Frequency-dependent and montage-based differences in phosphene perception thresholds via transcranial alternating...

Area of Science:

• Neuroscience
• Bioelectromagnetics
• Sensory Perception

Background:

• Transcranial alternating current stimulation (tACS) can induce phosphenes, visual artifacts perceived as light.
• Phosphene thresholds are used to estimate safe electrical stimulation limits for human neural functioning.
• The exact relationship between tACS parameters and phosphene perception thresholds requires further clarification.

Purpose of the Study:

• To systematically investigate how tACS stimulation location and frequency influence phosphene perception thresholds.
• To determine the specific tACS parameters that elicit the lowest phosphene perception thresholds.
• To assess the consistency of phosphene thresholds across participants for potential use in safety standards.

Main Methods:

• Utilized tACS to deliver electrical stimulation to the scalp in 24 participants.
• Investigated two stimulation sites: FPz-Cz and Oz-Cz.
• Tested stimulation frequencies ranging from 2 Hz to 30 Hz in 2 Hz increments.
• Employed a within-subject design to obtain phosphene perception thresholds.

Main Results:

• Phosphene perception thresholds were significantly lower with FPz-Cz stimulation compared to Oz-Cz.
• The lowest phosphene perception thresholds were consistently observed at a stimulation frequency of 16 Hz, irrespective of location.
• Minimal variation in thresholds was found across participants, indicating high reliability.

Conclusions:

• The location of tACS application and stimulation frequency critically impact phosphene perception thresholds.
• A 16 Hz stimulation frequency appears to be most sensitive for eliciting phosphenes.
• The low inter-subject variability supports the use of phosphene thresholds in establishing robust safety guidelines for tACS.