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Gamma oscillations (γ, 30-120 Hz) have been implicated in various cognitive functions and are associated with multiple neuropsychiatric disorders. Non-invasive gamma entrainment using sensory stimuli has emerged as a potential therapeutic approach, particularly for Alzheimer’s Disease patients. However, the comparative efficacy of different gamma frequencies sensory stimulation in entraining endogenous gamma oscillations remains under-explored.
The objective of this study is to investigate the effects of 40 Hz and 60 Hz rhythmic auditory stimulation (rAS) on steady-state power spectrum density (PSD) and aftereffects via electroencephalography (EEG). Employing a crossover within-subject design, young-adult healthy participants received both stimulation frequencies randomly. EEG data were recorded pre-stimulation, during stimulation, and post-stimulation.
The analysis, focused on the effects of 40Hz vs. 60Hz auditory stimulation on PSD, revealed a gradual increase in gamma band entrainment throughout the 40Hz and 60Hz rAS, persisting, as an aftereffect, in the minutes immediately following the stimulation. Particularly, 40Hz rAS increased low-gamma (30-47Hz) power across the whole brain, especially in the temporal cluster. Moreover, the high-gamma (53-70 Hz) power analysis revealed a cluster-dependent entrainment with 60Hz rAS increasing high-gamma mainly within the central cluster, while 40Hz rAS within the temporal cluster.
In conclusion, this study aims to elucidate the neural responses to different rAS frequencies, as the potential to entrain neural frequencies through sensory stimulation offers the opportunity to explore the link between brain oscillations and cognitive functions, which could have significant implications for neuroenhancement and rehabilitation programs.
