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

Summary

The purpose of this basic science study is to better understand human visual perception. Phosphenes are flashes of light that can be induced using Transcranial Magnetic Stimulation (TMS). The location of these phosphenes is known to change with eye movements, but the exact influence of these movements is not fully understood.

The main questions this study aims to answer are:

How does stimulating specific areas of the visual cortex relate to where a person perceives a phosphene? How do eye movements affect the accuracy of mapping these sensations? The study will enroll three groups of adults (aged 18-65): patients with Visual Snow Syndrome, color-blind participants, and healthy volunteers.

During the experiment, participants will receive single-pulse TMS to their visual cortex. Simultaneously, their eye movements will be monitored with an eye-tracker, and their brain activity will be recorded with EEG. Participants will be asked to report the location of the perceived light flashes. This will help create a map of the brain areas responsible for visual sensations and clarify how eye movements influence this process.

Conditions

• Visual Snow Syndrome
• Color Blindness
• Healthy Volunteer

Interventions

DEVICE

Transcranial Magnetic Stimulation (TMS)

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.

DEVICE

Electroencephalography (EEG)

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.

DEVICE

Eye-Tracking

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.

Sponsors & Collaborators

• I.M. Sechenov First Moscow State Medical University

  collaborator OTHER

• Skolkovo Institute of Science and Technology

  lead OTHER

Study Design

Allocation

NON_RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-09-10

Primary Completion

2026-12-10

Completion

2026-12-10

Countries

• Russia

Study Locations