Science and logic

Understanding the Architecture of Our ‘Second Brain’

Scientists have made an important step in understanding the organisation of nerve cells embedded within the gut that control its function – a discovery that could give insight into the origin of common gastrointestinal diseases, including irritable bowel syndrome and chronic constipation.

“Where were you when our hearts were bleeding …”

We interrupt your regularly scheduled Voltron with some well timed Naruto. Honestly, Itachi deserved so much more than he got. So here, take this!

So, as of recently, I now have a tablet! And this was the result of me breaking it in. I, like the piece of trash that I am, ended up drawing myself in Keith’s outfit with purple ears and all that. All I have to say is, pen pressure is a LIFE SAVER!!!!!!!!!!!!!

Take my trash and go, be free! I hope to start posting much more art in the future!

“You started a fire, and you’re burning up …”

Finished concept design of Pyrokinetic Keith for the Superhero AU I’m currently working on. I hope to start working on a full comic for this in the very near future. If anyone wants to know more, feel free to let me know!

Keith Kogane - Who Are You Really?

My official contribution to the Voltron fandom! Keith is my fave, and in accordance with season 2 as well as some friends egging me on, I couldn’t help myself and this Fanvid is the result! Enjoy <3

https://twitter.com/AltNatParkSer/status/824070855206600710 

https://www.nps.gov/subjects/climatechange/upload/ClimateChange_01-05_DigitalPrelim.pdf

https://twitter.com/AltNatParkSer/status/824081620240056321

(Image caption: MIT neuroscientists have identified neurons that are responsible for storing memories of familiar individuals. These cells, labeled green, are located in a region of the hippocampus known as the vCA1. Credit: Teruhiro Okuyama)

Scientists identify neurons devoted to social memory

Mice have brain cells that are dedicated to storing memories of other mice, according to a new study from MIT neuroscientists. These cells, found in a region of the hippocampus known as the ventral CA1, store “social memories” that help shape the mice’s behavior toward each other.

The researchers also showed that they can suppress or stimulate these memories by using a technique known as optogenetics to manipulate the cells that carry these memory traces, or engrams.

“You can change the perception and the behavior of the test mouse by either inhibiting or activating the ventral CA1 cells,” says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory.

Tonegawa is the senior author of the study, which appears in the Sept. 29 online edition of Science. MIT postdoc Teruhiro Okuyama is the paper’s lead author.

Tracking social memory

In a well-known study published in 2005, researchers at Caltech identified neurons in the human brain that respond specifically to images of celebrities such as Halle Berry or Brad Pitt, leading them to conclude that the brain has cells devoted to storing memories of people who are familiar.

Many of these cells were found in and around the hippocampus, which is also where the brain stores memories of events, known as episodic memories. The MIT team suspected that in mice, social memories may be stored in the hippocampus’ ventral CA1, in part because previous studies have suggested that this region is not involved in storing episodic memories.

The researchers set out to test this hypothesis using optogenetics: By engineering neurons of the ventral CA1 to express light-sensitive proteins, they could artificially activate or inhibit these cells by shining light on them as the mice interacted with each other.

First, the researchers allowed one mouse, known as the “test mouse,” to spend time with another mouse for two hours, letting the mice become familiar with each other. Soon after, the test mouse was placed in a cage with the familiar mouse and a new mouse.

Under normal circumstances, mice prefer to interact with mice they haven’t seen before. However, when the researchers used light to shut off a circuit that connects the ventral CA1 to another part of the brain called the nucleus accumbens, the test mouse interacted with both of the other mice equally, because its memory of the familiar mouse was blocked.

“The inhibition of ventral CA1 leads to impairment of the social memory,” Okuyama says. “They cannot show any preference for the novel mouse. They approach both mice equally.”

On the other hand, when the researchers stimulated ventral CA1 cells while the test mouse was interacting with a novel mouse, the test mouse began to treat the novel mouse as if they were already acquainted.

This effect was specific to social interactions: Interfering with the ventral CA1 did not have any effect on the mice’s ability to recognize objects or locations that they had previously seen.

Re-awakening memories

When the researchers monitored activity of neurons in the ventral CA1, they found that after a mouse was familiarized with another mouse, a certain population of these neurons began to respond specifically to the familiar mouse.

These patterns could be seen even after the mice appeared to “forget” the once-familiar mice. After about 24 hours of separation, the test mice began to treat their former acquaintances as strangers, but the neurons that had been tuned to the familiar mice still fired, although not as frequently. This suggests that the memories are still being stored even though the test mice no longer appear to remember the mice they once knew.

Furthermore, the researchers were able to “re-awaken” these memories using optogenetics. In one experiment, when the test mouse first interacted with another mouse, the researchers used a light-sensitive protein called channelrhodopsin to tag only the ventral CA1 cells that were turned on by the familiarization treatment. When these neurons were re-activated with light 24 hours later, the memory of the once-familiar mouse returned. The researchers were also able to artificially link the memory of the familiar mouse with a positive or negative emotion.  

Tonegawa’s lab has previously used this technique to identify hippocampal cells that store engrams representing episodic memories. The new study offers strong evidence that memory traces for specific individuals are being stored in the neurons of the ventral CA1, Tonegawa says. “There is some kind of persistent change that takes place in those cells as long as memory is still detectable,” he says.

Larry Young, a professor of psychiatry and director of the Center for Translational Social Science at Emory University, described the study as “one of the most fascinating papers related to social neuroscience I’ve ever seen.”

“In this paper, they identified a subset of cells in a particular brain region that is the engram — a set of cells that through its connections in the nucleus accumbens, actually holds the memory of another individual,” says Young, who was not involved in the study. “They showed that the same group of neurons fired repeatedly in response to the same animal, which is absolutely incredible. Then to go in and control those specific cells is really on the cutting edge.”

The whole process bears an intriguing analogy to quantum mechanics. Physical reality consists in a superposition of wave functions that determine the probability of finding a particle in a certain state. Whenever we care to measure, however, these probabilities collapse to a fixed all-or-none state. We never observe strange mixtures such as the famed Schrödinger’s cat, half alive and half dead. According to quantum theory, the very act of physical measurement forces the probabilities to collapse into a single discrete measure. In our brain, something similar happens: the very act of consciously attending to an object collapses the probability distribution of its various interpretations and lets us perceive only one of them. 

Consciousness acts as a discrete measurement device that grants us a single glimpse of the vast underlying sea of unconscious computations. 

A new study adds to a growing body of research that suggests we might have been thinking about Parkinson’s disease wrong this whole time.

Instead of being isolated to the brain, new evidence in mice suggests that the condition might actually start in the gut. And it could explain some of the strange coincidences seen in the disease, such as why most Parkinson’s patients complain of constipation up to a decade before other symptoms arise.

Parkinson’s disease is most commonly associated with tremors, stiffness, and difficulty moving, caused by neurons deep in the brain being killed off.

Although there are treatments to slow the progress of the condition, there’s no way to prevent or cure it, and researchers still don’t really understand what causes it and how it progresses.

For years, scientists have limited the search for the cause of Parkinson’s to the brain, but a growing body of evidence suggests that might be the wrong approach.

Parkinson’s might actually originate in the gut before spreading to the brain, it could explain some of the strange links researchers have seen with Parkinson’s patients.

Researchers have noticed that people with Parkinson’s often report constipation, as well as other digestive problems, up to 10 years before they notice tremors. There’s also evidence that people with Parkinson’s disease have different gut bacteria to other healthy adults.

Now a new study in mice has shown that the toxic fibres that build up around the nerve cells of Parkinson’s patients can influence the nerves in the brain in a matter of weeks.

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Muscle Memory

Running provides an array of health benefits, not least of which is better brain function. In humans, fitness and exercise is linked to better cognition and memory, for example. While in rodents, running has been shown to enhance both memory and the birth of new brain cells – just like the newly-formed neurons (fluorescent green) shown here in a section of adult mouse brain. Exercise gets the blood pumping and improves blood flow to the brain, which likely provides part of the benefit, but what’s in the blood matters too. Scientists have identified a protein, cathepsin B, secreted into the blood by exercising muscle that, in mice, was necessary for the brain-related benefits of exercise. Cathepsin B induces the production of two important nerve growth factors in cultured neurons, which may explain how this muscle protein prompts the production of new brain cells and, in turn, better memory.

Written by Ruth Williams

Image by Henriette van Praag and Linda Kitabayashi

Neuroplasticity and Behavioral Unit Laboratory of Neurosciences Biomedical Research Center, Baltimore MD, USA

Image copyright held by original authors

Research published in Cell Metabolism, June 2016

The Greenland shark, a massive carnivore that can be more than 16 feet long, hasn’t been studied much, and its life in the cold northern waters remains largely mysterious. Julius Nielsen, at the University of Copenhagen in Denmark, says there had been some hints that Greenland sharks grow very slowly, perhaps less than a centimeter per year. That suggested the huge sharks might be ancient.“We only expected that the sharks might be very old,” says Nielsen.

“But we did not know in advance. And it was, of course, a very big surprise to learn that it was actually the oldest vertebrate animal.”

He and some colleagues obtained 28 female Greenland sharks taken by research vessels as unintended bycatch from 2010 to 2013. The researchers then used radiocarbon dating techniques on the lenses of the sharks’ eyes.

If you’re suffering from depression and are looking for a sign to not go through with ending your life, this is it. This is the sign. We care.