To what extent does the harmfulness of an anticipated outcome affect our brain’s event monitoring system? Not at all, revealed a new study published in the February 2011 issue of Elsevier’s Cortex: the reaction is the same, regardless of how scary the anticipated event is.
Our brains are able to adapt to the unexpected using an built-in network that makes predictions about the world, and monitors how those predictions turn out. An area at the front of the brain, called the orbitofrontal cortex, plays a central role, and studies have shown that patients with damage to this area confuse memories with reality, and continue to anticipate events that are no longer likely to happen.
A team of researchers, supervised by Prof. Armin Schnider of the University Hospitals of Geneva in Switzerland, recorded functional magnetic resonance images (fMRI) while healthy volunteers performed a task in which they repeatedly saw a pair of faces and had to predict on which face a target was about to appear. The target could be a simple black disk (neutral stimulus) or a spider (potentially harmful stimulus). The researchers found a strong activation of the brain’s visual areas whenever the spider appeared. However, irrespective of whether the disk or the spider was the target, its unexpected absence activated a cerebral network including the orbitofrontal cortex.
The findings show that, while the potential harmfulness of an event strongly affects brain responses, it does not influence the way the brain reacts when the expected event does not occur. The study supports the notion that the orbitofrontal cortex is “at the centre of a specific cerebral network which functions as a generic outcome monitoring system,” says Louis Nahum, the first author of the study. “This capacity is probably as old in evolution as the instinctive reaction to threatening stimuli; its failure deprives the brain of the ability to remain in phase with reality,” notes Armin Schnider.
Ref.: “Neural response to the behaviorally relevant absence of anticipated outcomes and the presentation of potentially harmful stimuli: A human fMRI study,” Cortex. 2011 Feb; 47(2): 191-201
References^ Neural response to the behaviorally relevant absence of anticipated outcomes and the presentation of potentially harmful stimuli: A human fMRI study (www.ncbi.nlm.nih.gov)^ materials (www.eurekalert.org)