'Might Have Been' Key In Evaluating Behavior
May 17, 2007
"What might have been" or fictive learning affects the brain and plays
an important role in the choices individuals make - and may play a role in
addiction, said Baylor College of Medicine researchers and others in a report
that appears online in the Proceedings of the National Academy of Sciences.
These "fictive learning" experiences, governed by what might have
happened under different circumstances, "often dominate the evaluation of
the choices we make now and will make in the future, " said Dr. P. Read
Montague, Jr., professor of neuroscience at BCM and director of the BCM Human
Neuroimaging Laboratory and the newly formed Computational Psychiatry Unit.
"These fictive signals are essential in a person's ability to assess the
quality of his or her actions above and beyond simple experiences that have
occurred in the immediately proximal time."
Using techniques honed in previous experiments that studied trust, Montague and
his colleagues used an investment game to test the effects of these "what
if" thoughts on decisions in 54 subjects. Using functional magnetic
resonance imaging (fMRI) to measure blood flow changes in specific areas of the
brain, they precisely measured responses to economic instincts.
These blood flow changes in the brain reflect alterations in the activity of
nerve cells in the vicinity. In this case, they measured the brain's response to
"what could have been acquired" and "what was acquired."
This newly discovered "fictive learning" signal was measured,
localized and precisely parsed from the brain's standard reward signal that
reflects actual experience.
Each subject took part in a sequential gambling task. The player makes a new
investment allocation (a bet) and then receives a "snippet" of
information about the market - either the market went up and the investment was
a good one or the market goes down and the play had a loss. Each subject
received $100 and played 10 markets, making 20 decisions about each.
Montague and his associates found that fictive learning - the "what might
have happened" - affected the brains of the subjects and played an
important role in their decisions about the game. This effect manifested as a
distinct selective activation signal in a part of the brain called the ventral
caudate nucleus. The emotion of regret for a path chosen or not taken can be
strongly influential on future decision-making. The fictive learning signal
discovered by Montague and the team of researchers does not necessarily manifest
as such a conscious "feeling" but contributes to the brain's
computation and planning operations in a robust way that is now available to
rigorous experimental analysis in health and in diseases of the brain/mind.
"We used real world market data - the crash of 1929, the bubble of the late
1990s and so on - to probe each subject's brain response to fictive signals
(what could have been) as they navigated their choices. This means we now have a
kind of neural catalogue of how famous stock market episodes affect signals in
the average human brain," said Montague.
He plans to use the findings from this study to explore the balance of choices
between actual and fictive outcomes.
"These results provide a new tool for exploring issues related to
addiction," Montague said. "For example, why does a person choose
using a drug even though he or she can imagine the bad consequences that can
result" We now have a way to measure quantitatively the balance between
reward-seeking (like seeking a drug) and the thoughts that could
intervene."
"The brain has a well-defined system for pursuing actual rewards based on
actual outcomes. The system is complex, but recent research has begun to dissect
them in great detail. The importance of that work is that the reward guidance
signals are exactly those hijacked by drugs of abuse," said Dr. Terry
Lohrenz, an instructor in the neuroimaging laboratory at BCM and the report's
first author. "Identifying real neural signals to fictive outcomes now
positions us to understand how our more abstract thoughts - the way we
contextualize or frame our experience - guide our behavior."
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Others who took part in the study included Drs. Kevin McCabe of George Mason
University and Colin Camerer of California Institute of Technology.
Funding for this work came from the National Institute on Drug Abuse, the
National Institute of Neurological Disorders and Stroke, the Kane Family
Foundation and the Institute for Advanced Study in Princeton, N.J.
For the full text of this article click
here.
Contact: Kimberlee Barbour
Baylor College of
Medicine
Medical News Today: http://www.medicalnewstoday.com
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