Semantic activation in LSD: evidence from picture naming

This single-blind placebo-controlled study (n=10) investigated the effects of LSD (40-80μg) on lexical retrieval in a picture-naming task and found an increase in the rate at which subjects substituted items with similar words within the same semantic category. These results are consistent with the notion that LSD increases the spread of activation within semantic networks.


Introduction: Lysergic acid diethylamide (LSD) is a classic psychedelic drug that alters cognition in a characteristic way. It has been suggested that psychedelics expand the breadth of cognition via actions on the central nervous system. Previous work has shown changes in semantic processing under psilocybin (a related psychedelic to LSD) that are consistent with an increased spread of semantic activation.

Methods: The present study investigates this further using a picture-naming task and the psychedelic, LSD. Ten participants completed the task under placebo and LSD.

Results: revealed significant effects of LSD on accuracy and error correction that were consistent with an increased spread of semantic activation under LSD.

Discussion: These results are consistent with a generalised “entropic” effect on the mind. We suggest incorporating direct neuroimaging measures in future studies, and to employ more naturalistic measures of semantic processing that may enhance ecological validity.”

Authors: Neiloufar Family, David Vinson, Gabriella Vigliocco, Mendel Kaelen, Mark Bolstridge, David J. Nutt & Robin L. Carhart-Harris

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