Vestibular Modulation of the Abductor Hallucis and the Abductor Digiti Minimi Muscles in Response to Changes in Head Position, Visual Cues, and Cognitive Demand
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Date
2016-06
Authors
Wallace, Jonathan
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Maintaining standing balance involves processing of vestibular, visual, and
somatosensory information to produce dynamic motor responses. Bilateral electrical
vestibular stimulation (EVS) delivered through the mastoid processes can be used to
explore the vestibular system. The purpose of this experiment was to determine if
intrinsic foot muscles are modulated by vestibular activity and to elucidate any changes
in the association between the vestibular stimulation and electromyography (EMG)
responses in response to changes in head position, visual cues, and cognitive demand.
Indwelling EMG of the abductor hallucis (AH) and abductor digiti minimi (ADM) were
sampled while EVS was administered to quietly standing participants. The relationships
between the EVS input and the muscle activity (output) were characterized in both the
time and the frequency domains. When the head orientation was changed from left to
right, the biphasic vestibular response in the time domain was inverted. In conditions
including visual cues and increased cognitive demand, the vestibular responses
demonstrated reduced and increased amplitudes of the coherence function, respectively.
These findings indicate that the vestibular system modulates activity in the ADM and
AH during quiet standing balance tasks.
Description
55 pages. A thesis presented to the Department of Human Physiology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Arts, Spring 2016.
Keywords
Human physiology, Vestibular physiology, Vestibular, Abductor Digiti Minimi, Abductor Hallucis, Electrical Vestibular Stimulation, Standing balance, Young adult, Muscles