title: Performance on a probabilistic inference task in healthy subjects receiving ketamine compared with patients with schizophrenia.
abstract: Evidence suggests that some aspects of schizophrenia can be induced in healthy volunteers through acute administration of the non-competitive NMDA-receptor antagonist, ketamine. In probabilistic inference tasks, patients with schizophrenia have been shown to 'jump to conclusions' (JTC) when asked to make a decision. We aimed to test whether healthy participants receiving ketamine would adopt a JTC response pattern resembling that of patients. The paradigmatic task used to investigate JTC has been the 'urn' task, where participants are shown a sequence of beads drawn from one of two 'urns', each containing coloured beads in different proportions. Participants make a decision when they think they know the urn from which beads are being drawn. We compared performance on the urn task between controls receiving acute ketamine or placebo with that of patients with schizophrenia and another group of controls matched to the patient group. Patients were shown to exhibit a JTC response pattern relative to their matched controls, whereas JTC was not evident in controls receiving ketamine relative to placebo. Ketamine does not appear to promote JTC in healthy controls, suggesting that ketamine does not affect probabilistic inferences.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, UCL, London, UK. sle27@sussex.ac.uk
authors.forename: Simon
authors.initials: S
authors.lastname: Evans
authors.forename: Basil
authors.initials: B
authors.lastname: Almahdi
authors.forename: Pervez
authors.initials: P
authors.lastname: Sultan
authors.forename: Imrat
authors.initials: I
authors.lastname: Sohanpal
authors.forename: Brigitta
authors.initials: B
authors.lastname: Brandner
authors.forename: Tracey
authors.initials: T
authors.lastname: Collier
authors.forename: Sukhi S
authors.initials: SS
authors.lastname: Shergill
authors.forename: Roman
authors.initials: R
authors.lastname: Cregg
authors.forename: Bruno B
authors.initials: BB
authors.lastname: Averbeck
mesh_terms: D000328:Adult; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D014150:Antipsychotic Agents / Q000627:therapeutic use; D003657:Decision Making / Q000187:drug effects*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D005260:Female; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D008297:Male; D008875:Middle Aged; D020258:Neurotoxicity Syndromes / Q000175:diagnosis; D010352:Patient Dropouts; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D012559:Schizophrenia / Q000097:blood / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index; D013647:Task Performance and Analysis; D055815:Young Adult
chemical_list: D000778:Anesthetics, Dissociative; D014150:Antipsychotic Agents; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D007649:Ketamine