Corlett, P.
Department of Psychiatry, Yale University, New Haven, USA
Prediction error is the mismatch between expectation and experience, used as a teaching signal to update beliefs and an impetus to allocate attention toward potential explanations. Delusions could result from aberrant prediction errors, specified inappropriately, driving attention toward irrelevant stimuli, thoughts and percepts and forging the formation of odd and unusual beliefs. I will outline evidence favoring this model from functional neuroimaging studies of causal belief formation in patients with endogenous psychosis and healthy individuals exposed to a pharmacological "model psychosis"; the drug ketamine. A crucial feature of delusions is their tenacity. This feature may well also be explicable in terms of aberrant prediction error. Surprising events demand change in expectancies, necessitating making what we have learned labile and so updatable: updating, binding memories anew (memory reconsolidation). Under the influence of excessive prediction error, delusional beliefs may be repeatedly reconsolidated, strengthening them so they persist, impervious to contradiction.