SAR-161206-transcranial-magnetic-stimulation-for-the-treatment-of-cocai_051818.pdf

4144 therefore we searched among published studies

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41–44 Therefore, we searched among published studies that investigated the efficacy of TMS in the treatment of SUDs and focused on those applied to cocaine addicts. Papers were identified through NCBI PubMed research by using “TMS”, “addiction”, and “cocaine” as keywords. Among published studies, only six focused on the treatment of cocaine addic- tion. These are reviewed in the present paper, with particular reference to the stimulation protocol applied and outcome observed. TMS physiology Since 1985, when TMS was implemented for the first time in the study of motor-cortex excitability, the potential thera- peutic effect of brain stimulation is being investigated in different psychiatric disorders, such as major depression, obsessive–compulsive disorders, schizophrenia, and addic- tive disorders. 41,43–50 TMS can be described as a nonsurgical brain stimulation that is able to modulate cortical excitabil- ity through magnetic fields inducted over the scalp. 51 The passage of electric current in the coil induces a transient, high-intensity magnetic pulse that penetrates the scalp and reaches the neurons of the targeted cortical area painlessly in the conscious subject. Generally, 1 Hz frequency (or below) of consecutive stimuli, ie, repetitive TMS (rTMS), inhibits cortical excitability, whereas high frequency (5–20 Hz) produces increased cortical excitability. 43,44 This change in cortical activity is able to produce both physiologic and behavioral effects, depending on the parameters of stimula- tion applied. 52–54 The total duration of the session, the fre- quency of stimulation employed, the intensity (relative to motor threshold [MT]), and pattern of stimulation are the key factors in determining long-lasting TMS effects, since physi- ological and behavioral effects are mediated by the traditional phenomena of Hebbian synaptic plasticity, consisting in long- term potentiation (LTP) and long-term depression (LTD) of neuronal activity. 44,55,56 Despite variability in the protocol of stimulation applied, a number of studies (Table S1) have shown efficacy of TMS in reducing craving and consumption in alcoholics and nicotine-dependent subjects. Additional recent work highlights the therapeutic potential of rTMS in cue-induced craving for methamphetamine, heroin-cue craving, and food craving. 57–65 These findings suggest that rTMS modulates neural activity via two main mechanisms: through the frontostriatal glutamate-bearing afferents to medium spiny neurons of the ventral striatum, and projections from pyramidal neurons of the fifth layer of the PfCx impinging upon DA-containing midbrain neurons, thereby inducing DA release in the nucleus accumbens. 11,22,66,67 The effect of TMS to increase DA levels transiently in cortical areas and its ability to modulate reduced dopami- nergic activity in the limbic system appears to be among the mechanisms in restoring predrug functionality at a system level.
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