, Volume 234, Issue 13, pp 2031–2046 | Cite as

Dreamlike effects of LSD on waking imagery in humans depend on serotonin 2A receptor activation

  • Rainer KraehenmannEmail author
  • Dan Pokorny
  • Leonie Vollenweider
  • Katrin H. Preller
  • Thomas Pokorny
  • Erich Seifritz
  • Franz X. Vollenweider
Original Investigation



Accumulating evidence indicates that the mixed serotonin and dopamine receptor agonist lysergic acid diethylamide (LSD) induces an altered state of consciousness that resembles dreaming.


This study aimed to test the hypotheses that LSD produces dreamlike waking imagery and that this imagery depends on 5-HT2A receptor activation and is related to subjective drug effects.


Twenty-five healthy subjects performed an audiorecorded guided mental imagery task 7 h after drug administration during three drug conditions: placebo, LSD (100 mcg orally) and LSD together with the 5-HT2A receptor antagonist ketanserin (40 mg orally). Cognitive bizarreness of guided mental imagery reports was quantified as a standardised formal measure of dream mentation. State of consciousness was evaluated using the Altered State of Consciousness (5D-ASC) questionnaire.


LSD, compared with placebo, significantly increased cognitive bizarreness (p < 0.001). The LSD-induced increase in cognitive bizarreness was positively correlated with the LSD-induced loss of self-boundaries and cognitive control (p < 0.05). Both LSD-induced increases in cognitive bizarreness and changes in state of consciousness were fully blocked by ketanserin.


LSD produced mental imagery similar to dreaming, primarily via activation of the 5-HT2A receptor and in relation to loss of self-boundaries and cognitive control. Future psychopharmacological studies should assess the differential contribution of the D2/D1 and 5-HT1A receptors to cognitive bizarreness.


LSD Ketanserin 5-HT2A receptor Guided mental imagery Dreams Cognitive bizarreness Healthy subjects Self-boundaries and cognitive control Visual hallucinations 



This study was financially supported by grants from the Heffter Research Institute (1-190413), the Swiss Neuromatrix Foundation (2015-0103), the Usona Institute (2015-2056) and the Swiss National Science Foundation (SNSF, P2ZHP1_161626).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no competing interests.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric HospitalUniversity of ZurichZurichSwitzerland
  2. 2.Neuropsychopharmacology and Brain Imaging, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric HospitalUniversity of ZurichZurichSwitzerland
  3. 3.Department of Psychosomatic Medicine and PsychotherapyUniversity of UlmUlmGermany

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