What's the News: Scientists have built a brain implant that can restore lost memories and reinforce new ones. The implant, tested in a recent study in rats, brings back a memory by recording and replaying the electrical activity of neurons in a part of the hippocampus, the brain's long-term memory center. While the device is far from ready for use in humans, it's an important step toward memory-boosting implants that could one day help patients who have developed dementia or suffered a stroke. How the Heck:
The rats first practiced a simple memory task: To get a refreshing drink of water, hit one lever in a cage, then---after a short distraction---hit the other. They had to remember which lever they'd already pushed to know which one to push the second time,.
As the rats did this memory task, an array of electrodes recorded signals between two subregions of the hippocampus, called CA1 and CA3, which are involved in storing new information in long-term memory.
The researchers then gave the rats a drug that kept CA1 and CA3 from communicating. The rats still knew the general rules of the task---press one lever then the other, get water---but couldn't remember which lever they'd already pressed.
When the scientists played back the neural signals from CA1 they'd recorded earlier, however, the rats again remembered which lever they had hit, and pressed the other one.
When researchers played back the signals in rats not on the drug---amplifying the regular signals from CA1---the rats made fewer mistakes and remembered which lever they'd pressed for longer.
What's the Context:
This implant operates on the same principles as other neural prosthetics, communicating with the nervous system using electrical signals. Instead of sending signals from the brain to control a prosthetic arm or a computer cursor, however, this system sends the signals to another part of the brain.
The Future Holds:
The researchers plan to test the implant in primates soon.
The ultimate goal is to develop memory-boosting implants for human patients---but that's a far more complicated task than simply scaling up the electrode array used in rats. Our memories are far more detailed than the simple lever-pressing task, meaning recording and replaying them---or even figuring out how to---wouldn't be as easy. Plus, this technique relies on playing back neural signals that have already been recorded; in patients who already have severe memory deficits, that memory trace might be too weak to record.
Reference: Theodore W Berger, Robert E Hampson, Dong Song, Anushka Goonawardena, Vasilis Z Marmarelis, & Sam A Deadwyler. "A cortical neural prosthesis for restoring and enhancing memory." Journal of Neural Engineering, June 15, 2011. DOI:10.1088/1741-2560/8/4/046017
Image: Flickr / asplosh
