Scientists Turn Memory On, Off in Rats With Flip of Switch

By Maureen Salamon
HealthDay Reporter

FRIDAY, June 17 (HealthDay News) — Fixing faulty memories may one day be as easy as flipping a switch, according to scientists who restored brain function in rats even when they had been drugged to forget.

Building on prior research on the brain area known as the hippocampus, which is associated with learning, researchers from University of Southern California and Wake Forest University used an electronic system to duplicate neural signals linked to memory and turn the rats’ memories on and off at will.

“This actually looks like a real step . . . toward some future device that may be very real,” said Dr. Nicholas Schiff, an associate professor of neurology and neuroscience at Weill Cornell Medical College in New York City. “It’s obviously early, but it looks that, in proof of concept, something like this could partially restore function in a hippocampus not completely damaged.” Schiff was not involved in the study.

The study is published June 17 in the Journal of Neural Engineering.

In the experiment, 45 rats first learned a task by pressing one lever instead of another to receive a reward. The researchers used embedded electrical probes in the rats’ brains to record changes in brain activity between the two major regions of the hippocampus, which converts short-term memory to long-term during the learning process.

When the researchers used drugs to block normal neural interactions between the two regions, the previously trained rats could no longer display the long-term learned behavior. However, the long-term memory returned when the team activated the electronic device, which was programmed to duplicate the memory-encoding function of the hippocampus’ two major regions.

“Flip the switch on, and the rats remember. Flip it off, and the rats forget,” lead author Theodore Berger, a professor of biomedical engineering at USC’s Viterbi School of Engineering, said in a university news release. “The rats still showed that they knew ‘when you press left first, then press right next time’ . . . and they still knew in general to press levers for water, but they could only remember whether they had pressed left or right for five to 10 seconds.”

In the experiment, the “neural prosthesis” devised by the scientists replaced circuitry in the brain that no longer functions properly. That could eventually have implications for helping people afflicted with Alzheimer’s disease, stroke or other brain injuries to recover lost function, the researchers explained.

“Obviously, memory disorders are a hallmark of a number of different disorders of the nervous system, including Alzheimer’s, epilepsy and traumatic brain injury,” said another expert, Dr. Ashesh Mehta, director of epilepsy surgery at North Shore-LIJ Comprehensive Epilepsy Care Institute in New Hyde Park, N.Y.

“So there’s lots to be said if we could figure out the mechanism by which memory occurs,” Mehta added. And even though this study was done in animals, “the basic architecture of the hippocampus is preserved in humans,” he said.

The researchers next hope to duplicate the findings in monkeys.

Schiff said he thought such a device would potentially work better in patients whose loss of oxygen — from conditions such as cardiac arrest — had left them with brain injuries that would not progress, unlike Alzheimer’s.

“Alzheimer’s disease has its own underlying biology,” he said. “It knocks out cells in lots and lots of places in an inexorable way. But there are brain injuries where cells are closer to the experimental design here.”

More information

Bryn Mawr College has more information about the hippocampus.

SOURCES: Nicholas Schiff, M.D., associate professor, neurology and neuroscience, Weill Cornell Medical College, New York City; Ashesh Mehta, M.D., Ph.D., director, epilepsy surgery, North Shore-LIJ Comprehensive Epilepsy Care Institute, New Hyde Park, N.Y.; June 17, 2011, Journal of Neural Engineering

Last Updated: June 17, 2011