Gamma waves

Gamma waves are the fast end of brain-wave activity, with a frequency above about 30 Hz (commonly given as 30 to 100 Hz). Frequency here is measured in hertz (Hz), the number of cycles a second, so 40 Hz means about forty cycles each second; the 40 Hz point gets particular attention in research. These waves are read using EEG (electroencephalography), a painless test that records the brain's electrical activity through small sensors on the scalp, and they tend to be low in amplitude, meaning the waves are small and rapid rather than tall and slow.¹ Gamma activity rises during active concentration and attention, and is closely tied to "binding", the brain's job of combining separate features such as colour, shape, and sound into one unified perception. On EEG, "gamma oscillations" are "associated with sensory processing and cognition", and the gamma rhythm "is also linked to cognitive functions, including working memory and attention".²

EEG bands are simply named ranges of brain-wave speed. From slowest to fastest, the common labels are delta (about 0.5 to 4 Hz), theta (about 4 to 8 Hz), alpha (about 8 to 12 Hz), beta (about 13 to 30 Hz), and gamma (above about 30 Hz). Gamma sits right at the fast end, beyond the alert, busy beta band, so its presence is associated with intense, focused processing rather than rest. "Neural synchrony" here means groups of neurons firing in step; gamma is the rhythm most often seen when the brain is integrating information and holding attention, which is why it is linked to the binding of perceptions into a single experience.²

You may have seen 40 Hz light and sound stimulation tied to brain health. In mouse models of Alzheimer's disease, a 2016 study found that driving 40 Hz gamma activity reduced amyloid build-up and changed immune cells in the brain.³ This is genuinely interesting, but it is early-stage research: the strongest results are in mice, the human trials so far are small, and nothing here is a proven or approved treatment. Rhythmic sound can produce a matching rhythm in the hearing parts of the brain (the frequency-following response), but reliably pushing the whole brain into a sustained gamma state with audio is not established. No consumer audio product, Sonora included, treats, prevents, or slows dementia or any disease; treat any "gamma" or "40 Hz" track as a sound experience, not a medical intervention.