Phosphene Attributes Depend on Frequency and Intensity of Retinal tACS

Area of Science:

• Neuroscience
• Visual Perception
• Biomedical Engineering

Background:

• Phosphenes are visual sensations without external light stimuli.
• Electrical stimulation of visual pathways can induce phosphenes.
• Phosphene induction has potential applications in assistive devices for the visually impaired.

Purpose of the Study:

• To analyze subjective reports of phosphene perception induced by retinal transcranial alternating current stimulation (tACS).
• To investigate the relationship between tACS parameters (frequency, intensity) and phosphene characteristics.
• To assess the effectiveness of tACS in inducing phosphenes across different frequencies.

Main Methods:

• Subjective reports from 50 healthy participants were analyzed.
• Retinal tACS was applied at four frequencies (6, 10, 20, 40 Hz) with varying intensities.
• Participants reported phosphene types and attributes.

Main Results:

• tACS effectively induced phosphenes in at least 92% of participants.
• 41 distinct phosphene types were reported, most commonly light flashes and circles.
• Changes in tACS intensity altered phosphene attributes, with up to nine attributes affected.
• A positive correlation was found between the number of phosphene types and tACS frequency.

Conclusions:

• tACS is a reliable method for eliciting phosphenes.
• Phosphene perception is modulated by tACS frequency and intensity.
• The findings provide insights for optimizing tACS protocols for research and potential therapeutic applications.