If a pacemaker can keep a heart in working order by zapping it with electric shocks, why not do the same thing for malfunctioning brains?

This is the idea behind electroshock, or electroconvulsive therapy (ECT), whereby electric currents are shot through a patient's brain to provoke epileptic seizures. Electroshock therapy has been used for decades to treat major depression and other mental illnesses. While it often conjures frightening images of broken bones and memory loss, ECT has made great strides since it was first introduced 70 years ago. Although effective in treating depression, it is still fairly controversial in the medical world.

Medical advancements in ECT now give patients the option of having a device that administers the shocks implanted into their body. The treatment is called vagus nerve stimulation therapy (VNS). The generator, placed just below the skin in the chest area, continually stimulates the brain via the vagus nerve. One of the longest nerves in the brain, the vagus travels from the brain stem through organs in the neck, thorax and abdomen.

The idea of vagus nerve stimulation therapy, approved for use in depression in 2005 by the U.S. Government Food and Drug Administration, is to readjust the brain's chemistry with mild intermittent pulses of electricity.

The signals travel along the vagus nerve and stimulate the limbic system, an area that affects mood, motivation, sleep, appetite, alertness and other factors altered by depression. What happens in the brain isn't quite clear, but the brief electric pulses appear to change the levels of neurotransmitters, the chemicals that work together to give us emotions.