No evidence that LSD microdosing affects recall or the balance between distracter resistance and updating

In a randomized double-blind, placebo-controlled study, three different low doses of LSD (5 μg, 10 μg, and 20 μg) were tested for their effects on working memory in a modified delay-match-to-sample task that required ignoring or updating novel items. There was no evidence that any of the LSD microdoses affected the accuracy or efficiency of working memory recall, nor was there evidence for differential effects on ignoring or updating. These results are preliminary due to the small sample size, and larger studies are required to establish whether LSD microdoses affect short-term recall.

Study at a glance

Abstract

The effect of low doses (<=20 μg) of LSD on working memory, in the absence of altered states of consciousness, remain largely unexplored. Given its possible effects on serotonin 5-HT2A receptors and dopaminergic signalling, it could be hypothesised that LSD microdoses modulate working memory recall. Moreover, in line with computational models, LSD microdoses could exert antagonistic effects on distracter resistance and updating. Here, we tested this hypothesis in a randomised double-blind, placebo-controlled study comparing three different LSD microdoses (5 μg, 10μg and 20μg) with placebo. After capsule administration, participants performed a modified delay-match-to-sample (DMTS) dopamine-sensitive task. The standard DMTS task was modified to include novel items in the delay period between encoding and probe. These novel items either had to be ignored or updated into working memory. There was no evidence that LSD microdoses affected the accuracy or efficiency of working memory recall and there was no evidence for differential effects on ignoring or updating. Due to the small sample of participants, these results are preliminary and larger studies are required to establish whether LSD microdoses affect short-term recall.