It may be housed in an immovable shell of bone, but your brain—that three-pound fatty mass between your ears—is the most dynamic organ in your body. Your thoughts and actions add brain cells to the 100 billion already there, and create and strengthen the connections among them.Your brain is constantly inventing and reinventing itself. Knowing how your lifestyle choices dramatically affect these abilities can help you boost the power of your brain and keep it supercharged for the rest of your life.MORE: Be Better to Yourself“Your brain is the single-most magnificent, integrated and complicated miracle ever designed in the history of this or any universe,” says Paul Nussbaum, Ph.D., clinical neuropsychologist, adjunct professor of neurological surgery at the University of Pittsburgh School of Medicine and the author of “Save Your Brain.” “The fact that this miracle sits directly between our ears and is the ultimate portable and wireless device and literally defines who we are and what we imagine or choose to do is the reason everyone, beginning at an early age, needs to learn about this beautiful part of their being.”What do we need to learn, exactly? Mainly that what we have always assumed about our brains may actually be wrong.“Brain fitness is such a new field that people do have many misconceptions,” says Alvaro Fernandez, CEO of SharpBrains.com and co-author of “The SharpBrains Guide to Brain Fitness.” “For example, many people seem to assume that as long as their brain is working fine, there is no reason to pay more atten­tion to it. In reality, working on optimizing one’s brain is a bit like making sure to add gas to your car and change the oil reg­u­larly—it helps it work bet­ter and per­form longer.”Your Brain Is “Plastic”Imagine that emerging from all your brain cells, or neurons, is a huge network of wires forming 100 trillion connections. While it may seem that your adult brain is fully formed and done maturing, the truth is that it’s constantly adapting, making new connections and rerouting old ones. “Brain plasticity, or neuroplasticity, refers to the brain’s capacity to rewire itself through experience,” says Fernandez. As you learn things, your brain forms new connections among your existing neurons. It’s constantly changing, morphing and—if you play your cards right—improving. Plasticity explains how stroke patients can relearn skills they’ve lost due to brain damage. It also explains how a healthy part of the brain might assume the job of a damaged part. “Neuroplasticity doesn’t stop when we are 18 or 25 or 30,” explains Fernandez. “Every single day of our lives, no matter our age, we can change our brains for the better.”COLUMN: Keep Your Mind YoungUntil very recently, the prevailing wisdom among scientists was that by adulthood you had all the brain cells you’d ever have and that as you got older, those cells would gradually die. But there was a scientific sea change in 1998, when it was discovered that the mature adult brain forms new neurons in the learning and memory region called the hippocampus. “Neurogenesis [literally, “the birth of brain cells”] continues during a whole lifetime,” explains Fernandez.Your Brain Is ResilientNeuroplasticity and neurogenesis make your brain resilient against damage and decline. Remember the image of the huge network of wires? The more wires you have installed in your brain, the more likely you can cope with any illness that “burns out” some of the connections.Nussbaum says that building up resilience creates a jungle of connections: “Now, if you think of Alzheimer’s or another form of dementia as a weed-whacker, imagine how long it will take to make any kind of impact in cutting down the jungle.” Fernandez offers another image: “Think about it like this: The more money you have in the bank to start with, the more money you can withdraw over time without going bankrupt.”QUIZ: Are You Aging at the Right Pace?The concept of resilience, what neuroscientists call “cognitive reserve,” may explain why there are plenty of older adults (even centenarians) whose minds are still sharp. Chances are that those same people have remained mentally active and physically fit, too.You Are the Architect of Your BrainYou can make a difference in how healthy your brain is, and remains. Nussbaum and Fernandez offer these suggestions for how you can make easy lifestyle tweaks for lasting mental acuity:Keep moving: According to Nussbaum, your brain demands 25 percent of the blood from each heartbeat and relies on blood oxygen and nutrients to feed it. To keep your blood pathways healthy and to promote new neuron growth, both he and Fernandez advise taking a brisk daily walk (try for at least one mile) and doing aerobic exercise three times a week. Do whatever stimulates your heart—and soul: dancing, hiking, swimming, playing tennis. If you love it, you’ll stick with it. And that’s the point.MORE: The New Generation of Women GamersEat right: Healthy fats insulate your neurons’ connecting wires (in fact, your brain is 60 percent fat!). Your body can’t produce them, so they have to come from your diet. Nussbaum recommends including in your diet 8 ounces of Omega-3 fish a week (vegetarians can get their Omega-3s from algae supplements). Antioxidant-rich foods, such as bright fruits and vegetables, protect cells from free radical damage that can weaken cognitive function. Aim for six fist-sized servings a day. Watch your intake of refined sugar; too much could lead to insulin resistance in the brain, which has been linked to early Alzheimer’s.Embrace the new: Because brain resilience relies on doing what Nussbaum calls “novel and complex” activities (the more challenging and mind-broadening, the better), work on adding to your knowledge and skills. Take a class in that foreign language you’ve been dying to learn or lessons in that musical instrument you’ve always dreamed of playing. You can also mix things up by doing everyday things in an unusual way: Take different routes to work, alter tried-and-true recipes and do tasks with your nondominant hand whenever possible. Do “anything that gets you out of your daily routines and comfort level,” advises Fernandez.Chill out—alone and with others: Studies have shown that stress increases brain inflammation that can damage brain cells. Meditation, yoga, prayer, deep breathing and other mindfulness exercises can help you monitor and reduce your stress. And having fun with family and friends is a great way to relax and stimulate your brain. Indeed, research demonstrates that older women who are socially active are less likely to develop dementia.MORE: Making Time for New HobbiesPlay brain games: Puzzle books and online games (for instance, Fit Brains, which Nussbaum helped develop) can give your brain a fun workout, and gamelike strategies can help you sharpen your memory. For maximum brain-boosting results, why not try creating puzzles of your own for others to solve and have a special Game Night with family or friends? Everybody wins.“To anyone reading this,” says Fernandez, “please say ‘Hello!’ to the several thousand neurons that will be born in your brain today. How will you take good care of them?”