Short and long-term postural learning to withstand galvanic vestibular perturbations.
We investigated changes of postural responses to repeated bipolar galvanic vestibular stimulation on 5 consecutive days and once again after 3 months. Subjects consisted of 21 healthy volunteers. Except for the first day did the induced torque variance in response to galvanic vestibular stimulation not decrease within each test session, but there was a major reduction from day to day (p< 0.001) reflecting a continued processing of the postural experience gained during the stimulation. The decreased end level magnitude of postural responses after 5 days was retained after 3 months. The galvanic stimulation failed to induce larger torque variance compared to quiet stance toward the end of the 5 days as well as after 3 months, indicating a down-regulation of a repeated erroneous vestibular stimulation by the postural control system - i.e. sensory reweighting. This argues that a major adaptation effect to galvanic vestibular perturbation takes place after the exposure to the stimulation - similar to the concept of the consolidation process involved in motor learning. This should be considered when repeatedly assessing vestibular function both clinically and in studies. It implies that sensory training involved in rehabilitation from vestibular diseases/deficiencies should be executed with spaced intervals in order to procure more efficient learning processes and in the end, a better function.
Department of Otorhinolaryngology, Head and Neck Surgery, Clinical Sciences, Lund University Hospital, Lund, Sweden. Fredrik.Tjernstrom@med.lu.se
Fredrik
F
Tjernström
Ali
A
Bagher
Per-Anders
PA
Fransson
Måns
M
Magnusson
D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D003463:Cues; D004558:Electric Stimulation / Q000379:methods*; D005143:Eyelids / Q000503:physiopathology; D005260:Female; D006257:Head / Q000503:physiopathology; D006801:Humans; D007858:Learning; D008297:Male; D010806:Physical Education and Training / Q000379:methods*; D004856:Postural Balance; D011187:Posture; D019415:Torque; D015837:Vestibular Diseases / Q000209:etiology* / Q000503:physiopathology / Q000534:rehabilitation*; D055815:Young Adult