Brain Stimul
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The cerebellar influence on the motor cortex output is exerted mostly though the cerebellothalamocortical pathway (CTC). One way to explore this pathway is by the means of transcranial magnetic stimulation (TMS). A single-pulse conditioning magnetic stimulation delivered over the lateral cerebellum was shown to diminish the excitability of the contralateral motor cortex 5 milliseconds later (cerebellocortical inhibition [CBI]), most likely through transynaptic activation of cerebellar Purkinje cells, which in turn inhibit the tonic activity of the CTC. Repetitive TMS (rTMS) delivered over the lateral cerebellum was shown to induce a long-lasting change of the cortical excitability, as well, but the mechanism and time course of this effect are still debated. ⋯ Our findings suggest that repetitive cerebellar stimulation operate at a cerebellar level, rather then at a cortical level.
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The neocortex is the most common target of subdural electrotherapy and noninvasive brain stimulation modalities, including transcranial magnetic stimulation (TMS) and transcranial current simulation (TCS). Specific neuronal elements targeted by cortical stimulation are considered to underlie therapeutic effects, but the exact cell type(s) affected by these methods remains poorly understood. ⋯ We present experimental data indicating that cortical neuron morphology relative to electric fields and cortical cell type are factors in determining sensitivity to sub- and supra-threshold brain stimulation.
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Neuropathic pain results from injury to the central or peripheral nervous system and can prove itself refractory to classical medical treatment by anticonvulsants and antidepressants. In such cases, motor cortex stimulation is among the neurostimulation techniques available for its symptomatic control. This technique is based on surgical implantation of electrodes over the motor cortical representation of the painful area. ⋯ The limit of this approach is that MEPs cannot be recorded in patients with total or severe motor deficit. We have shown that intraoperative mapping of the cortical region corresponding to the painful area by recording MEPs could help select contacts to be activated for chronic stimulation. Therefore, the patients in whom intraoperative MEP mapping is possible could benefit from this technique, at least if we consider that it improves the accuracy of electrode placement and that motor cortex stimulation efficacy critically depends on this placement.
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The modulatory effects of transcranial direct current stimulation (tDCS) appear beneficial for different chronic pain syndromes; however, it is unclear whether this method can be used to treat refractory chronic pelvic pain. ⋯ Active tDCS treatment induces a modest pain reduction in refractory chronic pelvic pain patients as compared with sham tDCS treatment. These results can guide the design and implementation of further studies investigating this method of neuromodulation for the treatment of refractory chronic pelvic pain.
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Brain imaging studies performed over the past 20 years have generated new knowledge about the specific brain regions involved in the brain diseases that have been classically labeled as psychiatric. These include the mood and anxiety disorders, and the schizophrenias. As a natural next step, clinical researchers have investigated whether the minimally invasive brain stimulation technologies (transcranial magnetic stimulation [TMS] or transcranial direct current stimulation [tDCS]) might potentially treat these disorders. ⋯ There is much less data in all other diseases, and therapeutic effects in other psychiatric conditions, if any, are still controversial. Several issues and problems extend across all psychiatric TMS studies, including the optimal method for a sham control, appropriate coil location, best device parameters (intensity, frequency, dosage, and dosing schedule) and refining what subjects should be doing during treatment (activating pathologic circuits or not). In general, TMS or tDCS as a treatment for most psychiatric disorders remains exciting but controversial, other than prefrontal TMS for depression.