Frontiers in Systems Neuroscience (Apr 2015)
Task relevant variables are encoded in OFC neurons
Abstract
Prefrontal Cortex (PFC) in mammals is well known for playing a key role in executive function [1-3]. Orbitofrontal Cortex (OFC), as a part of the PFC, is thought to be mainly involved in reward processing, a fundamental function in goal-directed behavior. In particular it has been proposed that OFC is encoding the expected value of an outcome [4]. Previous studies in rats have shown that neurons in OFC have information about expected reward or punishment [5-7], and guide the relationship between stimulus and reward in a reversal associative learning task [8-9]. It has also been proposed to be involved in spatial representation as well as a proxy for confidence in perceptual decision making tasks [10-11]. In our experiment three rats performed an auditory categorization task while populations of neurons were recorded in OFC. The task was designed such that rats could use both sensory information and task history information in order to maximize reward income. We found that neurons in rats' OFC conveyed a wide variety of task related variables each one with a different time dynamics. Before stimulus onset OFC neurons showed significant amount of information regarding previous choice, previous reward and previous stimulus. After stimulus presentation neurons showed information about trial difficulty, as a proxy for trial's expected value, stimulus, and reaction time, a well known proxy for metacognitive processes as confidence. Information about decision was predominant at stimulus presentation and rat's response. Our results demonstrate that OFC in rats might not only be involved in reward processing but it also conveys a wide variety of task relevant variables. Our hypothesis is that OFC acts as a hub for complex decision-making tasks where all possible information is processed and conveyed to other brain regions responsible for decision execution.
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