RELATIONSHIP BETWEEN DUAL-TASK INTERFERENCE PATTERN AND SUPPLEMENTARY MOTOR CORTEX ACTIVATION: A CASE SERIES USING FUNCTIONAL NEAR INFRARED SPECTROSCOPY

C.S.L. Tsang^1,2, X. Li², M.Y.C. Pang²

¹The Chinese University of Hong Kong, Faculty of Medicine, Hong Kong, Hong Kong, ²The Hong Kong Polytechnic University, Department of Rehabilitation Sciences, Hong Kong, Hong Kong

Background: Walking while performing a secondary cognitive task is hardly avoidable in our daily living. Dual-task interference (decline in walking or/and cognitive task under dual-task condition) has been proposed to have a major impact on community ambulation. However, the underlying neural mechanisms of gait-related dual-task interference remain elusive although the involvement of the supplementary motor area (SMA) was implicated in previous research.

Purpose: The study aimed to investigate the relationship between different dual-task interference patterns and activation of the SMA during motor or cognitive single tasks and dual-task walking among community-dwelling healthy adults.

Methods: This was an observational exploratory study with repeated measures at a local university laboratory. Nine healthy participants with independent walking function (four women, aged 61.7±4.3 years, Montreal Cognitive Assessment score 29.0 ± 1.1) underwent a sequence of (1) single mobility task, (2) single cognitive task, and (3) cognitive-motor dual task, in random order. The mobility task involved treadmill walking at 75% of the maximum level ground walking speed. The cognitive task required the individual to perform serial-7-subtractions. In dual-task walking, the mobility and cognitive task were performed simultaneously. All tasks lasted for 1 minute. Number of correct responses (NCR) was recorded to indicate performance of the serial-7-subtractions. Activation of the bilateral SMA was measured using functional near infrared spectroscopy (fNIRS). Relative changes in concentration of oxygenated hemoglobin (HbO) were measured for its higher sensitivity in indicating hemodynamic changes.

Results: Among nine participants, four of them showed interference (i.e. decline in NCR) and five showed facilitation (increase in NCR) of cognitive performance. There was a significant DTI pattern*Hemisphere*Task interaction effect on HbO of measured at SMA (P=0.011,η²=0.466). Post-hoc analysis revealed that among those individuals who demonstrated interference pattern (n=4), greater HbO changes were observed under dual-task condition compared with single cognitive task condition (Cohen’s d=0.722) and single-task walking condition (d=0.676), but the results did not reach statistical significance. In contrast, among individuals with the facilitation pattern (n=5), HbO changes tended to be lower under dual-task condition when compared with the single cognitive task condition (d=0.544) and single-task walking condition (d=0.622).

Conclusions: Dual-task performance varied across participants, with some showing interference, while others demonstrating facilitation. In addition, preliminary findings provided by this study suggest different SMA activation pattern is associated with facilitation and interference under dual-task condition.

Implications: Activation of SMA is involved in dual-task walking. Different SMA activation may be associated with the presence of performance facilitation or interference. Research with a larger sample size is required to further explore how dual-task performance is related to activation of different brain regions.

Funding acknowledgements: This study was supported by a research grant provided by the Research Grants Council (General Research Fund: 15102921).

Keywords:
Dual-task walking
Dual-task interference
Supplementary motor cortex

Topics:
Older people

Did this work require ethics approval? Yes

Institution: The Hong Kong Polytechnic University

Committee: Institutional Review Board

Ethics number: HSEARS20160224002-03