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bioRxiv · 10.1101/2025.07.28.667302

Foot Sole Cutaneous Somatosensory Modulation Based on Balance Demands

Doroodchi, A.
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Abstract

Postural complexity may shape how the nervous system processes plantar cutaneous input. We tested whether somatosensory evoked potentials (SEPs) elicited by foot-sole stimulation scale with balance demands, hypothesizing larger responses for more complex tasks. Thirty-one healthy adults performed standing, straight-step, and diagonal-step conditions while receiving brief electrical stimulation to the stance foot sole; SEPs (P50, N90, peak-to-peak) were analyzed at Cz using pooled and order-specific approaches. In the pooled analysis, peak-to-peak SEP amplitude was greater for both stepping conditions than standing (Standing vs. Straight, P = 0.041; Standing vs. Diagonal, P = 0.026). Order-specific analysis showed an early amplification: the first SEP (0.5 s after the warning cue) was larger for diagonal than straight stepping (peak-to-peak, P = 0.009; N90, P = 0.027). Source localization at N90 revealed greater activation during stepping than standing in paracentral gyrus & sulcus, inferior parietal angular gyrus, and superior parietal gyrus, consistent with enhanced sensorimotor processing under higher postural demands. Moreover, right paracentral gyrus & sulcus activity was higher for diagonal vs. straight stepping for the first and fourth SEPs. Together, these findings indicate that increasing balance demands up-weight plantar afferent processing and recruit contralateral sensorimotor/parietal regions, particularly early in preparation, supporting the view that cortical sensory gain is tuned to postural complexity.

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Doroodchi, A.. 2025-07-31. Foot Sole Cutaneous Somatosensory Modulation Based on Balance Demands. https://doi.org/10.1101/2025.07.28.667302

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