INS Keynote Seminar – Valentin Wyart (Paris)
“Premature, self-confirmatory commitment to uncertain decisions during pharmacologically induced transition to psychosis: a placebo-controlled, double-blind EEG study in healthy human subjects”
In schizophrenia, early stages of psychosis are characterized by a state of pathological uncertainty (or ‘strangeness’) which is difficult to study in patients due to its transitional nature. Therefore, the alterations of mental processes which lead to full-blown delusions remain largely unknown. Here we studied a pharmacological model of this condition using ketamine, an NMDA receptor antagonist, in healthy subjects performing a decision-making task based on ambiguous probabilistic cues.
Computational modeling of subjects’ behavior under ketamine revealed a decrease in the precision of inference – the mental process of interpreting and accumulating evidence during decision-making. The analysis of simultaneously recorded EEG signals provided support for this selective alteration, by showing a degraded neural coding of the evidence provided by individual cues. Furthermore, upcoming decisions could be decoded earlier from EEG signals under ketamine, and evidence inconsistent with upcoming decisions were down-weighted in the inference process.
Together, these findings indicate a premature, self-confirmatory commitment to uncertain decisions under ketamine, a selective alteration of decision-making which could explain the stabilization of aberrant beliefs characteristic of psychosis.
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