Transcranial alternating current stimulation of α but not β frequency sharpens multiple visual functions

Area of Science:

• Neuroscience
• Visual Science
• Brain Stimulation

Background:

• Transcranial alternating current stimulation (tACS) modulates cortical activity.
• Previous studies showed 20 Hz (β) tACS increased motor cortex excitability more than 10 Hz (α) tACS.
• Alpha (α) oscillations are prominent in the primary visual cortex (V1).

Purpose of the Study:

• Investigate differential effects of α and β tACS on visual functions.
• Examine the influence of tACS on visual evoked potentials (VEPs) and contrast sensitivity.
• Determine the relationship between resting α oscillations and tACS-modulated VEPs.

Main Methods:

• Assessed after-effects of α and β tACS on pattern-reversal (PR) and focal-flash (FF) VEPs.
• Analyzed the relationship between resting α oscillations and PR-VEPs.
• Measured behavioral contrast sensitivity changes following tACS.

Main Results:

• α tACS modulated PR-VEP amplitudes, unlike β tACS, without affecting FF-VEPs.
• α tACS enhanced α phase synchronizations, increasing PR-VEP amplitudes.
• A positive correlation was found between PR-VEP amplitudes and resting α oscillations; α tACS improved contrast sensitivity.

Conclusions:

• α tACS influences distinct neuronal populations compared to β tACS.
• Results suggest α tACS sharpens visual functions by modulating V1 α oscillations.
• tACS frequency is critical for targeting specific visual functions.