All might not be lost. Researchers recently announced a discovery that could have significant implications later down the road for helping people with severe amnesia or Alzheimer’s disease.
The research tackles a highly debated topic of whether memory loss due to damaged brain cells means that memories cannot be stored anymore or if just accessing that memory is inhibited in some way.
Scientists from MIT found in new research that the latter is most likely the case, demonstrating how lost memories could be recovered using technology known as optogenetics, which a news release about the study described as when “proteins are added to neurons to allow them to be activated with light.”
“The majority of researchers have favored the storage theory, but we have shown in this paper that this majority theory is probably wrong,” Susumu Tonegawa, a professor in MIT’s biology department and director of the RIKEN-MIT Center at the Picower Institute for Learning and Memory, said in a statement. “Amnesia is a problem of retrieval impairment.”
First, the scientists demonstrated how “memory engram cells” — brain cells that trigger a memory upon experiencing a related sight or smell, for example — could be strengthened in mice.
The researchers then gave the mice anisomycin, which blocked protein synthesis in neurons, after they had formed a new memory. In doing so, the researchers prevented the engram cells from strengthening.
A day later, the scientists tried to trigger the memory in mice, but couldn’t see any activation that would indicate the mice were remembering it.
“So even though the engram cells are there, without protein synthesis those cell synapses are not strengthened, and the memory is lost,” Tonegawa explained of this part of the research.
The team first developed a clever technique to selectively label the neurons representing what is known as a memory engram – in other words, the brain cells involved in forming a specific memory. They did this by genetically engineering mice so they had extra genes in all their neurons. As a result, when neurons fire as a memory is formed, they produce red proteins visible under a microscope, allowing the researchers to tell which cells were part of the engram. They also inserted a gene that made the neurons fire when illuminated by blue light.
After the researchers induced amnesia, they used optogenetic tools on the mice and witnessed the animals experiencing full recollection.
“If you test memory recall with natural recall triggers in an anisomycin-treated animal, it will be amnesiac, you cannot induce memory recall. But if you go directly to the putative engram-bearing cells and activate them with light, you can restore the memory,” Tonegawa said.
With this discovery, the researchers wrote in the study published this week in the journal Science that they believe a “specific pattern of connectivity of engram cells may be crucial for memory information storage and that strengthened synapses in these cells critically contribute to the memory retrieval process.”
James Bisby, a neuroscientist at University College London, told New Scientist that it’s “not surprising that they could trigger the memories, but it is a cool way to do it.”
Thanks to Steven Weihing for bringing this to the It’s Interesting community.