June 20, 2011

Restoring Memories By Flipping A Switch

(Ivanhoe Newswire) -- Scientists have found a way to turn memories on and off in rats by flipping a switch.

In the experiment, the investigators had rats learn a task, pressing one lever rather than another to receive a reward. They used embedded electrical probes to record changes in the rats' brain activity between the two major internal divisions of the hippocampus. These are known as subregions CA3 and CA1. The hippocampus converts short-term memory into long-term memory during the learning process.

The researchers blocked the normal neural interactions between the two areas using pharmacological agents. The previously-trained rats then no longer displayed 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,'" Theodore Berger of the USC Viterbi School of Engineering's Department of Biomedical Engineering, was quoted as saying.

"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 team then went further and developed an artificial hippocampal system that could duplicate the pattern of interaction between CA3-CA1 interactions. Long-term memory capability returned to the pharmacologically-blocked rats when the team activated the electronic device programmed to duplicate the memory-encoding function.

The researchers also showed 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," the authors wrote.

SOURCE: Journal of Neural Engineering, June, 2011