How Does Anodal Transcranial Direct Current Stimulation of the Pain Neuromatrix Affect Brain Excitability and Pain Perception? A Randomised, Double-Blind, Sham-Control Study

Abstract

BackgroundIntegration of information between multiple cortical regions of the pain neuromatrix is thought to underpin pain modulation. Although altered processing in the primary motor (M1) and sensory (S1) cortices is implicated in separate studies, the simultaneous changes in and the relationship between these regions are unknown yet. The primary aim was to assess the effects of anodal transcranial direct current stimulation (a-tDCS) over superficial regions of the pain neuromatrix on M1 and S1 excitability. The secondary aim was to investigate how M1 and S1 excitability changes affect sensory (STh) and pain thresholds (PTh).MethodsTwelve healthy participants received 20 min a-tDCS under five different conditions including a-tDCS of M1, a-tDCS of S1, a-tDCS of DLPFC, sham a-tDCS, and no-tDCS. Excitability of dominant M1 and S1 were measured before, immediately, and 30 minutes after intervention respectively. Moreover, STh and PTh to peripheral electrical and mechanical stimulation were evaluated. All outcome measures were assessed at three time-points of measurement by a blind rater.ResultsA-tDCS of M1 and dorsolateral prefrontal cortex (DLPFC) significantly increased brain excitability in M1 (p < 0.05) for at least 30 min. Following application of a-tDCS over the S1, the amplitude of the N20-P25 component of SEPs increased immediately after the stimulation (p < 0.05), whilst M1 stimulation decreased it. Compared to baseline values, significant STh and PTh increase was observed after a-tDCS of all three stimulated areas. Except in M1 stimulation, there was significant PTh difference between a-tDCS and sham tDCS.Conclusiona-tDCS of M1 is the best spots to enhance brain excitability than a-tDCS of S1 and DLPFC. Surprisingly, a-tDCS of M1 and S1 has diverse effects on S1 and M1 excitability. A-tDCS of M1, S1, and DLPFC increased STh and PTh levels. Given the placebo effects of a-tDCS of M1 in pain perception, our results should be interpreted with caution, particularly with respect to the behavioural aspects of pain modulation.Trial RegistrationAustralian New Zealand Clinical Trials, ACTRN12614000817640, http://www.anzctr.org.au/.

Transcranial Direct Current Stimulation Targeting Primary Motor Versus Dorsolateral Prefrontal Cortices: Proof-of-Concept Study Investigating Functional Connectivity of Thalamocortical Networks Specific to Sensory-Affective Information Processing

“…Previous studies have reported somewhat similar findings. While one study reported increases in FC between left DLPFC and bilateral primary sensorimotor cortices after tDCS (Stagg et al, 2013), another study reported significant increases in M1 corticospinal excitability (Vaseghi et al, 2015 Overall, our results demonstrate that both active M1 tDCS and active DLPFC tDCS modulate FC across sensory networks, although the influence of M1 tDCS appears to be more robust. Importantly, the validity of our findings is significant since FC effects of VPL were only modulated with active M1 and DLPFC tDCS, but not with sham.…”

Transcranial direct current stimulation (tDCS) reverts behavioral alterations and brainstem BDNF level increase induced by neuropathic pain model: Long-lasting effect

“…Walsh and Cummins (1976) suggested that the output latency to leave the first quadrant is a behavior associated with emotional factors, which may indicate an increase in anxiety-like behaviors (Stanford, 2007;Walsh and Cummins, 1976). Most importantly, tDCS treatment reverted those CCI-induced effects; therefore, we can suggest that this effect could have resulted from the action of tDCS on cortical areas involved in the pain matrix, such as the thalamus; anterior cingulate cortex (ACC); insular cortex; frontal, premotor, primary sensory and motor cortices (Moseley, 2003;Vaseghi et al, 2015;Zaghi et al, 2009). Additionally, previous studies from our group using chronic inflammation and hyperalgesia induced by chronic restraint stress models (Spezia Adachi et al, 2012) showed an antinociceptive effect of cortical stimulation by tDCS.…”

A Modified Hodgkin-Huxley model to Show the Effect of Motor Cortex Stimulation on the Trigeminal Neuralgia Network

“…Although the primary motor cortex (M1) is not considered regularly as one of the pain neuromatrix, it plays a crucial role in modulating the pain in different chronic pain syndromes (25, 28, 35-37, 41, 45). It has some reciprocal connections with S1 (28, 37, 45).…”