You exercise your cardio-vascular system with aerobics. You strengthen your muscular system with weight training. You watch your diet to avoid pollutants and supply nutrients. All these good things provide your body with health and vitality. What's missing? Your brain.

You work your heart and muscles to improve their condition and tone. You want to have a low resting heart rate and slow deep breathing all the time. Exercise definitely helps all that. There is nothing better you can do for depression than regular exercise. But it's also very desirable to directly train the nervous system to operate efficiently and effectively. Anyone can become more sane.

When I tell you to exercise your brain I don't mean soduku and crossword puzzles. For almost everyone, stimulation is not the big issue. The problem is inadequate capacity for relaxation of the nervous system. I don't mean the kind of relaxation that you get after physical exhaustion or a few shots of tequila. I mean training the relaxation response.

The methods I describe below have permanent benefits for a broad range of issues. Most of them involve biological monitoring and biofeedback. Biofeedback means interactive training with a display of your physiological responses. It is like exercising with an inner body mirror.

These nervous system training devices quickly and reliably calm the brain, the most important organ in your body. They guide you toward optimal flow and function of your nerves.

A cheap and easy device for your mental gym is a digital thermometer. The biofeedback task is to increase your finger or toe temperature. This is a mind-body exercise with trial and error learning. The opposite of the fight 'r flight response is rest 'n digest. Learning how to bring blood flow to your extremities is a particular form of relaxation that can be mastered with training and practice. Google: "stress thermometer"for the $20 item.

A lie detector monitors subtle physiological reactions to detect stress. You can reduce stress by training with some of those same monitors. The Journey to Wild Divine is a rather sedate computer game with dozens of biofeedback challenges. You have the mouse in one hand and biofeedback sensors in the other. As you follow the beautiful road on the monitor you are prompted to increase or decrease your nervous energy levels in order to proceed in the game.

What's going on here is that you are consciously paving the road between activation and relaxation. As you intentionally clear the road you are expanding the range and flexibility of your physiological responses. This allows you greater freedom of response at all times. That means you can more easily calm yourself down after getting upset or maintain yourself in the optimal performance zone with greater resilience.

Another group of devices gets your heart rhythms and breathing in sync. The idea here is based on the observation that when we inhale our heart rate increases. And when we exhale, our heart rate decreases. Having a wide range of heart rates within a single breath is an excellent indicator of overall health.

The free way to train for heart rate variability is to breath at 6 breaths per minute: 5 seconds in, 5 seconds out. But using a watch is rarely a successful way to train. Counting your heart beats is slightly better. But to seriously train heart rate variability you need a computer program such as HeartMath ($300) or the hand held device made by StressEraser ($400). An alternate way to train heart rhythms is feel and hold warm expressive positive emotions.

The king of biofeedback training methods is brain wave biofeedback. This kind of training has a large body of research over 35 years showing substantial relief from a large number of mind and body problems. There is also strong evidence for peak performance training with students, athletes, performers and soldiers. Indeed the U.S. Army is beginning an aggressive training program for officers on 13 bases following the work done at West Point. The main emphasis for the Army is improved mental focus.

Consumers can buy an EEG and software for home or you can work with a biofeedback trainer. Google: EEG biofeedback or neurofeedback. Systems will cost over a thousand dollars to $2500 and may require a hot computer.

Neurofeedback involves use of equipment that amplifies and displays the electrical activity of the brain, (EEG). Sensors attached to the scalp are connected to an encoder which feeds the signals to a computer. Some of these systems up train certain brain wave frequencies and down train others. The most advanced software reduces excess brain wave volatility.

Sophisticated software allows for graphical display of the signals and includes programs based on complex mathematical formulas designed to provide the central nervous system with information in a form which is readily processed. The role that the conscious mind plays in this process is minimal. You simply absorb pleasing visual displays and sounds. Brief pauses guide the brain toward peace, resilience and flexibility. You can think of this as defragmenting your brain or removing brain crud.

The final healing gadget is not a biofeedback device but does have the most research support. Cranial Electrical Stimulation units run a very mild electrical current through your brain. So very mild you don't feel it. These devices are approved by the FDA for anxiety, depression and insomnia. Many research articles show relief from plenty of other problems too. You typically use this device for 30 to 60 minutes for 30 to 60 days. We know that it reduces excess slow brain wave activity. It seems to re-set your stress levels. It seems to trick the brain into producing serotonin. Some people feel the runners' high without the running.

All of these devices produce broad benefits that last for the long term. The particular benefit and size of the effect varies for each person. These gadgets work well for spiffing up your responsiveness or with multiple problems because the central nervous system is central to all that we do.