Effort-Based Reward (EBR) training enhances neurobiological efficiency in a problem-solving task: Insights for depression therapies

Authors

Massimo Bardi, Michael True, Catherine L. Franssen, Casey Kaufman, Amanda Rzucidlo, Kelly G. Lambert

Abstract

Effort-Based Reward (EBR) training strengthens associations between effort and rewards, leading to increased persistence in an unsolvable task when compared to control animals. EBR training involves placing animals in a test apparatus in which they are trained to dig in mounds to retrieve froot loop rewards (contingent group); these animals are compared to control animals that are given the same number of rewards, regardless of expended effort (noncontingent group). In the current study, the effect of EBR training on performance in a spatial task (Dry Land Maze) was explored to determine cognitive resilience during behavioral testing. Additionally, animals received BrdU injections during training to assess the role of neurogenesis on subsequent behavioral performance. Following the probe test, animals were perfused so that fos-immunoreactive (ir) cells in the hippocampus and cortical areas could be assessed. Behavioral results indicated that contingent rats were approximately 50% more efficient in locating and interacting with the previous baited well during the probe test than noncontingent animals, recruiting approximately 20% less c-fos ir-cells in the insular cortex, retrosplenial cortex, and dentate gyrus. A multidimensional scaling analysis grouped noncontingent animals together in a quadrant characterized by high latencies to find the previous baited well and higher ir-cell activation in the aforementioned areas. Thus, our data support the hypothesis that the EBR training enhances both cognitive functioning and emotional regulation during challenging events. Considering the ongoing controversy about the efficacy of pharmacological interventions in treating depression, the EBR model provides a valuable alternative for the investigation of the neurobiology of mood disorders.