Chronic stress impairs the function of multiple brain regions and causes severe hedonic and motivational deficits. One brain region known to be susceptible to these effects is the PFC. Neurons in this region, specifically neuronal projections from the prelimbic region (PL) to the nucleus accumbens core (NAcC), have a significant role in promoting motivated approach. However, little is known about how activity in this pathway changes during associative learning to encode cues that promote approach. Less is known about how activity in this pathway may be altered by stress. In this study, an intersectional fiber photometry approach was used in male Sprague Dawley rats engaged in a Pavlovian autoshaping design to characterize the involvement of the PL-NAcC pathway in the typical acquisition of learned approach (directed at both the predictive cue and the goal), and its potential alteration by stress. Specifically, the hypothesis that neural activity in PL-NAcC would encode a Pavlovian approach cue and that prior exposure to chronic stress would disrupt both the nature of conditioned approach and the encoding of a cue that promotes approach was tested. Results of the study demonstrated that the rapid acquisition of conditioned approach was associated with cue-induced PL-NAcC activity. Prior stress both reduced cue-directed behavior and impaired the associated cortical activity. These findings demonstrate that prior stress diminishes the task-related activity of a brain pathway that regulates approach behavior. In addition, the results support the interpretation that stress disrupts reward processing by altering the incentive value of associated cues.

An environmental cue that predicts the availability of a pleasurable reward can become a powerful incentive unto itself. The process by which this occurs is important to characterize not just because it is essential for normal behavior, but also because it may be involved in impulse control disorders and addiction (Colaizzi et al., 2020;Tomie et al., 2016). One useful model for the study of acquired incentive is conditioned approach (i.e., Pavlovian autoshaping; Brown & Jenkins, 1968), which assesses an animal's tendency to approach an otherwise motivationally neutral cue that predicts a rewarding outcome (Flagel & Robinson, 2017).Incentive learning involves many structures implicated in general reward learning, including the medial prefrontal cortex (mPFC).Many experiments have demonstrated a role for the mPFC in behaviors that require the use of cues to pursue specific rewards (Balleine &