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Psychopharmacology (2013) 225:227239 DOI 10.1007/s00213-012-2811-0
ORIGINAL INVESTIGATION
The NMDA antagonist ketamine and the 5-HT agonist psilocybin produce dissociable effects on structural encoding of emotional face expressions
Andr Schmidt & Michael Kometer & Rosilla Bachmann &
Erich Seifritz & Franz Vollenweider
Received: 8 May 2012 /Accepted: 10 July 2012 /Published online: 27 July 2012 # Springer-Verlag 2012
AbstractRationale Both glutamate and serotonin (5-HT) play a key role in the pathophysiology of emotional biases. Recent studies indicate that the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist ketamine and the 5-HT receptor agonist psilocybin are implicated in emotion processing. However, as yet, no study has systematically compared their contribution to emotional biases.
Objectives This study used event-related potentials (ERPs) and signal detection theory to compare the effects of the NMDA (via S-ketamine) and 5-HT (via psilocybin) receptor system on non-conscious or conscious emotional face processing biases.
Methods S-ketamine or psilocybin was administrated to two groups of healthy subjects in a double-blind within-subject placebo-controlled design. We behaviorally assessed objective thresholds for non-conscious discrimination in all drug conditions. Electrophysiological responses to fearful, happy, and neutral faces were subsequently recorded with the face-specific P100 and N170 ERP.
Results Both S-ketamine and psilocybin impaired the encoding of fearful faces as expressed by a reduced N170 over parieto-occipital brain regions. In contrast, while S-ketamine also impaired the encoding of happy facial expressions, psilocybin had no effect on the N170 in response to happy faces.
Conclusion This study demonstrates that the NMDA and 5-HT receptor systems differentially contribute to the structural encoding of emotional face expressions as expressed by the N170. These findings suggest that the assessment of early visual evoked responses might allow detecting pharmacologically induced changes in emotional processing biases and thus provides a framework to study the patho-physiology of dysfunctional emotional biases.
Keywords Glutamate . Serotonin . Ketamine . Psilocybin . Emotional processing biases . Event-related potential . Visual awareness . Non-conscious . Conscious
Introduction
Emotional processing including the recognition of other peoples feelings from their facial expression is fundamental to social interaction and behavior. The importance of face recognition in the human social functioning is shown by the fact that emotional faces increase neuronal activity relative to neutral faces in specific brain areas. For example, increased brain responses to emotional faces have...