The notion that deep-brain stimulation may have benefits for memory was prompted in part by serendipity.

WSJ: Memory Gets Jolt in Brain Research

But the vagus nerve doesn't target all areas of the brain, so some severe disorders, such as advanced Parkinson's, may require Medtronic's more invasive deep-brain stimulation method.

FORBES: Rewiring the brain

The Food and Drug Administration has approved deep-brain stimulation to treat Parkinson's and a movement disorder known as dystonia, and it is used to treat chronic pain and severe depression.

WSJ: Memory Gets Jolt in Brain Research

The medical device giant Medtronic is testing a related technique called deep-brain stimulation, in which electrodes from a device in the chest are surgically threaded several centimeters into the brain to the site of damage.

FORBES: Rewiring the brain

Questions remain about using deep-brain stimulation to treat dementia, including whether it would work for Alzheimer's patients and at what stage of decline, whether it is safe and how long the effect will last, said Dr. Salloway.

WSJ: Memory Gets Jolt in Brain Research

For 15 years, people have been having brain implants to provide deep brain stimulation to treat epilepsy and Parkinson's disease -- a reported 80, 000 people have now had such devices placed in their brains.

CNN: Brain implants: Restoring memory with a microchip

Women with severe, life-threatening anorexia experienced dramatic improvement for the first time in their lives after a breakthrough deep brain stimulation (DBS) experiment published today in The Lancet.

FORBES: Startling Treatment Breakthrough For Anorexia Leads To New Understanding Of Brain Disorders