Sensory Reweighting Revealed by Superior Parietal Cortex-Based Functional Connectivity in Chronic Ankle Instability: A Resting-State fMRI Study.

Abstract

Purpose: Individuals with chronic ankle instability (CAI) are believed to rely more heavily on visual input during postural control due to impaired somatosensory function; however, the neural mechanisms underlying sensory reweighting in CAI are not well understood. This study explored the neural and behavioral correlates of increased visual reliance in CAI through functional connectivity (FC) analysis.

Methods: This cross-sectional study enrolled 37 patients with CAI and 36 healthy individuals. Participants underwent postural stability assessments using the single-leg stance test, both with their eyes open and closed. Traditional and modified Romberg ratios were calculated. Resting-state functional magnetic resonance imaging was used to estimate FC between the superior parietal cortex (SPC) and visual, sensorimotor, and cerebellar regions, as well as the coefficient of variation of these FCs.

Results: Compared with healthy individuals, patients with CAI displayed significantly higher visual reliance, as indicated by the traditional and modified Romberg ratios of sway length (Cohen's d = 0.47-0.57). Patients with CAI also exhibited stronger FC between the SPC and higher-level visual cortices (Cohen's d = 0.56-0.62) and more unstable coefficient of variation for FC between the SPC and the cerebellar anterior lobe (Cohen's d = 0.64). Subregion analysis revealed that variability in FC between subregions I-IV of the cerebellar anterior lobe and anterior lateral area 7 of the SPC was negatively correlated with the modified Romberg ratio in the anterior-posterior direction (r = -0.35) among the patients.

Conclusions: The study revealed high visual reliance, strong yet variable SPC-based connections with visual cortices and variable SPC-based connections with the cerebellum among patients with CAI, suggesting that neural changes associated with sensory reweighting mechanisms underlie increased visual reliance during postural stability.