“Patients with brain injuries will be the first [candidates],” said Song. Such injuries tend to affect specific regions of the brain. Damage to the hippocampus is easier to target than degenerative diseases like Alzheimer’s, which tend to involve damage across multiple regions of the brain.
“It seems to me that one day we might be able to replace the hippocampus with something else,” says Jacobs. But he points out that it would be difficult to completely regenerate a healthy hippocampus, which contains tens of millions of neurons. “It’s hard to imagine how a handful of electrodes can replace millions of neurons in the hippocampus,” he said.
The electrodes used in this study were about a millimeter wide, and all of the volunteers implanted them deep enough into the brain to reach the hippocampus — about 10 centimeters deep. But by modern research standards they are quite crude and can only record between 40 and 100 neurons, Song said. Any memory prosthetics designed to treat memory disorders would require brain electrodes with hundreds of contacts, allowing them to record and stimulate hundreds or thousands of neurons. , he said.
Hampson, Song and their colleagues have yet to figure out how the memory prosthesis might work in practice. For example, when the device is always running – there are many life experiences, such as taking out the trash, that people with memory disorders don’t need to remember. “Why waste it? [brain] space?” Jacobs said.
But suggests that prosthetics can be used in conjunction with some kind of device that could tell if the device needs to run — perhaps by detecting when the brain needs to be ready to learn. .
And Song doesn’t know whether a memory prosthetic should run overnight. It is thought that as we sleep, the hippocampus replays some of the day’s encoded memories, to reinforce them in other brain regions. But and his colleagues don’t know whether a memory prosthetic that reconstructs this replay improves memory, or whether stimulating the hippocampus while a person is asleep is a good idea.
Either way, the prosthesis still has some way to be for clinical use, says Shapiro. “I think in principle it could work,” he said. “[But] We have a long way to go before we understand enough about memory that we can use this approach to replace hippocampal function. “