Dual-task study of cognitive and postural interference in patients with vestibular disorders.
OBJECTIVE: To study the relation between a mental task (silent backward counting) and posture in patients with vestibular deficits and to study the role of attention. STUDY DESIGN: In Experiment 1, postural sway and performance on the mental task were measured in a 2 x 2 dual-task design (with or without mental task and calf stimulation). In Experiment 2 a similar design was used, the only difference being that during trials without the mental task, patients were instructed to focus on their balance and provide a rating of body sway. SETTING: The study was carried out at a tertiary referral outpatient audiology clinic. PATIENTS: The first experiment included 20 patients and the second experiment 10 patients seen consecutively at the clinic on account of vertigo and dizziness. MAIN OUTCOME MEASURES: Performance on a mental task and on a force platform for measurement of anterior-posterior and lateral sway. RESULTS: Results showed no effect of the balance conditions on the cognitive task in Experiments 1 and 2. The mental task led to less body sway during calf stimulation in Experiment 1. In Experiment 2, when attention was focused on body sway, an opposite result was found, with more sway during the mental task in the condition of no calf stimulation. CONCLUSIONS: Control of body sway and cognitive functioning are to some extent related, most likely because of postural stability being prioritized in dual-task conditions.