{"id":94,"date":"2015-05-30T03:44:23","date_gmt":"2015-05-30T03:44:23","guid":{"rendered":"http:\/\/www.kurzweilai.net\/?p=253415"},"modified":"2015-06-02T03:57:12","modified_gmt":"2015-06-02T03:57:12","slug":"scientists-recover-lost-memories-using-brain-stimulation-by-blue-light","status":"publish","type":"post","link":"https:\/\/hoo.central12.com\/fugic\/2015\/05\/30\/scientists-recover-lost-memories-using-brain-stimulation-by-blue-light\/","title":{"rendered":"Scientists recover ‘lost’ memories using brain stimulation by blue light"},"content":{"rendered":"
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(credit: Christine Daniloff\/MIT)<\/p><\/div>\n

MIT researchers have found they were able to reactivate memories in mice that could not otherwise be retrieved, using optogenetics — in which proteins are added to neurons to allow them to be activated with light.<\/p>\n

The breakthrough finding, in a paper published Thursday (May 28) in the journal\u00a0Science<\/em>, appears to answer a longstanding question in neuroscience regarding amnesia.<\/p>\n

Damaged or blocked memory?<\/strong><\/p>\n

Neuroscience researchers have for many years debated whether retrograde amnesia — which follows traumatic injury, stress, or diseases such as Alzheimer\u2019s — is caused by damage to specific brain cells, meaning a memory cannot be stored, or if access to that memory is somehow blocked, preventing its recall.<\/p>\n

The answer, according to Susumu Tonegawa, the Picower Professor in MIT\u2019s Department of Biology and director of the RIKEN-MIT Center at the Picower Institute for Learning and Memory: \u201cAmnesia is a problem of retrieval impairment.\u201d<\/p>\n

Memory researchers have previously speculated that somewhere in the brain network is a population of neurons that are activated during the process of acquiring a memory, causing enduring physical or chemical changes.<\/p>\n

If these groups of neurons are subsequently reactivated by a trigger such as a particular sight or smell, for example, the entire memory is recalled. These neurons are known as \u201cmemory engram cells.\u201d<\/p>\n

Blocking, then activating memories with light<\/strong><\/p>\n

Until now, no one has been able to show that these groups of neurons undergo enduring chemical changes, in a process known as memory consolidation. One such change, known as \u201clong-term potentiation\u201d (LTP), involves the strengthening of synapses, the structures that allow groups of neurons to send signals to each other, as a result of learning and experience.<\/p>\n

To find out if these chemical changes do indeed take place, the researchers first identified a group of engram cells in the hippocampus that, when activated using optogenetic tools, were able to express a memory.<\/p>\n

When they then recorded the activity of this particular group of cells, they found that the synapses connecting them had been strengthened. \u201cWe were able to demonstrate for the first time that these specific cells — a small group of cells in the hippocampus — had undergone this augmentation of synaptic strength,\u201d Tonegawa says.<\/p>\n

The researchers then attempted to discover what happens to memories without this consolidation process. By administering a compound called anisomycin, which blocks protein synthesis within neurons, immediately after mice had formed a new memory, the researchers were able to prevent the synapses from strengthening.<\/p>\n

When they returned one day later and attempted to reactivate the memory using an emotional trigger, they could find no trace of it. \u201cSo even though the engram cells are there, without protein synthesis those cell synapses are not strengthened, and the memory is lost,\u201d Tonegawa says.<\/p>\n

But startlingly, when the researchers then reactivated the protein synthesis-blocked engram cells using optogenetic tools, they found that the mice exhibited all the signs of recalling the memory in full.<\/p>\n

\u201cIf you test memory recall with natural recall triggers in an anisomycin-treated animal, it will be amnesiac, you cannot induce memory recall,\u201d Tonegawa says. \u201cBut if you go directly to the putative engram-bearing cells and activate them with light, you can restore the memory, despite the fact that there has been no LTP.\u201d<\/p>\n

Memories are stored in a circuit of groups of cells in multiple brain areas, not synapses
\n<\/strong><\/p>\n

Further studies carried out by Tonegawa\u2019s group demonstrated that memories are stored not in synapses strengthened by protein synthesis in individual engram cells, but in a circuit, or \u201cpathway\u201d of multiple groups of engram cells and the connections between them.<\/p>\n

\u201cWe are proposing a new concept, in which there is an engram cell ensemble pathway, or circuit, for each memory,\u201d he says. \u201cThis circuit encompasses multiple brain areas and the engram cell ensembles in these areas are connected specifically for a particular memory.\u201d<\/p>\n

The research dissociates the mechanisms used in memory storage from those of memory retrieval, according to Ryan. \u201cThe strengthening of engram synapses is crucial for the brain\u2019s ability to access or retrieve those specific memories, while the connectivity pathways between engram cells allows the encoding and storage of the memory information itself,\u201d he says.<\/p>\n

Changes in synaptic strength and in spine properties have long been associated with learning and memory, according to Alcino Silva, director of the Integrative Center for Learning and Memory at the University of California at Los Angeles.<\/p>\n

\u201cThis groundbreaking paper suggests that these changes may not be as critical for memory as once thought, since under certain conditions, it seems to be possible to disrupt these changes and still preserve memory,\u201d he says. \u201cInstead, it appears that these changes may be needed for memory retrieval, a mysterious process that has so far evaded neuroscientists.\u201d<\/p>\n

\n

Abstract of\u00a0Engram cells retain memory under retrograde amnesia<\/em><\/strong><\/p>\n

Memory consolidation is the process by which a newly formed and unstable memory transforms into a stable long-term memory. It is unknown whether the process of memory consolidation occurs exclusively through the stabilization of memory engrams. By using learning-dependent cell labeling, we identified an increase of synaptic strength and dendritic spine density specifically in consolidated memory engram cells. Although these properties are lacking in engram cells under protein synthesis inhibitor\u2013induced amnesia, direct optogenetic activation of these cells results in memory retrieval, and this correlates with retained engram cell\u2013specific connectivity. We propose that 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.<\/p>\n","protected":false},"excerpt":{"rendered":"

MIT researchers have found they were able to reactivate memories in mice that could not otherwise be retrieved, using optogenetics — in which proteins are added to neurons to allow them to be activated with light. The breakthrough finding, in a paper published Thursday (May 28) in the journal Science, appears to answer a longstanding question […]<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49,43],"tags":[],"class_list":["post-94","post","type-post","status-publish","format-standard","hentry","category-cognitive-scienceneuroscience","category-news"],"_links":{"self":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/94"}],"collection":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/comments?post=94"}],"version-history":[{"count":1,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/94\/revisions"}],"predecessor-version":[{"id":95,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/94\/revisions\/95"}],"wp:attachment":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/media?parent=94"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/categories?post=94"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/tags?post=94"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}