A Transcranial Alternating Current Stimulator for Neural Entrainment

Abstract

Human cognition, perception, and memory are partially attributed to the synchronicity of neuronal dynamics in the prefrontal cortex, and growing evidence indicates that age-related decline in working memory is causally linked to dissonance in neuronal firing patterns. Neuromodulation of spike timing has been classically considered an invasive process, met with resistance due to technological and ethical constraints. Thus, non-invasive neurostimulation techniques have been used to treat and manage a diverse range of health conditions, and more recently it has been suggested to enhance human cognition and working memory. In this paper, we propose a low-cost transcranial alternating current neurostimulator wearable targeting frequencies in the theta wave band (4–8 Hz), which are crucial for the functioning of normal memory and attention. Prior work on transcranial stimulation indicates that modulating large-scale neural activity is achievable through both entrainment and resonance effects, by recruiting a larger population of neurons into task-relevant rhythmic firing networks. We conduct a simulation current density within the brain in response to the wearable, using SimNIBS, followed by experimental results of our board-level implementation with a test study of various electrodes, by connecting them to an impedance of 20 kΩ.