February 18, 2014

Can Deep Brain Stimulation Improve Memory?

Deep brain stimulation (DBS) may well provide a particular kind of memory boost.

If additional testing confirms that connection, DBS would have an entirely new application, particularly for people with Alzheimer’s. Now, it’s used to control the tremors that often accompany Parkinson’s disease, and to treat the symptoms of obsessive-compulsive disorder and other mental disorders, like depression.

The February 8 edition of the New England Journal of Medicine reported the results of the very small but intriguing study. Doctors implanted electrodes into the brains of seven patients with seizure disorder epilepsy, in order to pinpoint the exact origin of their convulsions.

Researchers then observed the seven play a video game in which the patients assumed the role of cab drivers in a virtual city, picking up cyber passengers and delivering them to one of six shops. The make-believe cabbies drove around the cyber city, figuring out where the shops were.

Occasionally, as they got the lay of the land, they received five-second jolts of DBS to the entohinal cortex – a part of the brain considered key to transforming daily experience into lasting memories. As they learned three of the six imaginary locations, study participants received DBS. When they learned the other three locations, they did not.

Here’s the interesting part: if they got zapped while they learned a particular location, they were more likely to remember it later.

Researchers observed the routes their gaming cabbies took from one pre-learned location to another.

Six of the seven epilepsy patients showed an average reduction of 64% in their “excess path length” when they traveled to places whose locations they had learned during one of those quick five-second sessions of DBS.

Five of the seven took shorter, faster routes to the stores they’d learned about while getting zapped.

Interestingly, there was no corresponding special memory enhancement when researchers stimulated their subjects’ hippocampus, an area of the brain -- adjacent to the entohinal cortex -- that helps form and store memories.

Said senior study author Dr. Itzhak Fried, a professor of neurosurgery at the David Geffen School of Medicine at UCLA: “Critically, it was the stimulation at the gateway into the hippocampus, and not the hippocampus itself, that proved effective."

Is There Memory Enhancement Potential for Early Dementia Patients?
That’s the $64,000 question. To begin with, these findings came from an extremely small study.

That’s not the only concern. Suzanne Haber, a brain researcher and professor of pharmacology and physiology at University of Rochester Medical Center in New York, cautioned that the brain damage found in epilepsy – which can create memory problems – is different from the brain damage associated with Alzheimer’s. In the latter case, according to most authorities, amyloid plaques and neurofibrillary tangles cause neurons to deteriorate, thus impairing cognition.

Said Haber:
The thing to bear in mind is that it's a first, important step. I think it was exciting that they were really able to show that stimulating that area was important for a certain kind of learning. It raises more questions, and many more experiments that can be done.

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