This power spectrum distribution shows a slightly different pattern for each measurement area on the head surface. Researchers who want to analyze EEG characteristics of a specific state usually observe power spectrum distributions first showing the distribution of power for each frequency component from 0 to 50 Hz, and then find meaning to find meaningfully changing frequency components. Some researchers even analyze the sub-divisions such as Low Alpha, Middle Alpha, and High Alpha. It is reported that gamma wave vibrates more rapidly than the beta wave, and is more emotionally irritated or related to advanced cognitive information processing such as reasoning and judgment.ĭelta, theta, alpha, beta, and gamma wave are frequency domains of brain waves that are conveniently classified for convenience. In particular, it may appear predominantly in anxiety, tension, and complicated calculations.
Alpha wave is closely related to brain development and is measured at 4 to 6 Hz in infancy, but the frequency increases with age and reaches adult values by 20 years.īeta wave usually appears in the brain's frontal area, and it appears when you are awake and doing all conscious activities, such as speaking. When you open your eyes, look at objects, or become emotionally excited, the alpha wave is suppressed. In particular, when a stable alpha wave appears, it is when you close your eyes and is in a true state.
In general, it appears continuously in the form of regular waves, with the largest recorded in the parietal and occipital regions and the smallest in the frontal region. Theta wave has been reported to be related to many different conditions such as memory, superpower, creativity, concentration, and anxiety, but the experimental protocol and subject characteristics are slightly different for each researcher, so the direction of increase and decrease in each cerebral cortex region is consistent.Īlpha wave usually appears in a relaxed state, such as relaxation, and the amplitude increases with a stable and comfortable state. Theta wave mainly occurs in the process leading to emotional stability or sleep and is more distributed in children than adults. Therefore, when an EEG measurement experiment is performed for a long time, the power spectrum of delta waves is not usually considered as an analysis factor because eye movement and body movement are essential. The frequency-domain of the artifacts caused by these eye movements or body movements is almost identical to the delta wave frequency domain, so it may appear as if the delta wave has increased. If the delta wave stands out even in the case of a healthy normal person, most of the cases when the brain waves are measured, the eyes are blinked or the body is moved heavily.
If the delta wave is much higher than the average range in awake people, it may be a malignant tumor of the cerebral cortex, anesthesia or coma. In general, brain waves are artificially called delta (δ) wave (0.2 ~ 3.99 Hz), theta (θ) wave (4 ~ 7.99 Hz), and alpha (α) wave (8 ~ 12.99 Hz), beta (β) wave (13 ~ 29.99 Hz) and gamma (g) wave (30 ~ 50 Hz) depending on the range of oscillating frequenciesĭelta wave is prominent, especially in deep sleep in normal people or in newborns. Power spectrum analysis assumes that the EEG is a linear combination of simple vibrations that vibrate at a specific frequency, and decomposes each frequency component in this signal to indicate its magnitude (or power). Frequently, when observing EEG, power spectrum analysis that classifies according to frequency is used. Therefore, it is not very useful to visually observe the EEG waveform. The EEG generated in this way looks like a waveform that vibrates in a very complex pattern. Changes in brain waves caused by glial cells and blood-brain barriers occur little by little, whereas changes in brain waves caused by nerve cell activity are large, fast, and diverse. The blood-brain barrier serves to select and pass only the necessary substances among various substances in the cerebral blood vessels. Gliocytes, which makeup half of the brain's weight, regulate the flow of ions and molecules at the synapse, and repair structures between nerve cells. The electrical activity of the brain reflected in the electroencephalogram (EEG) is determined by neurons, glia cells, and the blood-brain barrier, which is mainly caused by nerve cells.