This doctoral thesis reports a series of studies aimed at exploring the control of body equilibrium during perturbations of the bipedal stance in healthy humans, and its modifications by aging and Parkinson's disease (PD). With the use of two unique experimental paradigms, we investigated reflex interactions during forward whole head-and-body tilts (WHBT) in healthy young and elderly subjects, and PD patients. We discovered that the excitability of extensor muscle responses to the stimulation of flexion reflex (FR) afferents was enhanced during WHBTs in young normal subjects. Such a functional output suggested that the specific needs of balance maintenance could have governed the reflex interaction during WHBTs rather than limb withdrawal. / A significantly smaller proportion of elderly than young subjects showed an increase or a decrease of the FR in their ipsilateral tibialis anterior muscle (iTA) during WHBT. This indicated a lack of FR modifiability during dynamic perturbations of standing balance with aging. Such a change in reflex interaction could originate from a defect in the sensorimotor integration needed for the proper control of forward WHBT. / PD patients were first characterized by a large increase in the excitability of their muscle responses to forward WHBT, which was accompanied by a much smaller increase in soleus H-reflex excitability during similar WHBTs. Second, they manifested a reduced FR modifiability during WHBT in comparison with age-matched normal subjects. Our findings suggest that PD might involve a specific difficulty to generate appropriate output from the interaction between flexor and extensor muscle responses. We hypothesise that an abnormal control of spinal interneurons in PD could be responsible for the tilting disorder and altered reflex interactions observed in these patients.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.29106 |
| Date | January 1995 |
| Creators | Paquet, Nicole |
| Contributors | Hui-Chan, Christina W. Y. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (School of Physical and Occupational Therapy.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001496273, proquestno: NN08144, Theses scanned by UMI/ProQuest. |
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