UBC Theses and Dissertations

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UBC Theses and Dissertations

Insights into human dynamic balance control : postural response initiation explored through classical conditioning and startle Campbell, Adam Donald


As a scientific discipline, dynamic posturography aims to understand the neurological and biomechanical mechanisms that contribute to postural stability and corrective postural responses (PRs). The main focus of this thesis was to better understand the neurophysiology of corrective PRs that prevent falls that emerge from external forces applied to the body by balance perturbations. In a sequence of 4 studies, this thesis utilized novel applications of established techniques (classical conditioning and startle paradigms) to address questions regarding the role of sensory feedback in PRs initiation and the nature of PRs that are evoked by balance perturbations. The first of 4 experiments tested the link between sensory feedback derived by balance perturbations and PR initiation by attempting to trigger PRs using auditory cues that, prior to classical conditioning provided no relevant information pertaining to balance perturbations or postural stability. The second study examined the extent to which conditioned PRs may exist as prepared motor behaviours that could be initiated by startling acoustic stimuli in the absence of balance perturbations. The third study attempted to extend the previous findings of PR motor preparation into a more ecologically valid scenario involving unexpected balance perturbations. The fourth and final study in this thesis examined whether startle responses could contribute to first-trial effects observed on PRs evoked by the first in a repeated sequence of balance perturbations. Individually, each study provided highly novel contributions to the field of dynamic posturography. However, when taken together, they provide novel insight into both the mechanisms involved in PR initiation and the understanding of reactions evoked by balance perturbations.

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