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
URI: http://hdl.handle.net/10044/1/49006
DOI: https://dx.doi.org/10.​1212/​WNL.​0000000000004360
ISSN: 0028-3878
Publisher: American Academy of Neurology (AAN)
Start Page: 1179
End Page: 1185
Journal / Book Title: Neurology
Volume: 89
Issue: 11
Sponsor/Funder: Medical Research Council (MRC)
Funder's Grant Number: MR/J004685/1
Keywords: Science & Technology
Life Sciences & Biomedicine
Clinical Neurology
Neurosciences & Neurology
BILATERAL VESTIBULAR FAILURE
TRANSCRANIAL MAGNETIC STIMULATION
EYE-HEAD COORDINATION
FUNCTIONAL CONNECTIVITY
VESTIBULOOCULAR REFLEX
CORTICAL EXCITABILITY
MOTION
MECHANISMS
ADAPTATION
ACTIVATION
1103 Clinical Sciences
1109 Neurosciences
1702 Cognitive Science
Neurology & Neurosurgery
Publication Status: Published
Appears in Collections:Physics
Department of Medicine
Faculty of Medicine
High Energy Physics
Faculty of Natural Sciences



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