Successful Aging: A Neuroscientist Explores the Power and Potential of Our Lives

by Daniel J. Levitin

Most of us will face a range of mental challenges as we age, and they come from multiple sources. Due to plaque buildup and partially blocked arteries (arteriosclerosis), blood flow may not be as smooth as it used to be. A reduction in the ability to produce neurochemicals may cause neurons to fire less efficiently. Dopamine levels fall about 10 percent per decade, and serotonin- and brain-derived neurotrophic factor levels also fall off with increasing age. Years of alcohol consumption can lead to neuronal death and are implicated in brain shrinkage. A decrease in the efficiency of synaptic connections leads to a general slowing of mental processes. There is decay or failure to regenerate the insulating myelin sheath surrounding axons—causing reduced electrical conductivity. Finally, most adults experience a gradual reduction in brain volume after the age of thirty-five of about 5 percent per decade through age sixty, with the decline speeding up after age seventy. All of these factors lead to a general slowing of cognitive function.