Rat nucleus accumbens neurons predominantly respond to the outcome-related properties of conditioned stimuli rather than their behavioral-switching properties.

It has been proposed that nucleus accumbens neurons respond to outcome (reward and punishment) and outcome-predictive information. Alternatively, it has been suggested that these neurons respond to salient stimuli, regardless of their outcome-predictive properties, to facilitate a switch in ongoing behavior. We recorded the activity of 82 single-nucleus accumbens neurons in thirsty rats responding within a modified go/no-go task. The task design allowed us to analyze whether neurons responded to conditioned stimuli that predicted rewarding (saccharin) or aversive (quinine) outcomes, and whether the neural responses correlated with behavioral switching. Approximately one third (28/82) of nucleus accumbens neurons exhibited 35 responses to conditioned stimuli. Over 2/3 of these responses encoded the nature of the upcoming rewarding (19/35) or aversive (5/35) outcome. No response was selective solely for the switching of the rat's behavior, although the activity of approximately one third of responses (11/35) predicted the upcoming outcome and was correlated with the presence or absence of a subsequent behavioral switch. Our data suggest a primary functional role for the nucleus accumbens in encoding outcome-predicting information and a more limited role in behavioral switching.