Background Patients with bilateral vestibular failure (BVF) suffer from oscillopsia during head movements. This is secondary to the loss of the vestibulo-ocular reflex which is responsible for stabilising retinal images during head movements of high frequency or velocity. Previous studies documented decreased visual motion sensitivity in such patients at low velocities. The authors now examine motion coherence tasks, which have two advantages: (1) the task is associated with the functions of the middle temporal area; and (2) it affords testing at low and high motion velocities, as relevant for patients with oscillopsia due to BVF.
Methods Nine BVF patients and nine healthy control subjects were examined with a random dot pattern with variable percentages of dots moving in the target direction. Participants were asked to indicate in which of two possible directions they perceived the coherent motion. Horizontal and vertical planes were tested at speeds from 0.156 to 40°/s.
Results Motion coherence thresholds were lower at higher speeds in both groups (p<0.0001). BVF patients had raised motion coherence thresholds (p=0.002) across all velocities as compared with the control subject group.
Conclusion In a motion coherence paradigm, BVF patients show raised thresholds. This is the first demonstration of diminished visual motion processing at high velocities, supporting the view that the changes allow BVF patients to partly compensate for the oscillopsia. The findings are interpreted as an adaptive process likely to involve the middle temporal visual motion processing areas.
- Bilateral vestibular failure
- vestibulo-ocular reflex
- motion coherence
- middle temporal (MT) area
- clinical neurology
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Funding This work was supported by the German Ministry of Education and Research (BMBF), grant No 01EO0901 to the IFBLMU ‘Integriertes Forschungs- und Behandlungszentrum für Schwindel, Gleichgewichts- und Augenbewegungsstörungen’ and a post-doc grant to the first author by Deutsche Forschungsgemeinschaft (DFG, Germany) in collaboration with the Medical Research Council (UK), Grant No KA2284/2-1.
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was provided by the University College London, Department of Cognitive Neuroscience Ethics Approval Board (ethics approval no EA1144/001).
Provenance and peer review Not commissioned; externally peer reviewed.