The orbitofrontal cortex and its role in the assignment of behavioural significance.

Converging evidence suggests a specific role for the orbitofrontal cortex (OFC) in processing of reinforcer value and stimulus hedonicity. However, in a recent study posterior parts of the OFC were also activated in the absence of physical reward or positive reinforcement, namely when affectively neutral stimuli were perceived as salient and required an immediate adjustment of behaviour. This suggests that the OFC may be similarly responsive to different types of behaviourally significant events irrespective of their affective valence or the associated response demands. The present functional neuroimaging study aimed at testing this hypothesis. By systematically varying the exact nature of the behavioural significance of experimental stimuli we were able to directly compare neural responses to significant events that signalled the chance to gain a monetary reward for correct performance with brain activation related to salient, but affectively neutral events that occurred unexpectedly and required a rapid adjustment of behaviour towards these events. The observed commonalities in orbitofrontal activation for different types of significant events, which occurred independent of the hedonic value or the actual response requirements, confirmed the hypothesis that the OFC may be more generally involved in evaluating the behavioural relevance of salient environmental stimuli and is not restricted to the processing of reward and positive incentive value. Our findings thus further underscore the putative role of the OFC in the prioritisation of attentional selection and behavioural control.