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Press Association “Nerve cell stimulation 'may recall memories' in Alzheimer's patients” http://www.theguardian.com/society/2016/mar/16/nerve-cell-stimulation-recall-memories-alzheimers-patients

（まだマウスによる実験の段階だが）アルツハイマー症候群*1によって損なわれた記憶力は光刺戟によってニューロンを再活性化することによって恢復することができる。MITの利根川進氏*2らの研究。

The research, conducted in mice, raises the possibility of future treatments that reverse memory loss in early stages of the disease. Scientists used a technique called optogenetics, which uses light to activate cells tagged with a special photo-sensitive protein.
It was tested on mice with Alzheimer’s-like symptoms that quickly forgot the experience of 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 when placed in the chamber where the shock had been applied an hour earlier.
The optogenetic treatment helped the neurons re-grow 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, say the researchers.
Lead scientist Prof Susumu Tonegawa, from the Picower institute for learning and memory at the 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, specifically targeted memory cells in the hippocampus region of the brain previously identified by 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 forgotten memories was induced by stimulating new connections between the hippocampus and entorhinal cortex brain regions.
Tonegawa said: “It is 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.”

*2:See eg. http://web.mit.edu/biology/www/facultyareas/facresearch/tonegawa.html http://web.mit.edu/picowercenter/faculty/tonegawa.html https://en.wikipedia.org/wiki/Susumu_Tonegawa https://ja.wikipedia.org/wiki/%E5%88%A9%E6%A0%B9%E5%B7%9D%E9%80%B2