Visual motion detection in patients with absent vestibular function

Abstract

Labyrinthine defective subjects (LDS) experience oscillopsia during head movements due to the absence of the vestibulo-ocular reflex (VOR). The purpose of this study was to compare horizontal and vertical visual motion detection in LDS during (i) body-stationary and (ii) horizontal whole-body oscillation conditions. Twelve LDS and controls detected the onset of drift direction of a grating that moved with accelerating velocity. Thresholds were raised in the patient group in both conditions. The loss of the VOR per se cannot explain raised thresholds in the body-stationary condition nor during whole-body (horizontal) oscillation with vertical grating motion. Findings indicate changes in visual processing that make LDS less sensitive to visual motion. It is postulated that these changes are due to adaptive mechanisms involved to reduce oscillopsia.

Differential effect of visual motion adaption upon visual cortical excitability

“…It is known that patients with peripheral vestibular disorders can have excessive retinal image motion and oscillopsia (Deutschländer et al 2008;Kalla et al 2011;Shallo-Hoffmann and Bronstein 2003) and/or an enhanced visual motion sensitivity (visual dependence) (Bronstein 2005). This is important because following acute vestibular lesions, visual dependency measures are predictive of long-term clinical outcome (Cousins et al 2014).…”

Adaptive motion processing in bilateral vestibular failure

“…It was later found that sensitivity for slowly moving small targets8 and drifting gratings9 was impaired in BVF patients, even when patients' heads were stationary, and the VOR was inactive 8. Consequently, the mechanism that helps to suppress oscillopsia during head movements cannot be entirely switched off when the head is held still, thus suggestive of a generalised adaptive suppression in motion sensitivity perception in these patients, presumably in cortical areas responsible for multimodal motion processing 8 9…”

“…Since pursuit-optokinetic mechanisms suffice to stabilise retinal images at low velocities, it could be argued that the velocities previously examined are neither relevant to the patients' oscillopsia nor relevant to the known physiology of the VOR. We therefore decided to examine visual motion perception with the motion coherence paradigm,9 where a random moving dot pattern is used. In addition to being able to examine a wide range of velocities, an added advantage of this task for the study of BVF patients is that motion coherence is thought to involve integration of information across the display, which is closely associated with activity of the middle temporal area of the brain 10–12.…”

Cálculo de los tiempos de circularvección en una población con patología vestibular. Influencia del estímulo visual

“…En esas situaciones patológi-cas este fenómeno continúa adaptándose a la información recibida. Se produce un aumento de los umbrales de respuesta a los estímulos en movimiento y así se evita la oscilopsia 12 , o una menor activación o desactivación según las necesidades de control postural 13 .…”