Brain rhythms

Alpha rhythm (α-rhythm) - the oscillation frequency varies from 8 to 13 Hz. The amplitude is 5-100 μV, the largest amplitude appears with eyes closed and in a darkened room. It is recorded mainly in the occipital and parietal regions (visual parts of the brain).

General characteristics.

It is registered in 85-95% of healthy adults. Alpha rhythm is associated with a relaxed state of wakefulness, peace. Alpha waves occur when we close our eyes and begin to relax.

Depression of alpha rhythm (lack of alpha waves) occurs when a person opens his eyes or thinks about a task that requires certain visual representations. With an increase in the functional activity of the brain, the amplitude of the alpha rhythm decreases until it disappears completely. It can also be a sign of anxiety, anger, fear, anxiety, causing depression; disorders associated in one way or another with changes in the activity of activating systems of the brain and, as a result, with an increased level of activation of the autonomic and central nervous system.

Beta rhythm (β-rhythm) - the oscillation frequency varies from 14 to 40 Hz. The oscillation amplitude is usually up to 20 μV. Normally, it is very weakly expressed and in most cases has an amplitude of 3-7 μV. It is recorded in the anterior and central gyrus. It extends to the posterior central and frontal gyrus.

General characteristics.

Beta waves are the fastest. The beta rhythm is normally associated with higher cognitive processes and focusing, in the usual waking state, when we openly observe the events that occur, or are focused on solving any current problems.

Beta Depression The beta rhythm is associated with somatic, sensory and motor cortical mechanisms and gives a fading reaction to motor activation or tactile simulation. When performing or even mental representation of the movement, the beta rhythm disappears in the area of ​​the corresponding activity. An increase in beta rhythm is an acute reaction to stressful effects.

Gamma rhythm (γ-rhythm) - the oscillation frequency is higher than 30 Hz, sometimes reaches 100 Hz, the amplitude usually does not exceed 15 μV. It is registered in the precentral, frontal, temporal and parietal zones of the cerebral cortex.

General characteristics.

Usually very well observed when solving problems that require maximum attention.

Delta rhythm (δ-rhythm) - the oscillation frequency varies from 1 to 4 Hz. the amplitude is in the range of 20-200 μV (high-amplitude waves).

General characteristics.

The delta rhythm (slow waves) is associated with recovery processes, especially during sleep, and a low level of activation. With many neurological and other disorders, the delta waves are noticeably amplified. Excess amplified delta waves almost guarantee the presence of impaired attention and other cognitive functions. It occurs during natural and narcotic sleep, and is observed in the same way as when registering from areas of the cortex bordering on the area affected by the tumor.

Theta rhythm (θ rhythm) - the oscillation frequency of this rhythm is from 4 to 8 Hz. The amplitude ranges from 20 to 100 μV. It is registered in the frontal zones and the hippocampus.

General characteristics.

Theta waves appear when calm, relaxed wakefulness turns into drowsiness. Fluctuations in the brain become slower and more rhythmic. This condition is also called “twilight”, because in it a person is between sleep and wakefulness. Normally, theta waves are associated with a change in the state of consciousness . Often this condition is accompanied by a vision of unexpected, dreamlike images, accompanied by vivid memories. Most people fall asleep as soon as a noticeable amount of theta waves appear in the brain.

The theta rhythm is associated with search behavior, amplified by emotional stress, often observed with psychotic disorders, states of confusion, concussion.

A high level of theta rhythm can indicate a state of drowsiness and fatigue, which can be a manifestation of asthenic syndrome, chronic stress.

Kappa-rhythm (κ-rhythm) - the oscillation frequency of this rhythm lies in the range from 8 to 13 Hz. The amplitude is in the range of 5-40 μV. Registration of this rhythm occurs in the temporal region of the brain.

General characteristics.

Similar in frequency to the alpha rhythm. It is observed when alpha rhythm is suppressed in other areas in the process of mental activity.

Mu-rhythm (μ-rhythm) - the frequency of the rhythm fluctuations from 8 to 13 Hz. The amplitude usually does not exceed 50 μV. It is recorded in the Rolandic region, that is, according to the distribution of the beta rhythm (localized in the area of ​​the Roland groove).

General characteristics.

It has parameters similar to the alpha rhythm, but differs in the shape of waves that have rounded peaks and therefore look like arches. It is observed in 10-15% of individuals. It is associated with tactile and proprioceptive irritations and the imagination of movement. It is activated during mental stress and mental stress.

The oscillation frequency of the tau rhythm (τ rhythm) lies in the range from 8 to 13 Hz, the oscillation frequency of the lambda rhythm (λ rhythm) and sleep spindles coincides and ranges from 12 to 14 Hz. Registration of tau and lambda rhythms occurs in the temporal cortex. Carotid spindles are recorded throughout the cerebral cortex, but are most pronounced in the central leads.

General characteristics

The tau rhythm responds by blocking sound stimuli. In turn, sleepy spindles are a kind of outburst of activity.

When a person is excited or alert, alpha waves are replaced by low-voltage irregular fast oscillations. An increase in beta activity with a decrease in alpha activity may indicate an increase in psychoemotional stress, the appearance of anxiety states (with eyes closed). A decrease in alpha rhythm, an increase in theta rhythm indicates the manifestation of depression (with eyes closed).

Strengthening the beta component and the simultaneous weakening of the theta component is effective in various epileptic syndromes, with attention and hyperactivity disorder, post-stroke disorders (spasticity, paresis, plegia), post-traumatic syndromes, etc.

Theta and delta vibrations can occur in a waking person in small quantities and with an amplitude not exceeding the amplitude of the alpha rhythm. The contents of θ and δ, which exceed 40 μV in amplitude and occupy more than 15% of the recording time, are considered pathological.

• Bykov M.P. Anatomy of the brain. Photographic Atlas, Practical Medicine, 2009
• Kibardin G. M. Brain against aging.
• Kiroi V.N., Ermakov P.N. General characteristics of human EEG rhythms // Electroencephalogram and functional state of a person. - Rostov-on-Don: Publishing house Rost. University, 1998 .-- S. 48-76. - 264 p. - 300 copies. - ISBN 5-7507-0579-2 .
• Sapin M.R., Sivoglazov V.I. Anatomy and physiology of man. Academy Publishing Center, 2002