brainwave

Brainwaves are rhythmic or repetitive patterns of neural activity in the brain, arising from the synchronized electrical activity of large populations of neurons. They are most readily measured with electroencephalography (EEG), which records voltage fluctuations at the scalp and reflects ongoing cognitive, sensorimotor, and dream states.

These brainwaves are categorized into frequency bands, including delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz), and gamma (above about 30 Hz). The boundaries are approximate and brain activity often spans multiple bands. Band prominence varies with waking state, age, and location.

Brain electrical activity arises from postsynaptic potentials in cortical pyramidal neurons. EEG captures summed activity over populations, while magnetoencephalography (MEG) records magnetic fields from cortex. Invasive methods, such as electrocorticography (ECoG), offer higher spatial resolution. Researchers also use source localization to estimate underlying generators.

Different bands are associated with functional states: delta dominates deep sleep; theta is linked to drowsiness and some memory processes; alpha is common during relaxed wakefulness, especially with eyes closed; beta is often related to arousal and active thinking; gamma is studied in attention and perceptual binding, though interpretations are debated.

Clinical and applied uses include diagnosing epilepsy and monitoring sleep disorders. Abnormal EEG patterns can indicate pathology; neurofeedback trains individuals to regulate certain brainwave patterns in real time. Brain–computer interfaces translate EEG signals into device control. Commercial devices and products that promise brainwave-based enhancement exist, but evidence varies and claims should be viewed cautiously.