More grey matter is good. Right? Wrong. Loss of connections between the neurons is bad. Right? Wrong. Your brain is, quite literally, smarter than you think! Sometimes what may look like negative changes to you, turns out to be an adaptive way of optimising brain`s functioning so you can get most out of it!
Garden patch in your head
A baby is born with up to 100 billion neurons that make up the brain, or grey matter. When you stimulate baby`s brain with "pick-a-boos", out-of-tune lullabies and daily dose of Nick Junior, neurons branch out extensively, growing new dendrites (branches) and forming connections with other neurons. Neuroscientists, possibly because of limited imagination and suppressed attraction to gardening, call neuronal branches dendritic trees and a period of their maximal growth blooming. Here is what might a highly branched out neuron look like:
At a certain time, of course, your little one discovers that Nick Junior is not as much fun as the Babe Station. So the dendrites responsible for connections in the Nick Junior neural circuit are no longer of any use and they get simply eliminated, this is termed....get your gardening clogs on.... dendritic pruning!
Pruning of useless dendrites is one cause of the absolutely normal grey matter loss. On to the second.
When grey becomes white...
If Nick Junior only requires passive watching while munching on fish fingers, with the Babe Station you need to think fast and act appropriately. And before you think of anything rude, I only mean being able to turn it off as soon as mum walks into the room. So, the older we are, the faster our brains become, and all because clever mother-nature designed special insulation for neuronal axons called myelin to speed up signal transmission.
Myelination continues well into the third decade of life, and white matter is nothing more than myelinated nerve fibres. Increased volume of the white matter logically means decrease in the grey matter, again, perfectly normal. In fact, patients with certain conditions like attention-deficit hyperactivity disorder (ADHD) or fetal alcohol syndrome (FAS) display abnormally large volume of grey matter due to insufficient myelination.
Less is more
So, the good news is, not all grey matter loss is bad! Synaptic pruning and myelination have evolved to make your Babe Station experience as efficient as possible!
Thanks for reading!
References for the curious:
Sowell, E. R. (2007) Computational neuroanatomy presentation for UCLA Advanced Neuroimaging course (podcast)
Toga, A.W., Thompson, P.M. and Sowell, E.R. (2006) Mapping brain maturation, Trends in Neuroscience, 29 (3), 148-159
