Abstract
BackgroundTo enrich the hitherto insufficient understanding regarding the mechanisms of action of transcranial direct current stimulation (tDCS) in pain disorders, we investigated its modulating effects on cerebral pain processing using functional magnetic resonance imaging (fMRI).MethodsThirteen right-handed healthy participants received 20 min of 1.5 mA tDCS applied over the primary motor cortex thrice and under three different stimulation pattern (1.anodal-tDCS, 2.cathodal-tDCS, and 3.sham-tDCS) in a blinded cross-over design. After tDCS neural response to electric trigeminal-nociceptive stimulation was investigated using a block designed fMRI.ResultsPain stimulation showed a distinct activation pattern within well-established brain regions associated with pain processing. Following anodal tDCS increased activation was detected in the thalamus, basal ganglia, amygdala, cingulate, precentral, postcentral, and dorsolateral prefrontal cortex, while cathodal t-DCS showed decreased response in these areas (pFWE < 0.05). Interestingly the observed effect was reversed in both control conditions (visual- and motor-stimulation). Behavioral data remained unchanged irrespective of the tDCS stimulation mode.ConclusionsThis study demonstrates polarity-specific modulation of cerebral pain processing, in reconfirmation of previous electrophysiological data. Anodal tDCS leads to an activation of the central pain-network while cathodal tDCS does not. Results contribute to a network-based understanding of tDCS’s impact on cerebral pain-processing.
Highlights
To enrich the hitherto insufficient understanding regarding the mechanisms of action of transcranial direct current stimulation in pain disorders, we investigated its modulating effects on cerebral pain processing using functional magnetic resonance imaging
Sensory-discriminative components of pain are processed by primary (S1) and secondary (S2) somatosensory cortices, the thalamus, and posterior part of the insula in the lateral pain system [2], while affectivemotivational components are processed in the medial pain-system including the anterior cingulate cortex
Transcranial direct current stimulation is a noninvasive, safe, and painless technique which is applied in various chronic pain disorders such as fibromyalgia [12], spinal cord injury pain [13] and menstrual migraine [14]
Summary
To enrich the hitherto insufficient understanding regarding the mechanisms of action of transcranial direct current stimulation (tDCS) in pain disorders, we investigated its modulating effects on cerebral pain processing using functional magnetic resonance imaging (fMRI). Some pain and headache disorders appear to be caused by a dysbalanced network [11], and neuromodulatory approaches are increasingly used therapies. For anodal stimulation a raised and for cathodal stimulation a Naegel et al The Journal of Headache and Pain (2018) 19:99 decreased level of cortical excitability at the targeted brain area was previously shown [4, 15]. Pain reduction caused by stimulation of the primary motor-cortex may result from modulation of the pain processing network, but so far is only insufficiently understood
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