Here’s something to think about if you’re worrying about the effects of aging: Thinking keeps your brain young.

“We’ve become aware of this through brain scans,” said Dr. Henry Emmons, a Twin Cities psychiatrist. If we keep using our brains, “there is actual growth in the mind. The brain works faster.”

Yes, genetics plays a role in how we age, and we have no influence over that. But, he said, there are many other factors that we can control.

“I compare it to poker,” he said. “Genetics is the hand we’re dealt. But in poker, by deciding which cards to play, you can improve your hand. The same is true with the brain.”

Emmons and Minneapolis psychologist David Alter have collaborated on the book “Staying Sharp” (Touchstone, $25), a guide for creating a youthful brain. It’s an issue they take personally, Alter admitted.

“We’re both getting into our later 50s,” he said. “We face these challenges [of aging], but we face them with optimism. And it’s not just pie-in-the-sky optimism.”

That attitude is based on science that is disproving many of the myths about the supposed inevitability of losing mental abilities as we age.

“There is a widespread notion that the brain, in particular, deteriorates as we age,” they write. “It doesn’t have to be this way. These fearful losses of function are not a given.”

The book is structured around nine keys to brain health.

“These are skills or habits that we’re all able to develop with practice,” Emmons said. “The brain you will have a year from now you are creating today.”

One of the keys is to keep the brain active. Curiosity might have killed the cat, but it can prolong our lives.

“Curiosity reboots the brain, keeping it fresh and vital by balancing knowing with a hunger to know more,” the doctors write. “People who find ways to express curiosity in their daily lives tend to have longer, healthier and more fulfilling lives.”

The ruts we get caught in as part of our daily lives are brain cripplers, they said. As our routines become established, we go on autopilot. Before we know it, we’ve turned off our brains.

The solution: Change things around.

“Do things differently just for the sake of doing things differently,” Alter said. “Feed the brain something that it’s not used to dealing with.”

Even a small change — taking a different route to the grocery store — will force the brain to focus. And a brain that is focusing is one that is functioning.

“We’ve become so overstimulated in our society that we’ve lost the ability to be focused,” he said. “We need to cultivate that capacity.”

Cross training for the brain

Brain exercise needs to be varied, the doctors recommend.

“It’s like any exercise: If you do the same routine all the time, you’ll get better at that routine,” Emmons said. But exercising one part of the brain doesn’t necessarily extend into other areas any more than, say, doing bench press exercises makes someone a better marathoner.

“If you do the New York Times crossword puzzle every day, you’ll get better at doing crossword puzzles,” Alter said. “But we’re not just interested in getting better at crossword puzzles.”

Physical exercise also helps increase mental acuity, they said. Lethargy saps the brain’s power, while activity increases it. They describe movement as “a wonder drug for the brain.”

“You’d be very hard pressed to find anything medicinal that comes close to doing for the brain what movement does,” Emmons said. “We have to learn to move our body, even if it’s just to stand up and stretch every now and then. Get up and walk around once an hour. It’s important to incorporate those things into our lives.”

Sitting is the enemy

Emmons once told a group of people who were all on the far side of 75 that they actually had life easier back in the day before all the modern labor-saving devices came along. When they challenged him, he pointed out that our perpetual search for an easy life has backfired.

“Humans are meant to move, and it is only in the last couple of generations that the majority have become sedentary,” he said. “Our ancestors didn’t have to think about this. They couldn’t have avoided movement if they’d wanted to. But we can avoid it, and many of us do — to the detriment of our brains.”

Emmons does clinical work in Minneapolis with Partners in Resilience and is author of “The Chemistry of Joy” and “The Chemistry of Peace.” Alter is a teacher and co-founder of Partners in Healing, a holistic health center in Minneapolis. They’ve been friends for more than 25 years. They decided to collaborate on a book after realizing they shared a strong belief in the theory that we can influence the aging process.

“Aging is neither good nor bad,” Emmons said. “It’s something that happens to everyone. It’s what you do in response to it that matters.”