Dynamic cortical connectivity underlying proprioceptive processing during NMES-induced hand movements: Insights from an acute deafferentation model
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Updated: Nov 6, 2026
Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation
Published on: February 23, 2020
Objective:
Neuromuscular electrical stimulation (NMES) is a promising modality for restoring sensory feedback in upper-limb prosthetics. However, the dynamic cortical mechanisms underlying the perception of NMES-evoked muscle contraction, particularly under conditions of sensory loss (e.g., amputation), remain poorly understood. This study investigates the time-varying effective connectivity of the sensorimotor cortex in response to NMES using the ischemic nerve block (INB) technology to model acute deafferentation.
Methods:
64-channel EEG data were recorded from 11 able-bodied participants under a 2×2 factorial design involving INB states (before vs. block) and stimulation intensities (above vs. below motor threshold). The adaptive directed transfer function (ADTF) combined with graph theoretical analysis was employed to quantify dynamic causal interactions in the Beta band (15-30 Hz).
Results:
The NMES-evoked cortical response progressed through three stages with monotonically increasing network segregation and integration (PFDR ≤ 0.01 for all stage-wise comparisons). During the ischemic nerve block (INB), the clustering coefficient (CC) and global efficiency (Ge) decreased under above-threshold stimulation (cluster-level PFDR = 0.019 and PFDR = 0.013, respectively), whereas below-threshold stimulation elicited a transient CC increase (150-525 ms, PFDR = 0.019) followed by late Ge reductions. The differentiation of the network response between above and below motor-threshold stimulation was reconfigured rather than abolished during deafferentation. At the regional level, deafferentation attenuated contralateral somatosensory and ipsilateral motor driving, whereas ipsilateral somatosensory outflow was relatively enhanced.
Conclusion:
NMES-evoked muscle contractions modulate the dynamics of sensorimotor networks by acute deafferentation. Acute deafferentation attenuates network integration and increases the relative contribution of the ipsilateral hemisphere.
Significance:
These electrophysiological markers may inform the design and evaluation of closed-loop sensory feedback for neuroprostheses.
