The Impact of Dual-Tasking on the Vestibulo-Ocular Reflex.

Objective: Daily activities often involve performing multiple tasks simultaneously and require stable gait and posture. The vestibular system provides balance control through its reflexes mediated via the vestibulospinal tract and gaze stability mediated via the vestibulo-ocular reflex (VOR), which maintains stable vision during head motion while continuously adapting to environmental changes. Cognitive and motor activities reportedly can adversely affect balance function and vice versa. We hereby investigate how dual cognitive and motor tasks influence the VOR and its adaptability to varying target distances by means of the video head impulse test (vHIT).

Study design: Prospective interventional study.

Setting: Tertiary academic medical center.

Patients: Adults aged 18 to 40 without a history of instability disorders, otologic surgeries, or prior strokes.

Intervention: vHIT testing.

Main outcome measure: Sixteen participants underwent 14 vHITs under single-task and dual-task (cognitive or motor) conditions with far (1.5 m) and near (15 cm) target distances. Two types of activities were chosen for both the cognitive and motor tasks. The VOR gain and its adaptation, measured as the ratio of near-to-far gain, were assessed. A paired t-test was used to evaluate differences in reflex gain and adaptation between single- and dual-task conditions.

Results: There were no significant differences in VOR gain or adaptation between single-task and either cognitive or motor dual-task conditions. Similar reflex gains were observed between dual-task conditions for both far and near targets.

Conclusions: Gaze stability mediated by the VOR is a robust function with low sensitivity to external loads, unlike gait and posture balance control.