40Hz Auditory Entrainment Promotes Synchronization Between Frontal and Parietal Regions of the Brain

Gamma oscillations are known to play a critical role in memory and cognition tasks. The quality of neural activity in this oscillatory band is impaired due to Alzheimer's disease (AD) dementia. Recently, promoting gamma oscillations through sensory stimulation has shown promising therapeutic results in reducing structural and cognitive symptoms of AD. Further analysis on the effects of sensory entrainment on the brain's oscillatory activity could help better understand the mechanisms underlying the observed improvements and optimize the stimulation protocols for achieving better outcome. In this study, we investigate the effects of 40Hz auditory brain stimulation on synchronizing frontoparietal neural activity based on electroencephalogram data recorded from a cohort of elderly participants with memory complaints. We observed that the entrained gamma band activity encompasses the entire scalp with most responsive regions in the frontal and parietal lobes. In addition, the neural activity of frontoparietal regions are synchronized due to entrainment and the quality of synchronization is correlated with the strength of entrainment. In other word, participants with highly responsive entrained sites in the frontal and parietal cortices present the most synchronized activity between these two regions. Long distance synchronization across the brain can help improve functional connectivity and improve the disrupted network-level coordination of sensory and frontal regions responsible for high-level cognitive operations.