The Aging Brain

The brain weighs around 350 g at birth and increases to around 1,375 g by the age of 20. The largest increase in brain weight takes place in the first three years of life during which time it quadruples in size. Brain weight starts to decline between the ages of 45 - 50 and decreases by around 11 per cent from its maximal weight in young adulthood.

In the older brain tissue loss is most obvious on the surface and is seen as shrinkage of the natural convolutions in brain tissue. Changes are most prominent in the forebrain and less so in the cerebellum - the area at the back of the brain mainly responsible for balance and dexterity of movement.

In the young brain the ratio of gray to white matter is 1:28 and this declines to around 1:13 in the brains of people in their sixties. Curiously, there is evidence to suggest a reversal in trend as the brain ages further with gray to white matter back to 1:55 by the age of 90.