A new study has found that human emotions on belief, disbelief and uncertainty activate distinct regions of the brain.
It was also found that belief/disbelief affected areas are associated with the pleasantness/unpleasantness of tastes and odours.
The study, led by Sam Harris of the University of California, Los Angeles, involved 14 adults who underwent functional MRI scans during which they were presented with short statements that they had to evaluate as true, false or undecided.
In the study, each participant underwent three scans while they evaluated statements from a broad variety of categories such as mathematical, geographical, autobiographical, religious and factual.
The statements were designed to be clearly true, false or undecidable.
The analysis found that contrasting belief and disbelief trials yielded increased signal in the ventromedial prefrontal cortex (VMPFC), which is involved in linking factual knowledge with emotion.
"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 said.
The researchers noted that ethical belief showed a similar pattern of activation to mathematical belief suggesting that the physiological difference between belief and disbelief is not related to content or emotional associations.
The authors stated that the contrasts between disbelief and belief showed increased signal in the anterior insula, a region involved in the sensation of taste, the perception of pain, and the feeling of disgust, indicating that 'false propositions might actually disgust us'.
"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," they said.
Uncertainty evoked a positive signal in the anterior cingulate cortext (ACC) and a decreased signal in the caudate, a region of the basal ganglia, which plays a role in motor action.
Noting that both belief and disbelief showed an increased signal in the caudate compared to uncertainty, the authors suggested that the basal ganglia might play a role in mediating the cognitive and behavioural differences between decision and indecision.
"This would have obvious implications for the detection of deception, for the control of the placebo effect during the process of drug design, and for the study of any higher-cognitive phenomenon in which the differences between belief, disbelief, and uncertainty might be a relevant variable," the researchers said.
The study will publish online in the Annals of Neurology.