April 30, 2001
Surprise! Study shows brains enjoy the unexpected
By Kathi Ovnic
Most people love surprises, and scientists at Emory and the Baylor University College of Medicine may have discovered why some people actually crave the unexpected.
Through a unique collaboration between Gregory Berns in Emorys
functional neuroimaging group and Read Montague at Baylors Center
for Theoretical Neuroscience, scientists are beginning to reveal the biological
basis of the human attraction to surprising events. Sam McClure, a Baylor
doctoral candidate, also contributed to the study, published in the April
15 issue of the Journal of Neuroscience.
The scientists used functional magnetic resonance imaging to measure
changes in human brain activity in response to a sequence of pleasurable
stimuli, (in this case, fruit juice and water).
Until recently, scientists assumed that the neural reward pathways, which act as high-speed Internet connections to the pleasure centers of the brain, responded to what people like, Montague said.
However, when we tested this idea in brain-scanning experiments,
we found the reward pathways responded much more strongly to the unexpectedness
of stimuli instead of their pleasurable effects.
As a result, the brain was a clean slate, allowing scientists to see
clearly which area of the brain was registering activity. The area of
the brain called the nucleus accumbens, which scientists previously have
identified as a pleasure center of the brain, recorded a particularly
strong response to the unexpectedness of a sequence of stimuli.
We find that so-called pleasure centers in the brain do not react
equally to any pleasurable substance, but instead react more strongly
when the pleasures are unexpected, Berns said. This means
that the brain finds unexpected pleasures more rewarding than expected
ones, and it may have little to do with what people say they like.
Both Berns and Montague think their work may provide a better understanding
of addictive diseases and disorders of decision-making in humans.
They believe the new findings may help clarify the neural pathways involved
in addiction to drugs such as heroin and cocaine, which are known to disrupt
the normal function of the nucleus accumbens.
Other addictive disorders, such as gambling, also appear to influence
this same brain pathway.