Dopamine effects on evidence gathering and integration

Background: disturbances in evidence gathering and disconfirmatory evidence integration have been associated with the presence of or propensity for delusions. previous evidence suggests that these 2 types of reasoning bias might be differentially affected by antipsychotic medication. we aimed to investigate the effects of a dopaminergic agonist (l-dopa) and a dopaminergic antagonist (haloperidol) on evidence gathering and disconfirmatory evidence integration after single-dose administration in healthy individuals. methods: the study used a randomized,double-blind,placebo-controlled,3-way crossover design. participants were healthy individuals aged 18-40 years. we administered a new data-gathering task designed to increase sensitivity to change compared with traditional tasks. the bias against disconfirmatory evidence (bade) task was used as a measure of disconfirmatory evidence integration. results: we included 30 individuals in our study. in the data-gathering task,dopaminergic modulation had no significant effect on the amount of evidence gathered before reaching a decision. in contrast,the ability of participants to integrate disconfirmatory evidence showed a significant linear dopaminergic modulation pattern (highest with haloperidol,intermediate with placebo,lowest with l-dopa),with the difference between haloperidol and l-dopa marginally reaching significance. limitations: although the doses used for haloperidol and l-dopa were similar to those used in previous studies,drug plasma level measurements would have added to the validity of findings. conclusion: evidence gathering and disconfirmatory evidence integration might be differentially influenced by dopaminergic agents. our findings are in support of a dual-disturbance ac- count of delusions and provide a plausible neurobiological basis for the use of interventions targeted at improving reasoning biases as an adjunctive treatment in patients with psychotic disorders. © 2015 8872147 canada inc.