## Definition **Brain plasticity** (or neuroplasticity) is the capacity of the nervous system to modify its own structure, connectivity, and function in response to experience, learning, or injury. Synaptic connections between neurons strengthen when co-activated (Hebbian plasticity) and weaken when persistently inactive. At the systems level, entire cortical maps can reorganise — expanding representations for practiced skills and shrinking those for disused ones. ## Types of Plasticity Relevant to Learning **Synaptic plasticity** operates at the level of individual connections. Long-term potentiation (LTP) — the sustained increase in synaptic strength following repeated co-activation — is the cellular substrate of memory formation. Each successful retrieval of a memory re-triggers LTP and thereby strengthens the trace. **Structural plasticity** involves growth of dendritic spines, formation of new synapses, and (in certain regions such as the hippocampal dentate gyrus) neurogenesis — the birth of new neurons. Physical exercise increases hippocampal neurogenesis, which may partly explain its beneficial effects on memory. **Cortical remapping** occurs at the systems level: repeated skilled practice causes the cortical area devoted to the relevant effectors or representations to expand. String musicians show enlarged somatosensory representations for the fingering hand; Braille readers develop expanded tactile cortex for the reading finger. ## Plasticity Is Not Unlimited Three constraints are well-established: 1. **Sensitive periods.** Certain types of plasticity are far more available during early development (e.g., phonological categories, binocular vision, tonal language processing). Outside these windows the same learning requires far more effort. 2. **Architectural bias.** As described in [[Neuronal Recycling]], the brain does not reorganise arbitrarily — new skills colonise circuits whose evolutionary computation is compatible, not any available cortex. 3. **Consolidation requirement.** Plastic changes induced during waking practice are fragile until [[Consolidation and Sleep]] stabilises them. Sleep deprivation after learning significantly reduces long-term retention, demonstrating that plasticity requires an offline consolidation phase to become durable. ## Practical Upshot Because plasticity is experience-dependent and follows use-it-or-lose-it dynamics, deliberate, effortful practice — especially practice at the edge of current ability — is more effective than easy repetition. Errors are not obstacles to plasticity; they are its primary triggers (see [[Learning as Predictive-Error Minimisation]]). The brain updates its wiring most when predictions fail. ## Related - [[Neuronal Recycling]] - [[Learning as Predictive-Error Minimisation]] - [[Consolidation and Sleep]] - [[The Four Pillars of Learning]] - [[Active Engagement and the Testing Effect]] ## Sources - [[How We Learn (Dehaene 2020)]]