Cortical hemodynamic correlates of postural sway frequency redistribution during sensory-challenged quiet standing.

Abstract

BACKGROUND: Standing balance requires continual adjustment to the available sensory information. How changes in sway frequency composition relate to cortical hemodynamic responses during quiet standing remains unclear. RESEARCH QUESTION: Do eye closure and foam support alter anterior-posterior (AP) center-of-pressure (CoP) frequency composition, and are these changes associated with regional hemoglobin fluctuations and interregional coupling. METHODS: Forty-five healthy young adults completed eyes-open and eyes-closed standing on firm and foam surfaces. AP CoP relative energy was examined in four intervals: < 0.10, 0.10-0.50, 0.50-1.0, and 1.0-2.0 Hz. Functional near-infrared spectroscopy (fNIRS) measured oxygenated hemoglobin (HbO) fluctuations and interregional coupling. Repeated-measures analyses of variance were supplemented by baseline-adjusted correlations and influence-sensitivity analyses. RESULTS: Eye closure and foam support increased relative energy in the 0.50-1.0 Hz interval. Prefrontal-sensorimotor and premotor-parietal HbO coupling decreased on foam. The left-parietal interaction did not survive correction across eight bilateral regions. Changes in CoP relative energy were positively associated with parietal HbO fluctuations and negatively associated with interregional coupling. Association directions were unchanged in rank-based, leave-one-participant-out, and demographic-adjusted analyses. SIGNIFICANCE: Sensory-challenged standing was accompanied by covariation between AP sway frequency composition and task-epoch HbO measures. The findings link postural output to hemodynamic responses without identifying the sensory weights underlying that output.

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