Somatosensory electrical stimulation improves skill acquisition, consolidation, and transfer by increasing sensorimotor activity and connectivity

Abstract

The interaction between the somatosensory and motor systems is important for normal human motor function and learning. Enhancing somatosensory input using somatosensory electrical stimulation (SES) can increase motor performance, but the neuronal mechanisms underlying these effects are largely unknown. With EEG, we examined whether skill acquisition, consolidation, and interlimb transfer after SES was related to increased activity in sensorimotor regions, as assessed by the N30 somatosensory evoked potential or rather increased connectivity between these regions, as assessed by the phase slope index (PSI). Right- and left-hand motor performance and EEG measures were taken before, immediately after, and 24 h ( day 2) after either SES ( n = 12; 5 men) or Control ( n = 12; 5 men). The results showed skill acquisition and consolidation in the stimulated right hand immediately after SES (6%) and on day 2 (9%) and interlimb transfer to the nonstimulated left hand on day 2 relative to Control (8%, all P < 0.05). Increases in N30 amplitudes correlated with skill acquisition while PSI from electrodes that represent the posterior parietal and primary somatosensory cortex to the electrode representing the primary motor cortex correlated with skill consolidation. In contrast, interlimb transfer did not correlate with the EEG-derived neurophysiological estimates obtained in the present study, which may indicate the involvement of subcortical structures in interlimb transfer after SES. In conclusion, weak peripheral somatosensory inputs in the form of SES improve skill acquisition, consolidation, and interlimb transfer that coincide with different cortical adaptations, including enhanced N30 amplitudes and PSI. NEW & NOTEWORTHY The relationship between adaptations in synaptic plasticity and motor learning following somatosensory electrical stimulation (SES) is incompletely understood. Here, we used for the first time a multifactorial approach that examined skill acquisition, consolidation, and interlimb transfer following 20 min of SES. In addition, we quantified sensorimotor integration and the magnitude and direction of connectivity with EEG. Following artificial electrical stimulation, increases in sensorimotor integration and connectivity were found to correlate with skill acquisition and consolidation, respectively.

Somatosensory Electrical Stimulation Does Not Improve Motor Coordination in Patients with Unilateral Knee Osteoarthritis

“…Despite the tenability of this hypothesis and previous evidence for the effectiveness of SES in stroke, dystonia, and healthy participants [9,10,20], the form of SES used in the present study did not improve KOA patients’ motor function, including self-reported function, or relieve pain as compared to sham stimulation (Figure 2 and Figure 3; Table 1). At least part of the reason may lie in the differences in the neurophysiology of sensory and motor systems in KOA in comparison with stroke patients or healthy individuals.…”

Improved Functional Outcome After Peripheral Nerve Stimulation of the Impaired Forelimb Post-stroke

“…The stimulation parameters chosen in the present study were based on our previous report on spinal cord injury in the rat (30). Several clinical studies applying NMES alone suggested sensorimotor function improvement in stroke patients (62,63) although with stimulation frequencies between 10 and 50 Hz. Further, a report showed that activation at 5 Hz on the cortex did improve stroke patients' motor function (64).…”

“…(1) Peripheral nerve stimulation could recruit contralesional and surviving ipsilesional cortical neurons to undergo axonal remodeling and motor map reorganization (14,(65)(66)(67). (2) Peripheral nerve stimulation could affect all types of neural pathways including sensory, motor, proprioceptive, as well as polysynaptic transmission (44,45,63). In this way, future studies should investigate whether median nerve E-stim in this stroke model leads to plastic changes or modulation of structures along the ascending pathway, such as neural modulation in the periaqueductal gray (68).…”

Dynamic Causal Modeling of Neural Responses to an Orofacial Pneumotactile Velocity Array

“…Still, our results support that the passive somatosensory inputs can affect motor function. The cross-modality plasticity theory suggested that somatosensory stimuli could evoke neural responses to promote motor learning (Ackerley, Borich, Oddo, & Ionta, 2016;Ladda et al, 2014;Ludlow et al, 2008;Nasir et al, 2013;Sanes, 2003;Sanes & Donoghue, 2000;Veldman et al, 2018). Research has shown that the orofacial sensorimotor system is essential for sucking, swallowing, and speech production (Barlow, 1998;Barlow & Bradford, 1996;Barlow & Estep, 2006;Barlow, Lund, Estep, & Kolta, 2010;Barlow & Stumm, 2010;Sessle et al, 2007;Sessle et al, 2005;Smith, 2016).…”