Scientists have figured out how to to switch memories on and off in rats through the use of an electronic system that mimics neural signals. Researchers duplicated the brain mechanism linked to long-term learned behavior in the rats, even when they had been drugged to forget.
“Flip the switch on, and the rats remember. Flip it off, and the rats forget,” said Theodore Berger, Ph.D., of the University of Southern California.
For the study, rats learned a task in which they pressed one lever instead of another to earn a reward. Using embedded electrical probes, the research team, led by Sam A. Deadwyler, Ph.D., of the Wake Forest Department of Physiology and Pharmacology, tracked the rats’ brain activity between the two major internal divisions of the hippocampus, known as subregions CA3 and CA1.
“No hippocampus,” said Berger, “no long-term memory, but still short-term memory.” Previous research has shown that during the learning process, that CA3 and CA1 work together to convert short-term memory into long-term memory.
Using pharmacological agents, scientists blocked the normal neural interactions between the two areas. Remarkably, the previously trained rodents ceased to display the long-term learned behavior.
“The rats still showed that they knew ‘when you press left first, then press right next time, and vice-versa,'” Berger said. “And they still knew in general to press levers for water, but they could only remember whether they had pressed left or right for 5-10 seconds.”
The teams went further by developing an artificial hippocampal system that could duplicate the activity between CA3 and CA1.
The pharmacologically blocked rats regained their long-term memory when the electronic device programmed to duplicate memory-encoding function was activated.
The team went on to show that if a prosthetic device and its electrodes were implanted in animals with a normal, functioning hippocampus, the device could actually strengthen the memory being generated internally in the brain and enhance the memory capability of normal rats.
“These integrated experimental modeling studies show for the first time that with sufficient information about the neural coding of memories, a neural prosthesis capable of real-time identification and manipulation of the encoding process can restore and even enhance cognitive mnemonic processes,” according to the study.
The team hopes to eventually develop prostheses that could eventually help sufferers of Alzheimer’s disease or stroke.