Document Type

Thesis

Degree Name

Master of Kinesiology (MKin)

Department

Kinesiology and Physical Education

Faculty/School

Faculty of Science

First Advisor

Jayne Kalmar

Advisor Role

Supervisor

Abstract

Corticospinal excitability as measured via transcranial magnetic stimulation (TMS) is highly dependent on the task being performed at the time of stimulation. As such, this study sought out to measure corticospinal excitability during the relevant, daily task of writing and compare it to the conventional abduction task often utilized. We used single-pulse motor evoked potentials (MEPs) to provide a measure of corticospinal excitability and cortical silent period (CSP) duration, and paired-pulse conditioned MEPs to assess short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) recorded from the right first dorsal interosseous (FDI) of 19 participants on two randomized and counter-balanced days. On one day, participants performed the writing task, which consisted of writing the word name on a graphic tablet whose screen refreshed every 5-seconds. On the other day, the abduction task was performed and consisted of participants isometrically abducting their right index finger at a level that matched EMG levels during writing. Each day consisted of a pre-fatigue test where participants performed the designated task and corticospinal excitability was measured, a fatiguing task, and a post-fatigue test which was identical to the pre-fatigue test. There was a main effect of task on SICI, such that we saw greater inhibition during writing (F=4.91, [1,16], p=0.04). The writing task was further broken down into a printing task and a cursive writing task based on participant’s self-selected writing styles. Accordingly, we compared fatigue-induced changes in CSE in printers (n=8) and cursive writers (n=8). Following fatigue, ICF increased (35%±46%) in the printers but did not change in the cursive writing group (5%±13%). This study is the first to assess measures of corticospinal excitability during a handwriting task. Given that changes in intracortical excitability after a fatigue protocol depend on the motor task used to assess excitability, future studies should use paradigms that mimic functionally relevant motor tasks to better understand the role that CSE may play in the neural control of movement.

Convocation Year

2019

Convocation Season

Fall

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