Affiliations: [a] Department of Neurology, The Johns Hopkins University, School of Medicine, Baltimore, Maryland | [b] Department of Ophthalmology, The Johns Hopkins University, School of Medicine, Baltimore, Maryland | [c] Department of Otolaryngology, Head, and Neck Surgery, The Johns Hopkins University, School of Medicine, Baltimore, Maryland | [d] Department of Biomedical Engineering, The Johns Hopkins University, School of Medicine, Baltimore, Maryland | [e] Department of Physiology I, Erasmus University, Rotterdam, The Netherlands
Note: [*] Dr. Tiliket is a visiting scientist from the INSERM-Unité 94, 16 avenue du Doyen Lépine, 69500 Bran, France.
Note: [**] Reprint address: Dr. Mark Shelhamer, Pathology 2-210. The Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21287-6921.
Abstract: We investigated the influence of static head orientation and position, relative to the axis of body rotation, upon vestibular adaptation. With the head centered, displaced anterior to the axis of body rotation, or tilted 40∘ to 45∘ in roll or pitch, the gain of the vestibulo-ocular reflex (VOR) was trained (to go either up or down) for one hour using artificial manipulation of the visual surround to produce a visual-vestibular mismatch. Before and after each training session, the VOR was measured in darkness with the head in the training as well as in several non-training positions. We found that transfer of VOR adaptation to non-training positions was almost complete when comparing head eccentric versus head-centered rotations. For tilts, however, transfer of VOR learning was far less complete suggesting that static otolith signals provide a strong contextual cue that gates the expression of an adaptive VOR response. Finally, following training to increase than VOR, gain was greater for centripetally than centrifugally directed slow phases. Centripetally directed postsaccadic drift also developed. These fundings imply that the gain increase paradigm also leads to abnormal function of the velocity-to-position neural integrator, which holds eccentric positions of gaze.
Keywords: VOR, adaptation, context specificity, transfer
