Volitional hand activation intensifies cortical proprioceptive processing in the primary sensorimotor cortex

Proprioception refers to the sense of position and movement of the body and is essential for the planning and execution of movements, especially skilled hand movements. The somatotopic organization of the fingers in the human sensorimotor (SM1) cortex has previously been studied using passive tactile stimulation and active movements. However, the finger representations in response to proprioceptive stimulation in the SM1 cortex are incompletely understood. To address this, we investigated cortical representations of the index and ring fingers during kinematically matched passive and active finger movements using 3T fMRI and an MRI-compatible proprioceptive stimulator. Both active and passive conditions elicited significant activations in the SM1 cortex, with stronger and more extensive responses observed during the active condition. The results indicated that volitional activation of the fingers intensifies cortical proprioceptive processing in the SM1 cortex. This observation could be explained by the active state of the SM1 cortex and the increased sensitivity of peripheral proprioceptors during the active condition. Key pointsVolitional activation of the fingers intensifies cortical processing of proprioceptive afference and modulates the organization of finger representations in the SM1 cortex. This could be explained by the active state of the SM1 cortex and the increased sensitivity of peripheral proprioceptors during the active condition. Proprioceptive finger representations followed the classical somatotopic organization at the group level, although this organization was not consistently observed across all subjects.