Podcast with Francesca Cacucci on hippocampus development and grid cells

Why do grid cells, the brain's metric system for space, appear last in development, days after place cells and head direction cells are already active? Neuroscientist Francesca Cacucci explains what the developmental sequence of spatial circuits in the rat hippocampus reveals about how the navigation system bootstraps itself, and why the sudden emergence of grid cells around postnatal day 20 may mark a genuine cognitive transition. Subscribe for more from the Convergent Science Network podcast series. Francesca Cacucci joins Paul Verschure and Tony Prescott at the BCBT summer school to discuss her research on the development of spatial representations in the rat hippocampus and entorhinal cortex. Her laboratory has documented a clear developmental timeline: head direction cells appear first, as early as postnatal day 12–13, providing a compass signal before the eyes even open. Place-like responses emerge gradually from around postnatal day 16, initially broad and concentrated near environmental boundaries. Grid cells then appear abruptly around postnatal day 20 , coinciding with the onset of organized exploratory behavior and the age at which rats first succeed on hippocampal-dependent spatial tasks. The discussion challenges the original assumption that grid cells are the primary input driving place cell formation. Since place-like responses precede grid cells developmentally, Cacucci proposes that early place responses are broad associative responses combining head direction signals with boundary features, and that grid cells provide the metric sharpening needed to refine these into precise spatial representations. This is supported by evidence that when grid cells are pharmacologically disrupted in adults, new place fields in novel environments revert to boundary-anchored, broad responses , exactly what is seen in pre-grid-cell pups. The conversation explores parallels with human cognitive development, including the relationship to Piaget's stage theory and the surprising evidence that allocentric spatial processing may be the default mode across cultures rather than egocentric processing. Cacucci argues that development is not merely gradual refinement but includes sudden transitions , and understanding what triggers these transitions at the neural level is one of the field's most important open questions. She advocates for moving spatial neuroscience out of featureless laboratory boxes and into more naturalistic environments. Key topics include the developmental sequence of spatial cell types, the relationship between grid cells and exploratory behavior, attractor network models versus oscillatory models, why head direction cells precede all other spatial signals, and what comparative and cross-cultural evidence tells us about the evolution of spatial cognition. Part of the Convergent Science Network podcast series from the BCBT Summer School.