Abstract
Transcranial static magnetic field stimulation (tSMS) is a novel and inexpensive, non-invasive brain stimulation (NIBS) technique. Here, we performed non-invasive modulation of intra-epidermal electrical stimulation-evoked potentials (IES-EPs) by applying tSMS or sham stimulation over the primary motor (M1) and somatosensory (S1) cortices in 18 healthy volunteers for 15 min. We recorded EPs after IES before, right after, and 10 min after tSMS. The IES-EP amplitude was significantly reduced immediately after tSMS over M1, whereas tSMS over S1 and sham stimulation did not affect the IES-EP amplitude. Thus, tSMS may affect cortical nociceptive processing. Although the results of intervention for experimental acute pain in healthy subjects cannot be directly translated into the clinical situation, tSMS may be a potentially useful NIBS method for managing chronic pain, in addition to standard of care treatments.
Highlights
Epidural electrical stimulation of the primary motor cortex (M1) relieves pain (Tsubokawa et al, 1991a,b)
This study demonstrated that the amplitude of intra-epidermal electrical stimulation-evoked potentials (IES-evoked potentials (EPs)) (N2P2) decreased significantly by up to 15%–25% immediately and 10 min after a 15-min period of Transcranial static magnetic field stimulation (tSMS) over M1
The parameters for selective stimulation of Aδ fibers for recording EPs were based on the experimental protocol of our previous studies, which involves using trains tSMS Affect Cortical Nociceptive Processing of double pulses with an inter-stimulus interval (ISI) of 10 ms at an intensity that was approximately twice the sensory threshold (Otsuru et al, 2010)
Summary
Epidural electrical stimulation of the primary motor cortex (M1) relieves pain (Tsubokawa et al, 1991a,b). The amplitude of laser evoked potentials (LEPs) is attenuated by HF rTMS over M1 (facilitatory; de Tommaso et al, 2010), continuous theta-burst stimulation (TBS; inhibitory) over both M1 (Csifcsak et al, 2009b) and S1 (Poreisz et al, 2008), intermittent TBS (facilitatory) over S1 (Poreisz et al, 2008), and cathodal tDCS (inhibitory) over both M1 (Terney et al, 2008; Csifcsak et al, 2009a) and S1 (Antal et al, 2008) These conflicting results can be speculated as resulting from the differences in neural networks involved in the processing of acute provoked nociceptive stimuli in healthy subjects vs chronic pain in patients. Examination of acute pain in healthy controls could lead to optimization of new NIBS techniques and increase understanding of cortical regulation of nociceptive processing (reviewed in Mylius et al, 2012)
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