Modulating Human Cortical Plasticity With Transcranial Electrical Stimulation

Experience dependent plasticity is a fundamental property of the brain. It allows neural systems to adapt in response to environmental input and subserves the vital functions of learning and memory. Deficits in plasticity are also thought play a causal role in the pathophysiology of several psychiatric disorders, specifically schizophrenia (SZ). Treatments that can probe or even enhance plasticity have potential to be of great clinical and research value. Non-invasive neuromodulation via transcranial direct current stimulation (tDCS) is a promising method for modulating neural plasticity. tDCS delivers low-intensity direct current to cortical areas, thereby facilitating or inhibiting neural activity in a polarity specific manner. Due to its low cost and safety, tDCS has been employed in a wide variety of studies, but much remains unknown regarding its mechanism of action in humans. Experiments carried out in animal and tissue models indicate that tDCS modulates synaptic plasticity mechanisms of long term potentiation and depression (LTP/D), however, these findings have never been translated to human subjects, limiting the practical utility of the research. Recently developed electroencephalographic (EEG) based measures now allow the interrogation of synaptic plasticity non-invasively in humans, making it possible to explore the effects of tDCS on human brain plasticity.