Mental Gymnastics: Inflating a Shrinking Brain

As you age, you need to exercise your brain to prevent some of the natural shrinkage. Starting at age 50, your 3-pound brain gradually loses its volume in weight, so that, by age 75, it weighs roughly 2.6 pounds. A lot of the shrinkage in your brain is from a loss of water.

Different parts of your brain lose their volume at different rates. Your frontal lobes — which serve as your executive control center, giving you your sense of judgment and allowing you to avoid blurting out rude and inappropriate comments — show the greatest amount of shrinkage compared to any other part of your cortex. The frontal lobes can shrink up to 30 percent between the ages of 50 and 90.

Looked at another way, your frontal lobes lose 0.55 percent of their volume every year after age 50. As the frontal lobes shrink, you may lose some of your capacity to be in control — that is, you may be less inhibited about what you say or do. (Perhaps now you won't be as surprised by some of the rude comments that come out of your grandfather's mouth.)

Your frontal lobes also play a big role in your ability to pay attention long enough to form short-term memories. If your frontal lobes do an inadequate job, they can make you prone to absentmindedness. As you age, you may become more apt to forget where you placed your keys or why you walked into a room. The frontal lobes are also responsible for verbal fluency (which is the ability to find the words you want when you want them) and executive function, which may also require more mental effort as the years go by.

The second-most affected area is your parietal lobes. Because they control construction ability, coordination, and spatial orientation, these skills can also be affected, contributing to the increase in falls seen in older people. Your temporal lobes, which help you remember the gist of an experience, shrink up to 20 percent as you age. This means that your ability to remember what you hear and say falter as you get older. Your temporal lobes also have to try to interpret inadequate information coming in if your hearing is failing.

To combat this shrinkage of your temporal lobes, you need to push them to be more active. To keep those lobes sharp, do the following:

• Engage in debate — participate in a political campaign or join a community group.
• Listen to lectures and audiobooks and discuss them afterward. A local book club is a great forum to keep your mind actively engaged and get social enjoyment simultaneously.
• Engage in discussion with your spouse, partner, and lifelong friends about memories you collectively hold. Call up your college friend and talk about old times.

Intellectual activity like that has the same beneficial effect on the temporal lobes as pumping iron has on the biceps. (But don't worry — your head won't bulge out like a weightlifter's arms.)

As you age, your hippocampus also shrinks. Between the ages of 50 and 90, it loses up to 20 percent of its volume. The levels of the neurotransmitter acetylcholine — critical for memory and active in your hippocampus — fall as you age and as your hippocampus shrinks. Your hippocampus is centrally involved in moving your short-term memories into long-term memories.

The loss in volume of your hippocampus means that acquiring new memories may be a little more difficult compared to earlier in your life. However, the situation is far from hopeless. Your brain is highly affected by changes in your nutrition, so your job is to make sure that you have the best nutrition possible. Eat three balanced meals a day.

Your occipital lobes — commonly referred to as the visual cortex — lose mass, too. The occipital lobes' ability to process visual information falters, but like your temporal lobes, they have to deal with inadequate information coming in. This lack of information to process is largely due to the deterioration of your optic nerve and retina.

To keep your occipital lobes functioning well, do the following:

• Attend art and photo exhibits.
• Go on sightseeing trips.
• Share your pictures with friends and relatives.
• Use eyeglasses if you have them and update your prescription at least every other year with the help of your optician. Keep up with eye health through regular check-ups with your eye doctor.

Because the occipital lobes are responsible for interpreting visual information, doing things that demand visual memory provides a good workout for the lobes.

Keeping your neurons from shrinking

The shrinking in your brain isn't due only to the loss of water. Your dendrites shrink, too, and have fewer branches and therefore fewer connections. Your dendrites form the part of your neurons that reach out to other neurons and draw in information. Fewer dendrites and dendrite branches mean less opportunity to think and for connections form memories from multiple channels.

The more you challenge yourself intellectually, the more your brain develops new dendritic connections with other neurons. Your brain can make new dendritic connections throughout your life despite your age. One great way to fight the trend of memory loss is to learn new information, challenge yourself to branch out, and think in ways you haven't before. If you have more dendritic connections to start with, you experience less of an impact on your brain when you start to lose some over time.