Transcranial alternating current stimulation enhances individual alpha activity in human EEG

Area of Science:

• Neuroscience
• Electrophysiology
• Brain Stimulation

Background:

• Transcranial direct current stimulation (tDCS) is established for studying human cortical function.
• Transcranial alternating current stimulation (tACS) is a newer technique to modulate rhythmic brain activity.
• Previous evidence for tACS efficacy was indirect, based on behavioral outcomes, lacking direct electrophysiological proof.

Purpose of the Study:

• To provide direct electrophysiological evidence of tACS modulating ongoing human cortical activity.
• To investigate the effect of tACS on endogenous alpha brain oscillations.
• To explore the aftereffects of tACS on neural activity through computational modeling.

Main Methods:

• 10 healthy participants received tACS over the occipital cortex, targeting individual alpha frequency.
• A control group received sham stimulation for comparison.
• Electroencephalography (EEG) recorded brain activity; computational models simulated neural network dynamics and spike-timing-dependent plasticity (STDP).

Main Results:

• tACS significantly increased endogenous alpha power at parieto-central EEG electrodes compared to sham stimulation.
• Computational simulations demonstrated that tACS influences STDP.
• Simulations showed that tACS-induced STDP leads to lasting aftereffects on neural activity.

Conclusions:

• This study presents the first direct electrophysiological evidence of tACS interacting with human cortical oscillatory activity.
• tACS effectively modulates specific oscillatory brain activity, specifically alpha power.
• The findings highlight tACS's potential for advancing our understanding of brain oscillations and for therapeutic applications.