Protein-like virus essential for memory

A protein involved in cognition and storing long-term memories looks and acts like a protein from viruses. The protein, called Arc, has properties similar to those that viruses use for infecting host cells, and originated from a chance evolutionary event that occurred hundreds of millions of years ago.

The prospect that virus-like proteins could be the basis for a novel form of cell-to-cell communication in the brain could change our understanding of how memories are made, according to Jason Shepherd, Ph.D., a neuroscientist at University of Utah Health.

Researchers suspected that something was different about Arc when his colleagues captured an image of the protein showing that Arc was assembling into large structures. With a shape that resembles a capsule from a lunar lander, these structures looked a lot like the retrovirus, HIV. Prior work had shown that mice lacking Arc forgot things they had learned a mere 24 hours earlier. Further, their brains lacked plasticity.

 There is a window of time early in life when the brain is like a sponge, easily soaking up new knowledge and skills. Without Arc, the window never opens. Scientists had never considered that mechanisms responsible for acquiring knowledge could stem from foreign origins.  A protein important for cognition and memory named Arc can encapsulates genetic material (polyhedron enveloping the ribbon-like strands) and delivers it to brain cells in a manner similar to the way in which viruses infect host cells.

Seeing Arc's unusual propensity to form virus-like structures prompted researchers to scrutinize the protein sequence with a new set of eyes. They found that regions of the code were similar to that from viral capsids. An essential tool for viral infection, capsids carry virus' genetic information and deliver it from cell to cell in its victim.

Given that Arc looks like a viral protein, Shepherd and his colleagues designed a set of experiments to test whether it also acts like one. They first determined that several copies of Arc self-assemble into hollow virus-like capsids and stash its own genetic material, in this case mRNA, inside them. When the scientists added the capsids to mouse brain cells, or neurons, growing in a dish, Arc transferred its genetic cargo into the cells.

After viruses invade host cells, they emerge ready to infect once again. It appears that Arc works in a similar way. The scientists gathered Arc that had been released from mouse neurons and determined that the proteins and their cargo could be taken up by another set of neurons. Unlike for viruses, activating neurons mobilizes Arc, triggering the release of capsids.

A protein involved in cognition and storing long-term memories looks and acts like a protein from viruses, according to research by scientists at University of Utah Health. The protein, called Arc, has properties similar to those that viruses use for infecting host cells and could be the basis for a novel form of communication in the brain. An ancestor to retroviruses, called retrotransposons, inserted its genetic material into the animals' DNA, the event led to the mammalian. The significance of such an event is hinted at by the fact that it happened more than once.
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How challenges change thinking

Challenging situations make it harder to understand where you are and what's happening around you. A team of researchers showed participants video clips of a positive, a negative and a neutral situation. After watching the challenging clips -whether positive or negative - the participants performed worse on tests measuring their unconscious ability to acquire information about where and when things happen.

This suggests that challenging situations cause the brain to drop nuanced, context-based cognition in favor of reflexive action. Previous research suggests that long-term memories formed under stress lack the context and peripheral details encoded by the hippocampus, making false alarms and reflexive reactions more likely.

The researchers predicted that study participants would be less able to acquire spatial and sequential context after watching challenging clips, and that their performance would worsen the same way faced with either a positive or a negative clip. To test this, they used clips of film footage used previously to elicit reactions in stress studies: one violent scene (which participants experienced as negative), one sex scene (which participants experienced as positive), and one neutral control scene.

Immediately after watching the clips, two groups of participants performed tasks designed to test their ability to acquire either spatial or sequential context. Both the sex scene and violent scene disrupted participants' ability to memorize where objects had been and notice patterns in two different tasks, compared to the neutral scene. This supports the hypothesis that challenging situations- positive or negative cause the brain to drop nuanced, context-based cognition in favor of reflexive action.

Researchers suggest that the answer may lie in the hippocampus region of the brain, although they caution that since no neurophysiological techniques were applied in this study, this can't be proven. Since existing evidence supports the idea that the hippocampus is deeply involved in retrieving and reconstructing spatial and temporal details, downgrading this function when faced with a potentially dangerous situation could stop this context acquisition and achieve the effect seen in this behavioral study.

Reflexive reactions are less complex and demanding, and might stop individuals from making decisions based on unreliable information from unpredictable surroundings. Changes in cognition during high arousal states play an important role in psychopathology.
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Links between sleep, cognition and schizophrenia

Schizophrenia is associated with wide range of symptoms including visual and auditory hallucinations, cognitive problems and motivational issues.
People with the disease have trouble with learning and memory, cognition and a compound called kynurenine.
Kynurenic acid is a neuroactive metabolite of kynurenine that is formed in the brain. People with schizophrenia have higher than normal levels of kynurenic acid in their brains.

These higher levels might be connected with a range of symptoms seen in the disease like problems with learning and memory. The mechanisms underlying the cognitive impairments in patients is not clear. An interplay between higher kynurenic acid and sleep could be responsible. There is a lot of evidence in both humans and animals that sleep dysfunction leads to problems with learning and memory. People with schizophrenia often have problems with sleep.

Researchers examined rat, they made comparisons in the behavior of rats with increased kynurenic acid in their brains to animals with normal levels of the compound. They connected the animals' brains to a device that measured the amount and quality of sleep, and found that the animals with higher levels of kynurenic acid had significantly less rapid eye movement.

This is the sleep phase in which dreams occur, and it is thought to be critical for the consolidation of previous learning.
The researchers found that the group with high kynurenic acid also had problems with learning. To test this, they place rats in a box and shine light into the box. On one side of the box there is an opening into a darker area.

Rats are nocturnal animals, and prefer the dark, so the animals typically run to the dark area. Once in this area, they receive a small electric shock. When the experiment is repeated the next day, normal animals do not run to the dark location because of the electric shock. By comparison, animals with increased levels of high kynurenic acid, and impaired sleep, do not remember the shock and run into the dark area.

Kynurenic acid disrupts sleep, which then disrupts cognition. However, disruptions in sleep may cause increased kynurenic acid, which then leads to cognitive problems. Reducing kynurenic acid could reduce problems with sleep and cognition in patients with schizophrenia. High levels of kynurenic acid are a crucial aspect of schizophrenia.
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Healthy heart leads to healthy brain

Healthy lifestyle at 20 protects the brain at 40 and prevents brain shrinkage.
Neuroscientists monitored some participants for more than two decades and discovered that those that follow healthy lifestyle had less brain shrinkage.

Healthy lifestyle of a low-cholesterol diet, regular exercise, no smoking and eating less sugar at 20 prevents brain shrinkage at 40.

The American Heart Association created seven simple steps to improve heart health, these are- maintaining a healthy blood pressure, controlling cholesterol, reducing blood sugar, being active, eating healthy foods, losing weight and no smoking.

There is a link between smoking and smaller brain volume. Smoking can leads to thinning of the brain cortex, the outer part of the brain that is crucial for cognition.

Smoking increases the blood pressure and put the brain at the risk of stroke. A stroke occurs when high blood pressure causes the tiny vessels of the brain to break, causing bleeding.
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