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This Article Full Text Full Text (PDF) All Versions of this Article: 97/6/4341    most recent 01321.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Seemungal, B. M. Articles by Bronstein, A. M. Search for Related Content PubMed PubMed Citation Articles by Seemungal, B. M. Articles by Bronstein, A. M.

Vestibular Perception and Navigation in the Congenitally Blind

¹Department of Movement and Balance, Division of Neurosciences and Psychological Medicine, Imperial College, Charing Cross Hospital, London, United Kingdom; and ²Center for Sensorimotor Research, Julius Bernstein Center for Computational Neuroscience, Department of Neurology, Ludwig-Maximilians-Universitaet Muenchen, Munich, Germany

Submitted 16 December 2006; accepted in final form 15 March 2007

Vestibular input is required for accurate locomotion in the dark, yet blind subjects’ vestibular function is unexplored. Such investigation may also identify visually dependent aspects of vestibular function. We assessed vestibular function perceptually in six congenitally blind (and 12 sighted) subjects. Cupula deflection by a transient angular, horizontal acceleration generates a related vestibular nerve signal that declines exponentially with time constant 4–7 s, which is prolonged to 15 s in the evoked vestibular-ocular reflex by the brain stem "velocity storage." We measured perceptual velocity storage in blind subjects following velocity steps (overall perceptual vestibular time constant, experiment 1) and found it to be significantly shorter (5.34 s; range: 2.39–8.58 s) than in control, sighted subjects (15.8 s; P < 0.001). Vestibular navigation was assessed by subjects steering a motorized Bárány-chair in response to imposed angular displacements in a path-reversal task, "go-back-to-start" (GBS: experiment 2); and a path-completion task, "complete-the-circle" (CTC: experiment 3). GBS performances (comparing response vs. stimulus displacement regression slopes and r²) were equal between groups (P > 0.05), but the blind showed worse CTC performance (P < 0.05). Two blind individuals showed ultrashort perceptual time constants, high lifetime physical activity scores and superior CTC performances; we speculate that these factors may be inter-related. In summary, the vestibular velocity storage as measured perceptually is visually dependent. Early blindness does not affect path reversal performance but is associated with worse path completion, a task requiring an absolute spatial strategy. Although congenitally blind subjects are overall less able to utilize spatial mechanisms during vestibular navigation, prior extensive physical spatial activity may enhance vestibular navigation.