Good points. To take it further, what they used to think was the unused part of the brain is used. It is used to made associations. The association parts of the brain are much larger in humans than in other mammals.djb wrote:Just a note on my understanding of brain capacity and the loss of function. As I understand, the thought that we use only x% of our brain is just an old wives tale. Any loss of brain tissue is a significant loss and there is no unused reserve of brain tissue to draw from to make repairs. Once brain tissue is damaged or destroyed it is gone forever and cannot be replaced or repaired.
Now that does not mean that the brain is not adaptable. People with brain damage can and do learn how to compensate for their loss. Brain pathways are realigned and skills can be relearned if lost, but tissue is not replaced.
I think the x% concept comes from capacity of utilization and not actual tissue utilization. Sort of like a engine that runs at half throttle is only using 50% of its capacity. That does not mean that you could simply remove or damage half the engine and still expect it to run at 50% capacity. And in reality, the engine might not even be able to run or survive running at full throttle in the real world. But after you start breaking chunks off that engine you know you've got problems. Just maybe with some work, you just might be able to salvage your broken engine from the scrap pile and get it running again but at a diminished capacity and probably never near that original 50% level.
Us older folk may have wisdom and experience on our side, but the young ones got the better tools; that is until life gets them too.
It used to be thought that once brain cells died we would never get more. Very recent research has found different evidence, however. We do actually get more brain cells but only a paltry amount, so we can never regain a complete loss. What we can do with use is to grow new fibers and new connections between the fibers (axons and dendrites). We can grow many, many of these. That's why getting aerobic exercise to feed the brain is important. It's also why learning new things (languages, doing crossword puzzles) can help our brains stay smarter as we age.
The brain is plastic (flexible) when we are young. There are cases where a young child has had to have half the brain (one hemisphere) removed and functions reasonably well, doing well in school. There are some deficits, but way fewere than you'd think. As we age, it is much less plastic. But still, I have a relative who had a stroke when she was 101 or 102 years old. She could not walk. She did regain her ability to walk in a limited manner using a walker. She was a very determined woman who had used her brain to good advantage all her life, learning new things, traveling, etc. She was a teacher.
I have another family member with severe hearing. This is associated not with damage to the ear but to white matter deterioration in her brain. She was recently diagonsed with OSA and is now being treated. Perhaps the cpap will slow the progress of her hearing loss which will be a real blessing.