2027

Li, Feiyue; Byman, Anni; Chen, Junru; Mujunen, Toni; Piitulainen, Harri

Background Cortical processing of proprioceptive-dominant afference arising from the knee joint is largely unknown. Magnetoencephalography (MEG) can be used to quantify the cortical processing of the proprioceptive afference, but MEG-compatible and well-controlled stimulation of the knee joint is technically challenging, and thus has received less attention. New method We introduced a novel MEG-compatible stimulator that delivers controlled patellar tendon taps and elicits proprioceptive-dominant afferent input to the cortex in the knee joint. The stimulus intensity is adjustable, allowing graded activation of proprioceptive input and, when required, elicitation of the patellar-tendon reflex. Results The novel stimulator elicited clear muscular and cortical responses in both intensity conditions. Cortical responses demonstrated moderate to excellent intersession reliability for peak evoked field amplitude (ICC: 0.69–0.96), beta suppression (0.89–0.90) and beta rebound (0.96–0.97). Notably, beta suppression peaked more laterally than expected in both hemispheres. Peak EMG amplitudes in VL and VM muscles were reliable for both intensity conditions (ICC: 0.66–0.89), and stimulus kinematics remained consistent throughout measurements. Comparison with existing methods Previous robotic or motor-driven devices have been used to evoke cortical responses to knee-joint proprioceptive stimulation, but mechanical coupling across adjacent joints may limit knee-specific input. The present stimulator provides a mechanically simple and MEG-compatible tool that targets proprioceptive-dominant afferents of the knee joint more directly, reduces distal joint involvement. Conclusion The novel stimulator is a feasible and repeatable tool for studying cortical processing of proprioceptive afference from the knee joint using MEG.