Date of Award

2008

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

School

School of Exercise, Biomedical and Health Sciences

Faculty

Faculty of Computing, Health and Science

First Advisor

Kazunori Nosaka

Second Advisor

Dr Gary Thickbroom

Abstract

Various mechanisms may alter corticomotor excitability to agonist and antagonist muscles during passive and active limb movement depending on parameters of movement and their functional role. A better understanding of these relationships is important for understanding basic motor control mechanisms, and may be relevant to motor rehabilitation programs after brain injury. The purpose of the present study was to compare changes in corticomotor excitability to wrist flexor and extensor muscles during different phases of movement (flexion/extension), and at rest and during actively or passively-mediated length changes. Motor evoked potentials (MEP) of the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) were recorded from 17 participants during resting and four movement conditions (passive wrist flexion and extension, active wrist flexion and extension) with their palm inserted into a hand piece. Passive and active movements were carried out by moving the hand piece for 22.5° wrist flexion and 22.5° wrist extension from the neutral wrist position of 0° at a cycle rate of 1 Hz. transcranial magnetic stimulation (TMS) was delivered at the neutral position (0°) every ten cycles to obtain 12 MEPs. The mean MEP amplitude was compared across the resting, lengthening and shortening phases for passive and active movements for the FCR and ECR separately by a paired t-test. Comparison was also made between FCR and ECR, and between passive and active movements by a two-way repeated measures ANOVA. The MEP amplitude was significantly (P<0.05) reduced during passive lengthening for the FCR and ECR; but increased significantly during shortening only for the FCR compared with the resting state. In contrast, the MEP amplitude of the FCR and ECR increased in both active lengthening and shortening compared with the resting state, but the increase was significantly (P<0.05) greater for shortening than lengthening phase. These results suggest that changes in corticomotor excitability are similar between the FCR and ECR, and between passive and active movements, and suggest that common underlying mechanisms exist in the modulation of corticomotor excitability during passive and active wrist movements.

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