| Abstract | Mammals in general experience bouts of negative emotion when they unexpectedly experience a reduction in expected reward, known as unexpected reward downshifts (URDs). The specific biological and psychological mechanisms which have evolved to respond to downshifted rewards with behaviors related to anxiety, conflict, and even pain, are known collectively as frustration. The present set of experiments examined three neural pathways in and their role in the frustration response to URDs. Using a double-infection chemogenetic manipulation procedure, neurons originating in the nucelus accumbens (NAc) and synapsing onto the globus pallidus externus (GPe), globus pallidus internus (GPe), or ventral pallidum (VP), were activated during key moments in a reward loss paradigm. Animals were trained with 32% sucrose and downshifted to 2% sucrose. It was found that exciting the pathway between the NAc and GPe had no effect on their response to being downshifted, whereas activating either the pathway between the NAc to GPi or the pathway from the NAc to VP caused a significant increase in consummatory suppression and exacerbation of the frustration response. All these effects were in the absence of any gross motor effects shown in an open field. Overall, these findings provide new insights into how animals process the emotional value of rewards when their expectations are violated. |
