Background The potential therapeutic effects of 40Hz gamma stimulation in Alzheimer's Disease (AD) has recently been under study (Suk et al. Alzheimer’s and Dementia 2020; Adaikkan et al., Trends in Neuroscience 2020; Sedghizadeh et al. Alzheimer’s and Dementia 2020). While measuring the gamma power as a marker for brain entrainment is well established in the literature, some studies have focused on theta‐gamma coupling (TGC) (Etter, Guillaume, et al., Nature Communications 2019; Munia & Aviyente, Scientific Reports 2019) as TGC is known to play a critical role in working/spatial memory tasks. Synthetic 40Hz amplitude‐modulated auditory chirp sounds have been used to entrain gamma oscillations. As a natural alternative, we propose the canary song, which is innate, pleasant, and includes diverse modulating sounds with chirp frequencies up to 20Hz. Since harmonic components are present in entrained response of the brain (Jones et al., Journal of Alzheimer's Disease 2019) albeit at lower powers, entrainment with the 20Hz canary chirp song can be a substitute for the commonly used synthetic 40Hz sounds. Method We observed the entrainment characteristics for the complete course of a canary’s singing as well as for selective 20Hz chirp segments of the song on eight young adults with simultaneous EEG recording. We measured the power spectrum and TGC strength during the stimulus and rest intervals on selective independent components (IC) of the recorded response. Result Canary song’s 20Hz chirp increases the theta band and 20Hz oscillation activity. During the stimuli intervals, ICs were found in the response close to the midbrain area that were entrained by the 20Hz stimuli while also showing high power in the theta band. TGC with high values around 40 Hz was also observed during the 20 Hz chirp intervals. Conclusion Employing natural sounds for AD therapy campaigns offers a more pleasant and serene alternative to artificial sounds. We selected segments of canary’s natural song which can produce entrainment effects similar to those of the synthetic 40Hz auditory tones commonly used for brain entrainment. Other natural sounds such as those of cricket and woodpecker can also be good candidates for entraining the brain in AD therapy.

Background Non‐invasive 40Hz sensory‐induced brain entrainment has shown promising results in Alzheimer’s disease (AD) therapy (Chan et al., medRxiv, 2021; Chan et al., Alzheimer’s & Dementia, 2021). We previously reported on the network‐level mechanisms underlying the spatial and temporal coherence of the induced brain rhythms during gamma entrainment in dementia patients (Lahijanian et al., bioRxiv, 2021). Here, we posit that the induced gamma oscillations propagate as traveling waves circling each hemisphere of the cortex, and that the induction of such waves can explain the spatiotemporal coherence between the frontal and parietal/occipital regions reported to be involved in cognitive processes. Method EEG data were recorded from two healthy young adults during multi‐trial visual entrainment sessions with 22Hz flickering light. Due to the harmonic property of the brain’s entrained response (Jones et al., Journal of Alzheimer’s Disease, 2019), gamma entrainment was achieved at 44Hz. Separately, EEG data were recorded from 11 dementia patients in multi‐trial auditory entrainment sessions with 40Hz chirp input. The phase of the spatiotemporal pattern at the target gamma frequency was calculated across the entire scalp as an indicator of traveling waves. Result Shortly after the stimulation onset in the young healthy adults, a circling traveling wave is observed in each hemisphere (Fig. 1). The onset and the homogeneity of the induced wave pattern is modulated by the power of the 44Hz entrained oscillations (Fig. 2). The dementia patients can be divided into two groups of entrained and non‐entrained according to the induced gamma power (see Lahijanian et al., bioRxiv, 2021), and the travelling wave effect can be occasionally observed during the stimulation in the entrained group and not in the non‐entrained group. Conclusion Cortical traveling waves modulate the brain dynamics and play a critical role in functions ranging from sensory processing to memory consolidation (Muller et al., Nature Reviews Neuroscience, 2018). Gamma entrainment induces traveling waves that connect the occipital/parietal regions of the cortex to the frontal region through the temporal region. The traveling wave promotes spatiotemporal coherence across the brain and hence can serve as a network‐level mechanism for explaining the therapeutic effects of gamma entrainment.