Researchers have found that a person’s memory can be improved by stimulating areas deep inside the brain with electrical current, a finding that offers hope for nonpharmaceutical, noninvasive treatments that could boost memory impaired by Alzheimer’s disease, stroke, traumatic brain injury or aging.

Researchers at Northwestern University’s Feinberg School of Medicine say the study is one of the first to show long-term improvement in memory by driving an electrical current deep into the brain through powerful magnetic impulses known as Transcranial Magnetic Stimulation, or TMS.

The researchers found that healthy adults, ages 21 to 40, performed better on memory after receiving electromagnetic stimulation to their brains.

The researchers said the electrical current created by the magnetic field boosted the performance of a complex network involving several regions of the brain that are critical to forming memories, apparently by coordinating their activities with the hippocampus, an organ in the brain that is critical to memory formation and retrieval.

The team likened the effect to replacing a normal musical conductor with an extremely talented one who can smoothly coordinate different sections of an orchestra.

“The brain regions played together better after the simulation,” Joel Voss, an assistant professor of neuroscience at Northwestern University’s medical school and senior author of the study, said in a written statement.

The study -- which was funded by the National Institute of Mental Health and the National Institutes of Health’s National Institute of Neurological Disorders and Stroke -- is to be published Thursday in the journal Science.

In the study, the team focused on 16 people whose brains were first mapped using an MRI scanner to identify the individual networks and pathways involved in memory, which can differ slightly in different people. The subjects then took a memory test involving arbitrary associations between faces and words that they were asked to remember. After establishing a baseline performance, the subjects then received 20 minutes of brain stimulation per day over five consecutive days. Twenty-four hours after their last session of brain stimulation, the subjects were subjected to the memory tests again, and then again a week later with a fake, placebo brain stimulation. (The order of the real brain stimulation and the placebo was reversed for half the participants, who were not told which was which.)

The results showed that the subjects’ performance on the memory tests improved after receiving the electro-magnetic brain stimulation, Voss said. At least three days of stimulation were required to see an effect.

In an interview, Voss said the study built on previous work that demonstrated that electrical current applied to superficial areas of the brain improved memory for short periods of time. But Voss’ team attempted to stimulate the hippocampus deep inside the brain by beaming powerful magnetic impulses at an area about a centimeter from the skull that had a high degree of connectivity to the hippocampus.

“We can only stimulate the superficial part. And so we find, for each individual, part of their memory network that’s close to the surface that we actually can stimulate. So we stimulate it and we change, remarkably, the function of the whole network,” Voss said.

Voss said the researchers’ work had nothing to do with the unproven belief held by some practitioners of alternative medicines that wearing ordinary magnets can confer various health benefits.

“The magnetic field we’re inducing is about 10,000 times as powerful as the magnetic field of the earth,” Voss said. “So it’s just like an MRI scanner ... a very powerful magnet that is flashed on and off rapidly to induce a current in a wire, and those wires happen to be the brain’s neurons. ”

Voss said researchers suspect that the current improves connectivity between regions of the brain, probably by providing additional energy that makes it easier for the neurotransmitter sto convey signals to each other. The idea is that networks in the brain reshape and adapt themselves in response to stimulation – a concept known as neuroplasticity – whose mechanism has been studied in animals but is less clear in human beings.

“At a cellular level, we do not know the mechanisms of this, and it’s going to take a lot of studies to figure it out,” Voss said. He said an upcoming trial will focus on whether electrical stimulation has an effect on people in the early stages of memory loss.