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

by Daniel J. Levitin

older minds might process information more slowly than younger ones, but they can intuitively synthesize a lifetime of information and make smarter decisions based on decades of learning from their mistakes.

how well we age depends on two parallel streams: the confluence of a number of factors reaching back into our childhoods; and our responses to stimuli in our environments, and shifts in our individual habits.

Learning how to avoid certain environments, habits, and stimuli that influence our personalities in negative ways is a crucial part of aging well.

when we’re actively engaged and excited about life, our levels of mood-enhancing hormones such as serotonin and dopamine increase, and the production of NK (natural killer) and T cells (lymphocytes) also increases, strengthening our immune systems and cellular repair mechanisms.

Sleep deprivation at any age is bad for you. It has been tied to diabetes in pregnancy, postpartum depression in new fathers, and bipolar disorder at all ages. You may have read that “old people” don’t need as much sleep as young people and can get by on four or five hours a night. This myth has recently been exposed by Matthew Walker at UC Berkeley. It’s not that we need less sleep as we get older—it’s that changes in the aging brain make it difficult for older adults to get the sleep they need. And the consequences are serious. Sleep deprivation in the aged is directly responsible for cognitive decline, not to mention increased risk of cancer and heart disease. Grandma didn’t forget where she put her glasses because she’s senile—it’s because she’s sleep-deprived. Walker has found evidence that sleep deprivation increases the risk of Alzheimer’s.

AD is selective with regard to sex. Sixty-five percent of patients are women, and a woman’s chances of getting AD now exceed her chances of getting breast cancer.

The choices we make dictate much of the lives we lead. But we are also affected by random things that happen to us, and the choices that others make.

the biggest single determinant of living a productive and happy life is something that you’re born with (partly) and something that you can decide to change: your personality.

Booker T. Washington wrote that “character, not circumstance,” makes the person. Ralph Waldo Emerson wrote, “No change of circumstances can repair a defect of character.”

The Big Five dimensions are: Extraversion Agreeableness Conscientiousness Emotional Stability versus Neuroticism Openness to Experience + Intellect (also called Imagination)

EXTRAVERSION includes talkative, bold, energetic, and their opposites, quiet, timid, and lethargic. People who score high on the Extraversion dimension tend to

be comfortable around other people, start conversations, and don’t mind being the center of attention. AGREEABLENESS includes warm, cooperative, generous, and the opposites cold, adversarial, and stingy. People who score high on this dimension tend to be interested in other people, sympathize with others’ feelings, and make people feel at ease. CONSCIENTIOUSNESS includes organized, responsible, careful, and practical, and the opposites disorganized, irresponsible, sloppy, and impractical. People who score high on this dimension tend to be prepared, be diligent, pay attention to details, and do what they say they will do. EMOTIONAL STABILITY includes stable, contented, and at ease, and unstable, discontented, and nervous. People who score high on this dimension are not easily bothered by things, are relaxed, and don’t change their moods a lot. OPENNESS (also called INTELLECT and IMAGINATION) includes curious, intelligent, and creative, as well as uninquisitive, dumb, and uncreative. It includes cognitive and behavioral flexibility. People who score high on this dimension are quick to understand things, have a vivid imagination, and like trying new things, new restaurants, and going to new places. It is separate from intellectual ability but speaks to a propensity to enjoy intellectual, cultural, aesthetic, and artistic experiences.

Older adults tend to be better at controlling impulses; that is, they’re better at self-control and self-discipline and tend to be better at rule-following than young adults—traits that have to do with Factor III (Conscientiousness). Self-control increases steadily every decade after the age of twenty. Some of this has to do with the development of the prefrontal cortex, which continues through the early twenties, and yet we see additional age-related dispositional changes in impulse control that we haven’t found a cause for yet.

With age, men typically show increased emotional sensitivity, and women experience decreasing emotional vulnerability.

Individuals appear to become more self-content in old age, an aspect of Emotional Stability called the La Dolce Vita effect: the sweet life. Older adults are more content with what they have, more self-contained and laid-back, less driven toward productivity. Mood disorders, anxiety, and behavioral problems decrease past age sixty, and onset of these problems after that age is very rare.

Older adults are less likely to engage in risky or thrill-seeking behaviors and tend to be more morally responsible and less open to new experience. In terms of the Big Five factor model, older people show declines in Extraversion and Openness and increases in Emotional Stability and Agreeableness.

Perhaps the most important traits to foster and develop throughout the life span are those in Factor III, Conscientiousness. Conscientious people are more likely to have a doctor and to go see one when they’re sick. They’re more likely to get regular medical checkups and to reliably keep up with their professional, family, and financial commitments. This may sound like a mostly practical matter, but Factor III traits are highly correlated with a panoply of positive life outcomes, including longevity, success, and happiness.

There is an inherent asymmetry in the amount and kind of information we have about ourselves versus what we know about others.

One tangible thing that we can all do to avoid misjudging others is to exercise compassion, to allow for the possibility that you might be wrong in attributing a trait to someone’s behavior.

The HPA (hypothalamic-pituitary-adrenal) axis is an endocrine system that controls the secretion of stress hormones (glucocorticoids) including cortisol. Exposure to high levels of glucocorticoids can be particularly detrimental for the aging hippocampus and is associated with decrements in learning and memory. Among the things that psychotherapy is best at, stress reduction is one of the most important things you can do for your overall health.

Curiosity, Openness, Associations (as in sociability), Conscientiousness, and Healthy practices are the five lifestyle choices that have the biggest impact on the rest of our lives.

Like other brain systems, memory wasn’t designed; it evolved to solve adaptive problems in the environment. What we think of as memory is actually several biologically and cognitively distinct systems. Only some things that you experience get stored in memory. This is because one of the evolutionary functions of memory is to abstract out regularities from the world, to generalize. That generalization allows us to use objects like toilets and pens—you can use a new toilet, or a new pen, without special training because functionally, it is the same as other toilets or pens you’ve used.

As we age, our brains become better and better at this kind of pattern matching and abstraction, and although dot patterns seem pretty far removed from anything of real-world importance, the experiment illuminates that abstraction occurs without our conscious awareness, and it accounts for one of the most widespread traits that oldsters have: wisdom. From a neurocognitive standpoint, wisdom is the ability to see patterns where others don’t see them, to extract generalized common points from prior experience and use those to make predictions about what is likely to happen next. Oldsters aren’t as fast, perhaps, at mental calculations and retrieving names, but they are much better and faster at seeing the big picture. And that comes down to decades of generalization and abstraction.

Our memory systems form a hierarchy. At the highest level are explicit memory and implicit memory. They contain what they sound like—explicit memory contains your conscious recollections of experiences and facts; implicit memory contains things that you know without your being aware of knowing them.

Explicit memory comes in two broad types, reflecting two different neurological systems. One of these is general knowledge—your memory of facts and word definitions. The other is episodic knowledge—your memory of specific episodes in your life, often autobiographical.

Two particular brain regions, crucial to some kinds of memory, are the ones that decay and shrink with age and with Alzheimer’s disease: They are the hippocampus (Greek for seahorse, because its curved shape resembles that sea creature) and the medial temporal lobe (neurology-speak for the middle part of a structure just behind and above your ears). The hippocampus and medial temporal lobe are important for forming some of the kinds of explicit memory, and they’re not needed for implicit memory. This is why eighty-eight-year-old Aunt Marge, lost in a fog of amnesia-induced disorientation, cannot remember you, where she is, or what year it is but still knows how to use a fork, adjust the television station, read, and is excited to see appetizing food, all forms of implicit memory. The impaired brain structures affect her explicit memory but not her implicit memory.

Long-term memories are also easily disrupted, and when that happens, it can erase, or more often rewrite, your permanent store of information, causing you to believe things that just aren’t so—the

This is how memory works in the brain—as soon as you retrieve a memory, it becomes editable, just like a text document; it enters a vulnerable state and can get rewritten without your intent, consent, or knowledge. Often, a memory is rewritten by new information that gets colored in during one recollection, and then that new information gets grafted onto and stored with the old, all seamlessly, without your conscious awareness. This process can happen over and over again until the original memory in your brain has been replaced with subsequent interpretations, impressions, and recollections.

Autobiographical memory is perhaps the system that is most closely associated with your sense of self, of who you are and what experiences shaped you. The autobiographical memory system informs your life choices in important ways. Without it, you wouldn’t know if you are capable of hiking for two hours, if you can eat food with peanuts in it, or whether or not you’re married. And yet, the autobiographical memory system is prone to huge distortions. It’s a goal-oriented system. It recalls information that is consistent with your goals or perspective. We all tend to recontextualize our own life stories and the memories that formed them, based on the stories we tell ourselves or others tell us. Our original memories become corrupted, in effect, to conform to the more compelling narrative.

a huge misunderstanding that most of us have about our personal memories is that they are accurate. We think it because some of them feel accurate; they feel as though they are like video recordings of things that happened to us, and that they haven’t been tampered with. And that’s because our brains present them to us that way.

Another way that our memories are defective is that we often store only bits and pieces of events or facts, and then our brains fill in the missing pieces based on logical guesses.

The brain mixes up—confabulates—what it really knows with what it infers, and doesn’t often make a meaningful distinction between the two. When we age, we begin to confabulate more, as our brains slow down and the millions of memories we hold begin to compete with one another for primacy in our recollection, creating an information bottleneck. We all have, etched in our minds as true, things that never happened, or are combinations of separate things that did.

multiple-trace theory, or MTT. Every experience lays down a unique trace, and repetitions of an experience don’t overwrite earlier traces; they simply lay down more, near-identical but unique traces of their own. The more traces that there are for a given mental event, the more likely you’ll recall it and that you’ll recall it accurately and rapidly. This is how you learn things—by repeating them, playing around with them, exploring them—laying down multiple, related traces of the concept, experience, or skill.

The key to remembering things is to get involved in them actively. Passively learning something, such as listening in a lecture, is a sure way to forget it. Actively using information, generating and regenerating it, engages more areas of the brain than merely listening, and this is a sure way to remember it.

the biggest difference in the human versus monkey prefrontal cortex, and between the teenage and adult prefrontal cortex, is the presence of neurons that are GABA receptors—lots of them. That’s right, the inhibition neurochemical. Much of what it means to be human, and to be an adult, involves inhibiting responses that we might naturally make.

Starting at around age two, the brain begins this two-decade-long pruning process, getting rid of synaptic connections that aren’t being used. By age ten, the brain will have pruned out 50 percent of the connections it had at age two, and this pruning continues into your twenties. Some adult, late-onset mental disorders, such as schizophrenia, may result from incomplete pruning of the prefrontal cortex during adolescence. You might ask, “Why don’t all neurons connect to every other neuron and just stay that way?” For one thing, the brain would be gigantic if it did this—twenty kilometers across. For another, pruning lets us sculpt an efficient brain in response to our particular environment. The pruning forces the brain to specialize, to create local circuits that can function apart from others and that can automate certain tasks. The end result is thousands of modules, each doing their own thing.

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.

Much of this volume and weight reduction comes from shrinkage of the prefrontal cortex and hippocampus. The prefrontal cortex is what we use to set goals, make plans, divide a large project up into smaller pieces, exercise impulse control, and decide what we’re going to pay attention to.

The prefrontal cortex is also the first cortical region to show wear and tear as we get older. “That is why one of the most significant problems in older adults is the ability to keep track of thoughts and prevent stray ones from interfering,” says Art Shimamura. “Brain fitness as we age depends significantly on maintaining a healthy and active prefrontal cortex. The more we engage this brain region during daily activities, the better we will be able to control our thoughts and think flexibly.”

Another big factor in mental decline has to do with myelin, that fatty coating around axons that serves as an insulator. White-matter tracts—the transmission lines of the brain, the myelin-coated axons—decay with age starting at age fifty or so, and remyelination slows down to the point where it can no longer keep up. While the gray matter of the human frontal lobe and hippocampus shrinks an average of about 14 percent between the ages of thirty and eighty, shrinkage of white matter is even more drastic, averaging 24 percent. Moreover, unlike gray matter, which shows a more gradual shrinkage over time, the decline in white matter is particularly steep between the ages of seventy and eighty. It’s not that the tracts themselves disappear; it’s that the loss of insulation causes misfirings and disturbances of the electrical signal and slows down the transmission of thoughts in the brain.

This leads to a generalized slowing in older adults, affecting all of our mental systems, including the transmission of perceptual information, memory, decision making, and motor movements. That in turn may account for memory problems and other cognitive slowing because the white-matter tracts that are most compromised are those in the prefrontal cortex and the hippocampus.

Now, with declining efficacy of the prefrontal cortex and the medial temporal lobe, along with overall shrinking brain volume and white-matter reduction, you can see why older adults can find it more difficult to integrate and act on the information coming in from multiple sources, and why they find multitasking especially difficult. This is why when we age, we can have a harder time both focusing and switching our attention. It’s why we get distracted. And it’s why we have trouble dealing with new technology, especially new cell phones: The brain has slowed down, it’s smaller, and the shaping of our...

One of the most important things we can do to promote neural health involves myelin, which is 80 percent lipids. Our bodies’ ability to create and maintain myelin relies on dietary fats. Without them, or with a reduced ability to metabolize them, we see even more decay of the myelin sheath than is caused by aging alone. Not every word retrieval problem or lost wallet is due to demyelination, but improving and maintaining myelination does help. Two easy mechanisms are eating fatty fish and getting enough vitamin B12.

Cognitive reserve is the idea that people with more education and who are more intelligent may be able to withstand biological degradation better than others. Cognitive reserve is like that extra secret gas tank that Volkswagens used to have in the old days (how ingenious was that?). It is the capacity of the mature brain to roll with the punches, to sustain the effects of disease or injury that would otherwise impair others.

A stroke is the restriction of blood flow in the brain that causes cell death. Strokes come in three types. When a clot forms in the brain, preventing oxygenated blood from reaching particular regions, it’s called an ischemic stroke. (Ischemia is the word used for restrictions of blood supply.) If the clot is only temporary, the resulting stroke is called a transient ischemic attack, or TIA. These are usually warning signs for subsequent strokes. When a weakened blood vessel in the brain bursts and causes internal bleeding, it’s called a hemorrhagic stroke. (A hemorrhage is the escape of blood from a blood vessel.)

For years, doctors advised people over fifty or sixty to take a baby aspirin (around 80 mg) every day as a preventative, to thin the blood, thus reducing the risk of a blood clot or ischemic stroke. The problem with this is that if you have a hemorrhagic stroke, the thin blood won’t clot and the damage from internal bleeding will be more severe. It’s one of those weird situations in medicine where you effectively have to choose how you want to die or be otherwise damaged: Would I rather have the damage from a clot or from a rupture?

As of 2019, there is mounting evidence that taking the low dose aspirin is preventively not worth the risk, and a study of twelve thousand Europeans found that it had no effect on stroke.

One of the most protective things you can do against aging is to learn a manual skill when you’re young and keep it up. The next best thing you can do is to start learning something new when you’re old.

the signals hitting our sensory receptors are often incomplete or distorted, and our sensory receptors don’t function perfectly. There are other cases in which what our receptors might tell us about the world is wrong and the brain needs to step in. Rock further showed how our perceptual system uses logical inferences to help us perceive the world. Perception doesn’t just happen—it entails a string of logical inferences and is the outcome of unconscious inference, problem solving, and outright guesses about the structure of the physical world.

Given what is hitting the sensory receptors, the brain tries to work out what is the most likely thing that is happening. Perception is the end product of a chain of events that starts with sensory input and includes a cognitive, interpretive component. Have I convinced you that the brain is full of tricks and that the world is not always as it appears? Here’s where it gets really interesting. The brain fills in missing information without your knowing it. And the older you get, the more it does this. This perceptual completion is also based on the logic of perception.