Alpha wave

As we relax in preparation for and pass into sleep, the active desynchronised awake EEG characterised by the low-amplitude (5-10 pV) high-frequency (10-30 Hz) beta waves becomes progressively more synchronised giving larger (20-30 pV) and slower (8-12 Hz) alpha waves, and then even slower (1-4 Hz) and bigger (30-150 pV) delta waves. This so-called slow-wave sleep is interrupted at intervals of some 1-2h by the break-up and desynchronisation of the EEG into an awake-like pattern. Since this is accompanied by rapid eye movements, even though sleep persists and can be deeper, the phase is known as rapid eye movement, REM or paradoxical, sleep. It is a time when dreaming occurs and when memory may be secured. 

Figure 22.4 Idealised EEG-like patterns in sleep and waking. When we are awake and aroused the EEG is desynchronised (a). As we become drowsy and pass into sleep the EEG waves become more synchronised with 8-12 Hz alpha waves (b), sleep spindles then appear (c) before the EEG becomes even more synchronised with slow (about 1-2 Hz) high-voltage waves characteristic of deep slow-wave sleep (SWS). About every 90 min this pattern is disrupted and the EEG becomes more like that in arousal (d) except that the subject remains asleep. This phase of sleep is also characterised by rolling, rapid eye movements, the so-called REM sleep. SWS is consequently also known as non-REM sleep. These tracings have been drawn to show the main features of the different EEG phases of sleep and as such are much simpler than those that are actually recorded...

Figure 3.8 Effects of tf-amphetamine on the wake EEG Mean EEG spectral values for six healthy male subjects who took placebo. 5 mg and 10 mg of d-amphetamine on separate occasions in a balanced crossover trial are shown Whereas the EEG trace 2 h after placebo (upper third) shows a rapid decline in alpha waves and an increase in theta waves (see arrows pointing to the alpha decrease and the theta increaee), the corresponding changes occurred later after 5 mg (middle third) andlOmg (tower third) d-amphetamine The decay of alpha and increaee of theta activities occurred after 2 mm on placebo, but only after 7 min on 5 mg d-amphetanine and after 12 mn on 10 mg of d-amphetamine, thus reflecting a vigilance-stabilizing effect of tf-aiphetamine (Matejcek, 1979, with permission)...

Figure i. Records taken from a cat chronically prepared with electrodes to record the eye movements (EOG), the electroencephalogram from both sides of the skull (EEG), and the activity of the neck muscles (NMG). The animal was kept in an air-conditioned, sound-attenuated room supplied with a oneway mirror for observation. The records were taken while the animal was awake and active (top left), awake and resting (top right—note alpha waves), just dropped off to sleep (middle left —note "spindles"), in deeper sleep (middle right—note slow waves in EEG) in still sounder sleep (bottom left—note very slow waves), and in paradoxical sleep (bottom right—arousal pattern in EEG). (Note eye movements in awake animal and in paradoxical sleep). Note also reduced electrical muscle activity in paradoxical sleep. Calibrations vertical line at top middle = 100 microvolts (or o.oooi volt), horizontal line = l second. Original from author s laboratory. 

Rinkel and his co-workers (1952) studied the effect of LSD-25 on the EEG of human volunteers. They noted only slight changes, characterized by a small but distinct acceleration of the alpha-wave rhythm. 

Alpha electroencephalogram EEG that shows 8-13 Hz waves (alpha waves) in all... 

In a placebo-controlled, randomized, double-blind, three-fold crossover clinical study, 12 healthy volunteers were evaluated for the effects of a single dose of kava extract equivalent to 120 mg kavalactones and 10 mg diazepam. Measurements were taken directly before, and two and six hours post ingestion. The washout period before crossover was seven days. After kava administration, a non-significant increase compared to placebo was noted in the quantitative EEG in the delta/theta intensity in the occipital and frontal areas, as well as a reduction of the alpha-wave relative intensity (P < 0.05). An increase in beta activity typically found with benzodiazepines was not observed with kava. The placebo group witnessed a decline in the relative intensity of the slow delta- and theta-waves and an increase in the alpha-waves (P < 0.001). Maximal effects of diazepam were usually observed two hours after application, as opposed to the kava extract where the effects had not decreased even after six hours. The critical flicker frequency in the psychophysiological tests was found to be lower under the influence of kava extract and diazepam compared to placebo (P < 0.05). In contrast, significant increases in performance in the Pauli Test after the administration of kava extract were noted which were not present with the placebo or diazepam (P < 0.05) (Gessner and Cnota, 1994). 

Kobayashi, K., Nagato, Y, Aoi, N., Juneja, L. R., Kim, M., Yamamoto, T., and Sugi-moto, S. 1998. Effects of L-theanine on the release of alpha-waves in human volunteers. Nippon Nogeikagaku Kaishi 72 153-57. 

Mason, R. 2001. 200 mg of zen L-theanine boosts alpha waves, promotes alert relaxation. Altem. Complementary Ther. 7 91-95. 

They had found that they could more easily catalog Herman s memories and distinguish real events from the rest of the noise in his brain by first having Herman produce mu waves between 8 and 13 Hz. (This took Herman a few days of practice, but he soon learned to generate mu waves whenever he wanted to.) These brain waves arose at a few frequencies within the alpha waves produced by a wakeful but relaxed brain. Malcolm told Herman that mu waves were the resting rhythms generated by neurons in the sensorimotor cortex, a diffuse region of the brain that lay on top of the head, between the ears. 

Recording electrical activity with electrodes surrounding the head made it possible to try to relate the mind to the brain. Slow electrical brain waves, called theta waves, were observed during states of low mental activity. At high degrees of arousal, fester beta waves were recorded. Alpha waves were recorded at medium levels of arousal. The greater the state of arousal, the greater the number of alpha and beta waves. 

In the 1960s, people were fascinated by Indian yogis who were able to alter their states of consciousness by meditation. They were able to control bodily functions, including blood pressure. Benson believes that meditation can help treat high blood pressure, chronic pain, insomnia, and many other physical ailments, as well as in management of stress. Meditating lowers the levels of stress hormones, and boosts the alpha waves to levels seen during sleep. 

Xenopus central pattern generator neuron A model of Xenopus embryo swimming central pattern generator neurons with HH currents was modified by Tabak and Moore [1998] to include a voltage-and magnesium-sensitive NMDA channel current and a Rail alpha-wave mechanism for non-NMDA postsynaptic currents. 

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