Psychedelics and Facial Expressions: the impact of an LSD microdose on the process of encoding emotional facial expressions

Low doses of LSD (13 µg and 26 µg) reduce the amplitude of two event-related brain potentials—the P300 and N170 components—measured via scalp electrodes during a visual oddball task in healthy adults. These reductions resemble those seen with full doses of LSD. Event-related spectral perturbations showed decreased power in the alpha and some theta frequency bands, while intertrial coherence remained uniform. The findings suggest that microdoses of LSD can produce subtle changes in brain activity related to attention and stimulus processing without inducing full psychedelic effects, supporting their potential for therapeutic use.

Study at a glance

Abstract

While LSD may have had a harsh reputation in decades previous, current research has been investigating its potential as a therapeutic modality. It has been shown that full doses of LSD are capable of providing therapeutic effects however, the concept of "microdosing", or the repeated use of very low doses has become increasingly popular. Yet, the literature does not provide consistent results to explain LSD's effects. The objective of the current study was to examine the effects of LSD (13 µg and 26 µg) versus placebo by use of electroencephalogram, event-related potential (ERP), event-related spectral perturbation (ERSP), and intertrial coherence (ITC) responses in healthy adults. Twenty healthy men and women, ages 18 to 35, participated in three EEG sessions in which they received placebo or LSD (13 µg and 26 µg) under double-blind conditions. During peak drug effect, EEG recordings were obtained by use of electrodes placed on scalp to identify the P300 and N170 components evoked during the visual oddball task. During the oddball task, LSD reduced ERP amplitudes of the P300 and N170 components. ERSPs exhibited decreases in power for the alpha frequency band and some theta frequencies. ITCs displayed relatively uniform distribution between trials. The reductions in P300 and N170 amplitudes were similar to those seen in full doses of LSD. Therefore, it is feasible to predict that microdoses of LSD may result in subtle behavioral and cognitive changes without requiring the full psychedelic effects of the drug.