Christopher D. Fiorillo, Philippe N. Tobler, Wolfram Schultz (2003)
Abstract
Uncertainty is critical in the measure of information and in assessing the
accuracy of predictions. It is determined by probability P, being maximal at P
0.5 and decreasing at higher and lower probabilities. Using distinct stimuli to
indicate the probability of reward, we found that the phasic activation of
dopamine neurons varied monotonically across the full range of probabilities,
supporting past claims that this response codes the discrepancy between predicted
and actual reward. In contrast, a previously unobserved response covaried
with uncertainty and consisted of a gradual increase in activity until the
potential time of reward. The coding of uncertainty suggests a possible role for
dopamine signals in attention-based learning and risk-taking behavior.
"The brain continuously makes predictions
and compares outcomes (or inputs) with
those predictions. Predictions are fundamentally
concerned with the probability
that an event will occur within a specified
time period. It is only through a rich representation
of probabilities that an animal can
infer the structure of its environment and
form associations between correlated events."
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