Effects of Transcranial Direct Current Stimulation (tDCS) in the Normalization of Brain Activation in Patients with Neuropsychiatric Disorders: A Systematic Review of Neurophysiological and Neuroimaging Studies

Abstract

Background. People with neuropsychiatric disorders have been found to have abnormal brain activity, which is associated with the persistent functional impairment found in these patients. Recently, transcranial direct current stimulation (tDCS) has been shown to normalize this pathological brain activity, although the results are inconsistent. Objective. We explored whether tDCS alters and normalizes brain activity among patients with neuropsychiatric disorders. Moreover, we examined whether these changes in brain activity are clinically relevant, as evidenced by brain-behavior correlations. Methods. A systematic review was conducted according to PRISMA guidelines. Randomized controlled trials that studied the effects of tDCS on brain activity by comparing experimental and sham control groups using either electrophysiological or neuroimaging methods were included. Results. With convergent evidence from 16 neurophysiological/neuroimaging studies, active tDCS was shown to be able to induce changes in brain activation patterns in people with neuropsychiatric disorders. Importantly, anodal tDCS appeared to normalize aberrant brain activation in patients with schizophrenia and substance abuse, and the effect was selectively correlated with reaction times, task-specific accuracy performance, and some symptom severity measures. Limitations and Conclusions. Due to the inherent heterogeneity in brain activity measurements for tDCS studies among people with neuropsychiatric disorders, no meta-analysis was conducted. We recommend that future studies investigate the effect of repeated cathodal tDCS on brain activity. We suggest to clinicians that the prescription of 1-2 mA anodal stimulation for patients with schizophrenia may be a promising treatment to alleviate positive symptoms. This systematic review is registered with registration number CRD42020183608.

Increased both cortical activation and functional connectivity after transcranial direct current stimulation in patients with post-stroke: A functional near-infrared spectroscopy study

“…Using tDCS with the anodes and cathodes on F3 and F4 electrodes can improve the cognitive ability of individuals with cognitive impairment after stroke (20) and change their cortical excitability (21). In animal studies (22,23), direct currents have been shown to change brain excitability.…”

Repeated Sessions of Transcranial Direct Current Stimulation on Adolescents With Autism Spectrum Disorder: Study Protocol for a Randomized, Double-Blind, and Sham-Controlled Clinical Trial

“…Therapeutically, tDCS is used to alter local neuronal excitability that is assumed to be in a dysfunctional hypo- or hyperactive state ( 45 ). Effects of the stimulation expand by changes in the neural network into more distant regions and lead to reorganization of neuronal circuits ( 45 , 57 ). Due to encouraging results in the treatment of various neuropsychiatric disorders in adults ( 58 – 61 ), tDCS has gained attention in the treatment of childhood and adolescent neuropsychiatric disorders over the past years ( 45 , 62 – 64 ).…”

Early augmentation by using neuromodulation in psychiatric disorder: a kaleidoscopic view

“…A systematic review of neuropsychological and neuroimaging studies of patients with neuropsychiatric disorders, reported that the clinical effect of tDCS is closely linked with symptom severity 31 . This finding suggests that when the symptoms are more severe (in the acute phase), choosing tDCS as early augmentation strategy may help reduce the symptoms.…”