparatory state under a number of different manual task types and conditions to investigate the nature of movement preparation. We used single-pulse Transcranial Magnetic Stimulation (TMS) in combination with electromyography (EMG) to measure summary analogues of the motor output pathway during three different studies. The first was a delayed-response task involving button-presses with the index finger while the contralateral hand held a tonic contraction. Here we showed a release of inhibition in the non-responding hand, as evidenced in shorter cortical silent periods. Experiment two involved a two-dimensional reach across a tablet surface to acquire targets. Here, motor evoked potentials (MEPs) measured during reach preparation did not change from baseline. Experiment three was a delayed-response task involving a choice between an out-and-back reach across the tablet surface and a button press using the thumb and forefinger of the same hand. Here also MEPs during the preparatory period were unchanged from baseline. While these findings stand in contrast to previous findings, they may suggest that certain task-related parameters, such as feedback and task complexity may influence whether preparatory inhibition is observable. They also add to a small but growing body of work that challenges the proposed models of preparatory inhibition. This dissertation includes previously published co-authored material.
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Keywords
corticospnal excitability, electrophysiology, movement preparation, preparatory inhibition, transcranial magnetic stimulation