A dual-task study of interference between mental activity and control of balance

OBJECTIVE: This study aimed to examine interference between mental activity and control of balance. STUDY DESIGN: In a mixed design, dual-task study, the performance of patients and healthy control subjects was compared on computerized dynamic posturography, on a visuospatial mental task, and when performing the mental task while balancing. SETTING: The study was performed at a tertiary referral outpatient neuro-otology clinic. PATIENTS AND SUBJECTS: The patient group comprised 24 patients seen consecutively at the clinic because of vertigo and dizziness. The control group consisted of 24 subjects with no complaint or medical history of dizziness or balance disorder, matched with the patients for age and gender. MAIN OUTCOME MEASURES: Performance on a visuospatial mental task and on the computerized dynamic posturography test (conditions 4 and 5) was measured. RESULTS: Balancing on the posturography test resulted in a deterioration in performance on the mental task for both patients and control subjects. The effect was more marked when subjects had their eyes closed. Results on the balance test showed that normal subjects and patients with normal balance also swayed more when performing the mental task, whereas patients who had failed the posturography test swayed less when performing the mental task. CONCLUSIONS: These results show that mental performance deteriorates when performing a demanding balance task. In addition, in both normal subjects and patients, balance also may be affected by mental activity in complex and varied ways that merit further investigation.