If you practice biceps curls at the gym, you will get bigger muscles that are also stronger. So far, the same seemed true for the brain. Thanks to neuroplasticity, practice triggers neuronal and synaptic growth (i.e., brain volume growth), which correlates with better performance. In this fascinating Scientific American article we learn that as the brain masters a new skill, some brain areas do get bigger but eventually shrink back to normal! The performance gain acquired through practice stays present, in spite of the shrinkage.
Studying the auditory cortex of rats, they found that the expansion of a ‘skill-specific’ brain area with training is only short lived, even when changes in ability are long lasting.
So what does change? Although newly learned perceptual skills don’t show up in a bird’s eye view of the cortex, they must have some neurobiological basis. Kilgard suggests that learning probably results from a few parsimonious tweaks at a more microscopic level, involving relatively small numbers of neurons and synapses.
Kilgard speculates that the expanding cortical map is like a search committee. It’s generating a huge range of candidate solutions to a problem the brain has been tasked with, but doesn’t yet know how to solve. […] Once a good solution is found, the search committee is disbanded. Efficient changes that impart skill are retained, and the non-meaningful changes are winnowed away as the map shrinks.