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. 2026 Feb 2;17:1644741. doi: 10.3389/fnagi.2025.1644741

Figure 1.

Uneven Terrain Walking Speed and N-Back Working Memory tasks are depicted. Image A shows four difficulty levels of terrain: flat, low, medium, and high, with varying peg sizes and densities. Image B displays the N-Back task sequence, with increasing difficulty from 0-back to 3-back, highlighted with blue squares and arrows indicating task order.

Schematic overview of the overground uneven terrain walking task (A) and the n-back task (B). Participants walked at their typical pace over a novel custom-made overground uneven surface comprising four terrains: flat, low, medium, and high terrain unevenness while walking speed was measured. The four terrain surfaces were created by using rigid foam disks of various heights. The percentages indicate the proportion of disks of the specified height (A). Participants performed the n-back task, including four n-back levels: 0-back, 1-back, 2-back, and 3-back, while prefrontal cortical activity was recorded with fNIRS (B).