Plasticity degeneracy underlies flexible formation and reconfiguration of spatial representations in hippocampal granule cells

The hippocampus, a brain region crucial for learning and memory, creates neural representations of space that must be both stable and adaptable. Researchers explored this challenge using hippocampal granule cells, which convert diffuse spatial information into distinct spatial patterns called place-fields. Instead of pinpointing a single plasticity mechanism for precise place-field formation, the team demonstrated that various combinations of plasticity can achieve this goal.

Through a population-based approach, they tested different levels of plasticity in granule cells, which receive inputs from both grid cells and contextual cues. Contrary to expectations, they found that sharp, localized synaptic strengthening alone is not sufficient to create stable spatial representations. Instead, a diverse set of plasticity pathways - involving excitatory synapses and intrinsic ion channels - could all lead to the same functional outcomes, such as the emergence, stabilization, remapping, and suppression of place-fields.

Notably, the researchers discovered that these diverse plasticity combinations were not random but rather converged on constrained functional states through targeted amplification and global suppression of spatial firing. This extensive plasticity degeneracy suggests that hippocampal spatial coding is not driven by unique plasticity rules but rather by a repertoire of alternative routes capable of performing the same computations.

The findings highlight the brain's remarkable flexibility in encoding spatial information and the complex interplay of multiple plasticity mechanisms in achieving this flexibility.