Neural changes to transcranial alternating current stimulation in the gamma range over the left frontoparietal...

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Cognitive dysfunction can be improved by transcranial alternating current stimulation (tACS) at gamma frequencies.
• tACS targets frontal and parietal regions to enhance cognitive functions.

Purpose of the Study:

• To investigate the neural changes induced by 40 Hz tACS in individuals with cognitive impairments.
• To analyze alterations in cortical current source density (CSD) and inter-regional connectivity.

Main Methods:

• 11 sessions of 40 Hz tACS (2.0 mA) applied to F3 and P3 electrode positions for 25 minutes.
• Electroencephalography (EEG) recordings before and after tACS.
• eLORETA used to reconstruct cortical CSD from EEG signals; power and connectivity analyzed across spectra.

Main Results:

• A consistent decrease in CSD at stimulating sites across beta and gamma bands (P < 0.01).
• A trend of increased CSD in the right hemisphere, potentially due to inter-hemispheric rivalry.
• Significant increase in connectivity strength between left frontal and parietal regions (P = 0.017).

Conclusions:

• tACS application leads to regional oscillation desynchronization and enhanced inter-regional crosstalk.
• Observed neural changes suggest common mechanisms underlying tACS neurophysiological effects, consistent with previous 5 Hz tACS studies.