The effect seemed to be specific because high-frequency rTMS of the contralateral homologous cortical region right DLPFC was completely ineffective on pain measures. To our knowledge, this is the first evidence that hf rTMS given 10 Paain 20 min after capsaicin application on left DLPFC induces a significant bilateral anti-nociceptive effect on capsaicin pain model in healthy subjects.
Acute Pain
The majority of the reports on modulation of pain neural network have principally targeted motor cortex [ 7 — 13 ]. Recently, however, other cortical areas and in particular DLPFC stimulation showed significant effect on pain control [ 19 — 28 ]. Indeed, DLPFC appears to be a potential candidate region to modulate the experience of pain given that it is a critical structure for working memory and attention functions [ 3233 ]. Recently, this hypothesis received experimental support by MRI studies of neural connection with the technique of diffuse tensor imaging that Pain Perception Of Pain Essay anatomical connections between prefrontal cortices and brainstem structures known for http://pinsoftek.com/wp-content/custom/sociological-imagination-essay/the-cox-proportional-hazard-model.php role in pain modulation like periaqueductal gray and nucleus cuneiformis [ 34 ].
In agreement with our results, the role of left prefrontal cortex activation in pain control has been recently reported by Borckardt et al. The antinociceptive effects of left DLPFC were also showed by tDCS technique through stimulation of this area with anodal activating currents in healthy subjects [ 28 ]. These papers, however, explored pain reduction only on the body area contralateral to the brain area stimulated somatotopicand are only partly comparable with our read article as they did not evaluate potential bilateral effects of the brain stimulation performed.
Only two studies, those by Graff-Guerrero et al. Graff-Guerrero et al.
Introduction
This could seem in contrast with our results, as we used hf rTMS that is known to have activatory effects and found antinociceptive effects by left DLPFC. However, it could be argued, according to the theory of interhemispheric rivalry, that following depression of the right side, an indirect activation of the opposite left side DLPFC occurred through removal of transcallosal interhemispheric inhibition in a way similar to what we tried to induce by directly performing hf rTMS over left DLPFC.
This also appears in agreement with the results reported by Tamura et al. Moreover, Pain Perception Of Pain Essay we Perceptkon in a recent paper, left DLPFC activation was also able to exert control over motor cortical excitability restoring intracortical inhibition that had been reduced by capsaicin application [ 35 ].
The perception of pain.
With regards to the relationship between motor and prefrontal cortices in pain modulation, Graff-Guerrero et al. This would point towards a more general role for DLPFC in pain control in agreement with the top-down model proposed by Lorenz et al.
This view, however, has been recently challenged by the results of Nahmias et al. These differences do not appear easy to explain: in our opinion, a critical role may have been played by the different methodological Pain Perception Of Pain Essay, as it is known that varied effects of DLPFC rTMS on acute pain may be influenced by the type of experimentally induced pain. Indeed, pain elicited PPerception capsaicin and mediated by activation of C-fiber pathways has been shown to be reduced by slow rTMS of right motor cortex [ 12 ], whereas the same rTMS procedure has been shown to increase the acute laser-implemented pain primarily involving A delta fibers [ 13 ]. Under this respect, the results by Nahmias et al.
Different types of pain
Indeed, if we speculate that right DLPFC is involved in control of pain arising by A delta fibers activation, then activation by fast rTMS of this area could reduce pain [ 25 ], while inhibition through slow stimulation would increase it [ 13 ]. Unfortunately, Nahmias et al. However, inference about this issue could be given by Borckhardt et al.]
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