A method to turn memories on and off with the flip of a switch, has been developed by the scientists.
Using an electronic system that duplicates the neural signals associated with memory, they managed to replicate the brain function in rats associated with long-term learned behaviour, even when the rats had been drugged to forget.
"Flip the switch on, and the rats remember. Flip it off, and the rats forget," said Theodore Berger of the USC Viterbi School of Engineering's Department of Biomedical Engineering.
In the experiment, the researchers had rats learn a task, pressing one lever rather than another to receive a reward. Using embedded electrical probes, the experimental research team, led by Sam A. Deadwyler of the Wake Forest Department of Physiology and Pharmacology, recorded changes in the rat''s 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."
In a dramatic demonstration, the experimenters blocked the normal neural interactions between the two areas using pharmacological agents. The previously trained rats then no longer displayed the long-term learned behaviour.
"The rats still showed that they knew 'when you press left first, then press right next time, and vice-versa,' said Berger.
"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,” added Berger.
"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," said the paper.
The study will be published in the Journal of Neural Engineering.