Podcast with Greg Recanzone on cortical plasticity and somatosensory cortex

If the adult brain cannot change, how did you learn anything after childhood? Neuroscientist Greg Recanzone revisits the revolution in adult cortical plasticity , from the landmark digit amputation experiments to his own work showing that perceptual training reshapes somatosensory maps through mechanisms fundamentally different from developmental critical periods. Subscribe for more from the Convergent Science Network podcast series. Greg Recanzone joins Paul Verschure and Tony Prescott at the BCBT summer school to tell the story of how adult cortical plasticity went from heresy to established fact. Beginning with Mike Merzenich and Jon Kaas's digit amputation studies in monkeys, Recanzone describes how the somatosensory map in area 3b completely reorganized to look like a normal four-fingered monkey , not just filling in a gap, but rebuilding topographic order. This was the key insight: receptive fields are dynamic, continuously adjusting synaptic weights relative to neighboring neurons. The consensus that emerged distinguishes developmental plasticity, which involves anatomical rewiring, from adult plasticity, which operates through synaptic weight changes and modulation of inhibition. The discussion then turns to Recanzone's own experiments training monkeys on a vibrotactile frequency discrimination task. The trained skin showed expanded cortical representation, enlarged receptive fields, and, most importantly, dramatically tighter temporal fidelity across the neuronal population. Individual neurons responded no better than untrained controls, but the trained population locked their responses to each stimulus cycle with far less variability, producing a louder and cleaner signal. This enhancement depended critically on task engagement and reward: passive stimulation with identical physical input produced no comparable changes, confirming that neuromodulatory signals gated by attention and reinforcement are essential for adult plasticity. Key topics include why Merzenich and Kaas faced years of resistance to their plasticity findings, how the reorganization following digit amputation differs from visual and auditory cortex lesion effects, why receptive field enlargement during training reflects Hebbian co-activation rather than task demands, what the role of neuromodulators like acetylcholine and dopamine is in gating cortical map changes, how Mike Kilgard's basal forebrain stimulation experiments confirmed that neuromodulation alone can drive map reorganization, and what the practical limits of adult cortical plasticity are for rehabilitation and skill learning. Part of the Convergent Science Network podcast series from the BCBT Summer School.