Thank you for making me so wonderfully complex!
Your workmanship is marvelous... Psalm 139:14 NLT
Your workmanship is marvelous... Psalm 139:14 NLT
"Neuroscientists who study memory have long believed that when 
we recall these memories, our brains turn on the same hippocampal circuit that was activated when the memory was originally formed. However, MIT neuroscientists have now shown, for the first time, that recalling a memory requires a "detour" circuit that branches off from the original memory circuit.
Previous research has shown that encoding these memories involves cells in a part of the hippocampus called CA1, which then relays information to another brain structure called the entorhinal cortex. In each location, small subsets of neurons are activated, forming memory traces known as engrams.
Why would the hippocampus need two distinct circuits for memory formation and recall? The researchers found evidence for two possible explanations.
--One is that interactions of the two circuits make it easier to edit or update memories. As the recall circuit is activated, simultaneous activation of the memory formation circuit allows new information to be added.
The researchers found that the subiculum connects to a pair of structures in the hypothalamus known as the mammillary bodies, which stimulates the release of stress hormones called corticosteroids. That takes place at least an hour after the fearful memory is recalled.
Scientists made a key breakthrough with the identification of the Arc protein in 1995, observing how its role in the plastic changes in neurons was critical to memory consolidation.
The researchers knew they were onto something when they captured an image of Arc that looked an awful lot like a viral capsid, the isohedral protein coat that encapsulates a virus’s genetic material for delivery to host cells during infection.
The main issue that challenges neuroscientists’ understanding of 
memory is that proteins don’t last very long in the brain, even though memories last nearly a lifetime.
So for memories to remain, there must be plastic changes, meaning that neuron structures actually have to change as a result of memory consolidation.
This is where Arc comes into play. Previous research on rats illustrated how Arc disrupts memory consolidation, suggesting that Arc is vital in neuronal plasticity.
It turns out the Arc capsid encapsulated its own RNA. When they put the Arc capsids into a mouse brain cell culture, the capsids transferred their RNA to the mouse brain cells — just like viral infection does.
“We went into this line of research knowing that Arc was special in many ways, but when we discovered that Arc was able to mediate cell-to-cell transport of RNA, we were floored,” says the study’s lead author, postdoctoral fellow Elissa Pastuzyn,.... “No other non-viral protein that we know of acts in this way.”
About a decade ago, a group of neurons known as "time cells" was discovered in rats. These cells appear to play a unique role in recording when events take place, allowing the brain to correctly mark the order of what happens in an episodic memory.
Located in the brain's hippocampus, these cells show a characteristic activity pattern while the animals are encoding and recalling events, explains Bradley Lega.
By firing in a reproducible sequence, they allow the brain to organize when events happen, Lega says. The timing of their firing is controlled by 5 Hz brain waves, called theta oscillations, in a process known as precession.
Lega investigated whether humans also have time cell....What the team found was exciting: Not only did they identify a robust population of time cells, but the firing of these cells predicted how well individuals were able to link words together in time (a phenomenon called temporal clustering). Finally, these cells appear to exhibit phase precession in humans, as predicted.
"For years scientists have proposed that time cells are like the glue that holds together memories of events in our lives," according to Lega.
Researchers have long known that as animals travel a path they've 
been on before, neurons encoding different locations along the path will fire in sequence much like time cells fire in the order of temporal events....As rats moved through these spaces, their neurons not only exhibited forward, predictive mini-sequences, but also backward, retrospective mini-sequences. The forward and backward sequences alternated with each other, each taking only a few dozen milliseconds to complete.
"While these animals were moving forward, their brains were constantly switching between expecting what would happen next and recalling what just happened, all within fraction-of-a-second timeframes," Pfeiffer says."
ScienceDaily/Inverse
