Things We Learned About the Brain in 2018

Keit

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It's this time when everyone makes lists and summaries about what has been happening in 2018. And one of the science sites made such a list about brain related discoveries. Some of them are really curious, like the one about memories being similar to viral infection, but some of them weren't mentioned on the forum yet. There's more info and links to papers in the original link.

So here are several examples:

A new kind of neuron
It's not every day that scientists discover a completely new type of cell in the human brain, especially one that's not found in neuroscientists' favorite nonhuman subjects, mice. The "rosehip neuron," so named because of its bushy appearance, had eluded scientists until this year, partly because it's so rare.

This elusive brain cell makes up only about 10 percent of the first layer of the neocortex, one of the newest parts of the brain in terms of evolution (meaning the far-distant ancestors of modern humans didn't have this structure). The neocortex plays roles in vision and hearing. Researchers don't yet know what the rosehip neuron does, but they found that it connects to other neurons called pyramidal cells, a type of excitatory neuron, and puts the brakes on them.

U.D., the neuroscience patient
A boy, known in the medical literature as "U.D." had one-third of the right hemisphere of his brain removed four years ago in order to reduce his debilitating seizures. The part of the brain that was removed included the right side of his occipital lobe (the brain's vision-processing center) and most of his right temporal lobe, the brain's sound-processing center. Now age 11, U.D. can't see the left side of his world, but he functions just as well as others his age in cognition and vision processing, even without that key part of the brain.

That's because both sides of the brain process most aspects of vision. But the right is dominant in detecting faces, while the left is dominant in processing words, according to a case study written about U.D.

That study showcases the plasticity of the brain; in the absence of U.D.'s right vision-processing center, the left center stepped in to compensate. Indeed, researchers found that the left side of U.D.'s brain detected faces just as well as the right would have.

The next discovery was mentioned on SOTT, and personally I find it most fascinating, as it does show a direct connection between brain and gut, and how our diet definitely influences the way we think and process information.

The brain may contain bacteria
In the latest example of bacteria being "literally everywhere," scientists appear to have found evidence of microbes living harmlessly in our brains...

"The brain has always been thought of as a sterile site," said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, who was not involved in the study. "To find [bacteria] there doing no harm sort of breaks a lot of the dogma" on this, Adalja said.

The surprising finding was accidental. The researchers were looking for differences in the brains of people with and without schizophrenia using a detailed imaging technique called electron microscopy. But the scientists kept coming across mysterious rod-shaped objects in the images...

In the new study, the researchers analyzed samples from 34 postmortem analyses of human brains and found bacteria in every brain. Importantly, the researchers found no signs of inflammation or bacterial disease in the brains they examined.

The bacteria seem to prefer certain parts of the brain, as the microbes tended to cluster in areas known as the hippocampus, prefrontal cortex and substantia nigra, according to the study abstract. And often, the bacteria were found in star-shaped brain cells known as astrocytes that were near the blood-brain barrier.

When the researchers sequenced genetic material from the bacteria, they found that most of the microbes were from groups of bacteria that are typically found in the human gut, known as Firmicutes, Proteobacteria and Bacteroidetes, according to Science Magazine.

To attempt to rule out the possibility that the brain samples were contaminated, the researchers analyzed mouse brains that were preserved immediately after death. The scientists also found "abundant bacteria" in the mouse brains, and the bacteria were in similar locations to those in human brains, according to the abstract. And when the researchers analyzed "germ-free" mice, which are genetically engineered to not have any bacteria living in them, the scientists did not find any bacteria in the brains.

Even so, Adalja said the findings will need to be reproduced to make sure they are not the result of contamination. But based on the steps the researchers have taken so far, Adalja said he suspects that it is "a real finding."

The findings raise the possibility that, like the human gut, the brain may have a "microbiome." Previous studies have suggested that bacteria in the gut may affect the brain indirectly, for example, by producing chemicals or proteins that make their way into the brain. But the new findings suggest a direct effect.

The brain is magnetic
Our brains are magnetic. Or, at least, brains contain particles that can be magnetized. But scientists don't really know why these particles are in the brain or where they originated. Some researchers believe that these magnetizable particles serve a biological purpose, while others say the particles got into the brain because of environmental contamination.

This year, scientists mapped out where these particles are located in the brain. The results of their study, the researchers said, provide evidence that the particles are there for a reason. That's because in all the brains the scientists examined — from seven people who died in the early 1990s between ages 54 to 87 — the magnetic particles were always concentrated in the same areas. The investigators also found that most parts of the brain contained these little magnets.

Many animal brains also have magnetic particles, and there's even some suggestion that animals use these particles to navigate. What's more, a type of bacteria called magnetotactic bacteria use the particles to orient themselves in space.

Your brain keeps making new nerve cells, even as you get older
That's a big deal. For decades, researchers believed that aging brains stop making new cells. But recent research has offered strong evidence to the contrary, and a new paper published today (April 5) in the journal Cell Stem Cell tries to put the notion to bed entirely. Aging brains, the researchers showed, produce just as many new cells as younger brains do...

Boldrini and her colleagues sliced the hippocampi, an area of the brain important for learning and memory, into slivers, and counted the number of newly formed cells — those that had yet to fully mature — under a microscope...

The older brains weren't completely unchanged. While they had as many new cells as younger brains, they seemed to be making fewer new blood vessels, and not forming new connections between brain cells as quickly.

It's important to note that the science of brain-cell formation in old age is far from mature. As recently as March 7, a paper published in the journal Nature challenged this idea that older brains keep making new nerves. In studies of sick and healthy brains, the authors found a sharp decline in the production of new brain cells, beginning around adolescence, with no new nerve cells detected in the brains of adults.

Boldrini suggested that the difference between her team's results and those of the Nature paper could have been traced to the brains the different groups were examining, and the methods used to examine them. The brains described in the Nature paper, she said, came from a wider range of people with different health conditions, including epilepsy, and may have been preserved using different techniques. Those preservation techniques, she said, may have destroyed evidence of new cells.

Because all the "healthy" brains in the Columbia study exhibited new cell growth, Boldrini and her team suggested that the continued ability to produce new cells in the hippocampus might be a key feature of brains that remain healthy into old age.

Your brain on stress
Bad news: Stress may shrink the brain. That's according to a study published in October of this year.

In the study, researchers looked at more than 2,000 healthy, middle-age people and found that those with higher levels of the stress hormone cortisol had slightly smaller brain volumes than people with normal amounts of the hormone. People with higher cortisol levels also performed more poorly on memory tests than did people with normal levels of the hormone. Both findings, it should be noted, are associations between stress and the brain and not cause-and-effect findings.
 
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