UC Berkeley

Every day, often without thinking about it, you create and achieve goals. These goals range in complexity from brushing your teeth in the morning, to avoiding traffic on your way to school, to figuring out how you're ever going to graduate from Berkeley. The intricate workings of your prefrontal cortex enable the planning and execution of such behaviors. For years, scientists have studied the mechanisms of simple choice behavior and learning in the form of stimulus- and action-outcome associations but the question of how increasingly complex and temporally-extended learning arises remains largely unknown. Informed by converging work from the fields of psychology and computer science, we set out to understand the computations performed at the level of single cells that may contribute to the ideation, mental maintenance, and stringing together of actions to perform a hierarchical gambling task. We recorded extracellular activity from two subjects as they performed an n¬-armed bandit task and compared and contrasted the information processed simultaneously in three distinct brain areas: the lateral prefrontal cortex, the orbitofrontal cortex, and the anterior cingulate cortex. While our data do not support the preferential processing of superordinate versus subordinate goals in prefrontal cortex, we did find many signals that may underlie hierarchical behavior. These include value and action encoding that depended on the hierarchical level, as well as encoding of past choices that could be used to chunk actions at the same level of the hierarchy. Understanding these mechanisms could help elucidate how the complex behavioral repertoire of the primate is implemented.