Chapter 8: Aging

In this Chapter…

• Aging in different ways
• What we know and don’t know about aging

Aging in Different Ways

• Severe declines in memory, intelligence, verbal fluency, etc. are not a part of normal aging
• Effects of age on brain function are very subtle and selective
  • Once most people reach their 70s, they may find themselves forgetting names, phone numbers, etc.
  • The response to conflicting information slows down as well
• Dementia: a progressive and severe impairment in mental function that interferes with activities of daily living
  • Types of dementia:
  • Alzheimer’s disease- the most common
  • Cerebrovascular disease
  • Pick’s disease
  • Lewy body disease

What we know and don’t know about aging

• The brain reaches its maximum weight near the age of 20
• Subtle changes in the chemistry and structure of the brain begin in midlife for most people
• The brain is at risk of losing some neurons but not widespread neuron loss
  • This distinguishes normal aging from neurodegenerative disease
• After the damage or loss of neurons, the remaining healthy ones are able to expand dendrites and fine-tune connections with other neurons
  • If the cell body is intact, the damaged neuron can induce changes in its axon and dendrites to regrow them
• The brain cannot generate new neurons
  • Not many stem cells exist in the brain
  • The stem cell number in the brain actually decreases as a person ages

Changes in Intellectual Capacity

• As people age, the speed of carrying out tasks is slower but their vocabulary improves
  • There is an increase in the type of intelligence relying on learned or stored information but a decrease in the type that depends on the ability to deal with new information
• The brain is only as resilient as its circuitry
  • When the circuitry breaks down, neurons adapt by expanding their roles
  • Larger portions of the brain are “recruited” so older people can reach performance levels similar to younger adults
• Motor learning generates new synapses
  • This is how aerobic exercise improves cognitive performance
• Many theories for normal brain aging:
  • Specific “aging genes” turned on
  • Accumulation of mutations/other types of DNA damage
  • Hormonal influences
  • The immune system has gone awry
  • Accumulation of oxidative damage caused by free radicals
  • Free radicals: cell byproducts that destroy fats and proteins vital to cellular functions
• Physical and mental exercise are both effective means of slowing the effects of brain aging