40 Hz audiovisual stimulation improves sustained attention and related brain oscillations

Attokaren, Matthew K.; Zhang, Lu; Mettupalli, Sindhura; Singer, Annabelle C. · 2026 · Crossref

DOI: 10.1162/imag.a.1229

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Summary

This study investigates whether acute, non-invasive 40 Hz audiovisual stimulation improves sustained attention and modulates associated neural oscillations in healthy adults. While 40 Hz "flicker" stimulation has shown promise in reducing Alzheimer’s pathology in animal models, its acute cognitive effects in humans remain unclear. Specifically, it is unknown whether exogenously driven gamma oscillations enhance or disrupt endogenous neural processes underlying attention. The authors hypothesized that 40 Hz audiovisual flicker would improve performance on an attentional vigilance task and alter brain activity patterns linked to arousal and attention. The researchers conducted a controlled experiment with 62 healthy adults (ages 18–40) randomly assigned to one of three groups: 40 Hz flicker, random flicker (sham), or constant light (control). Participants performed a psychomotor vigilance task (PVT) for one hour while undergoing sensory stimulation and simultaneous 32-channel scalp EEG recording. The 40 Hz group received flashing lights and sounds at 40 Hz, the sham group received non-periodic flicker with the same average on-time, and the control group received constant light. EEG data were analyzed to assess power spectral density in delta, theta, alpha, beta, and gamma bands, as well as functional connectivity using the weighted phase lag index. Results demonstrated that participants in the 40 Hz group exhibited significantly better vigilance performance than both control groups, characterized by higher accuracy and faster reaction times. Neurophysiologically, the 40 Hz group showed the expected increase in gamma-band power at the stimulation frequency. Surprisingly, they also displayed significantly reduced delta power (2–4 Hz), a frequency band associated with reduced arousal and fatigue. Additionally, the 40 Hz stimulation increased functional connectivity in the lower alpha band (8–10 Hz). Crucially, across all participants, lower delta power and higher lower alpha functional connectivity were significantly correlated with improved task accuracy and faster reaction times. These findings indicate that 40 Hz flicker enhances vigilance not only by entraining gamma oscillations but also by suppressing delta activity and strengthening alpha-band network connectivity. The study concludes that acute 40 Hz audiovisual stimulation improves sustained attention in healthy adults through complex neural mechanisms extending beyond the gamma frequency range. By reducing delta power and enhancing alpha functional connectivity, the stimulation appears to optimize brain states for alertness and cognitive processing. These results suggest potential therapeutic applications for attention disorders and cognitive enhancement, highlighting the broader impact of sensory-driven gamma entrainment on neural networks involved in arousal and attention.

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• neuro workload indices