Memories lost due to Alzheimer’s may be recoverable
The proof-of-concept research, conducted in mice, raises the possibility of treatments that would reverse memory loss in early stages of the disease.
Optogenetics uses light to activate cells tagged with a special photo-sensitive protein. It was tested on mice with Alzheimer’s-like symptoms, who quickly forgot receiving a mild electric shock to their feet. After tagged cells in their brains were stimulated with light, their memory returned, and they displayed a fear response in the chamber where the shock had been applied an hour earlier.
The optogenetic treatment helped the neurons regrow small buds, called dendritic spines, which form synaptic connections with other cells.
Although the same technique cannot be used in humans, the research points the way to future memory-retrieving therapies.
Lead scientist Susumu Tonegawa, from the Picower Institute for Learning and Memory, at Massachusetts Institute of Technology (MIT) in the US, said: “The important point is, this a proof of concept. That is, even if a memory seems to be gone, it is still there. It’s a matter of how to retrieve it.”
The research, published in the journal, Nature, targeted memory cells, in the hippocampus region of the brain, which were previously identified by Prof Tonegawa’s team. Two different strains of mice, genetically engineered to develop Alzheimer’s symptoms, plus a control group of healthy animals, were used in the experiment.
Longer-term activation of ‘lost’ memories was induced by stimulating new connections between the hippocampus and entorhinal cortex brain regions.
Prof Tonegawa added: “It’s possible that, in the future, some technology will be developed to activate or inactivate cells deep inside the brain, like the hippocampus or entorhinal cortex, with more precision.
“Basic research, as conducted in this study, provides information on cell populations to be targeted, which is critical for future treatments and technologies.”
British expert Richard Morris, a neuroscientist at the University of Edinburgh, said: “When someone with early Alzheimer’s is forgetful, it is tempting to suppose that the memory is lost. However, echoing classic work by Elizabeth Warrington, at the National Hospital, in Queens Square, London, over 30 years ago, forgetfulness can also happen when the recall or retrieval mechanisms of the brain are compromised.
“This fine study, using a genetic mouse model of Alzheimer’s disease, coupled to optogenetics, offers the tantalising idea that ‘tagged’ memories can be reactivated by light.”
