Single-session gamma sensory stimulation entrains real-time electroencephalography but does not enhance perception,...

Studies have shown that gamma (40 Hz) audiovisual stimulation can enhance gamma oscillations and improve cognitive functioning in patients with Alzheimer's disease. However, despite promising long-term results, the efficacy of short-duration or single-session 40 Hz entrainment in humans has been questioned by behavioral studies that fail to find observable cognitive aftereffects, for two possible reasons: 1) lack of validated gamma entrainment, as most studies lacked concurrent electroencephalography (EEG) data to verify that gamma neural entrainment did take place, and 2) lack of diverse cognitive tests, as most studies did not test a wide range of cognitive factors.

This study aimed to increase sensitivity for detecting single-session gamma entrainment. We employed 1) mid- and post-stimulation EEG monitoring to ensure entrainment worked, and 2) a comprehensive cognitive battery that probes perception, attention, working memory, and long-term memory.

Participants received 30 min of synchronized 40 Hz light and sound stimulation, followed by a visual perceptual task, attentional network task, change detection working memory task, and long-term picture memory task, with concurrent EEG.

We observed robust 40 Hz EEG entrainment during stimulation but no significant 40 Hz oscillation after stimulation, and no significant cognitive improvements.

Despite robust 40 Hz online entrainment, gamma sensory entrainment requires consistent long-term exposure to induce cognitive and neurological changes. Future research should determine the optimal duration and frequency of 40 Hz stimulation to maximize its therapeutic potential.