Podcast with Stephen Noctor on cortical development and precursor cells

How does the brain build itself from a handful of precursor cells into billions of neurons organized in precise layers? Developmental neurobiologist Stephen Noctor explains the remarkable choreography of cell division, migration, and differentiation in the ventricular zone , where future neurons bounce up and down like yo-yos before embarking on journeys equivalent to climbing four Empire State Buildings. Subscribe for more from the Convergent Science Network podcast series. Stephen Noctor joins Paul Verschure and Tony Prescott at the BCBT summer school to describe his research on the precursor cells that generate the cerebral cortex. Using fluorescent labeling and time-lapse imaging in rat brain slices, Noctor has captured the movements of individual precursor cells as they undergo interkinetic nuclear migration , rapidly descending to the ventricular surface to divide, then slowly rising back through the ventricular zone in a process that may be largely passive. His movies reveal surprising behaviors: cells that pause, reverse direction, and emit transient processes that may serve as feedback conduits during migration. The discussion traces cortical construction from its earliest stages. Excitatory neurons are generated in the ventricular and subventricular zones and migrate radially outward, while inhibitory interneurons originate in the ganglionic eminences and travel tangentially. Noctor estimates fewer than ten distinct precursor cell types, which become progressively restricted in their output as development proceeds. He describes the inside-out lamination of the cortex, where later-born neurons migrate past earlier-born ones to settle just beneath the marginal zone , a process dependent on the signaling molecule reelin, without which the cortex inverts. Key topics include the orientation of cell division planes and what they reveal about fate determination, the role of radial glial fibers as scaffolds for migration, why the human brain generates roughly five billion cortical neurons over the course of pregnancy, the forgotten discoveries of Frederick Sauer from 1935, and how understanding normal development establishes a foundation for investigating neurodevelopmental disorders. Part of the Convergent Science Network podcast series from the BCBT Summer School.