Study of Visual Perception Phenomena: Phosphene Mapping Induced by TMS and Its Relationship With Eye Movements

Single-pulse TMS is applied to specific areas of the visual cortex to non-invasively induce the perception of phosphenes (brief flashes of light). Stimulation is delivered using a TMS device, with the operator controlling the intensity and frequency parameters to a level equal to the phosphene-evoking threshold. During stimulation, participants are seated comfortably and asked to report the location of perceived phosphenes on a monitor and a physical grid, helping to map the cortical visual field.

Continuous brain electrical activity is recorded using a 128-channel gel-based EEG system (Skoltech). The EEG cap is fitted to the participant's head to capture neural responses with high temporal resolution throughout the session. The collected data is used to analyze brain activity changes, including the P300 component and other event-related potentials, to identify neural correlates of phosphene perception and the effects of TMS.

Eye movements are continuously monitored using a Tobii Defusion 2 eye-tracker (Skoltech) operating at 60 Hz. This device provides high-accuracy measurements of gaze fixation and saccades. Participants are instructed to fixate their gaze on one of five predetermined points on a screen (center, top, bottom, left, right), with the fixation point being determined randomly for each trial. The eye-tracking data is analyzed to assess the influence of gaze position on phosphene localization and to study any stimulation-induced changes in eye movement patterns.