Effect of sequential and simultaneous motor-cognitive dual-task on cerebral hemodynamics and behavioral performance in healthy adults: an fNIRS study

Abstract Background Task complexity and individual characteristics influence cerebral hemodynamics and behavioral performance in motor-cognitive dual tasks (DT). However, the impact of task sequencing (sequential vs. simultaneous) remains unclear. This study used functional near-infrared spectroscopy (fNIRS) to examine how different DT sequences affect brain activity and behavior in healthy adults. Methods Twenty-eight right-handed adults (14 men, 14 women, 22.53 ± 3.46 years) completed five treadmill tasks: motor single-task (MST), cognitive single-task (CST), sequential motor-cognitive DT (M-CDT), sequential cognitive-motor DT (C-MDT), and simultaneous DT (CMDT). fNIRS measured oxyhemoglobin (Oxy-Hb) concentrations and functional connectivity (FC) across 10 brain regions. Gait and cognitive performance data were recorded. Results Oxy-Hb was lowest during MST, while C-MDT and CMDT showed higher activation in multiple brain regions. FC was strongest in C-MDT, particularly between cognitive and motor areas. CMDT increased the lower extremity support phase, whereas C-MDT resulted in faster walking speed. No significant differences in cognitive performance were observed across DT conditions ( P > 0.05). Conclusion Sequential initiation of cognitive tasks prior to motor tasks may promote more efficient cortical engagement during dual-task performance, supporting the “posture second” hypothesis. Further studies involving larger and more diverse populations and a broader range of tasks are needed to confirm and extend these findings.