Adaptation of vestibular tone studied with electrical stimulation of semicircular canal afferents

RF Lewis, K Nicoucar, W Gong, C Haburcakova… - Journal of the …, 2013 - Springer
RF Lewis, K Nicoucar, W Gong, C Haburcakova, DM Merfeld
Journal of the Association for Research in Otolaryngology, 2013Springer
Damage to one vestibular labyrinth or nerve causes a central tone imbalance, reflected by
prominent spontaneous nystagmus. Central adaptive mechanisms eliminate the nystagmus
over several days, and the mechanisms underlying this process have received extensive
study. The characteristics of vestibular compensation when the tone imbalance is presented
gradually or repeatedly have never been studied. We used high-frequency electrical
stimulation of semicircular canal afferents to generate a vestibular tone imbalance and …
Abstract
Damage to one vestibular labyrinth or nerve causes a central tone imbalance, reflected by prominent spontaneous nystagmus. Central adaptive mechanisms eliminate the nystagmus over several days, and the mechanisms underlying this process have received extensive study. The characteristics of vestibular compensation when the tone imbalance is presented gradually or repeatedly have never been studied. We used high-frequency electrical stimulation of semicircular canal afferents to generate a vestibular tone imbalance and recorded the nystagmus produced when the stimulation was started abruptly or gradually and when it was repeatedly cycled on and off. In the acute-onset protocol, brisk nystagmus occurred when stimulation started, gradually resolved within 1 day, and reversed direction when the stimulation was stopped after 1 week. Repeated stimulation cycles resulted in progressively smaller nystagmus responses. In the slow-onset protocol, minimal nystagmus occurred while the stimulation ramped-up to its maximum rate over 12 h, but a reversal still occurred when the stimulation was stopped after 1 week, and repeated stimulation cycles did not affect this pattern. The absence of nystagmus during the 12 h ramp of stimulation demonstrates that central vestibular tone can rebalance relatively quickly, and the reduction in the stimulation-off nystagmus with repeated cycles of the acute-onset but not the slow-onset stimulation suggests that dual-state adaptation may have occurred with the former paradigm but not the latter.
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