Transfer memory :

Neurobiologist David Glanzman made headlines in May 2018 after releasing results of a study he conducted on a type of sea snail called the sea hare. An attempt to better understand the mechanisms of memory, Glanzman theorized memories that cause defensive reflexes may be coded in RNA and not brain cells. To test his hypothesis, Glanzman implanted wires in the tails of sea hairs. He then shocked the snails repetitively until they were sensitized enough to automatically contract their gills when prodded in a fleshy spot of their bodies known as the siphon. Glanzman then extracted RNA from these snails and injected it into a new group of snails that had not been sensitized.

The new snails, with the new RNA in place, responded by contracting their gills when prodded in the siphon. Glanzman also exchanged RNA between two groups of snails that had not been sensitized, and no snails from those groups responded to being prodded. 
What does this say about memory? It's not clear. It may indicate that certain memories, specifically those related to semi-involuntary defensive responses, are not necessarily encoded in the brain. However, it's unclear whether the same cna be said for human memories as they are vastly more complex.

Researchers at Albert Einstein College of Medicine developed a mouse model in which molecules crucial to making memories (beta-actin mRNA) were given fluorescent "tags" so they could be tracked. This clip shows them traveling within a live brain cell in real time. Researchers watched fluorescently glowing beta-actin mRNA molecules form in the nuclei of neurons and travel within dendrites, the neuron's branched projections.They discovered that mRNA in neurons is regulated through a novel process described as "masking" and "unmasking," which allows beta-actin protein to be synthesized at specific times and places and in specific amounts.

Explicit memory:  The hippocampus, the neo cortex and the amygdala. ​The hippocampus, located in the brain's temporal lobe, is where episodic memories are formed and indexed for later access. Episodic memories are autobiographical memories from specific events in our lives, like the coffee we had with a friend last week. 

How do we know this? 

In 1953, a patient named Henry Molaison had his hippocampus surgically removed during an operation in the United States to treat his epilepsy. His epilepsy was cured, and Molaison lived a further 55 healthy years. However, after the surgery he was only able to form episodic memories that lasted a matter of minutes; he was completely unable to permanently store new information.

​As a result, Molaison’s memory became mostly limited to events that occurred years before his surgery, in the distant past. He was, however, still able to improve his performance on various motor tasks, even though he had no memory of ever encountering or practising them. This indicated that although the hippocampus is crucial for laying down memories, it is not the site of permanent memory storage and isn’t needed for motor memories. 

1 of 5: Transferring memory from one organism to another

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2 of 5: beta-actin mRNA travelling within dendrites

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3 of 5: How does your memory work?

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4 of 5: reading memories

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5 of 5:  the science of memory

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brain decoding:

Neuroscientists are starting to decipher what a person is seeing, remembering and even dreaming just by looking at their brain activity. They call it brain decoding. In this Nature Video, we see three different uses of brain decoding, including a virtual reality experiment that could use brain activity to figure out whether someone has been to the scene of a crime.

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