Downregulation of early visual cortex excitability mediates oscillopsia

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Title: Downregulation of early visual cortex excitability mediates oscillopsia
Author(s): Ahmad, H
Roberts, E
Patel, M
Lobo, R
Seemungal, B
Arshad, Q
Bronstein, A
Item Type: Journal Article
Abstract: Objective; Identifying the neurophysiological mechanisms that mediate adaptation to oscillopsia in patients with bilateral-vestibular failure (BVF); an observational study. Methods; We directly probe the hypothesis that adaptive changes which 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 whilst performing a visual-motion adaptation paradigm during the following conditions: (i) BASELINE measures (i.e. static), (ii) during visual-motion (i.e. MOTION PRE ADAPTATION) and, (iii) during visual-motion following 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 MOTION PRE ADAPTATION and MOTION ADAPTED conditions, we observed significantly attenuated cortical excitability in patients. Again this attenuation in excitability was stronger in less symptomatic patients. Conclusion; Our findings provide neurophysiological evidence that cortically-mediated adaptive mechanisms in V1/V2 play a critical role in suppressing oscillopsia in patients with bilateral vestibular failure.
Publication Date: 16-Aug-2017
Date of Acceptance: 6-Jun-2017
ISSN: 0028-3878
Publisher: American Academy of Neurology (AAN)
Journal / Book Title: Neurology
Copyright Statement: This paper is embargoed until publication. Once published it will be available fully open access.
Sponsor/Funder: Medical Research Council (MRC)
Funder's Grant Number: MR/J004685/1
Keywords: Neurology & Neurosurgery
1103 Clinical Sciences
1109 Neurosciences
1702 Cognitive Science
Publication Status: Accepted
Embargo Date: publication subject to indefinite embargo
Appears in Collections:Department of Medicine
Faculty of Medicine

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