Scientists have shown that using deep brain stimulation (DBS), a technique already used to treat Parkinson's disease, can boost memory by causing new brain cells to be formed.A 'pacemaker' fitted with electrodes is inserted into the brain through holes drilled in the skull.Well-timed pulses from electrodes implanted in the brain can enhance memory in some people, scientists reported in the Journal of Biology. In the most rigorous demonstration to date of how a pacemaker-like approach might help reduce symptoms of dementia, head injuries and other conditions.The hope is that such sensitive, timed implants could bolster thinking and memory in a range of conditions, including Alzheimer’s and other dementias, as well as deficits from brain injury.

    The report is the result of decades of work decoding brain signals, helped along in recent years by large Department of Defense grants intended to develop novel treatments for people with traumatic brain injuries, a signature wound of the Iraq and Afghanistan wars.Previous attempts to stimulate human memory with implanted electrodes had produced mixed results: Some experiments seemed to sharpen memory, but others muddled it. The new paper resolves this confusion by demonstrating that the timing of the stimulation is crucial.        

    The device sends electrical impulses to specific parts of the brain and has also been shown to provide benefits for a range of conditions including chronic pain, major depression and obsessive compulsive disorder.

The new study is the latest chapter in an extraordinary, decades-long collaboration among cognitive scientists, brain surgeons and people with severe epilepsy being evaluated for an operation. The preoperative “evaluation” is a fishing expedition of sorts, in which doctors sink an array of electrodes through the top of the skull and wait for a seizure to occur, to see whether it’s operable. Many of the electrodes sit in or near memory areas, and the wait can take weeks in the hospital. Cognitive scientists use this opportunity, with patients’ consent, to present memory tests and take recordings.This approach — called direct neural recording, and piggybacking entirely on the clinical placement of the electrodes — has become the leading edge of research into the biology of human memory. This study used data from 150 patients, and had 20 collaborators from institutions around the country, including Emory University, the University of Washington, the Mayo Clinic and the University of California, San Francisco.In a series of experiments, the researchers had patients memorize lists of words and later, after a distraction, asked them to freely recall as many of the words as they could. All the while, the scientists monitored a handful of “hot spots” in the brain which, previous work had shown, were strongly related to memory encoding.