Interaction of electrical stimulation and voluntary hand movement in SII and the cerebellum during simulated therapeutic functional electrical stimulation in healthy adults

Abstract

The therapeutic application of functional electrical stimulation (FES) has shown promising clinical results in the rehabilitation of post-stroke hemiplegia. It appears that the effect is optimal when the patterned electrical stimulation is used in close synchrony with voluntary movement, although the neural mechanisms that underlie the clinical successes reported with therapeutic FES are unknown. One possibility is that therapeutic FES takes advantage of the sensory consequences of an internal model. Here, we investigate fMRI cortical activity when FES is combined with voluntary effort (FESVOL) and we compare this activity to that produced when FES and voluntary activity (VOL) are performed alone. FESVOL revealed greater cerebellar activity compared with FES alone and reduced activity bilaterally in secondary somatosensory areas (SII) compared with VOL alone. Reduced activity was also observed for FESVOL compared with FES alone in the angular gyrus, middle frontal gyrus and inferior frontal gyrus. These findings indicate that during the VOL condition the cerebellum predicts the sensory consequences of the movement and this reduces the subsequent activation in SII. The decreased SII activity may reflect a better match between the internal model and the actual sensory feedback. The greater cerebellar activity coupled with reduced angular gyrus activity in FESVOL compared with FES suggests that the cortex may interpret sensory information during the FES condition as an error-like signal due to the lack of a voluntary component in the movement.

Time-dependent changes in motor cortical excitability by electrical stimulation combined with voluntary drive

“…Moreover, the changes in the applied muscle gradually increased in the later temporal phases and hence we hypothesized that for the agonist muscle, the combination method may cause a summation effect along with the stimulation time in the motor cortex. The finding on the effect in the agonist muscle was consistent with the results of functional MRI studies [19,20], indicating that peripheral electrical stimulation modulates activity not only in M1 but also in multiple brain areas, particularly the somatosensory cortex and the cerebellum [21]. Both the afferent input and temporal summation may activate the neural activity in the motor cortex of the agonist muscle.…”

“…The afferent input because of the electrical stimulation of the periphery can influence the excitability of the corresponding motor area [1,4,16]. A study conducted by Iftime-Nielsen et al [21] indicated that specific changes in the secondary somatosensory area activity in response to combined VC and NMES may reflect a better match between the internal model [22] and the actual sensory feedback. This combination of NMES and VC had a significant effect on MMG-MEP size in the agonist muscle.…”

Modulation of proprioceptive feedback during functional electrical stimulation: an fMRI study

“…When sensory feedback was intact (i.e. BASE and INFL) we tested the differences between VOL, FES‐as and FES‐ev in order to confirm the previously reported bilateral S2 activation during the FES‐ev and FES‐as conditions compared with VOL (Iftime‐Nielsen et al ., ). These tests were performed using t ‐contrasts in order to reveal the directional changes in the BOLD fMRI signal between the different tasks, i.e.…”

Rehabilitation with Functional Electrical Stimulation in Stroke Patients

“…Iftime-Nielsen et al [36] reported that neuromuscular stimulation combined with voluntary activation produces more activation of the cerebellum and less activation of secondary somatosensory cortex than dose neuromuscular stimulation alone in normal subjects. Neuroimaging studies of FES-evoked (FES delivered in the absence of voluntary activation) and FES-assisted (FES delivered to augment voluntary activation) movements have suggested bilateral secondary somatosensory cortex (S2) activation is related to the application of therapeutic FES [36].…”

“…Neuroimaging studies of FES-evoked (FES delivered in the absence of voluntary activation) and FES-assisted (FES delivered to augment voluntary activation) movements have suggested bilateral secondary somatosensory cortex (S2) activation is related to the application of therapeutic FES [36]. Another study suggested FES-related S2 activation is mainly a sensory phenomenon and does not reflect integration of sensory signals with motor commands [37].…”