Deep Sleep Stimulation and Delta Waves

Delta Waves

Before getting into deep sleep stimulation, we need to understand the role that delta waves play in regenerating the brain. Our brain waves in deep sleep have these long-burst brain waves that are very different from our waking life brain waves. These long-burst brain waves are called delta waves. Deep sleep measurement occurs using electrodes attached to the skull. When we don’t get the deep sleep we need, it inhibits our ability to learn and for our cells and bodies to recover. Deep sleep is how we convert all those interactions that we make during the day into our long-term memory and personalities. As we get older, we’re more likely to lose these regenerative delta waves. So in way, deep sleep and delta waves are actually a marker for biological youth.

Scientific Validation of Deep Sleep Stimulation

SleepSpace is leveraging cutting edge neuroscience research with a grant we received from the National Institute of Aging. In the grant we describe a system we are developing that uses sound to make sleep more regenerative, improve memory, and next day cognition. The grant is entitled, non pharmacological improvement of sleep structure in older people . The goal of the grant is designed to develop a deep sleep stimulation system on accessible consumer devices such as the Apple Watch, Fitbit, Google Watch, and Oura Ring. Below is a drawing of the type of system we are developing, which will be available on all major smart phone devices in 2019.

10 years of cutting edge research has demonstrated that sounds can be used to entrain the brain into deeper sleep. In two of these studies, human subjects were stimulated during sleep with brief tones (50 millisecond duration) that were played via headphones or speakers between 0.8 and 2 Hz, a rate that approximated the natural cellular oscillation of cortical neurons during sleep.1,2 The auditory stimulation led to higher slow wave power compared to the flanking periods during which the stimulation was not present, with increases in slow wave power present during all 3 sleep cycles. Interestingly, tones were effective in increasing slow waves not only at the beginning of the night, when slow waves are more abundant, but even more effective later in the night when slow waves are typically fewer and smaller.2 Two other papers also tested the effect of tones presented at a slow rate on SWA.3,4 When auditory stimulation started during wakefulness, before sleep, and continued for the first 90 min of sleep, it significantly delayed sleep onset. However, once sleep was established, 0.8-Hz stimulation significantly increased and entrained endogenous slow oscillation activity. This effect was stronger when auditory stimulation was given in phase with the ongoing rhythmic occurrence of slow oscillation up states.3 Importantly, the enhancement of declarative memory by auditory stimulation was observed in a paired-associated learning task, whereas sham stimulation did not enhance the retention of word-pair memories.3

1. Riedner B.A., Bellesi M., Hulse B.K., Santostasi G., Ferrarelli F., Cirelli C., and Tononi G. (2013) Enhancing slow waves using acoustic stimuli. Sleep 36, A41.

2. Tononi G., Riedner B.A., Hulse B.K., Ferrarelli F., and Sarasso S. (2010) Enhancing sleep slow waves with natural stimuli. MedicaMundi 54, 73-79.

3. Ngo H.V., Claussen J.C., Born J., and Molle M. (2013) Induction of slow oscillations by rhythmic acoustic stimulation. J. Sleep Res. 22, 22-31.

4. Ngo H.V., Martinetz T., Born J., and Molle M. (2013) Auditory closed-loop stimulation of the sleep slow oscillation enhances memory. Neuron 78, 545-553.