How Experience Influences Hippocampal Place Cells to Form Adaptive Cognitive Maps

The mammalian brain constructs mental representations of the environment, known as cognitive maps, which are essential for navigation. Central to this process are hippocampal place cells (PCs), particularly in the CA1 region, which activate when an animal is in specific locations within its surroundings. These cells help encode spatial and goal-related information, contributing to the development of these cognitive maps.

Recent research has turned to understanding how experience influences the formation and adaptation of these maps. A study conducted by scientists at Baylor College of Medicine and published in Nature Neuroscience has provided new insights. They discovered that experience leads to synaptic adjustments in the mouse brain, affecting the activity of hippocampal PCs and enabling the construction of flexible, goal-oriented spatial representations.

In this study, researchers recorded the activity of CA1 hippocampal neurons in 22 adult mice engaged in spatial learning tasks on a treadmill. Utilizing both two-photon imaging and in vivo intracellular recordings, they observed that in familiar environments, PCs tended to be referenced either to specific locations or to reward goals in roughly equal measure. However, upon exposure to new environments, these representations shifted, with the PCs predominantly referencing goal locations. This suggests that as animals encounter novel spaces, their hippocampal maps adapt, favoring goal-related information to optimize navigation.

Further analysis revealed that individual CA1 neurons received both spatial and goal-related synaptic inputs simultaneously. The ratio of these inputs correlated with how PCs referenced space or goals. Behavioral timescale synaptic plasticity—the dynamic strengthening or weakening of synapses—appeared to underpin these changes, indicating that experience-dependent synaptic adjustments facilitate the flexible encoding of space and goals.

Overall, these findings highlight that the ability of hippocampal place cells to support adaptive cognitive maps is, at least partly, driven by the reorganizational capacity of synaptic inputs based on experience. This understanding could pave the way for further research into how neural plasticity shapes spatial learning and memory, with potential implications for conditions affecting cognition and navigation.