Abstract
Low-frequency peripheral electrical stimulation using a matrix electrode (PEMS) modulates spinal nociceptive pathways. However, the effects of this intervention on cortical oscillatory activity have not been assessed yet. The aim of this study was to investigate the effects of low-frequency PEMS (4 Hz) on cortical oscillatory activity in different brain states in healthy pain-free participants. In experiment 1, PEMS was compared to sham stimulation. In experiment 2, motor imagery (MI) was used to modulate the sensorimotor brain state. PEMS was applied either during MI-induced oscillatory desynchronization (concurrent PEMS) or after MI (delayed PEMS) in a cross-over design. For both experiments, PEMS was applied on the left forearm and resting-state electroencephalography (EEG) was recording before and after each stimulation condition. Experiment 1 showed a significant decrease of global resting-state beta power after PEMS compared to sham (p = 0.016), with a median change from baseline of −16% for PEMS and −0.54% for sham. A cluster-based permutation test showed a significant difference in resting-state beta power comparing pre- and post-PEMS (p = 0.018) that was most pronounced over bilateral central and left frontal sensors. Experiment 2 did not identify a significant difference in the change from baseline of global EEG power for concurrent PEMS compared to delayed PEMS. Two cluster-based permutation tests suggested that frontal beta power may be increased following both concurrent and delayed PEMS. This study provides novel evidence for supraspinal effects of low-frequency PEMS and an initial indication that the presence of a cognitive task such as MI may influence the effects of PEMS on beta activity. Chronic pain has been associated with changes in beta activity, in particular an increase of beta power in frontal regions. Thus, brain state-dependent PEMS may offer a novel approach to the treatment of chronic pain. However, further studies are warranted to investigate optimal stimulation conditions to achieve a reduction of pain.
Highlights
In various pain conditions evidence has been found for central sensitization (Coderre et al, 1993; Banic et al, 2004; Latremoliere and Woolf, 2009; Woolf, 2011)
The present study investigated for the first time the effects of peripheral electrical stimulation using a matrix electrode (PEMS) on cortical oscillatory activity
Experiment 1 showed that low-frequency PEMS (4 Hz) resulted in a significantly larger reduction of global beta power compared to sham stimulation; the median change from baseline was −16% for PEMS and −0.54% for sham
Summary
In various pain conditions evidence has been found for central sensitization (Coderre et al, 1993; Banic et al, 2004; Latremoliere and Woolf, 2009; Woolf, 2011). Modulating the excitability of the central nociceptive system offers a promising target for neurostimulation techniques to reduce pain. Peripheral electrical stimulation (PES) is commonly used to facilitate motor rehabilitation and treat pain via the induction of plastic changes in corticospinal excitability (Klein et al, 2004; Chipchase et al, 2011; Dimyan and Cohen, 2011). Low frequency PES has been demonstrated to reduce pain perception and the spinal and cortical response to nociceptive stimuli (Jung et al, 2009, 2012; Rottmann et al, 2010). Evidence for the clinical efficacy of PES interventions such as transcutaneous electrical nerve stimulation (TENS), a commonly used PES intervention to treat pain, is inconclusive (Catley et al, 2015; Johnson et al, 2015), leaving room for improvement
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