Neurotypica

Practice doesn't just strengthen connections between neurons---it attracts infrastructure. When you repeatedly use a neural pathway, the brain builds support systems around it: glial cells wrap the axons in myelin (fatty insulation), increasing conduction speed and temporal precision; metabolic support ramps up, nourishing and repairing the route; structural proteins consolidate the pathway's reliability. This is white matter support---the scaffolding that makes well-practised routes fast, efficient, and stable.

The more you use a pathway, the more infrastructure accumulates around it. Adolescents famously have less white matter than adults, which is what brain scientists mean when they say "teenage brains are undeveloped." The routes exist, but they haven't been fortified yet. This makes adolescent brains more plastic---easier to repurpose, quicker to update---but also less efficient and less stable. Adults, by contrast, have more myelinated pathways, which makes execution faster and more reliable but also more inertial. The infrastructure that speeds performance is the same infrastructure that resists change.

This architecture explains why the plasticity-stability trade-off isn't just about connection strength---it's about the physical scaffolding built around those connections. When you want to change a well-established behaviour, you're not just retraining synapses; you're working against or around the infrastructure that supports the old route. This is why pivoting entrenched patterns takes time: you need to either gradually reroute around the fortified pathway or wait for the old infrastructure to atrophy from disuse while new infrastructure builds around the alternative.

Practically, this means train the route you want to be fast by practising it in context repeatedly---that's what signals the brain to invest infrastructure. But also expect lag when trying to change deeply practised patterns; the infrastructure won't dismantle overnight. Gradual rerouting, spacing practice, and rest (especially sleep, which consolidates new routes) all help build new support without excessive interference from the old scaffolding.