When scientists talk about memory and learning, the hippocampus, a small, seahorse-shaped structure located deep inside the brain, gets most of the credit for these vital cognitive functions.

What you don’t hear much about: The prefrontal cortex (PFC), a much larger part of the brain located just behind and slightly beneath the forehead. Known as the “executive” part of the brain because it controls judgment, insights and impulse control, the PFC is just as important when it comes to staying sharp mentally, learning new information and controlling processes involved in memory.

Unfortunately, millions of Americans don’t follow simple lifestyle habits that promote optimal functioning of the PFC. Result: Lapses in judgment (such as making risky maneuvers when driving)…disorganized thinking (including an inability to prioritize tasks)…shorter attention spans (resulting in difficulty with reading and other activities that require focus)…and impairments in learning and memory.

IMPROVE YOUR BRAIN—LIVE LONGER

The PFC needs good “fuel” to thrive. That’s why people with healthful habits tend to have a larger PFC than those who don’t take good care of themselves. As a result, they’re more likely to live longer (because their judgment about risks is better), and they’re less likely to develop Alzheimer’s disease.

Important findings: A 2007 study of Catholic nuns and priests found that those who had the most self-discipline were 89% less likely to develop Alzheimer’s disease. Self-discipline is one of the traits that is enhanced when you have a robust PFC.

POWER UP YOUR “WIRING”

People with healthful habits have less damage to myelin, the fatty coating on brain cells, than people who are less conscientious about their health. Brain cells that are sheathed in myelin work 10 to 100 times faster than unmyelinated cells. People with healthful habits also tend to have better blood circulation in the brain, which improves thinking as well as memory.

To protect your PFC—and other key parts of the brain…

Rethink your alcohol intake. Millions of Americans drink a glass or two of red wine a day because it’s good for the heart. But the cardio-protective properties of alcohol—it raises HDL “good” cholesterol and reduces clots, thus reducing the risk for a heart attack—may be offset by the damage it can do to the brain. Alcohol decreases the size and functioning of the PFC. What’s more, even moderate drinking (two drinks daily for men and one for women) can impair brain circulation.

My advice: If your doctor agrees that you can forgo the cardiovascular benefits of drinking wine, limit your intake to no more than two or three alcoholic beverages per week.

“Water” your brain. The brain is 80% water. People who don’t drink enough water or who drink a lot of dehydrating liquids, such as alcohol or caffeinated coffee or tea, often have impairments in cognition and judgment, which can occur when the PFC is damaged.

My advice: Drink plenty of water—eight glasses (64 ounces) of water every day is typically sufficient. If you like, add a splash of lemon or lime juice for flavor.

Slow down on the omega-6s. Most Americans get far too many inflammation-promoting omega-6 essential fatty acids in their diets—primarily from cooking oils (such as corn and vegetable), fatty red meats and processed foods—that are harmful to the brain. That’s why a plant-based, anti-inflammatory diet is among the most effective ways to reduce damage to the PFC and other areas of the brain.

My advice: Eat lots of greens—including salads—along with vegetables, fruit, whole grains and legumes. Approximately three servings of lean protein daily will help balance blood sugar and keep you feeling sharp. Also, eat at least three servings weekly of cold-water fish such as salmon, mackerel and sardines. The omega-3s in these fish have potent anti-inflammatory effects. Fish oil supplements (1 g to 3 g daily) are also helpful. Check with your doctor first if you use a blood thinner.

Aim to change your diet so that your intake of omega-6 fatty acids is no more than three times higher than your intake of omega-3s. Good rule of thumb: A plant-based diet that’s high in fish provides the ideal 3:1 (or lower) ratio of omega-6s to omega-3s.

Try green tea and rhodiola. Distractibility, disorganization and poor impulse control are commonly associated with children who may be suffering from attention-deficit/hyperactivity disorder (ADHD), but many adults (who may or may not have ADHD) also struggle with such symptoms.

Often linked to low activity in the PFC, these symptoms can be reversed, in part, with green tea and rhodiola, a plant-based supplement frequently used as an energy booster. In one study, researchers at my clinic did brain scans before and after giving patients green tea and rhodiola. Two months later, scans showed a significant increase in circulation in the PFC.

How it helps: Green tea appears to benefit the PFC by increasing the availability of dopamine, a brain chemical that controls the brain’s reward and pleasure centers. It also helps regulate emotional responses, such as the motivation to take positive actions. Rhodiola is an “adaptogen,” a substance that normalizes the body’s functions by boosting blood flow to the brain and raising dopamine and serotonin levels.

My advice: Take 200 mg of rhodiola and drink two to three cups of green tea daily (avoid drinking it in the evening since the tea’s caffeine can interfere with sleep…or drink decaffeinated green tea).

Keep your BMI in check. People who are overweight—with a body mass index (BMI) of 25 or higher—have less circulation in the PFC than those of normal weights. Excess body weight is associated with atherosclerosis, diabetes and other conditions that impede circulation throughout the body.

Danger: A high BMI can cause the brain to shrink. Research has shown that people who are obese typically have about 8% less brain tissue than normal-weight adults.

My advice: At least once a year, check your BMI by using an online calculator, such as the National Heart, Lung and Blood Institute’s www.nhlbiSupport.com/bmi/. A BMI of 18.5 to 24.9 is considered normal. If your BMI is 25 or higher, you need to lose weight.

Don’t ignore sleep problems. An estimated 18 million Americans have sleep apnea, a condition in which breathing intermittently stops during sleep. Unfortunately, the condition is undiagnosed in most of these people.

Why does this matter? Scans on patients with sleep apnea show brain changes that resemble early Alzheimer’s disease. Poor sleep decreases blood flow to the PFC and other parts of the brain. Snoring, daytime fatigue and morning headaches are common symptoms of sleep apnea. Your doctor may recommend tests in a sleep laboratory.

My advice: If you’re overweight, sleep apnea can often be reduced or even eliminated with weight loss. Many patients also benefit from continuous positive airway pressure (CPAP) units, which help keep the airways open during sleep.

Also important: Avoid sleepless nights. Patients with chronic insomnia have a higher risk for cognitive declines than people who sleep well. To prevent insomnia, follow the tried-and-true strategies—relax in a warm bath before bed…reduce arousal by not watching TV or using a computer in the hour before bedtime…and go to bed and wake up at the same times every day.

Also helpful: Melatonin. The standard dose of this sleep hormone supplement is 1 mg to 6 mg taken a half hour before bed. Start with the lower dose and increase it over a period of weeks, if necessary.

Check with your doctor first if you take an antidepressant, blood pressure medication, blood thinner, steroid or nonsteroidal anti-inflammatory drug—melatonin may interact with these medications.

Source: Daniel G. Amen, MD, a brain-imaging specialist and assistant clinical professor of psychiatry and human behavior at the University of California, Irvine, School of Medicine. He is the founder, CEO and medical director of the Amen Clinics and the author of several books, including Use Your Brain to Change Your Age: Secrets to Look, Feel, and Think Younger Every Day (Crown Archetype).