When does the brain begin to decline?

Brain decline - begins to show signs of decline after a certain proportion of the nerve cell or neurons of which it is formed to destroy. The age at which this happens varies. A grown man has no more nerve cells than he did when he was born. These cell do not multiply as the body grows, as bone and skin cells do. Indeed, as a person grows older he has fewer and fewer nerve cells, because those destroyed are not replaced. At the age of 70 or 80, as many as a quarter of the nerve cells may have destroyed. That is the reason some old people cannot hear well or have poor memories. Yet others manage to retain their faculties and abilities until they are very old. Recent techniques have made it easier for scientists to study how our brains function, but there is still a great deal to discover.