Research hints that electrically stimulating the brain can speed learning

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A little brain boost is something we could all use now and then. A new

option may be on the horizon. Researchers at the National Institute

for Neurological Disorders and Stroke, in Bethesda, MD, are studying

how applying gentle electrical current to the scalp can improve learning.

Previous small-scale studies have suggested that a stream of current

can improve motor function, verbal fluency, and even language

learning. To explore how effective such stimulation can be as a

learning tool, Wassermann, a neuroscientist at the National

Institute for Neurological Disorders and Stroke, is using an approach

known as transcranial direct current stimulation (TDCS), in which an

electrical current is passed directly to the brain through the scalp

and skull. The technology for TDCS, which has been available for

decades, is simple and fairly crude. (In the 1960s, it was used to

improve mood in people with psychiatric disorders, although that

effect hasn't been repeated in more recent studies.) And in contrast

to people undergoing electroconvulsive therapy, a seizure-inducing

treatment used for severe depression that requires anesthesia, people

undergoing TDCS feel just a slight tingle, if anything.

The device is simple: a nine-volt battery that's been approved by the

Food and Drug Administration for delivering drugs across the skin is

connected to large flat sponges that are moistened and then applied to

the head. It delivers a gentle 2 to 2.5 milliamps of current spread

over a 20 to 50 square millimeter area of the scalp for up to 15

minutes. Little of that current actually reaches the brain--about half

is shunted away from the target area, and the other half quickly

dissipates as it gets farther from the scalp.

Wassermann's team targets part of the brain known as the dorsolateral

prefrontal cortex, a brain area involved in higher-level organization

and planning, as well as in working memory. Because activity in this

region has been shown in previous imaging studies to predict an

individual's ability to recall information, the idea is that giving it

an electrical boost will enhance memory function.

In preliminary results from the new study, which is part of a larger

government-funded project to examine TDCS for cognitive enhancement,

researchers found that direct current stimulation could improve memory

in participants asked to learn and then recall a list of 12 words. The

effect was significant in the early learning stages: in the first few

trials, in which participants were given the same list over and over

again, people in the treatment group could remember more words. But

the learning curve for those working without the device quickly caught

up to the zapped learners. " Now we want to see if we can enhance

recall, not just encoding, " says Wassermann. " Ultimately, you'd just

want to do the stimulation during encoding. "

Wassermann says that the preliminary studies are meant to help

evaluate how practical the technology is. " We're beginning to think

about whether this technology has a role in cognitive enhancement in

healthy people--whether it's ethical, whether there is a need and a

place for this, " he says. Wassermann originally became interested in

noninvasive brain stimulation as a treatment for people with

neurodegenerative disease, but a series of preliminary tests in

patients have been unsuccessful. " It probably won't work in a badly

damaged brain, " he says. So his team is shifting its attention toward

exploring transcranial stimulation as a learning tool in healthy people.

Very little is known about how TDCS works. Scientists theorize that

the mild current primes the neurons for action but does not trigger

the voltage spikes that neurons use to communicate. " Presumably, it is

polarizing neurons and making them more or less likely to respond to

inputs, " says Warren Grill, a neural engineer at Duke University, in

Durham, NC. " But what's happening at the level of the synapse, where

the business of learning really takes place, we don't know. "

Because the level of stimulation in TDCS is so low, it is considered

safer than another noninvasive alternative, transcranial magnetic

stimulation. In this approach, which is under investigation as a

therapy for stroke and other brain disorders, an electric coil placed

over the head generates a magnetic field that passes through the

skull, exciting neurons in the brain below. However, because the

procedure does trigger neural activity, it carries a risk of seizure.

Cognitive enhancement with drugs such as Ritalin, prescribed for

attention deficit disorder, is already widespread, of course. A survey

published online at Nature in April found that one in five

respondents, most of whom were academics and scientists, reported

using such drugs for nonmedical use. Electrical stimulation may prove

even easier to access. " Half the people in this room could build this

type of device with parts from RadioShack, " Wassermann told a crowd at

a neurotechnology conference in Cleveland last week.

source: http://www.technologyreview.com/Biotech/21007/page1/