Meditation and the brain: EEG Coherence
What is an EEG measurement?
The human brain emits faint electrical impulses that can be measured and recorded by EEG (electroencephalographic) monitoring devices. To perform an EEG measurement, sensors (electrodes) are placed on the scalp to detect and record patterns of the brain’s electrical activity. An EEG measurement identifies wavelengths (or frequencies) of brainwaves. The brainwave data recorded by the EEG and analyzed by computer programs can be used for clinical and research purposes.
How does the Transcendental Meditation technique affect the brain?
A typical EEG pattern is a rapidly changing composite or combination of different frequencies—waves moving up and down at different rates—some slow, some fast. During ordinary waking consciousness, EEG patterns are complex, scattered and disorderly. In contrast, during the practice of the Transcendental Meditation technique, brainwaves tend to become much more rhythmic and orderly. Examination of the EEG data clearly shows that during practice of the TM technique, EEG signals from different parts of the brain’s surface—known as the cortex—become more correlated or similar over time. During TM practice, brainwaves from many regions of the brain fall into “phase” with each other and tend to remain so throughout meditation—moving synchronously over large areas in the frontal regions and extending eventually toward the posterior regions. This correlation between EEG signals can be precisely calculated and is called EEG coherence*.
Why is brainwave coherence important?
Higher coherence, as measured in a number of scientific studies, is associated with more integrated and effective thinking and behavior, including greater intelligence, creativity, learning ability, emotional stability, ethical and moral reasoning, self-confidence and reduced anxiety. Everything good about the brain depends upon its coherent functioning. The key to “total brain functioning” EEG studies showing high levels of brainwave coherence during practice of the Transcendental Meditation technique, along with studies that show synchronized alpha power in the frontal cortex during the TM technique, have established the EEG signature for the state of “restful alertness” commonly experienced during TM practice. Remarkably, research shows that regular practice of the TM technique leads to long-term changes in brain function, as seen in meditators who experience this restful alertness throughout their daily activity and are found to display the EEG signature of restful alertness even outside of their TM practice. This growing maintenance of brainwave coherence throughout the day is directly correlated with healthier, more integrated brain functioning.
Researchers have long known that most experiences, whether sensory or cognitive, enliven only local, specific portions of the brain. Studies on brain patterns during TM practice indicate that the technique enlivens very high levels of coherence over a remarkably wide area of the brain—creating more efficient coordination of brain activity and stimulating growth of what scientists call “total brain functioning.”
EEG tracings during the Transcendental Meditation technique:
This charts shows what high EEG coherence looks like in an EEG tracing as typically seen during the practice of the Transcendental Meditation technique. Note that the signals between any pairs of sensors seem to rise up and down together—maintaining a stable phase relationship—indicating that the whole brain is highly correlated. This integrated state of brain function corresponds to the subjective experience of heightened wakefulness or restful alertness. Research has shown that the TM technique cultures the brain to behave more coherently and efficiently overtime, as seen in a person’s improved response to stimuli—with better performance on spatial tasks, memory tasks, creativity scores and reaction time tests. Such global coherence is not reported from other meditation practices.
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*Technical: EEG coherence is a measure of correlation or synchrony of the EEG waves recorded from two points on the scalp. Mathematically, it is the absolute value of the cross-correlation function in the frequency domain of two electrical signals. Coherence is considered to reflect the number and strength of connections between two brain areas (Levine 1976).
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