Overview

We used to think the brain was like a computer: hardwired. Once you were an adult, you couldn’t grow new neurons, and if you had a stroke, that part was dead forever. We were wrong. The brain is like plastic (hence “plasticity”). It can mold, reshape, and rewire itself based on experience.

Core Idea

The core idea is “Neurons that fire together, wire together.” (Hebb’s Law). If you practice piano, the part of your brain controlling your fingers gets bigger and stronger. If you stop, it shrinks. The brain is a “use it or lose it” organ.

Formal Definition

The ability of the neural networks in the brain to change through growth and reorganization. These changes range from individual neuron pathways making new connections, to systematic adjustments like cortical remapping.

Intuition

Think of a forest.

  • Pathways: If you walk the same path every day, the grass gets trampled and it becomes a highway (strong habit).
  • Neglect: If you stop walking a path, the weeds grow back and it disappears (forgetting).
  • Rewiring: If a tree falls (stroke) blocking the path, you can trample a new path around it.

Examples

  • London Taxi Drivers: They have to memorize 25,000 streets (“The Knowledge”). MRI scans show their Hippocampus (memory center) is physically larger than average people. The learning changed their anatomy.
  • Stroke Recovery: A patient loses the ability to move their left arm. By forcing them to use it (Constraint-Induced Movement Therapy), the brain recruits healthy areas to take over the job of the dead areas.
  • Phantom Limb Pain: When an arm is amputated, the brain map for the arm is still there. Sometimes the face map (which is next door in the brain) invades the arm map. So when you touch your face, you feel it in your missing hand.

Common Misconceptions

  • It’s always good: Plasticity can be bad. PTSD is “negative plasticity”—the brain learns to be afraid too well. Addiction is the brain rewiring itself to crave drugs.
  • You can learn anything instantly: It takes massive repetition. The brain is plastic, but it’s stiff plastic.
  • Synaptic Pruning: In babies, the brain has too many connections. As they grow, it cuts away the useless ones to become efficient.
  • Neurogenesis: The growth of new neurons. We now know this happens in the adult hippocampus (boosted by exercise).

Applications

  • Education: Growth Mindset (Carol Dweck). Teaching kids that their intelligence isn’t fixed, but can grow with effort, actually helps them learn because it aligns with how the brain works.
  • Rehab: Brain-Computer Interfaces that help paralyzed people retrain their brains to move robotic arms.

Criticism / Limitations

  • Limits: You can’t regrow a whole brain. Plasticity has limits, especially as we age.

Further Reading

  • Doidge, Norman. The Brain That Changes Itself. 2007.
  • Merzenich, Michael. Soft-Wired. 2013.