[tt] Electrically stimulating the brain can speed learning

[Hughes, James J.]

http://www.technologyreview.com/Biotech/21007/?nlid=1172

Thursday, June 26, 2008

Want to Enhance Your Brain Power?
Research hints that electrically stimulating the brain can speed
learning.

By Emily Singer

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, Eric
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.