Unveiling Cortical Dynamics: Neural Responses and Information Transfer in Gripping Tasks of Different Frequencies

Objectives: Upper-limb grasp training is essential for motor rehabilitation, as it induces complex neural changes including motor cortex activation, sensory feedback integration, and communication between the central and peripheral nervous systems. This study aims to investigate brain dynamics associated with different hand precision tasks performed at varying force-tracking frequencies, providing physiological insights for optimizing training methods. Methods: Force-tracking tasks at three different frequencies were designed to examine the neural response characteristics and patterns of information transfer in both the brain and arm muscles. Eighteen healthy volunteers were recruited, and grouped based on their maximum voluntary contraction levels. During task performance, electroencephalogram (EEG) signals were recorded across the entire scalp, and surface electromyography (sEMG) signals were simultaneously collected. sEMG was recorded from the extensor carpi radialis and flexor carpi ulnaris muscles, and its median frequency (MDF) was analyzed to assess muscle fatigue under different movement patterns.Event-related synchronization (ERS) of the EEG was used to observe the activation of cortical motor units, while phase transfer entropy (PTE) was employed to reconstruct the neural information transmission network between the cortex and muscles during the three tasks. Results: Significant differences in MDF changes were observed between the preparation and resting phases across all groups for the three grasping frequency tasks (p < 0.01). Notably, after grip movements with lower muscle fatigue, ERS in the cortex was more pronounced, and information transmission strength was highest in the motor cortices of both hemispheres. Additionally, all grasping tasks enhanced the information reception strength in ipsilateral brain regions and the information transmission strength in contralateral brain regions. The grasping frequency associated with the strongest ERS also showed the most significant enhancement in information transfer during the task. Discussion: These findings suggest that lower fatigue levels at specific movement frequencies lead to more active information transmission in the motor cortex, providing a foundation for personalized rehabilitation strategies tailored to different rehabilitation populations.