Optogenetic activation of the ventral tegmental area-hippocampal pathway facilitates rapid adaptation to changes in spatial goals.

Animal adaptation to environmental goals to pursue rewards is modulated by dopamine. However, the role of dopamine in the hippocampus, involved in spatial navigation, remains unclear. Here, we studied dopaminergic inputs from the ventral tegmental area (VTA) to the hippocampus, focusing on spatial goal persistence and adaptation. Mice with VTA dopaminergic lesions struggled to locate and update learned reward locations in a circular maze with dynamic reward locations, emphasizing the importance of VTA dopaminergic neurons in the persistence and adaptation of spatial memory. Further, these deficits were accompanied by motor impairments or motivational loss even when dopamine receptors in the dorsal hippocampus were selectively blocked. Stimulation of VTA dopaminergic axons within the dorsal hippocampus enhanced the mice's ability to adapt to changing reward locations. These findings provide insights into the contribution of dopaminergic inputs within the hippocampus to spatial goal adaptation.

Utilizing a Reconfigurable Maze System to Enhance the Reproducibility of Spatial Navigation Tests in Rodents.

Several maze shapes are used to test spatial navigation performance and behavioral phenotypes. Traditionally, each experiment requires a unique maze shape, thus requiring several separate mazes in different configurations. The maze geometry cannot be reconfigured in a single environment to accommodate scalability and reproducibility. The reconfigurable maze is a unique approach to address the limitations, allowing quick and flexible configurations of maze pathways in a repeatable manner. It consists of interlocking pathways and includes feeders, treadmills, movable walls, and shut-off sensors. The current protocol describes how the reconfigurable maze can replicate existing mazes, including the T-shaped, plus-shaped, W-shaped, and figure-eight mazes. Initially, the T-shaped maze was constructed inside a single experimental room, followed by modifications. The rapid and scalable protocol outlined herein demonstrates the flexibility of the reconfigurable maze, achieved through the addition of components and behavioral training phases in a stepwise manner. The reconfigurable maze systematically and precisely assesses the performance of multiple aspects of spatial navigation behavior.

The Reconfigurable Maze Provides Flexible, Scalable, Reproducible, and Repeatable Tests.

Multiple mazes are routinely used to test the performance of animals because each has disadvantages inherent to its shape. However, the maze shape cannot be flexibly and rapidly reproduced in a repeatable and scalable way in a single environment. Here, to overcome the lack of flexibility, scalability, reproducibility, and repeatability, we develop a reconfigurable maze system that consists of interlocking runways and an array of accompanying parts. It allows experimenters to rapidly and flexibly configure a variety of maze structures along the grid pattern in a repeatable and scalable manner. Spatial navigational behavior and hippocampal place coding were not impaired by the interlocking mechanism. As a proof-of-principle demonstration, we demonstrate that the maze morphing induces location remapping of the spatial receptive field. The reconfigurable maze thus provides flexibility, scalability, repeatability, and reproducibility, therefore facilitating consistent investigation into the neuronal substrates for learning and memory and allowing screening for behavioral phenotypes.