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Abstract:
Clinical neuroscientists have recently been investigating
deficits in decision making in people with damage to the
ventromedial prefrontal cortex. These deficits are apparent using a
simple gambling paradigm as described by Bechara, Damasio, and
colleagues at the University of Iowa. The use of the Iowa gambling
task has now been extended to other populations including
Huntington Disease as well as substance abusing subjects. Despite
the rapid rise in popularity of this gambling paradigm for
revealing deficits in decision making, little is known about the
specific mechanisms responsible for the deficit. We have developed
formal decision models for the Iowa gambling task and have applied
cognitive modeling analyses to our datasets from the Huntington's
Disease and substance abuse studies. Our results provide
theoretically based parameter estimates for individual differences
in how trial by trial selections change across the task. The
parameter estimates decompose the behavioral deficit into
motivational and cognitive components by including parameters to
describe effects of the stable card by card wins, infrequent
losses, and sensitivity to losses. Several of the models have good
fits with data from healthy subjects as well as the two study
groups. Links between the theoretically derived parameter estimates
for the best models and the neuropsychological models of
Huntington's disease and substance abuse will be discussed.
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