# Cortical hemodynamic responses in older stroke patients during a walking-based Stroop dual task: a functional near-infrared spectroscopy study

## TL;DR

This study used fNIRS to examine brain activity in older stroke patients during walking tasks with varying cognitive demands, finding increased prefrontal and motor cortex activation during more complex tasks.

## Contribution

The study reveals heightened cognitive-motor interference in older stroke survivors during dual-task walking, emphasizing conflict processing as a key rehabilitation target.

## Key findings

- Greater activation in the right prefrontal cortex and bilateral motor cortices during incongruent tasks.
- Increased functional connectivity between prefrontal and motor regions under higher cognitive load.
- Reduced walking speed and step length during incongruent tasks compared to simpler conditions.

## Abstract

This study aimed to investigate cortical hemodynamic responses in older stroke patients during a walking-based Stroop dual task using functional near-infrared spectroscopy (fNIRS).

Thirty-four stroke patients aged over 55 years performed three walking-based Stroop dual tasks while undergoing fNIRS recording: (a) color naming only (congruent task, CT), (b) color naming without color cues (neutral task, NT), and (c) incongruent color–word Stroop naming (incongruent task, IT). Gait parameters (walking speed, step length, stride width) and dual-task performance were measured. fNIRS data were analyzed to quantify cortical activation and functional connectivity (FC), focusing on the left and right prefrontal cortices (LPFC and RPFC) and motor cortices (LMC and RMC).

fNIRS revealed greater activation in the RPFC and bilateral motor cortices during the IT compared with the CT. Overall FC strength increased in the NT and IT, particularly between the LPFC and RPFC, LPFC and RMC, and RPFC and LMC. Walking speed and step length were significantly reduced in the IT compared with the CT, and dual-task performance declined under both higher-load conditions.

Increasing Stroop-related cognitive demands during walking elicited greater prefrontal–motor activation and connectivity, accompanied by measurable dual-task costs in gait and performance. Slightly negative HbO values in the motor cortices during the simplest condition are likely driven by residual systemic influences rather than true deactivation, and our main inferences rely on within-subject contrasts across conditions. These findings indicate heightened cognitive–motor interference in older stroke survivors and highlight conflict processing as a key mechanism that may inform targeted dual-task rehabilitation strategies.