Michael Kometer, B. Rael Cahn, David Andel, Olivia L. Carter, and Franz X. Vollenweider
Background: Recent findings suggest that the serotonergic system and particularly the 5-HT2A/1A receptors are implicated in visual processing and possibly the pathophysiology of visual disturbances including hallucinations in schizophrenia and Parkinson’s disease.
Methods: Toinvestigatetheroleof5-HT2A/1Areceptorsinvisualprocessingtheeffectofthehallucinogenic5-HT2A/1Aagonistpsilocybin (125 and 250 g/kg vs. placebo) on the spatiotemporal dynamics of modal object completion was assessed in normal volunteers (n 17) using visual evoked potential recordings in conjunction with topographic-mapping and source analysis. These effects were then considered in relation to the subjective intensity of psilocybin-induced visual hallucinations quantified by psychometric measurement.
Results: Psilocybindose-dependentlydecreasedtheN170and,incontrast,slightlyenhancedtheP1componentselectivelyoveroccipital electrode sites. The decrease of the N170 was most apparent during the processing of incomplete object figures. Moreover, during the time period of the N170, the overall reduction of the activation in the right extrastriate and posterior parietal areas correlated positively with the intensity of visual hallucinations.
Conclusions: Theseresultssuggestacentralroleofthe5-HT2A/1A-receptorsinthemodulationofvisualprocessing.Specifically,areduced N170 component was identified as potentially reflecting a key process of 5-HT2A/1A receptor–mediated visual hallucinations and aberrant modal object completion potential.