Specific brain activation patterns associated with two neuromuscular electrical stimulation protocols

Abstract

The influence of neuromuscular electrical stimulation (NMES) parameters on brain activation has been scarcely investigated. We aimed at comparing two frequently used NMES protocols - designed to vary in the extent of sensory input. Whole-brain functional magnetic resonance imaging was performed in sixteen healthy subjects during wide-pulse high-frequency (WPHF, 100 Hz–1 ms) and conventional (CONV, 25 Hz–0.05 ms) NMES applied over the triceps surae. Each protocol included 20 isometric contractions performed at 10% of maximal force. Voluntary plantar flexions (VOL) were performed as control trial. Mean force was not different among the three protocols, however, total current charge was higher for WPHF than for CONV. All protocols elicited significant activations of the sensorimotor network, cerebellum and thalamus. WPHF resulted in lower deactivation in the secondary somatosensory cortex and precuneus. Bilateral thalami and caudate nuclei were hyperactivated for CONV. The modulation of the NMES parameters resulted in differently activated/deactivated regions related to total current charge of the stimulation but not to mean force. By targeting different cerebral brain regions, the two NMES protocols might allow for individually-designed rehabilitation training in patients who can no longer execute voluntary movements.

Functional Electrical Stimulation (FES): Clinical successes and failures to date

“…The enhancement of these molecular and cellular metabolic events are all markers supporting long-established clinical data demonstrating that using FES is likely to result in signi icant muscle strength gains whether the strength de icits were a result of damage to the musculoskeletal, neurological or cardiovascular-pulmonary systems [11][12][13][14][15]. Moreover, FES activation of skeletal muscles has been shown to enhance arterial, venous and lymphatic low [16][17][18][19], while concurrently transmitting multimodal afferent signals to multiple sites within the brain's regions of interest (ROI) [1][2][3][4]. Collectively, the science supporting the mechanisms and clinical bene its of utilizing FES in the management of physical and functional de icits is robust, yet FES utilization as a common treatment option in daily clinical practice is limited at best.…”

“…The limited availability of clinically valued coupling of FES with other rehabilitation technologies such as EEG controlled FES [55,56], or wearable robots and virtual reality systems [57], is also recognized in the literature [36]. Attempts to improve the resolution of FES induced muscle contraction by using multiplexers and arrays of small electrodes [39,58] or manipulation of pulse parameters [1] have yielded some interesting discoveries and electronic innovations. But these research efforts have also failed so far to become a viable commercial product in rehabilitation medicine.…”

“…Typical FES is comprised of a stimulator delivering via non-invasive surface electrodes, electric pulses of very short duration, typically lasting 10-500 μsec. These pulses excite peripheral sensory and motor nerves thereby causing contraction of skeletal muscles while concurrently modulate neural connectivity throughout the central and peripheral neural networks [1][2][3][4]. In numerous peer-reviewed scienti ic clinical publications, these stimulators are termed neuromuscular electrical stimulators (NMES).…”

Why brain-controlled neuroprosthetics matter: mechanisms underlying electrical stimulation of muscles and nerves in rehabilitation

“…Altered cortical activations in stroke patients after using FES were also shown in the lower-limbs with drop-foot stimulation, suggesting that SMA and angular gyrus regions play an important role in mediating carryover effects [ 43 ]. Moreover, short-term lower-limb FES application elicited significant activations of the sensorimotor networks (i.e., cerebellum and thalamus), with different neural activations achieved by adjusting the stimulation parameters [ 149 ]. Therefore, it seems that somatosensory cortex activations can be relayed to the motor cortical areas via cortico-cortical and/or cerebello-thalamo-cortical connections during electrical stimulation of muscles and nerves [ 26 ].…”

Rewiring the Lesioned Brain: Electrical Stimulation for Post-Stroke Motor Restoration

“…NMES also induces cortical plasticity by modulating the ascending pathways through the Ia muscle fiber afferents. 102,115,116 Additionally, somatosensory inputs to the motor cortex are essential for motor learning and control, and play critical roles in the motor recovery process. 100,117 NMES above the motor threshold increases excitability of corticomotor pathway by activating sensory axons and recruiting synaptic motoneurons and motor reflex.…”