JHIBRG:Abstract Feb 21 2008

Decision-Making under Risk in Macaque Monkeys

Many decisions have to be made despite uncertainty about the eventual outcome of the chosen action. The proper evaluation of risk depends on accurately weighing the evidence in favor of risk-seeking or risk-avoiding behavior. This process is of fundamental importance for decision-making in daily life. The behavioral attitude towards risk is highly variable and depends on the internal state and perceived external context of the decision-maker at the moment of choice. We studied the neural mechanism of these processes in macaque monkeys working in a gambling task that requires them to make decisions under conditions of variable risk. We studied the influence of context on decision-making by varying the gambling task, so that the monkey is exposed to the same gamble sets under two different contexts (i.e. the “framing task”).

During decision-making, we expect to find three different types of neuronal activity in the brain. First, before the decision is made, reward and risk expectations associated with each option should be represented. Second, decision-related activity should indicate the choice while the decision is made. Third, after the decision, outcome-related activity should exist so that the reward and risk expectations associated with the particular choice can be updated. In addition, when the context affects choice behavior, the influence of different contexts should be represented on the neural level.

Medial frontal cortex (MFC) is likely to be involved in regulating the influence of risk and context on decision-making. MFC is thought to receive a feedback signal evaluating a particular action and to use that information to select an action leading to a desired outcome. Therefore, we expect MFC neurons to carry signals related to the outcome of particular actions, including the reward, perceived risk, and context. To investigate the cortical representation of risk cost and different context, we recorded single cell activity in MFC while monkeys worked in a gambling task.