Real-Time FNIRS Investigation of Discrete and Continuous Cognitive Demands During Dual-Task Walking

Abstract

Younger adults who are walking and doing additional tasks at the same time may not realize if their performance suffers, putting some at greater risk for injury and impairment during certain tasks. This thesis has addressed this confound by developing a divided attention paradigm focusing on discrete and continuous demand manipulations. The work assessed in motorcognitive processing changes with cerebral and behavioral monitoring of over-ground walking with or without cognitive tasks. Participants (n = 19, 18-35 years, 13 females) were asked to walk at their usual pace [usual walking condition (SM)], walk at their usual pace while performing a cognitive task [dual-task condition (DT)] as well as conduct a cognitive task while standing [single cognitive condition (SC)]. All participants conducted two discrete [simple response time (SRT) & go-no-go (GNG)] and two continuous cognitive tasks [N-back (NBK) & double number sequence (DNS)] of increasing demand. The study revealed significant brain and behavior interactions during the most demanding continuous cognitive task, the DNS. The findings demonstrated lower accuracy rates, slower walk speeds as well as greater cerebral oxygenation in DNS DT in comparison to single task conditions. With increasing cognitive demands and tasks, there were longer response times, as well as lower accuracy rates. The behavioral findings were qualified by marginally significant interactions in a 2 x 4 RM ANOVA between SC-DT task and demand for accuracy rate [F (3, 54) = 2.66, p = 0.06, η2 =.13], significant interactions in response time [F (2, 36) = 4.1, p = 0.026, η2 =.18] as well as significant SM-DT task and demand findings for walk speed [F (3, 54) =5.3, p = 0.003, η2 =.23]. The 2 x 2 x 4 RM ANOVA revealed significant HbO2 interactions between walking tasks (single and dual), hemisphere and demand [F (3, 54) = 5.730, p = 0.002, η2 =.24] in the DNS only. The data suggests that greater demand manipulations with continuous cognitive tasks may be sensitive to both prefrontal cortex (PFC) and behavioral assessments in younger adults (YA). Further validation of the discrete-continuous demand paradigm in motor studies may provide a basis for cognitive assessment with applications in motor learning, cognitive training, aging and more.