Non-Invasive Brain Stimulation: Neuromodulation by Transcranial current Stimulation and its Effects in Neuropsychological Disorders

Trancranial direct current stimulation (tDCS) can modulate neuronal activity by increasing (anodal tDCS) or decreasing cortical neuronal excitability (cathodal tDCS) in different brain regions. Effects of stimulation depend on electrode montage and size, current density and duration of tDCS. This review focuses on memory and language functions in healthy subjects and patients (Parkinson disease, Alzheimer disease, Aphasia). In general anodal stimulation led to improvements while after cathodal tDCS no effects or decreases in performance were observed. Future research should consider the interaction of stimulation parameters and evaluate the potential of transorbital alternating current stimulation (tACS) that may induce more sustainable effects. Thus, stable visual field improvements at a 2-months-follow-up were observed in patients with optic nerve lesions after a 10-day treatment course of tACS. Non-invasive brain stimulation is expected to gain increased importance in clinical applications.