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Neural responses during behavior vary substantially across brain regions. Whether this variability reflects region-specific latent dynamics encoding distinct cognitive variables, or a shared latent dynamics expressed through different population geometries, remains unclear.
We analyzed simultaneous recordings from hippocampus (HC), parietal (PC), and prefrontal (PFC) cortex in rats performing a memory-guided decision in a double T-maze [1]. At a T-junction, animals turned left or right based on their position at trial onset (choice), or as imposed by a movable wall (matched guided control). From spike trains, we inferred a dynamical model for a one-dimensional latent variable x(t). Using nonparametric maximum-likelihood inference with NeuralFlow [2], we recovered, for each region and condition: the potential Φ(x) and diffusion coefficient D governing the dynamics; the two onset distributions p₀(x), one per incoming direction; each neuron's tuning curve f(x), defining the population geometry.
The inferred potential was on average an inverted-U whose unstable midpoint drives x to one of the two latent space boundaries. This profile recurred across all three regions, indicating a shared computation rather than region-specific ones. By contrast, the p₀(x) distributions differed across regions. HC showed the strongest modulation by working-memory demand, with distinct onsets during choice, but not guided, trials. PFC was the only region in which onsets encoded incoming directions in both choice and guided trials, tracking task-relevant information even when not required to guide behavior. The embedding geometry was likewise region-specific. Single-neuron tuning was sparser and more peaked in HC (lower entropy, higher Gini), broader and more mixed in PFC, and intermediate in PC.
Together, these results indicate that regions engaged in a common decision process share latent dynamics while embedding it through distinct population geometries. This supports the hypothesis of a collective computation with region-specific representations, rather than distinct computations implemented independently in each region.
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