Stanford Neurosciences Institute Seminar Series Presents
Decision-making under uncertainty: Probing the neural basis of mental models
Alla Karpova, Ph.D
Janelia Group Leader, HHMI
Host: Ben Barres
In order for animals to survive in complex, natural and ever-changing environments they must be able to make inferences about the world on the basis of sparse and often ambiguous data. One way to effectively navigate a complex environment is by attempting to construct an internal model of the environment’s governing rules. Such an internal model not only computes an estimate of the current environmental state based on available data, but discovers and incorporates general principles about the causal rules that operate in the environment. The overall interest of my lab is to understand how model-based inference is accomplished by neural circuits. Over the past few years we have focused on the role that the rodent medial prefrontal cortex (mPFC), an area homologous to primate anterior cingulate cortex (ACC), plays in encoding the causal model. We have designed behavioral tasks in which these rules change suddenly or evolve in a very complex manner—in some cases eliciting abrupt changes in the workings of the internal model and in others leading to the abandonment of attempts at model construction. Recordings of the activity of neuronal ensembles in mPFC revealed that moments of abrupt change in behavioral strategy are associated with sudden transitions in the pattern of neural activity across the mPFC, one interpretation of which is that such changes signify a reset of prior expectations. In addition, inactivation of mPFC by local muscimol administration revealed that the influence of mPFC on behavior is suppressed when attempts to build an internal model are unsuccessful. Finally, selective enhancement or suppression of Locus Coeruleus input into mPFC, respectively, abolished or restored model-based control of behavior and, with it, sensitivity to environmental feedback. Together, our findings point to a key and selective role for mPFC in generating, evaluating, and refining the internal model—a set of hypotheses about the rules of the environment —under conditions of uncertainty, and argue that noradrenergic action in mPFC controls the extent to which behavioral choices are guided by the internal model or made independently of prior experience and beliefs.