Rat memory restored by installing replay electronics

With a flick of a switch and a burst of electrical activity, rats have been given access to lost memories. The concept might one day help people with brain damage remember how to perform everyday tasks.

Theodore Berger at the University of Southern California in Los Angeles, and colleagues, used electrodes implanted within the hippocampus to record patterns of brain activity while rats learned how to operate a sequence of levers to gain a reward.

Next, the team obliterated the memory of the task by injecting chemicals into the hippocampus that block the signalling between neurons needed to access long-term memories. When tested, the rats could no longer perform the task.

However, when the team used the electrodes to stimulate the brain with the same pattern of activity recorded when the rats first learned the task, their ability to operate the levers in the correct sequence was restored. The rats could temporarily access the original memory, even though the chemical blockade was still in place. When fed scrambled versions of the code, the rats could no longer perform the task.

Ultimately, the researchers hope to create implants that contain codes for 20 to 30 simple tasks, enabling people with brain damage to recover basic abilities that have been lost, such as speaking or dressing themselves.

Berger says that encoding these tasks will be very difficult. "These are very basic capabilities that we are investigating, and it has taken us a lot of effort to get this far," he says.