Delta Waves and Sleep: How Neurofeedback Enhances Deep Rest

Sleep is important for overall health. While there are good habits that a person can choose to help promote sleep, like avoiding caffeine late in the day, exercising early and avoiding blue light from computers, phones and TV,  some may still have difficulty sleeping. In fact, it’s been estimated that 50 to 70 million people in America suffer from some kind of sleep disorder. Addressing sleep problems is a game changer in the pursuit of wellness. This is due to the renewing power of sleep. Sleep heals and refreshes many body systems and organs, including the brain. During restorative deep sleep, the brain essentially gets washed. The glymphatic system flushes out waste that can build up in the brain throughout the day. Brain waves can reveal a lot about sleep and present an opportunity for intervention. For example delta waves in the brain are associated with deep sleep and may be trained using neurofeedback.

Sleep Science in Health and Disease

REM and Non-REM Sleep

Healthy sleep involves both REM and non-REM sleep (Bear, Connors, Paradiso, 2016). Rapid eye-movement (REM) sleep is a phase in which the sympathetic nervous system is active. Electroencephalography (EEG) during REM sleep appears similar to an awake EEG. Conversely non-REM, which is also called deep sleep, is marked by parasympathetic activity which drives the rest, digest and heal functions of the body. This is why deep sleep is characterized by its ability to restore health. 

Non-REM: The Low Power Sleep Mode

Non-REM deep sleep gives the brain and body a chance to rest and heal (Bear, Connors, Paradiso, 2016). The body relaxes and muscles release tension. It’s like a low power mode for the body, with less need for the body and brain to use up energy. This deep sleep stage is associated with its own EEG rhythms.

Sleep and Health Conditions: A Reciprocal Relationship?

Sleep is Complex

Despite decades of study, the complexity of sleep continues to puzzle even the most experienced scientists. What is known is that there are several neuromodulators involved, including norepinephrine, acetylcholine, 5-hydroxytryptophan and histamine (Bear, Connors, Paradiso, 2016). Deep sleep as a brain state is guided by slow delta waves in the brain. During sleep states, neurons in the thalamus play a role in synchronizing the rhythms of electrical activity in the brain. 

Sleep is More than a Healthy Habit

For sleep to go well, a brain needs to be healthy enough to coordinate the necessary biological processes. While sleep is partly influenced by healthy habits, getting good quality sleep is more than choosing when to exercise or consume caffeine. In many ways, sleep is a function of brain health. This concept is most evident when considering how various health conditions affect sleep. 

Health Conditions and Sleep Quality

Conditions like brain trauma, or neuroinflammation from a bacterial or viral infection, environmental exposures or even chronically elevated blood sugar in diabetes mellitus, may all disrupt brain health in a manner that affects sleep. These conditions have the potential to influence sleep quantity or quality through various biological processes.

Reciprocal Relationship of Health and Sleep Quality

While problems with getting good quality sleep may arise from existing health conditions, the relationship between health and sleep seems to be reciprocal. Sleep also seems to be influenced by behaviors like the time of day that a person exercises or looks at blue lights from TV, phone or computer screens close to bedtime, as well as caffeine consumption in the afternoon or evening. Loss of sleep, or poor quality sleep can have a detrimental effect on long term health. In the short term, inadequate sleep can leave a person feeling excessively tired, fatigued and struggling to think clearly the following day. Regardless of what may be causing the sleep problems, it is clear that intervention is important for restoring wellness.

Delta Waves and Sleep

What Are Delta Wave Frequencies?

Delta wave functioning can be an indicator of general brain health. Delta is measured in a quantitative EEG (qEEG) with a frequency range of 0.5 to 4 Hz. Data from an EEG can be used to interpret dominant frequency. For example, if there is a dominant frequency at 4 Hz, then that’s the faster side of a delta range, showing a brain state corresponding to sleep. When dysfunction is detected in delta waves in the brain, it is associated with a variety of neurological symptoms.

Delta Waves and Sleep Quality

 Delta is dominant in the first of the sleep cycles, considered non-REM sleep. Healthy delta wave functioning is associated with enhanced sleep quality. Since sleep is a physically restorative process for the brain and the body, it is essential to address any delta wave frequency dysfunction.

Dysfunctional Delta Waves and Sleep

In the video, Digging into Delta, Dr. Richard Soutar teaches in depth about dysfunctional delta waves and sleep. He explains that as seen on a qEEG brain map, delta dominance normally occurs when alpha decreases in both frequency and amplitude, and theta increases as the brain state shifts into sleep. When it comes to delta waves and sleep problems, there are distinct ways that qEEG brain maps show delta wave functioning. For example, an eyes-open qEEG brain map that shows abnormal delta, that is either regional or diffuse, can be an indicator of poor sleep. 

Dr. Soutar also explains that when interpreting how delta waves and sleep symptoms are connected, the type of qEEG needs to be considered. For example, when an eyes-closed qEEG brain map shows abnormal delta waves in the brain, locally or regionally, there is a correlation with inflammation. He goes on to explain that lesions in the brain, whether created by traumatic brain injury, environmental toxins, bacterial or viral infections; correlate with the location of focal delta dysfunction on a brain map. Delta waves and sleep drive processes that renew and restore health to the brain and body. Without it, the brain may not be as effective in clearing out excess waste, impacting things like energy and cognitive clarity.

Neurofeedback Training to Enhance Sleep

Sensorimotor rhythm (SMR) neurofeedback training has been used to improve sleep in people suffering from insomnia. In a case study, a 29 year old woman who was experiencing mild anxiety, cognitive impairments and sleep problems received SMR neurofeedback training. After 20 sessions, she experienced relief in her anxiety symptoms and cognitive functioning, and her sleep quality improved.

In another study, 24 participants with insomnia completed sensorimotor rhythm (SMR) training. After only 10 sessions their deep sleep, recorded by polysomnograph, increased along with their own ratings of sleep quality. Additionally, cognitive benefits were observed for 16 of the 24 participants.

Delta Waves and Sleep: Restoring Health

Good quality sleep is essential for brain functioning and overall health. Low energy and difficulty concentrating can be a consequence of not being able to get deep, restorative sleep. Healthy functioning of delta waves in the brain helps to drive the deep sleep that restores health to the brain and body. Without it, the brain may not function optimally, affecting many aspects of daily life. Delta wave frequency training is a non-pharmacological approach to renewing sleep quality and promoting wellness.

For those struggling with disrupted sleep, training the brain to return to healthy delta wave patterns can make a measurable difference. Neurofeedback offers a way to observe and influence these brain rhythms in real time. But not all systems provide the same level of insight. NewMind’s platform stands apart by offering the ability to view delta wave activity directly—something most other dry sensor systems simply don’t provide.

Ready to Sleep Deeply Again?

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Works Cited

Bear, M. F., Connors, B. W. & Paradiso, M. A. (2016). Neuroscience: Exploring the Brain (4th ed., pp. 650-669). Wolters Kluwer.

de Andrés, I., Garzón, M. & Reinoso-Suárez, F. (2011). Functional anatomy of non-REM sleep. Frontiers in Neurology, 2(70), 1-14. https://doi.org/10.3389/fneur.2011.00070 

Model Systems Knowledge Translation Center (MSKTC), (2010). Sleep and Traumatic Brain Injury. https://msktc.org/tbi/factsheets/sleep-and-traumatic-brain-injury 

National Institute of Neurological Disorders and Stroke. (2025, February). Brain Basics: Understanding Sleep. U.S. Department of Health and Human Services, National Institutes of Health. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep 

NewMind Technologies. (2019, June 12). Digging into Delta [Video]. Youtube. https://www.youtube.com/watch?v=ew7c2ouHxdE 

Patel, A. K., Reddy, V., Shumway, K. R., et al. (2024). Physiology, Sleep Stages. StatPearls.  https://www.ncbi.nlm.nih.gov/books/NBK526132/

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Rom, S., Zuluaga-Ramirez, V., Gajghate, S., Seliga, A. & Winfield, M., et al., (2019). Hyperglycemia-Driven Neuroinflammation Compromises BBB Leading to Memory Loss in Both Diabetes Mellitus (DM) Type 1 and Type 2 Mouse Models. Molecular Neurobiology, 56(3), 1883–1896. https://doi.org/10.1007/s12035-018-1195-5 

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