Neural circuit dynamics underlying learning and memory reorganization in freely moving primates

Dr. Kari Hoffman is an associate professor of Psychology at Vanderbilt University.

Memories shape how we interpret the world, adapting behavior to familiar situations and improving how we respond to new challenges. But how does our neural circuitry draw on a lifetime of experience to enable such flexibility? I will describe tasks learned by freely moving macaques that probe two forms of flexible cognition shared with humans. These tasks contrast 1. arbitrary associations between objects encountered in spatiotemporal sequences with 2. structured associations (here: object categories) inferred from their environmental context. Using wireless, high-density recordings from the hippocampus, medial prefrontal cortex, and retrosplenial cortex during learning and sleep, we observed coordinated long-range interactions and local CA1 microcircuit organization that may support the effective formation and deployment of memories in these tasks. We detected cell assemblies (patterns of synchronously firing single unit ensembles) that reflected newly and remotely learned task sequences. Both New and Old classes of assemblies reactivated during sleep, but they differed in their network structure, stability, and reactivation properties. Furthermore, assembly coupling evolved rapidly after learning, forming higher-order “metassemblies” whose organization depended on memory age, providing neural scaffolds that link experiences while preserving their distinct elements. These emerging views of neural circuit organization offer a rare glimpse into how the primate brain integrates and reorganizes experiences accumulated across a lifetime.

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Hosted by Dr. Alison Preston

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