helps them do it. To understand how, imagine pulling one of our Japanese maples out by its roots, and then, while my wife has a heart attack, holding it over the top of our other maple. Don’t let them touch. The root system of the top tree is now hovering over the branches of the bottom.
Now imagine these two trees are neurons. The telodendria (roots) of the upper neuron lie close to the dendrites (branches) of the lower cell. In the real world of the brain, electricity flows from the dendrites of the top neuron down its axon and arriving at the telodendria, where it immediately encounters the space between the two. The gap must be jumped if information is to be transferred. This junction is called a synapse, and the space it creates, the synaptic cleft. How to pole-vault the space?
The solution lies at the tips of those root-like telodendria. There are small bead-like packets at those tips containing some of the most famous molecules in all of neuroscience. They’re called neurotransmitters. I’ll bet you’ve heard of some of them: dopamine, glutamate, serotonin.
When an electrical signal reaches the telodendria of one neuron, some of these biochemical celebrities are released into the synaptic cleft. It’s the equivalent of saying, “I need to send a message to the other side.” The neurotransmitters dutifully sail across the gulf. It’s not a long journey; most of these spaces are only about 20 nanometers in length. Once the neurotransmitters have crossed, they bind to receptors on the dendrites of the other neuron, like a boat tying up to a dock. This binding is sensed by the cell, alerting it with signal that says: “Oh, I better do something.” In many cases, that “do something” means becoming electrically excited too. It then passes along this excitement down the chain from dendrites to axons to its telodendria.
While jumping the space between two neurons using biochemicals is a neat trick, the electrical circuits aren’t usually this simple. If you can imagine lining up thousands of cellular Japanese maples root-to-branch, you’d have something approximating an elementary neural circuit in the brain. And even that’s too simple. The typical number of connections a single neuron makes with other neurons is around seven thousand. (That’s only an average: some have more than a hundred thousand!) Under the microscope, neural tissue looks like thousands of maple trees have crashed together in one space, whipped by an F5 tornado.
These are the structures that change so flexibly when the brain learns something new. These are the structures that become damaged as we age. However, there’s another fascinating reason that the damage of aging is incredibly individual.
The brain doesn’t just react to changes in the outside environment. Remarkably, the brain can respond to changes it observes happening to itself. How does it do that? We’ve no idea. We do know that if it senses the changes are likely to be negative, it can create work-arounds to fix the problem.
Cells erode, lose connections, or simply stop functioning. These alterations could easily lead to behavioral changes, but they don’t always. The reason is that the brain kicks into compensatory overdrive and reroutes itself according to a new plan.
The major culprit in aging is a hot topic. Some scientists speculate about immune system deficiency (the immunologic theory). Others blame dysfunctional energy systems (the free radical hypothesis; mitochondrial theory). Others point to systemic inflammation. Who is correct? The answer is all of them. Or none of them. Each hypothesis has been found to explain only certain aspects of aging. The sum total is that many systems get hit as we grow old, but which ones sign off first is individually experienced.
There are nearly as many ways to transit through the aging process as there are people on the planet. It’s a theme as familiar as shopping for jeans: one size does not fit all. Discernible generalizable patterns do exist, and studying the brain is a great way to see some of them. But to get an accurate view, we’re going to have to gaze at an occasionally cloudy statistical mirror. It’s okay. We’ll still look fabulous. We’ll just be a little older.
Our goal is to learn how to create lifestyles that will continually grease the biological gears controlling how long we live. And how well we live. Fortunately for us, geroscience is well funded. Scientists have discovered many cool things we can do as our brains age. All of these discoveries over the years add up to one thing: science is literally changing our minds about the optimal care and feeding of the brain. All of it is captivating. A great deal of it is unexpected. One of the most delightful is the subject of our first chapter. It’s the jovial power of having lots of friends.
SUMMARY
• Geroscience is the field of inquiry dedicated to studying how we age, what causes us to age, and how we can reduce the corrosive effects of aging.
• Aging is mostly due to the breakdown of our biological maintenance departments, our body’s increasing inability to repair the day-to-day wear and tear adequately.
• Today, we humans are living much longer than we have for the majority of our existence. We are the only species capable of living past our prime.
• The human brain is so adaptable that it reacts to changes not only in its environment but also within itself. Your aging brain is capable of compensating for breakdowns in its own systems as you get older.
brain rule
Be a friend to others, and let others be a friend to you
My favorite kind of pain is in my stomach when my friends make me laugh too hard.
—Anonymous
At some point, you have to realize that some people can stay in your heart but not in your life.
—Sandi Lynn, author of Forever Black
HERE’S A SENTENCE YOU probably don’t want to hear from Dad an hour after your wedding: “I’ll tell you what. If it lasts more than a year, I’ll give you a hundred bucks.”
Unfortunately, that’s exactly what happened to Karl Gfatter, a story he enthusiastically relates in a nursing home, wheelchair bound now, his loving bride at his side. And Dad had to pay up, probably many times over, for Karl and Elizabeth have stayed together for more than seven decades. Karl related this comment to the local media, who dropped by as he and Elizabeth were celebrating a recommitment ceremony in honor of their seventy-fifth wedding anniversary. They were surrounded by residents, staff, clergy. And rice. Plus lots of joy, smiles, and even some tears, creating the feeling you’d just walked onto the set of It’s a Wonderful Life. Both were radiant, bright as buttons. “We eloped because they didn’t want us to get married yet. They said we were too young!” Elizabeth laughed.
What Karl and Elizabeth may not know is that having a long marriage—and a room full of friends—is helping to keep their brains young. Friendships, and the social activities that surround them, are the major focus of this chapter. We’ll discuss the cognitive power of maintaining friendships over many years, along with the opposite: loneliness. Then we’ll dance our way toward a surprisingly beneficial brain booster.
Socializing: vitamins for the brain
You’d have a hard time finding someone more socially active—and intellectually lively—than wealthy
