Award Date

1-1-1996

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Kinesiology

Number of Pages

203

Abstract

An understanding of how locomotion occurs can help prevent or possibly restore its loss. Observations of coordination and reflex gating during locomotion display characteristics indicative of subcortical influence. These findings support the existence of neural circuits in the spine and cerebellum that coordinate muscle activity and reflex activity during locomotion. These circuits are generally called central pattern generators (CPG's). A task that strains the modulation of reflexes but not coordination (e.g., out-of-phase walking) may yield dissociative patterns of errors, which would provide important information about the complexity of the subcortical circuitry. In the present study, nine participants walked on a treadmill at 0.83 Hz cadence, timing their heelstrikes to a metronome which varied the phase lag between each leg from 0.5 to 1.0 {dollar}\pi{dollar} radians at 0.1 {dollar}\pi{dollar} intervals. A stimulus was delivered to the sural nerve of the left leg, and reflexes were measured in the ipsilateral and contralateral tibialis anterior and contralateral gastrocnemius through electromyography. Analyses of variance revealed a significant main effect of stimulus delay on the contralateral tibialis anterior response (F = 10.11, p {dollar}<{dollar} 0.05), which is consistent with previous studies. The absence of differences between phase lag conditions for both temporal coordination and reflex intensities suggests that they may be controlled by the same subcortical circuitry. Within this explanation, two plausible alternatives exist. There may exist a single CPG that not only coordinates muscular contractions, but also phasically inhibits activity of Ia afferents to modulate reflexes using a feed-forward control scheme. Alternatively, there may also exist two separate circuits which are strongly entrained, producing synchronous outputs for both coordination and reflex gating. (Abstract shortened by UMI.).

Keywords

Central Control; Dual; Generator; Hypothesis; Locomotion; Patterns; Subcortical; Test

Controlled Subject

Neurosciences; Psychology, Experimental; Kinesiology; Psychobiology

File Format

pdf

File Size

3133.44 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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