Perturbation-evoked cortical responses and altered causal information flow reflect more effortful but less efficient...

Effective responses to sudden mechanical perturbations require coordinated neural processes for generating rapid, situation-specific postural reactions. Sensorimotor impairments following anterior cruciate ligament reconstruction (ACLR) may disrupt this coordination and contribute to inefficient postural control strategies. Therefore, the present study investigated perturbation-evoked behavioral and cortical dynamics in individuals after ACLR compared with asymptomatic controls. Seventeen athletes after ACLR (8 female, 23.6 ± 3.7 years) and thirteen controls (4 female, 25.9 ± 4.2 years) underwent 100 unpredictable platform translations in bipedal stance. Postural responses were examined using statistical parametric mapping of anterior-posterior hip acceleration. Cortical dynamics were assessed via mobile electroencephalography by quantifying perturbation-evoked potentials (PEP N1) and effective connectivity derived from renormalized partial directed coherence. Compared to controls, the ACLR group exhibited significantly higher hip acceleration during early voluntary adjustment and late re-stabilization phases of the postural response. Due to the different approaches of group-level comparisons, 20 participants (11 ACLR / 9 CON) showing characteristic event-related potentials were used for the PEP analysis, whereas 30 participants (17 ACLR / 13 CON) were eligible for the effective connectivity analysis utilizing probabilistic dipole densities. N1 amplitudes of the PEPs were significantly higher in the ACLR group, whereas fronto-central information flow was significantly lower early after perturbation, but significantly higher during re-stabilization. These results suggest that postural responses after ACLR may rely on increased cortical activation and altered dynamics within a fronto-central network,  pointing at greater voluntary control and reduced automatization of sensorimotor processes, likely predisposing individuals after ACLR to an elevated risk of dysfunction and re-injury.