You are your brain maps: What I mean here is that although we have a common genetic code that instructs our brains to develop into ‘adult human brain’, we know that there is tremendous individuality. Because experience (in utero and in the world) influences brain connectivity, it is probably true that no two brains are alike. Our experiences sculpt neural circuits in a ‘use it or lose it’ fashion so our brains are uniquely modified based on our experiences. Remember that we talked about “injury-induced plasticity” (read the post After brain injury, neuroplasticity is like a bowl of popcorn).Well the concept that experience and learning modifies synapses and maps is called “experience-induced plasticity” and is very important for every brain on earth including the brain challenged by trauma, MS, Parkinson’s, stroke or any other injury.

Experience-induced plasticity happens at all ages. Even a very old person has a malleable brain (an old dog CAN learn new tricks!). Learning is a good example of experience-induced plasticity. When we learn something (like skateboarding in the post What is Neuroplasticity?), synapses are either strengthened or pruned, dendrites branch out to make new connections and blood vessels and support cells grow to support the change. So everyone has a slightly different brain map that reflects their own learning and life experience.

We know that rodents housed in enriched environments with plenty of opportunity for social interaction and physical activity have more synapses per neuron and more complex dendritic branching in neurons (remember that dendrites are the branches of the neuron that reach out to other neurons; see work by Greenough, Kleim and others). With the development of exquisite brain mapping techniques, we are now able to examine changes in groups of neurons (maps) in humans. Work published by Elbert in Science in 1995 showed that the cortical map serving the playing hand of string players expanded beyond normal boundaries and the this expansion depended on how early in life the person began playing and how much they practiced. Proficient Braille proof readers had enlargement of the brain map representing the reading finger. The map enlargement was larger on workdays suggesting that the brain made plastic changes fairly quickly on an ‘as needed’ basis (see work by Pascual-Leone). These research findings emphasize to me the flexibility of the brain and what a beautiful organ it really is! Can we harness the brain’s experience-induced plasticity to help the brain re-wire after injury?