Pharmacological Modulation of Belief Salience

Delusions in psychiatry are viewed as a form of aberrant belief. Consequently it is important to understand the cognitive and neural processes involved in beliefs to provide insights into how these processes go awry in the formation of delusions. Beliefs have been defined as 'a disposition to express, assent to, or otherwise act in accordance with some proposition'. Some beliefs are widely held within a given society (e.g the earth revolves around the sun; eating humans is wrong), whereas others vary in association with subcultural and individual differences (e.g God created the universe; abortion is wrong). Similarly, the conviction or agreement with which an individual's beliefs and values are held may change over time, to the extent that some beliefs and values may be lost, and others acquired. Also, the perceived relevance of beliefs and values to oneself may vary. For example, beliefs that the 'earth revolves around the sun' and that 'global warming is occurring' may both be held with conviction, but the latter may be perceived as having higher relevance to the self in terms of risk, and potential life-style changes. Hence, self-relevance is a dimension of beliefs that is potentially dissociable from the conviction (level of agreement) with which a belief is held. Further, some propositions expressing beliefs and values may be regarded as more interesting than others. This raises the question of what neurobiological processes contribute to the sense of conviction for, and perceived self-relevance and interest of beliefs and values?

The mesolimbic dopamine system is a candidate neural system implicated in mediating the motivational salience of perceptions and ideas, 'whereby events and thoughts come to grab attention, drive action, and influence goal-directed behaviour because of their association with reward or punishment'. In human studies, haloperidol has been used to show that dopamine activity influences action-value estimates represented in the striatum during instrumental conditioning, as would be expected from earlier studies of feedback-based learning. Still other data suggest that brain regions rich in dopaminergic inputs play a role in processing the salience of rewarding events. What is not known is if these dopaminergic rich regions also modulate the motivational salience of more complex 'stimuli' including ideas and beliefs.

Main hypothesis:

Prediction 1:

At a neurobiological level, the hypothesis is that the mesolimbic dopamine system is recruited to tag representations (ideas and beliefs) as motivationally salient. Potentiation of dopamine transmission should increase salience of beliefs (as indicated by increases in agreement, self-relevance and interest toward propositions within science, paranormal, politics, moral, and religious themes in the Beliefs and Values Inventory while attenuation of dopamine transmission should be associated with decreased salience. Answers of items within themes will be summed to create summary scores that will be split by agreement, interest, and self-relevance dimensions.