Effects of LSD-25 on the EEG and Photic Evoked Responses

Abstract

SINCE the accidental discovery of the Psychosomimetic properties of Lysergic acid diethylamide (LSD-25) by Stoll,¹ in 1947, a great amount of work has been carried out to elucidate the behavioral effects and pathophysiological mechanisms of action of this substance. The literature on this topic is steadily growing and contains now more than 1,000 publications.² There are several studies available that report on the electroencephalographic changes resulting from LSD administration to humans as seen by surface recordings^3-9 and there are also some observations on changes in the human depth electrogram.^10-13 It is generally agreed that the amplitude of the EEG decreases, α-rhythms tend to disappear and the tracings become of the lowvoltage fast or desynchronized type. Gastaut⁴ reported that the average α-frequencies are increased by 0.5 to 4 cycles per second (cps) and Grey Walter⁷ noted an increase from 11.6 to