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Dynamical systems analysis reveals a novel hypothalamic encoding of state in nodes controlling social behavior ![](https://www.world-wide.org/tweet_button.png)
Aditya Nair, Tomomi Karigo, Bin Yang, Ann Kennedy, David Anderson
Date / Location: null / null
All animals possess a repertoire of survival behaviors, such as aggression and reproduction, that are under strong evolutionary constraints. In vertebrates, the hypothalamus plays a key role in regulating these behaviors. The prevailing view of this neural system posits that hypothalamic nuclei are organized as ‘labeled lines’ – populations of behavior-specific neurons with characteristic transcriptional and connectomic profiles. This model seems to fit regions such as the medial preoptic area (MPOA, whose activation causes reproductive behaviors), which contains multiple behavior-specific neuronal populations with distinct transcriptional profiles. However other structures, such as the ventromedial hypothalamus (VMHvl, whose activation causes scalable aggression), have rich dynamics but only weak tuning for experimenter-identified behaviors like attack and mating.
We adopt an unsupervised dynamical systems framework to characterize neural activity of ESR1 neurons in the MPOA and VMHvl of interacting mice in a user-unbiased manner. Strikingly, we find activity in the VMHvl is organized by state rather than behavior: the low-dimensional dynamics of our fit model reveal one dimension with slow-ramping dynamics and persistent activity that correlates with escalating aggressive or reproductive behavior. Intriguingly, the time constant of this dimension is a strong predictor of time animals spend fighting. These ramping representations suggest a generic function for the VMHvl to encode intensity of motivational states and are compatible with results of functional perturbation experiments. Importantly, ramping dynamics are not an arbitrary result of our fitting process, as models fit to MPOA activity revealed states that precisely correlate with the animals’ behavior. The low-dimensional dynamics of the MPOA contained behaviorally tuned factors that display rotational dynamics during mating episodes, suggesting an encoding of actions rather than state. Thus, our analysis of dynamics reveals two distinct organizations of computation in the hypothalamus, one based on action encoding populations in MPOA and another population encoding motivational state in VMHvl.
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