Tag: Neurons

Scientists Discover A New Type Of Brain Cell In Humans

An international team of 34 scientists has identified a new type of brain cell in humans not found in other well-studied species.

The discovery of “Rosehip” neurons, published today in the journal Nature Neuroscience, raises a number of questions: How does it influence human behavior and experience?

How does it differentiate us from other species? Can it be found in primates and other cognitively advanced species?

But there is one issue this discovery highlights immediately: there’s a neuron in human brains that is missing from the brains of mice and other animals used to model human brains in experiments.

Does this mean current animal models yield distorted results? “If we want to understand how the human brain works, we need to study humans or closely related species,” says Trygve Bakken, co-author of the paper and a neuroscientist at the Allen Institute for Brain Science.




The flow of info

Rosehip neurons are inhibitory neurons that form synapses with pyramidal neurons, the primary excitatory neurons in the prefrontal cortex.

We all have inhibitory neurons and excitatory neurons,” says Bakken, “but this particular type of inhibitory neuron is what’s new in this study. It’s special based on its shape and its connections and also the genes that it expresses.

When a traffic signal turns red it helps controls the flow of traffic. Similarly, inhibitory neurons help control the flow of electrochemical information.

The type of information rosehip neurons control, and why they appear particular to humans, is yet to be discovered. “It has these really discrete connections with [pyramidal] neurons,” says Bakken.

It has the potential to sort of manipulate the circuit in a really targeted way, but how that influences behavior will have to come in later work.”

Found in the neocortex of human brains

The researchers identified rosehip neurons by looking at brain samples from two males who died in their 50’s and donated their bodies to science.

The brain slabs were tissue from the neocortex, a most recent evolutionary development inside our skulls responsible for higher-order thinking.

The neocortex, the outermost layer of cells, is greatly expanded in humans–about a thousandfold compared to mice,” says Bakken.

From neurological studies, if you have a stroke in your neocortex for example, it really impacts your ability to do these sorts of high-order cognitive processing.

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Honey Bees Can Understand Nothing

Zero, zilch, nothing, is a pretty hard concept to understand. Children generally can’t grasp it until kindergarten. And it’s a concept that may not be innate but rather learned through culture and education.

Throughout human history, civilizations have had varying representations for it. Yet our closest animal relative, the chimpanzee, can understand it.

And now researchers in Australia writing in the journal Science say the humble honey bee can be taught to understand that zero is less than one.

The result is kind of astounding, considering how tiny bee brains are. Humans have around 100 billion neurons. The bee brain? Fewer than 1 million.

The findings suggest that the ability to fathom zero may be more widespread than previously thought in the animal kingdom — something that evolved long ago and in more branches of life.




It’s also possible that in deconstructing how the bees compute numbers, we could make better, more efficient computers one day.

Our computers are electricity-guzzling machines. The bee, however, “is doing fairly high-level cognitive tasks with a tiny drop of nectar,” says Adrian Dyer, a Royal Melbourne Institute of Technology researcher and co-author on the study.

Their brains are probably processing information in a very clever [i.e., efficient] way.”

But before we can deconstruct the bee brain, we need to know that it can do the complex math in the first place.

How to teach a bee the concept of zero

Bees are fantastic learners. They spend hours foraging for nectar in among flowers, can remember where the juiciest flowers are, and even have a form of communication to inform their hive mates of where food is to be found.

Researchers train bees like they train many animals: with food. “You have a drop of sucrose associated with a color or a shape, and they will learn to reliably go back to” that color or shape, Dyer explains.

With this simple process, you can start teaching bees rules. In this case, the researchers wanted to teach 10 bees the basic rules of arithmetic.

So they put out a series of sheets of paper that had differing numbers of objects printed on them. Using sugar as a reward, the researchers taught the bees to always fly to the sheet that had the fewest objects printed on it.

Once the bees learned this rule, they could reliably figure out that two shapes are less than four shapes, that one shape is smaller than three. And they’d keep doing this even when a sugary reward was not waiting for them.

And then came the challenge: What happens when a sheet with no objects at all was presented to the bees? Would they understand that a blank sheet — which represented the concept of zero in this experiment — was less than three, less than one?

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How Your Brain Tells Time

In the middle of your brain, there’s a personal assistant the size of a grain of rice. It’s a group of about 20,000 brain cells that keeps your body’s daily schedule.

Partly in response to light signals from the retina, this group of neurons sends signals to other parts of the brain and the rest of the body to help control things like sleep, metabolism, immune system activity, body temperature and hormone production on a schedule slightly longer than 24 hours.

Daniel Forger, a mathematics professor at the University of Michigan who uses math to study biological processes, wants to understand this brain region, called the suprachiasmatic nucleus (SCN) in excruciating detail.




He is building a mathematical model of the entire structure that he thinks will shed important light on our circadian rhythm, and perhaps lead to treatments for disorders like depression and insomnia, and even diseases influenced by the internal clock like heart disease, Alzheimer’s and cancer.

I think we’re going to be able to have a very accurate model of the circadian rhythm, all the key proteins, all the electric activity of all 20,000 neurons,” he says.

We’ll be able to track all of them for days on a timescale of milliseconds.

Forger has already taken a few steps down this path and found some surprises.

In a paper published in a recent issue of the journal Science, Forger, along with colleagues Mino Belle and Hugh Piggins of the University of Manchester in England and others, showed that the firing pattern of the time-keeping neurons in the SCN was not at all what researchers had long thought.

Researchers who studied the electrical activity of the SCN had believed that the neurons there helped the body keep time by sending lots of electrical signals during the day, and then falling silent at night. Makes sense. Lots of non-teenage creatures are active during the day and quiet at night.

But when Forger used experimental data to build a mathematical model of the electrical activity, he calculated that there should be lots of activity at dawn and dusk, and a state of “quiet alertness” during the day. That didn’t make much intuititve sense.

Worse, the cellular chemistry during this quiet period that Forger’s model predicted would, in normal cells, lead quickly to cell death.

Skepticism doesn’t begin to describe what I was met with,” says Forger. “Experimentalists told me, ‘That’s crazy.’”

Researchers in the field simply assumed Forger’s model was wrong. Forger refined it and reworked it, and got similar results.

Meanwhile, his British colleagues began to probe the fact that there are two types of cells in the SCN, ones that have very strong molecular clocks and do the timekeeping, and others that behave more like normal brain cells.

While previous researchers had recorded the activity of all of the cells in the SCN, Belle and Piggins were able to set up an experiment using mice that would record only the activity of the clock cells. Their experimental results matched Forger’s predictions.

When we got the results, they were shocking,” Forger says. “They were dead on.”

The cells in the SCN that don’t keep time followed the pattern researchers were familiar with, active during the day, quiet at night.

The time-keeping cells went bananas in the morning and at night, but then during the day they stayed in a bizarre state of excitement during which they emitted very few impulses. Why these cells can stay alive in this state remains a mystery.

Forger has been down this path before. Another study of his, published in 2007, reversed the thinking on how gene mutations affect circadian rhythms within cells.

Scientists studying a hamster that had a malfunctioning internal clock (its daily rhythm lasted 20 hours instead of 24) found that it had a mutation in a gene called tau.

The fuzzy rodent was given the extremely appropriate name “Tau Mutant Hamster.

They thought Tau Mutant Hamster’s mutation caused an enzyme that helped cells keep time to be less active. Forger predicted that it would instead make the enzyme more active. Experiments later proved he was right.

Now Forger is turning his attention to the entire SCN. He thinks that math is the only way we can understand the sheer complexity of what is happening–neurotransmitters coming and going, protein clocks being built up and broken down, electricity bouncing around.

To piece it all together, you need more than intuition,” he says. “You need math to see what’s going on.”

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Growing Human Brain Cells In The Lab

When researchers like Gan find potential new drugs, they must be tested on human cells to confirm they can benefit patients. Historically, these tests have been conducted in cancer cells, which often don’t match the biology of human brain cells.

The problem is that brain cells from actual people can’t survive in a dish, so we need to engineer human cells in the lab,” explained Gan, senior investigator at the Gladstone Institutes. “But, that’s not as simple as it may sound.”

Many scientists use induced pluripotent stem cells (iPSCs) to address this issue. IPSCs are made by reprogramming skin cells to become stem cells, which can then be transformed into any type of cell in the body.

Gan uses iPSCs to produce brain cells, such as neurons or glial cells, because they are relevant to neurodegenerative disease.




Human brain cells derived from iPSCs offer great potential for drug screening. Yet, the process for producing them can be complicated, expensive, and highly variable.

Many of the current methods produce cells that are heterogeneous, or different from one another, and this can lead to inconsistent results in drug screening.

In addition, producing a large number of cells is very costly, so it’s difficult to scale up for big experiments.

To overcome these constraints, Michael Ward, MD, PhD, had an idea.

A New Technique Is Born

I came across a new method to produce iPSCs that was developed at Stanford,” said Ward, a former postdoctoral scholar in Gan’s lab who is now an investigator at the National Institutes of Health.

I thought that if we could find a way to simplify and better control that approach, we might be able to improve the way we engineer human brain cells in the lab.”

Ward and his colleague Chao Wang, PhD, discovered a way to manipulate the genetic makeup of cells to produce thousands of neurons from a single iPSC. This meant that every engineered brain cell was now identical.

The team further improved the technique to create a simplified, two-step process. This allows scientists to precisely control how many brain cells they produce and makes it easier to replicate their results from one experiment to the next.

Their technique also greatly accelerates the process.

While it would normally take several months to produce brain cells, Gan and her team can now engineer large quantities of them within 1 or 2 weeks, and have functionally active neurons within 1 month.

The researchers realized this new approach had tremendous potential to screen drugs and to study disease mechanisms. To prove it, they tested it on their own research.

They applied their technique to produce human neurons by using iPSCs. Then, they developed a drug discovery platform and screened 1,280 compounds.

Their goal is to identify the compounds that could lower levels of the protein tau in the brain, which is considered one of the most promising approaches in Alzheimer’s research and could potentially lead to new drugs to treat the disease.

A Powerful Tool for the Entire Scientific Community

We have developed a cost-effective technology to produce large quantities of human brain cells in two simple steps,” summarized Gan.

By surmounting major challenges in human neuron-based drug discovery, we believe this technique will be adopted widely in both basic science and industry.

Word of this useful new technology has already spread, and people from different scientific sectors have come knocking on Gan’s door to learn about it.

Her team has shared the new method with scores of academic colleagues, some of whom had no experience with cell culture.

So far, they all successfully repeated the two-step process to produce their own cells and facilitate scientific discoveries.

Details of this new technique were also published on October 10, 2017, in the scientific journal Stem Cell Reports.

With some of the roadblocks out of the way, Gan hopes more discoveries will soon help the millions who suffer from Alzheimer’s disease.

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Scientists Discovered That Taste Comes From The Brain, Not The Tongue

Researchers in the US have turned taste on and off in mice simply by activating and silencing certain brain cells.

This demonstrates for the first time that taste is hardwired in the brain, and not dictated by our tastebuds, flipping our previous understanding of how taste works on its head.




It was previously thought that the taste receptors on our tongue perceived the five basic tastes – sweet, salty, sour, bitter, and umami – and then passed these messages onto our brain, where it registered what we’d just tasted.

But the new study shows that although our tongues do detect the presence of certain chemicals, it’s our brains that perceive flavour.

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