RT Journal Article
SR Electronic
T1 The Known Unknowns: Neural Representation of Second-Order Uncertainty, and Ambiguity
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 4811
OP 4820
DO 10.1523/JNEUROSCI.1452-10.2011
VO 31
IS 13
A1 Dominik R. Bach
A1 Oliver Hulme
A1 William D. Penny
A1 Raymond J. Dolan
YR 2011
UL http://www.jneurosci.org/content/31/13/4811.abstract
AB Predictions provided by action-outcome probabilities entail a degree of (first-order) uncertainty. However, these probabilities themselves can be imprecise and embody second-order uncertainty. Tracking second-order uncertainty is important for optimal decision making and reinforcement learning. Previous functional magnetic resonance imaging investigations of second-order uncertainty in humans have drawn on an economic concept of ambiguity, where action-outcome associations in a gamble are either known (unambiguous) or completely unknown (ambiguous). Here, we relaxed the constraints associated with a purely categorical concept of ambiguity and varied the second-order uncertainty of gambles continuously, quantified as entropy over second-order probabilities. We show that second-order uncertainty influences decisions in a pessimistic way by biasing second-order probabilities, and that second-order uncertainty is negatively correlated with posterior cingulate cortex activity. The category of ambiguous (compared with nonambiguous) gambles also biased choice in a similar direction, but was associated with distinct activation of a posterior parietal cortical area; an activation that we show reflects a different computational mechanism. Our findings indicate that behavioral and neural responses to second-order uncertainty are distinct from those associated with ambiguity and may call for a reappraisal of previous data.