This study aimed to compare cognitive-motor interference and related brain activity between people with subcortical stroke and those without stroke history.
Ten people with subcortical chronic stroke and 10 control individuals without stroke history (aged ≥ 50 years old, Montreal Cognitive Assessment score ≥ 22 points, able to walk continuously ≥ 1 min) participated in this case-control study. Each participant performed the following tasks in random order: (1) single-task walking, (2) single-task serial-3-subtractions/clock test (while standing), and (3) walking combined with a serial-3-subtractions/clock test (dual-task). Three trials (45 seconds in duration each) were conducted for each test condition. Participants were instructed to walk at their normal speed while generating as many correct answers in the subtraction/clock test as possible during dual-task walking (i.e., no prioritization). Gait speed was measured by MobilityLab system. Relative changes in concentration of oxygenated hemoglobin (△HbO) in bilateral PFC were measured with 40 channels of a continuous-wave system in fNIRS (NIRSport2). For both △HbO and gait parameters, dual-task cost was calculated as (dual-task performance minus single-task performance) × 100%) / (single-task performance).
Overall, the PFC showed higher △HbO in the stroke group than the control group, with medium effect size (ES=0.515, 95%CI [-0.328, 1.239]). The stroke group had greater dual-task cost for gait speed during dual-task serial-3-subtractions than controls (ES=0.536, 95%CI [-0.209, 1.323]). Such between-group difference during dual-task clock test was not significant (ES=0.228, 95%CI [-0.329, 0.784]). The dual-task cost of △HbO for both the serial-3-subtractions (ES=0.394, 95%CI [-0.168, 0.951]) and clock test (ES=0.193, 95%CI [-0.364, 0.748]) was not significantly different between groups. There existed a moderate correlation between increased △HbO in PFC of the non-lesioned hemisphere and greater gait speed during dual-task serial-3-subtractions in the stroke group (r=0.512).
Our findings suggest that increased activation of the PFC is associated with the presence of cognitive-motor interference among people with subcortical stroke. Interestingly, the stroke group has greater PFC activation during dual-tasking than the control group, probably due to the less neural efficiency and lower cognitive capacity in the former group. As a result, the same dual-task condition may impose a relatively higher cognitive demand on people with subcortical stroke. A greater brain activation level ensues, to maintain the dual-task performance. Dual-task serial-3-subtraction task better distinguishes dual-task performance between individuals with subcortical stroke and healthy controls, compared with the dual-task clock test. Study with a greater sample size is needed to further examine the role of PFC in dual-task walking in different subtypes of stroke (e.g, cortical vs subcortical).
The current study highlights the greater cognitive-motor interference during dual-task walking post-stroke and provides some insights into the underlying neural mechanisms. Physiotherapy intervention should incorporate treatment strategies to address dual-task walking deficits. More research is called for to decipher the neuroplastic changes associated with recovery of dual-task walking function.
Gait
Cognition
