Aging and Mental Function
Research suggests that the effects of age on brain function vary widely. Almost everyone gets a little forgetful in old age, forgetting names or telephone numbers and responding more slowly to conflicting information. Do not worry, this perfectly normal. However, another group of elderly individuals develops senile dementia, an impairment in mental function that interferes with daily live. There is a small third group where the mental function seems unaffected by age. For example, the (official) oldest human, Jeanne Calment, kept her wits during her 122-year lifespan.
Neuroscientists are increasingly able to distinguish between the processes of normal aging and disease. Although some changes occur in normal aging, they are not as severe as once thought.
The aging brain
Near age 20, the brain reaches its maximum weight. Subsequently it loses about 10 percent of this weight over a lifetime. Some neurons might be lost, but widespread neuron loss is not a normal process of aging. Furthermore, brain tissue can respond to damage by expanding dendrites and tuning interneuron connections.
The cause of brain aging is still not known. There are two major groups of theories:
- Aging genes: some genes, that cause changes in the brain, are switched on during old age.
- Free radicals: cell byproducts of the destruction of fats and proteins cause damage.
Scientific studies have shown that some mental functions decline, while others seem to improve. For example, the speed of carrying out cognitive tasks became slower, while vocabulary increased. It seems that intelligence relying on stored or learned information declined less severely than that which uses the ability to deal with new information.
The environment also has an effect. A challenging and stimulating environment stimulates the dendrite development in the frontal cortex, although with a slower and smaller response than in young animals . Aerobic exercises have been shown to improve blood circulation in the brain and to stimulate synapse formation. Motor learning seems to generate new synapses. So, aerobic exercise can improve human cognitive performance.
In recent years, with new knowledge and technologies, much has been learned about the aging af the brain. However, many questions still remain to be unanswered. For example, does protein production decline in all neurons with age? Does aging alter the gene expression in the brain, and if so, how? Are there gender differences in the aging of the brain, maybe as a consequence of the hormonal differences between men and women?
It is speculated that certain genes are involved in these processes. By researching these genes and the proteins they encode for, scientists hope to become able to influence the survival and function of these genes, leading to the possibility of maintaining full mental capacities when aging.
Brain Facts: A Primer on the Brain and the Nervous System. Society for Neuroscience.