Why glial cells – so critical for human intelligence ?
1. Human Glial Cells Make Rats 4 Times Smarter.
It is really surprising to note that despite glial cells making up to 90% of a
human brain, neuroscientists in the 1850s actually choose to ignore them and set the pace for research of our neurons instead. glial cells have since then being considered as a glue that hold the brain cells together. But in past 2 decades, neuroscientists have began to take interest in glial cells and attempted many experiments with them.
To test whether the unique properties of human astrocytes would, first, survive in a normal mouse brain and, second, have some beneficial effect, the researchers isolated human glial progenitor cells and labeled them with a fluorescent protein so they could be identified after transplantation. They injected these cells into the forebrain of mice and examined the results from 2 weeks to 20 months later. They found that mature human astrocytes grew and inserted themselves into the mouse brain, by six months replacing most of the mouse astrocytes. They maintained their unique human size and sent long twisted cellular processes (filaments) through layers of cortical gray (neuron) matter just as they do in the human brain.
They found that these glial stem cells actually proliferate and took over rats original glial cells.
As the mice grew, neuroscientist have discovered that rats with human glial cells become 4 times smarter than their peers.
Just as in humans, the astrocytes participate in the transmission of signals in the gap junctions (synapses) between neurons and, surprisingly, they increased the speed and strength of the signal transmission in mice. This is how the mice became ‘smarter.’ This new research have shed new light on the new roles of glial cell on human intelligent as they have proved themselves capable of improving cognitive capabilities in rats.
Image: After the scientists implanted the cells they monitored them using microscopes. Here, the human cells are shown in green
University of Rochester Medical Centre neurologist Dr Steven Goldman, who led the research, said: “We believe that this is the first demonstration that human glia have unique functional advantages.”
The discovery could also implicate the cells in the formation of disease.
‘This finding also provides us with a fundamentally new model to investigate a range of diseases in which these cells may play a role,’ said Dr Goldman.
Astrocytes are far more abundant, larger, and more diverse in the human brain than they are in other species.
In humans, individual astrocytes project scores of fibres that can simultaneously connect with large numbers of neurons, and in particular their synapses, the points of communication where two adjoining neurons meet.
As a result, individual human astrocytes can potentially coordinate the activity of thousands of synapses, far more than in mice.
It was this observation that gave the researchers the idea for the study – and a hint that that human astrocytes might play a significant role regulating our higher cognitive functions.
This in turn suggested that, when transplanted into mice, human glia may influence underlying patterns of neural activity.
“In a fundamental sense are we different from lower species, our advanced cognitive processing capabilities exist not only because of the size and complexity of our neural networks, but also because of the increase in functional capabilities and coordination afforded by human glia”, said Dr Goldman.
The research team decided to determine if human glial cells might provide the human brain with unique capabilities by seeing what happened when these cells were allowed to co-exist with the normal nerve cells of mice.
They transplanted these cells into the brains of new born mice.
As the mice matured, the human glial cells outcompeted the mice native glial cells, while at the same time leaving the existing neural network intact.
Image: Individual human astrocytes can potentially coordinate the activity of thousands of synapses, far more than in mice.
“The human glia cells essentially took over to the point where virtually all of the glial cells and a large proportion of the astrocytes in the mice were of human origin, and essentially developed and behaved as they would have in a person’s brain,” said Dr Goldman.
The team then set out to examine the functional impact that these cells had on the animals’ brains, specifically the ability of the brain to form new memories and learn new tasks.
They found that two important indicators of brain function drastically improved in the mice with human glia.
First the researchers noted that the speed of brain wave transmission in the transplanted mice was faster than normally observed in mice, and more similar to that of human brain tissue.
Second, the researchers also looked at a process that measures how long the neurons in the brain are affected by a brief electrical stimulation.
In this test as well, the researchers found that the transplanted mice developed in a way that suggested improved learning capability.
On the basis of these findings, the team then evaluated the mice in a series of behavioural tasks designed to test memory and learning ability.
They found that the transplanted mice were more rapid learners and both acquired new associations, and performed a variety of tasks significantly faster than mice without the human glial cells.
“The bottom line is that these mice demonstrated an increase in plasticity and learning within their existing neural networks, essentially changing their functional capabilities,” said Dr Goldman.
“This tells us that human glia have a species-specific role in intellectual capability and cognitive processing. While we’ve suspected for a while that this might be the case, this is really the first proof of this point,” he added.
The researchers believe that this knowledge provides the medical community with a new tool to understand and treat neurological disorders to which glial abnormalities contribute.
2. The brain’s “support cells” may fire electrical impulses like neurons.
University College, London examined glia known as oligodendrocyte precursor cells (OPCs), they were astounded to find that, just like neurons, one subtype fired electrical signals in response to electrical stimulation. Before this study little was known about the function of OPCs, says study leader Ragnhildur Karadottir, except that they could develop into new oligodendrocytes, a type of glial cell that forms an insulating sheath around neurons like the rubber on an electrical cord.
“We were very surprised,” Karadottir says. “The first thing one learns in neuroscience is that neurons fire action potentials and glia do not.” The researchers suspect that, in these glia, action potentials—the rapid electric currents that travel along nerves—might serve as a signal to insulate an active neuron.
3. Humans have the largest ratio of glial cells to neuron in the entire animal kingdom.
For every neuron, there are 9 glial cells surrounding it. Furthermore, neuroscientist have discovered that the ratio of glial cells to neurons increase as you move up the evolutionary trees. In basic organism like worms, they had less than one glial cells per neurons. For monkeys, the number of glial cells and neuron are 1:1, whales is 7.7:1 but for human, it is at 9:1. We have the largest highest number of glial cells per neurons .
Furthermore a specific type of glial cells known as astrocytes are found in exceptional high concentrations in our brain cortex, a part of the brain responsible for higher thoughts.
3. Glial Cells Can Communicate Among Themselves
Scientists at Yale, most notably Ann H. Cornell-Bell and Steven Finkbeiner, have shown that calcium waves can spread from the point of stimulation of one astrocyte to all other astrocytes in an area hundreds of times the size of the original astrocyte. Furthermore, calcium waves can also cause neurons to fire. And calcium waves in the cortex are leading scientists to infer that this style of communication may be conducive to the processing of certain thoughts. If that isn’t convincing, it was recently shown that a molecule that stimulates the same receptors as THC can ignite astrocyte calcium release.
5. Glial Cells Play A Huge Role In Imagination
Neuroscientist have noted that neurons cannot fire on its own, it requires electrical impulses from other neurons to activate it before it fires off its own electrical impulses. Usually the source of electrical impulses comes from our sensory organs. This left neuroscientist pondered about the roles of neurons in higher level of thoughts like imagination and creativity. How can we be in such deep thoughts when we have shut off all our sensory?
New studies have began to emerge that perhaps our glial cells played a huge roles in creativity. During our deep thoughts, the source of electrical impulses does not come from our sensory organ, instead comes from our glial cells which is capable of stimulating neuron with their calcium waves.
6. Albert Einstein with IQ 160 Have Extraordinary Number of Glial Cells
Image: Dr. Thomas Harvey holding a jar containing what’s left of Albert Einstein Brain.
When the famed physicist Albert Einstein passed away in 1955, his brain were removed shortly after death and preserved. Back then, technology were not as advanced and neuroscientist could not decipher the secrets of his brain. But as imaging technology improves, neuroscientist began to observed that Albert Einstein brain were actually lighter and smaller than average but have an extraordinary number of glial cells than others.
And even more surprising is that the concentration of such glial cells were the highest in regions of brain that control spatial awareness and mathematics. This could explain why Albert Einstein become excellent physicist. But more importantly explains the critical roles of glial cells play in human intelligent.
Adapted from various articles of