Electroencephalography (EEG) is the science of recording the spontaneous rhythmic electrical activity of a living brain through electrodes on the scalp.
The rhythmic activity varies in frequency and amplitude with age, attention, sleep, and chemical concentrations of oxygen, carbon dioxide, glucose, ammonia, and hormones.
Definitions of the changes in EEG rhythms were developed that identified and classified psychoactive drugs, monitored the depth of anesthesia, and evaluated the efficacy of the seizures induced in convulsive therapy (electroshock).
In 1929 Hans Berger, a German psychiatrist, reported continuous electrical rhythms from the intact human head using electrodes on the scalp.
The continuous electrical activity varied in frequencies and amplitude with drowsiness and sleep, and with mental problem solving.
Episodic runs and bursts of high voltage slow frequencies were recorded in patients with epilepsy.
Assessment methods in human volunteers were developed that recorded the changes in the resting subject at different dosages, both on acute single administrations and repeated daily dosing.
In patients who failed to respond to prescribed treatments, those who were considered "pharmacotherapy resistant," EEG studies showed that the chemicals did not elicit identifiable brain changes.
The technology was applied in anesthesia, identifying the efficacy of individual seizures in convulsive therapy, in studies of sleep patterns, and the relation of evoked potentials to speech and psychological tests.
Social changes in attitudes to the ethics of testing drugs and treatments in patients, prisoners, children, and volunteers inhibited the continued development of the science and its abandonment.
The science then successfully focused on alert male volunteers (since the EEG varied with menstrual cycles in women).
Different methods developed to sustain a monitored level of alertness using hand held buzzers that sounded off when the subject relaxed and dozed.
In the beginning the EEG recordings were made on paper and changes measured visually, scored by ruler and calipers.
Digital computer methods using period analysis, power spectral density, and amplitude analyses followed.
The measures related the EEG changes to the common classes of psychoactive drugs—antidepressant, anxiolytic, antipsychotic, hallucinogen, deliriant, euphoriant, and mood stabilizer being the most frequent.
Pharmaco-EEG studies were economically useful in clinically classifying new agents, dosage ranges and durations of effects, and separating active from inactive substances.
The list of successful applications is extensive; some specific examples are the identification of mianserin (GB-94) and doxepin as antidepressants of the imipramine class; of the inactivity of flutroline as a proposed antipsychotic in man despite activity in dogs; and of equivalent EEG activity of the laevo and dextro enantiomers of 6-azamianserin (mirtazapine) despite differences in preclinical trials.
Studies of different cannabis formulations (hashish, marijuana, tetrahydrocannabinol-∆-9 extract each showed the same patterns in EEG, cardiovascular, and clinical profiles.
Specialized equipment to monitor ongoing identification of anesthesia stages are common in modern surgical units.
Stille G, Herrmann W, Bente D, Fink M, Itil T, Koella WP, Kubicki S, Künkel H, Kugler J, Matejcek M, Petsche H. Guidelines for pharmaco-EEG studies in man.
Wikler A. Pharmacologic dissociation of behavior and EEG 'sleep patterns' in dogs: Morphine, n-allynormorphine and atropine.
Fink M. EEG classification of psychoactive compounds in man: Review and theory of behavioral association.
In: Efron D, Cole JO, Levine J, Wittenborn JR. (Eds): Psychopharmacology: A Review of Progress 1957-1967 U.S.G.P.O., Washington, D.C., 497-507, 1968; Fink M., Itil T. Neurophysiology of the phantastica: EEG and behavioral relations in man.
Annu Rev Pharmacol 9:241-258, 1969; Bradley P and Fink M. (Eds): Anticholinergic Drugs and Brain Functions in Animals and Man.
Relation of EEG delta activity to behavioral response in electroshock: Quantitative serial studies.
Fink M and Irwin P. Pharmaco-EEG study of 6-azamianserin (ORG-3770): Dissociation of EEG and pharmacologic predictors of antidepressant activity.