The geometry of knowledge in the hippocampal-prefrontal system
Decision making is associated with frontal brain circuits and spatial navigation with the hippocampus. In addition, recent work in spatial decision making tasks found single neurons in both areas encoding space conjunctively with other task-relevant variables. However, circuit function is not determined by tuning alone, but also by representational geometry, i.e. the representation of…
Recent studies have highlighted the role of frontal brain circuits and the hippocampus in decision making and spatial navigation. Single neurons in both areas have been found to encode space in conjunction with other task-relevant variables. However, the functioning of these circuits is influenced not only by tuning but also by the representational geometry, which refers to the representation of task-relevant variables in neural state space.
To investigate this further, researchers utilized Neuropixel recordings in a complex spatial decision making task, coupled with nonlinear dimensionality reduction. Their findings revealed an intrinsically low-dimensional neural manifold in the medial prefrontal cortex (mPFC), where key task variables were represented as smooth gradients.
This geometric pattern in the mPFC mirrored that of the hippocampal-prefrontal cortex (HPC) map. Remarkably, the mPFC and HPC manifolds from a single mouse were able to predict behavior across other mice and brain areas. Additionally, the researchers discovered a non-linear representational map between the mPFC and HPC manifolds, demonstrating temporal alignment.
The researchers conclude that the representational geometry in the HPC and mPFC is distributed and time-aligned using low-dimensional neural codes.
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