Interpreting Prefrontal Recruitment During Walking After Stroke: Influence of Individual Differences in Mobility and Cognitive Function

Abstract

Background : Functional near-infrared spectroscopy (fNIRS) is a valuable neuroimaging approach for studying cortical contributions to walking function. Recruitment of prefrontal cortex during walking has been a particular area of focus in the literature. The present study investigated whether task-related change in prefrontal recruitment measured by fNIRS is affected by individual differences in people post-stroke. The primary hypotheses were that poor mobility function would contribute to prefrontal over-recruitment during typical walking, and that poor cognitive function would contribute to a ceiling in prefrontal recruitment during dual-task walking (i.e., walking with a cognitive task). Methods : Thirty-three adults with chronic post-stroke hemiparesis performed three tasks: typical walking at preferred speed ( Walk ), serial-7 subtraction ( Serial7 ), and walking combined with serial-7 subtraction ( Dual-Task ). Prefrontal recruitment was measured with fNIRS and quantified as the change in oxygenated hemoglobin concentration (ΔO 2 Hb) between resting and active periods for each task. Spatiotemporal gait parameters were measured on an electronic walkway. Stepwise regression was used to assess how prefrontal recruitment was affected by individual differences including age, sex, stroke region, injured hemisphere, stroke chronicity, 10-meter walking speed, balance confidence measured by Activities-specific Balance Confidence (ABC) Scale, sensorimotor impairment measured by Fugl-Meyer Assessment, and cognitive function measured by Mini-Mental State Examination (MMSE). Results : For Walk , poor balance confidence (ABC Scale score) significantly predicted greater prefrontal recruitment (ΔO 2 Hb; R 2 = 0.25, p = 0.003). For Dual-Task , poor cognitive function (MMSE score) significantly predicted lower prefrontal recruitment (ΔO 2 Hb; R 2 = 0.25, p = 0.002). Conclusions : Poor mobility function predicted higher prefrontal recruitment during typical walking, consistent with compensatory over-recruitment. Poor cognitive function predicted lower prefrontal recruitment during dual-task walking, consistent with a recruitment ceiling effect. These findings indicate that interpretation of prefrontal recruitment should carefully consider the characteristics of the person and demands of the task.

Backward locomotor treadmill training combined with transcutaneous spinal direct current stimulation in stroke: a randomized pilot feasibility and safety study

“…In sum, only two of the six participants (33%) were able to independently complete all six BLTT sessions. This finding is akin to previous walking rehabilitation studies that have reported that baseline walking severity level may influence training ability ( Burke et al , 2014 ; Dobkin et al , 2014 ; Bernhardt et al , 2016 ; Boyd et al , 2017 ), which may be associated with the magnitude of post-stroke cognitive and physical limitations in this subgroup, ( Kurz et al , 2012 ; Hawkins et al , 2018 ; Chatterjee et al , 2019 ). Therefore, it is possible that our BLTT protocol, in its present form, is too tasking for severely impaired individuals and future protocols will need modification to further accommodate those with severe walking impairment.…”

“…For example, stroke commonly impacts chronologically older individuals, which is associated with a decline in gait speed, joint range of motion and spatiotemporal ability ( Stacy et al , 2007 ). Moreover, functional neuroimaging studies have reported an increased tendency for prefrontal compensatory recruitment during normal walking in this population ( Kurz et al , 2012 ; Chatterjee et al , 2019 ). In addition, backward walking is characteristically more physically demanding than walking forward ( Flynn et al , 1994 ; Terblanche et al , 2005 ) and requires movement patterns that tend to be particularly difficult after stroke (i.e.…”

Functional Status Is Associated With Prefrontal Cortex Activation in Gait in Subacute Stroke Patients: A Functional Near-Infrared Spectroscopy Study

“…Other recent findings suggest that people with poorer mobility such as elders or neurological patients exhibits a higher PFC activation than control groups during walking, reflecting a higher cognitive demand (7,9). In stroke, lower mobility was associated with a higher (and saturated) recruitment of the PFC in walking tasks (7,10). Hence, the challenge for upcoming studies investigating brain activation during walking in stroke patients relies on a better understanding of the relationship between the cortical control of gait and functional independence.…”

Multimodal Imaging of Brain Activity to Investigate Walking and Mobility Decline in Older Adults (Mind in Motion Study): Hypothesis, Theory, and Methods

“…fNIRS has also provided evidence of "CRUNCH-like" changes in cortical activity during walking. Evidence of prefrontal over-recruitment during typical steady state walking has been reported in several populations with compromised mobility, including older adults (Chen et al, 2017;Mirelman et al, 2017;Hawkins et al, 2018) and people with stroke (Hawkins et al, 2018;Chatterjee et al, 2019), Parkinson's disease (Maidan et al, 2016a,b), and multiple sclerosis (Hernandez et al, 2016). This is potentially consistent with recruitment of attentional resources to maintain functional walking and compensate for weakness, sensory loss, and/or other impairments affecting control of walking (Clark, 2015).…”

“…These data are consistent with over-recruitment of prefrontal resources in older adults during typical steady state walking. Another study reported data suggesting a ceiling effect for prefrontal recruitment during complex walking in adults poststroke (Chatterjee et al, 2019). The participants performed dual-task walking (with serial-7 subtraction) while prefrontal activity was recorded with fNIRS.…”