Modulating Gamma Oscillations Promotes Brain Connectivity to Improve Cognitive Impairment

Area of Science:

• Neuroscience
• Cognitive Science
• Neurology

Background:

• Dementia, particularly Alzheimer's disease (AD), imposes a significant global economic burden with limited effective treatments.
• Gamma-band oscillations (40 Hz) are crucial for cognitive functions and have shown potential in clearing amyloid-β plaques by activating microglia.

Purpose of the Study:

• To investigate the efficacy of 40-Hz high-frequency repetitive transcranial magnetic stimulation (rTMS) in improving cognitive function in patients with probable AD.
• To explore the neural mechanisms underlying the cognitive improvements induced by 40-Hz rTMS.

Main Methods:

• Thirty-seven patients with probable AD received 40-Hz rTMS over the bilateral angular gyrus.
• Resting-state electroencephalography (EEG) and power spectral density analysis were used to assess gamma-band oscillations.
• Magnetic resonance imaging (MRI) and transcranial magnetic stimulation-EEG (TMS-EEG) were employed to evaluate brain structure and functional connectivity.

Main Results:

• 40-Hz rTMS significantly improved cognitive function for up to 8 weeks compared to sham stimulation.
• EEG analysis revealed modulation of gamma-band oscillations in the left posterior temporoparietal region.
• MRI and TMS-EEG showed that 40-Hz rTMS prevented gray matter loss, enhanced local and global functional integration, and strengthened information flow and dynamic connectivity within the brain.

Conclusions:

• Modulating gamma-band oscillations via 40-Hz rTMS is a promising therapeutic strategy for improving cognitive function in probable AD.
• The treatment enhances brain connectivity, including local, long-range, and dynamic connections, contributing to cognitive benefits.