Heteronymous La Facilitation

Abstract

known about age-related changes in the integrity of interneuronal spinal mechanisms such as presynaptic inhibition. One recent report demonstrated decreased heteronymous la facilitation with aging, most likely a result of increased presynaptic inhibition with age (Morita et al., 1995). Further, although it has been determined that tonic levels of presynaptic inhibition change when comparing standing with and without back support in young subjects (Katz et al., 1988). the response of presynaptic inhibition in different body positions (e.g., weight bearing vs. non-weight bearing) in young and elderly subjects has yet to be established. Moreover, given the report of a relationship between reflex modulation and postural control in elderly subjects (Koceja et al., 1995), the mechanisms responsible for reflex modulation in young and elderly subjects seems warranted. The purpose of this study was to utilize the heteronymous facilitation protocol as described by Hultborn et al. (1987) to examine changes in presynaptic inhibition in young and elderly subjects in the supine and standing body positions.