Downregulation of early visual cortex excitability mediates oscillopsia suppression
Authors
Ahmad, HenaRoberts, Ed
Patel, Mitesh
Lobo, Rhannon
Seemungal, Barry M.
Arshad, Qadeer
Bronstein, Adolfo M.
Issue Date
2017-08-16
Metadata
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Objective: To identify in an observational study the neurophysiologic mechanisms that mediate adaptation to oscillopsia in patients with bilateral vestibular failure (BVF). Methods: We directly probe the hypothesis that adaptive changes that mediate oscillopsia suppression implicate the early visual-cortex (V1/V2). Accordingly, we investigated V1/V2 excitability using transcranial magnetic stimulation (TMS) in 12 avestibular patients and 12 healthy controls. Specifically, we assessed TMS-induced phosphene thresholds at baseline and cortical excitability changes while performing a visual motion adaptation paradigm during the following conditions: baseline measures (i.e., static), during visual motion (i.e., motion before adaptation), and during visual motion after 5 minutes of unidirectional visual motion adaptation (i.e., motion adapted). Results: Patients had significantly higher baseline phosphene thresholds, reflecting an underlying adaptive mechanism. Individual thresholds were correlated with oscillopsia symptom load. During the visual motion adaptation condition, no differences in excitability at baseline were observed, but during both the motion before adaptation and motion adapted conditions, we observed significantly attenuated cortical excitability in patients. Again, this attenuation in excitability was stronger in less symptomatic patients. Conclusions: Our findings provide neurophysiologic evidence that cortically mediated adaptive mechanisms in V1/V2 play a critical role in suppressing oscillopsia in patients with BVF.Citation
Ahmad H., Roberts RE., Patel M., Lobo R., Seemungal B., Arshad Q., Bronstein A. (2017) 'Downregulation of early visual cortex excitability mediates oscillopsia suppression', Neurology 89 (11) pp. 1179-1185; doi: 10.1212/WNL.0000000000004360Publisher
Academic Academy of NeurologyJournal
NeurologyAdditional Links
http://n.neurology.org/content/89/11/1179Type
Journal articleLanguage
enDescription
© 2017 The Authors. Published by American Academy of Neurology. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1212/WNL.0000000000004360ISSN
0028-3878ae974a485f413a2113503eed53cd6c53
10.1212/WNL.0000000000004360
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