Downregulation of early visual cortex excitability mediates oscillopsia suppression.pdf (458.69 kB)
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Downregulation of early visual cortex excitability mediates oscillopsia suppression.

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journal contribution
posted on 19.07.2019, 14:39 by H Ahmad, RE Roberts, M Patel, R Lobo, B Seemungal, Q Arshad, A Bronstein
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.

Funding

The research was funded by the UK Medical Research Council (MR/J004685/1) and supported by the National Institute for Health Research (NIHR) Imperial Biomedical Research Centre.

History

Citation

Neurology, 2017, 89 (11), pp. 1179-1185

Author affiliation

/Organisation/COLLEGE OF LIFE SCIENCES/Biological Sciences/Neuroscience, Psychology and Behaviour

Version

VoR (Version of Record)

Published in

Neurology

Publisher

American Academy of Neurology (AAN), Lippincott, Williams & Wilkins

eissn

1526-632X

Acceptance date

06/06/2017

Copyright date

2017

Available date

19/07/2019

Publisher version

https://n.neurology.org/content/89/11/1179

Language

en