Exploring the Effects of Transcranial Electrical Stimulation on Natural Vision and Cortical Activity

Abstract

Transcranial alternating current stimulation (tACS) is a non-invasive neuromodulation technique that can elicit visual phenomena known as phosphenes and potentially modulate visual cortical processing. This study systematically investigated how tACS parameters—frequency, current intensity, and electrode montage—affect subjective phosphene perception and objective visual evoked potentials (VEPs) in healthy adults. Using a within-subject design, eight participants underwent 40 stimulation conditions while reporting phosphene characteristics and completing pre/post VEP recordings. Results showed that phosphene perception increased with current intensity, peaked at 16 Hz, and was significantly higher with a fronto-central (FPz–Cz) montage compared to occipital (Oz–Cz) stimulation. Phosphene features such as brightness, shape, and spatial location varied systematically with stimulation parameters, while discomfort remained minimal. Although VEP analyses did not reveal statistically significant changes, trends suggested reduced N2 latency post-stimulation, indicating potential enhancement of cortical processing. These findings support the feasibility of tACS as a tool for modulating visual perception and cortical activity, with implications for non-invasive visual rehabilitation.