How Eye Movements Stabilize Posture in Patients With Bilateral Vestibular Hypofunction

Area of Science:

• Neuroscience
• Human Physiology
• Biomechanics

Background:

• Chronic bilateral vestibular hypofunction (BVH) causes oscillopsia and instability, particularly without visual input.
• The role of specific visual inputs, like retinal slip and eye movements, in compensating for vestibular loss is debated.

Purpose of the Study:

• To investigate how BVH patients use visual information, including eye movements, to maintain posture stability.
• To compare the postural control strategies of BVH patients and healthy individuals under various visual conditions.

Main Methods:

• Static posturography was used to assess posture stability in 21 chronic BVH patients and 21 healthy controls.
• Participants stood in darkness, fixated a stable target, or pursued a moving target under goggles inducing slow eye movements (4.5 Hz) or saccades (1.2 Hz).
• Non-linear analysis (wavelet transform, fractional Brownian-motion) of center of foot pressure (CoP) data was performed.

Main Results:

• BVH patients showed significantly worse posture stability in darkness compared to controls.
• Posture stability improved substantially in BVH patients when fixating a visual target or during pursuit eye movements (slow and saccadic).
• Control participants' postural performance was less affected by the visual conditions.

Conclusions:

• BVH patients significantly enhance posture stability by utilizing extraocular signals from eye movements more than healthy individuals.
• BVH patients shift towards a more automatic posture control mode in dual-task conditions (posture and visuo-motor task).