Chapter 1. Brain Development: Middle Adulthood

Synopsis

S. Stavros Valenti, Hofstra University

The Brain in Middle Adulthood

Many people describe a more positive outlook on their lives between the ages of 30 and 65 — greater knowledge, improved relationships, more satisfying careers, or newfound leisure activities. Ironically, this increasing sense of fulfillment in middle adulthood appears in spite of senescence, the gradual decline in the optimum functioning of all bodily systems. The brain changes associated with senescence begin in emerging adulthood and continue throughout middle age and beyond.

Changes in Gyri and Sulci of the Cerebral Cortex

^{As the amount of brain tissue gradually diminishes during normal aging, there is a compensatory increase in the volume of cerebrospinal fluid that causes enlargement of the ventricles.}

Starting in the early 20s and continuing through the life span, there is a gradual loss of brain volume as the gyri (“hills”) of the cerebral cortex become narrower and the sulci (“valleys”) become wider. This loss of brain volume is offset by an increase in the size of the ventricles, which are the inner chambers of the brain filled with cerebrospinal fluid.

Thinning of Gray and White Matter

^{As a general rule, normal aging is associated with loss of gray matter, but the rate of loss varies considerably between different areas of the brain.}

One of the first signs of the aging brain is the thinning of the gray matter layer, where neurons are concentrated. This thinning is usually detectable in a person’s early 20s, but the process may start even earlier. In contrast, the white matter in the brain increases until about age 40 when it begins to decrease.

Play the animation to view brain changes of gray and white matter during the adult years.

Brain Changes and Behavior

Although there are clear signs of aging in the brain during middle adulthood, these changes do not seem to be associated with a drop in the quality of life at home or on the job. Some of the brain changes, such as the reduction in the number of synapses (gray matter), are part of an overall process of “fine-tuning” of the neural circuits. This fine-tuning leads to more efficient information processing.

There are many factors affecting a person’s thoughts, feelings, and behaviors. These factors include general health, knowledge and expertise, and motivation to perform. Researchers have much to learn about how health, experiential, and motivational factors interact with age-related brain changes in middle adulthood.

Play the animation to watch again some of the brain changes that occur during the middle adult years.

Microscopic Brain Changes

When observed under the microscope, the thinning of the gray matter is due mainly to a loss of neurons and a reduction in the number of synapses. The thinning of the white matter is due to a loss of axons and their myelin sheaths and a loss of glial (support) cells.

Play the animation to observe the thinning of gray matter and white matter during the adult years.

Assessment: Check Your Understanding

Assessment: Check Your Understanding

Assessment: Check Your Understanding

Assessment: Check Your Understanding

Assessment: Check Your Understanding