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While many people will have completed their winter solstice festivals by now, there are many others who will still be taking part in religious celebrations for days to come. But what makes some people believers, others non-believers and yet others uncertain. Functional magnetic resonance imaging studies carried out by researchers in the USA could provide new clues about faith. Writing in the January issue of Annals of Neurology, graduate student Sam Harris and professor of psychiatry and fMRI pioneer Mark Cohen of the UCLA Center for Cognitive Neuroscience together with Sameer Sheth of the Massachusetts General Hospital have used fMRI to observe the differences in the brains in different cognitive states of belief, disbelief and uncertainty. Their work might one day allow neuroimaging of such cognitive functions to be distinguished reliably, in real time. The human mind is a prolific generator of beliefs about the world, the researchers explain. Indeed, the capacity of our minds to believe or disbelieve linguistic propositions is a powerful force in behaviour control and emotion. However, until now the foundations of this process in the brain was not at all understood. In their experiment in belief, Cohen and colleagues scanned fourteen adult volunteers at UCLA's Brain Imaging Center. The volunteers were presented with written statements covering a broad range of topics, including mathematics, geography, factual knowledge, word definitions, religion, ethics, and biographical facts about themselves. The researchers asked each of the subjects to rate the various statements as true, false, or dubious. They then compared the scans acquired when the volunteers believed, disbelieved or could not judge the truth-value of the written propositions. The scientists had anticipated that the difference between belief and disbelief would be largely mediated by activity in the frontal lobes the part of the brain most enlarged and differentiated in humans. Indeed, when belief and disbelief were contrasted, the investigators saw differences principally in a region known as the ventromedial prefrontal cortex (VMPFC), near the front of the brain along its midline. "The involvement of the VMPFC in belief processing suggests an anatomical link between the purely cognitive aspects of belief and human emotion and reward," the researchers say, "The fact that ethical belief showed a similar pattern of activation to mathematical belief suggests that the physiological difference between belief and disbelief may be independent of content or emotional associations." The team found that the areas that are specifically engaged in disbelief include the cingulate areas of the limbic system, and the anterior insula, a brain region known to report certain sensations, such as pain and disgust, and to be involved largely in negative appraisals of sensations like taste and smell. "Our results appear to make sense of the emotional tone of disbelief, placing it on a continuum with other modes of stimulus appraisal and rejection," the researchers add, "False propositions might actually disgust us." During periods of uncertainty, however, the researchers saw a different pattern in the scans. A different portion of the cingulate cortex, located closer to the front of the brain, showed a much stronger signal when volunteers were shown statements of dubious content. This so-called "anterior cingulate" cortex frequently shows up in studies of conflict monitoring, error detection, and cognitive interference. When compared to both belief and disbelief, the state of uncertainty also showed decreased signal in the caudate, a region of the basal ganglia, which plays a role in motor action. Uncertainty, by its nature, differs from belief and disbelief because it keeps us in an unsettled state preventing us from taking action on the basis of a specific interpretation of the world. Cohen and colleagues suggest that the basal ganglia may play a role in mediating the cognitive and behavioural differences between decision and indecision. The results as a whole offer us new insight into how our brains form beliefs about the world. "What I find most interesting about our results," says Harris, "is the suggestion that our view of the world must pass through a bottle-neck in regions of the brain generally understood to govern emotion, reward, and primal feelings like pain and disgust." Evaluating mathematical, ethical, or factual statements uses very different kinds of mental processing, but actually accepting or rejecting these statements apparently relies upon the same, more primitive, process that seems to be independent of the actual content. "I think that it has long been assumed that believing that "two plus two equals four" and believing that "George Bush is President of the United States" have almost nothing in common as cognitive operations," explains Harris, "But what they clearly have in common is that both representations of the world satisfy some process of truth-testing that we continually perform." Harris suggests that this work adds yet more evidence to the notion that reason and emotion are much more closely linked than we previously believed. From a practical point of view, the findings have implications for the detection of deception, for the control of the placebo effect during drug design, and for the study of higher cognitive phenomena underpinned by belief, disbelief and uncertainty. Related links: The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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