The Aging Brain

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The Aging Brain

Up to the teen years, we process information with greater and greater speed (Fry & Hale, 1996; Kail, 1991). But compared with teens and young adults, older people take a bit more time to react, to solve perceptual puzzles, even to remember names (Bashore et al., 1997; Verhaeghen & Salthouse, 1997). The neural processing lag is greatest on complex tasks (Cerella, 1985; Poon, 1987). At video games, most 70-year-olds are no match for a 20-year-old.

Slower neural processing combined with diminished sensory abilities can increase accident risks. As Figure 3 indicates, fatal accident rates per mile driven increase sharply after age 75. By age 85, they exceed the 16-year-old level. Older drivers appear to focus well on the road ahead, but attend less to vehicles approaching from the side (Pollatsek et al., 2012). Nevertheless, because older people drive less, they account for fewer than 10 percent of crashes (Coughlin et al., 2004).

The point to remember The aging brain is plastic, and partly compensates for what it loses by recruiting and reorganizing neural networks.

Brain regions important to memory begin to atrophy during aging (Fraser et al., 2015; Schacter, 1996). The blood-brain barrier also breaks down beginning in the hippocampus, which furthers cognitive decline (Montagne et al., 2015). No wonder adults, after taking a memory test, feel older. “[It’s like] aging 5 years in 5 minutes,” jested one research report (Hughes et al., 2013). In early adulthood, a small, gradual net loss of brain cells begins, contributing by age 80 to a brain-weight reduction of 5 percent or so. Earlier, we noted that late-maturing frontal lobes help account for teen impulsivity. Late in life, some of that impulsiveness seems to return as inhibition- controlling frontal lobes begin to atrophy (von Hippel, 2007). This helps explain older people’s occasional blunt questions and comments (“Have you put on weight?”). But good news: The aging brain is plastic, and partly compensates for what it loses by recruiting and reorganizing neural networks (Park & McDonough, 2013). During memory tasks, for example, the left frontal lobes are especially active in young adult brains, while older adult brains use both left and right frontal lobes.

Figure 3

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Age and Driver Fatalities

Chart showing the rate of fatal accidents per 10,000 drivers and per 100 million miles. Fatal accidents per 10,000 drivers start at about 6 at age 16 to 19, level off at about 2 from roughly age 30 to 60, and increase to almost 4 from age 75 on. Fatal accidents per 100 million miles start at about 9 at age 16 to 19, drop to about 2 from roughly age 30 to 60, and rise to about 5 for age 70 to 74 and then spike to almost 12 from age 75 on.

Slowing reactions contribute to increased accident risks among those 75 and older, and their greater fragility increases their risk of death when accidents happen (NHTSA, 2000). Would you favor driver exams based on performance, not age, to screen out those whose

slow reactions or sensory impairments indicate accident risk?

Exercise and Aging

Exercise helps counteract some effects of aging. Physical exercise not only enhances muscles, bones, and energy and helps to prevent obesity and heart disease, it also stimulates brain cell development and neural connections, thanks perhaps to increased oxygen and nutrient flow (Erickson et al., 2013; Fleischman et al., 2015; Pereira et al., 2007). Exercise aids memory by stimulating the development of neural connections and by promoting neurogenesis, the birth of new hippocampus nerve cells. And it increases the cellular mitochondria that help power both muscles and brain cells (Steiner et al., 2011).

Sedentary older adults randomly assigned to aerobic exercise programs exhibit enhanced memory, sharpened judgment, and reduced risk of significant cognitive decline (DeFina et al., 2013; Liang et al., 2010; Nagamatsu et al., 2013). Exercise also helps maintain the telomeres (Leslie, 2011). These tips of chromosomes wear down with age, much as the end of a shoelace frays. Telomere wear and tear is accelerated by smoking, obesity, and stress. Children who suffer frequent abuse or bullying exhibit

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shortened telomeres as biological scars (Shalev et al., 2013). As telomeres shorten, aging cells may die without being replaced by perfect genetic replicas (Epel, 2009).

The message is clear: We are more likely to rust from disuse than to wear out from overuse. Fit bodies support fit minds.

Multiple-Choice Question

The aging brain partly compensates for a loss of brain cells by recruiting and reorganizing existing neural networks. Which of the following BEST illustrates this ability?

neurogenesis plasticity atrophy telomere shortening

Correct. Plasticity refers to the ability of the brain to continue to grow new neural networks or reorganize existing networks; it is one way that the aging brain compensates for the loss of brain cells.

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