Low-Dose LSD Alters Early and Late Event-Related Potentials to Emotional Faces.

Introduction: Despite widespread popular interest in the use of low doses of Lysergic acid diethylamide (LSD) to improve mood, little is known about how these doses affect emotional processing in the brain. In this study, we tested the effect of a single low dose of LSD (26 µg) compared with placebo on electroencephalogram (EEG) event-related potentials (ERP: N170, P300 and Mismatch Negativity) in healthy adults, while participants viewed angry, happy, and neutral faces. We hypothesized that the drug might affect either neutral faces, which are sometimes perceived as threatening, or emotional faces.

Methods: Healthy young adults (n = 39) received LSD (26 µg or placebo sublingually) before completing an oddball task with emotional facial expressions during EEG recording. The N170 and P300 evoked potentials were recorded using EEG. LSD and placebo were administered in double-blind, randomized order separated by at least 7 days. During the oddball task, three emotional faces were presented infrequently (angry, happy, neutral) in a block design, and a cartoon face was presented frequently.

Results: LSD significantly reduced the amplitude of the occipitotemporal N170 ERP to Neutral faces, but not angry or happy faces. LSD also reduced the amplitude of the midline posterior parietal P300 ERP to neutral and happy faces, but not angry faces.

Discussion: These differential effects of LSD on the amplitude of the N170 and P300 to neutral and emotional faces add to our understanding of how low doses of LSD might affect the brain response to social and emotional information.