Neuromodulation : journal of the International Neuromodulation Society
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The efficacy of repetitive transcranial magnetic stimulation (rTMS) in clinically relevant neuroplasticity research depends on the degree to which stimulation induces robust, reliable effects. The high degree of interindividual and intraindividual variability observed in response to rTMS protocols, such as continuous theta burst stimulation (cTBS), therefore represents an obstacle to its utilization as treatment for neurological disorders. Brain-derived neurotrophic factor (BDNF) is a protein involved in human synaptic and neural plasticity, and a common polymorphism in the BDNF gene (Val66Met) may influence the capacity for neuroplastic changes that underlie the effects of cTBS and other rTMS protocols. While evidence from healthy individuals suggests that Val66Met polymorphism carriers may show diminished or facilitative effects of rTMS compared to their homozygous Val66Val counterparts, this has yet to be demonstrated in the patient populations where neuromodulatory therapies are most relevant. ⋯ Our findings strongly suggest that BDNF genotype differentially affects neuroplastic responses to TMS in individuals with chronic stroke. This provides novel insight into potential sources of variability in cTBS response in patients, which has important implications for optimizing the utility of this neuromodulation approach. Incorporating BDNF polymorphism genetic screening to stratify patients prior to use of cTBS as a neuromodulatory technique in therapy or research may optimize response rates.
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Randomized Controlled Trial
A Randomized, Sham-Controlled Trial of Repetitive Transcranial Magnetic Stimulation Targeting M1 and S2 in Central Poststroke Pain: A Pilot Trial.
Central poststroke pain (CPSP), a neuropathic pain condition, is difficult to treat. Repetitive transcranial magnetic stimulation (rTMS) targeted to the primary motor cortex (M1) can alleviate the condition, but not all patients respond. We aimed to assess a promising alternative rTMS target, the secondary somatosensory cortex (S2), for CPSP treatment. ⋯ S2 is a promising nrTMS target in the treatment of CPSP. The DRD2 T/T genotype might be a biomarker for M1 nrTMS response, but this needs confirmation from a larger study.
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To synthesize and critically appraise literature exploring patient perceptions regarding the therapeutic use of noninvasive brain stimulation. ⋯ The findings from this review suggest that rTMS is well accepted as a therapeutic treatment among psychiatric populations, providing support for its clinical utility. Future work is needed to determine if similar findings exist for other conditions (eg, chronic pain) and for other therapeutic forms of brain stimulation (eg, tDCS).
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Randomized Controlled Trial
Electric Field Strength From Prefrontal Transcranial Direct Current Stimulation Determines Degree of Working Memory Response: A Potential Application of Reverse-Calculation Modeling?
Transcranial direct current stimulation (tDCS) for working memory is an enticing treatment, but there is mixed evidence to date. ⋯ Higher electric fields at the left DLPFC from uniform 2 mA doses appear to drive working memory improvements from tDCS. Individualized doses from reverse-calculation modeling significantly reduce electric field variance at the cortex. Taken together, using reverse-calculation modeling to produce the same, high electric fields at the cortex across participants may produce more effective future tDCS treatments for working memory.
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Cognitive dysfunction (CD) is a commonly reported symptom of major depressive disorder (MDD). Patients with treatment-resistant depression (TRD) tend to experience greater rates of CD; however, treatment options are limited. Repetitive transcranial magnetic stimulation (rTMS) is effective in treating affective symptoms in patients with TRD, but its potential effect on CD in TRD has not been established. ⋯ rTMS may be associated with improvements in verbal memory in patients with TRD who present with global CD and who are clinical responders to the treatment. These findings warrant replication in a larger sample as well as further investigations into the neural mechanisms of cognitive improvement after rTMS.