Older adults demonstrate superior vestibular perception for virtual rotations.
Adult ageing results in a progressive loss of vestibular hair cell receptors and afferent fibres. Given the robustness of vestibulo-ocular and vestibular-evoked whole-body responses to age-related deterioration, it was proposed that the vestibular system compensates centrally. Here we examine the potential for central compensation in vestibular sensitivity with adult ageing by using a combination of real and virtual rotation-based psychophysical testing at two stimulus frequencies (0.1 & 1Hz). Real rotations activate semi-circular canal hair cell receptors naturally via mechanotransduction, while electrical current used to evoke virtual rotations does not rely on mechanical deformation of hair cell receptors to activate vestibular afferents. This two-pronged approach allows us to determine the independent effects of age-related peripheral afferent receptor loss and potential compensatory mechanisms. Older adults had thresholds for discriminating real rotations that were significantly greater than young adults at 0.1Hz (7.2 vs. 3°/s), but the effect of age was weaker (non-significant) at 1Hz (2.4 vs. 1.3°/s). For virtual rotations, older adults had greater thresholds than young adults at 0.1Hz (1.2 vs. 0.5mA), however, older adults outperformed young adults at 1Hz (0.6 vs. 1.1mA). Based on these thresholds, we argue that central vestibular processing gain is enhanced in older adults for 1Hz real and virtual rotations, partially offsetting the negative impact of normal age-related hair cell receptor and primary afferent loss. We propose that the frequency dependence of this compensation reflects the physiological importance of the 1-5Hz range in natural vestibular input.
School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
Ryan M
RM
Peters
School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; Institute for Computing, Information, and Cognitive Systems, University of British Columbia, Vancouver, BC, Canada; Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada. Electronic address: jsblouin@mail.ubc.ca.
Jean-Sébastien
JS
Blouin
Department of Human Physiology, University of Oregon, Eugene, OR, USA.
Brian H
BH
Dalton
School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada; International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada.
J Timothy
JT
Inglis
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D040542:Mechanotransduction, Cellular; D009039:Motion Perception; D011581:Psychological Tests; D012399:Rotation; D014722:Vestibule, Labyrinth / Q000502:physiology*; D055815:Young Adult
Ageing; Galvanic; Hair cell receptors; Psychophysics; Semi-circular canals