Disrupted Sensorimotor Integration, Rather Than Regional Cortical Activation, Is Associated with Force Sense Deficits in Chronic Ankle Instability: A Partial Directed Coherence Analysis.

OBJECTIVE: Chronic ankle instability (CAI) involves force control deficits that may impair postural stability, yet their neural basis remains unclear. This study examined alterations in sensorimotor network connectivity and their relationship with force sense deficits in CAI. METHODS: Thirty individuals with CAI and 27 healthy controls performed ankle plantarflexion and dorsiflexion force-matching tasks while electroencephalography and electromyography were recorded. Source-level cortical signals were reconstructed, and partial directed coherence was used to quantify cortico-cortical connectivity within the sensorimotor network, including the primary motor cortex (M1), primary somatosensory cortex (S1), premotor cortex (PMC), supplementary motor area (SMA), and inferior parietal lobule (IPL), as well as cortico-muscular connectivity between these cortical regions and the lower-limb muscles, including the soleus (SOL) and tibialis anterior (TA), in the beta and gamma bands. Force-matching performance was quantified using absolute error (AE%). Group differences in task performance and connectivity measures were examined using t-tests or Mann-Whitney U tests, and their associations were assessed using Pearson or Spearman correlations. RESULTS: Individuals with CAI exhibited higher AE% than healthy controls during both plantarflexion and dorsiflexion. These deficits were characterized by significant reductions in beta-band cortico-cortical connectivity (e.g., S1 → M1 and IPL → SMA during both plantarflexion and dorsiflexion) and in descending cortico-muscular connectivity (M1 → SOL during plantarflexion; PMC/SMA → TA during dorsiflexion). An additional increase in ascending connectivity (e.g., SOL → IPL) was observed during plantarflexion, and it was negatively correlated with AE% in the CAI group (all corrected p < 0.05). CONCLUSION: Force sense deficits in CAI are associated with disrupted sensorimotor network connectivity rather than altered regional cortical activity, highlighting the importance of network-level integration for rehabilitation.