Alzheimer's Disease (AD) is a progressive neurodegenerative disorder, associated with memory loss, behaviour changes and physical impacts (Whitewell, 2018). It is the most common form of dementia. Reliable treatments to slow its progression are in high demand and 40Hz sensory stimulation may offer a solution.

Humans with AD and mouse models of the disease exhibit lower gamma oscillations which are important for multiple areas of cognition (McDermott et al., 2018). Studies show that auditory and visual 40Hz stimulation elicit greater gamma oscillations in mice with AD pathology and alleviates symptoms (Martoerall et al., 2019; Olsen, 2021;Traikapi & Konstantinou, 2021).
In humans, pilot studies have shown 40Hz sound stimulation to improve cognitive deficits (Figure 1) in mild to moderate AD patients (Clements-Cortes et al., 2016).

Studies indicate that greater volumes elicit greater gamma oscillations compared to lower (Schadow et al., 2007).
Figure 1: Change in SLUMS Scores (from Clements-Cortes et al., 2016).
SLUMS = St. Louis University Mental Status Test, measuring cognitive deficits
Immersive soundscapes such as forest and beach sounds present calming and therapeutic effects in and out of care homes (Cheng & Sabran, 2022; Houben et al., 2019; Voisin et al., 2021).

Combining soundscapes and 40Hz sound stimulation may be beneficial to AD management as studies show sounds and music can help patients remember long- term memories and balance the sound stimulation.

Literature Gap
There is limited research on the effects of stimulation volume and on including 40Hz sound in combination with soundscapes and how this can be effective in the treatment and management of AD. Early investigation and optimisation of different stimulation protocols on gamma oscillations and on participant perceptions can be carried out in healthy older adults, prior to their administration to people with AD.