March 8, 2013
Scientists Find Specific Human Brain Cells That Make Mice Smarter
WATCH VIDEO: [Forebrain Engraftment In Mice]
redOrbit Staff & Wire Reports - Your Universe OnlineA group of non-neural cells found in the human central nervous system may be more essential to the complexity of our brains than previously believed, according to new research published in Thursday´s edition of the journal Cell Stem Cell.
A team led by Steven A. Goldman and Maiken Nedergaard of the University of Rochester Medical Center´s (URMC) Center for Translational Neuromedicine transplanted a special type of glial cells known as astrocytes into mice. By doing so, they learned that the cells could influence communication within the rodent´s brain, allowing the creatures to learn at a faster pace than before.
Astrocytes, which are found in the brain and spinal cord, are responsible for a variety of tasks within the body, including providing nutrients to the nervous tissue and helping to repair nervous system organs following traumatic injuries. According to Goldman and Nedergaard, they are larger and more complex in humans than they are in other creatures, leading them to believe that they may be part of the reason that has given mankind higher-level cognitive functions than other species.
“This study indicates that glia are not only essential to neural transmission, but also suggest that the development of human cognition may reflect the evolution of human-specific glial form and function,” Goldman, co-senior author of the study, said in a statement. “We believe that this is the first demonstration that human glia have unique functional advantages. This finding also provides us with a fundamentally new model to investigate a range of diseases in which these cells may play a role.”
Previous research conducted at URMC has helped scientists learn the role that astrocytes and other glia cells play in brain function. Experts at the New York-based research hospital demonstrated that astrocytes communicate with neurons and with each other, rather than just supporting the neurons.
As Nedergaard explained, while the main role of these cells is to enhance neural transmission, she and her colleagues have also determined that as astrocytes evolve and become larger, more complex, and more diverse — as they have in humans — the complexity of brain function also increases.
Since there are a greater number of astrocytes in men and women than in other species, and they are larger and more diverse, the researchers believe that they could possibly coordinate far more synapses than in mice or similar animals. The URMC researchers' observations led them to believe that these glial cells could help regulate humanity´s higher cognitive functions, and that if they are transplanted into mice, they could have a similar affect.
“In a fundamental sense are we different from lower species,” Goldman said. “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.”
“I have always found the concept that the human brain is more capable because we have more complex neural networks to be a little too simple, because if you put the entire neural network and all of its activity together all you just end up with a super computer [sic],” added Nedergaard. “But human cognition is far more than just processing data, it is also comprised of the coordination of emotion with memory that informs our higher abilities to abstract and learn.”
In order to determine whether or not human glial cells did enhance the brain´s capabilities, the URMC researchers isolated some of the cell progenitors that give rise to astrocytes and transplanted them into the brains of neonatal mice. As those rodents matured, the implanted glial cells overwhelmed the host´s native cells, but did so without damaging the creature´s pre-established neural network.
“The human glia cells essentially took over to the point where virtually all of the glial progenitor 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,” Goldman said.
Closer analysis revealed that the human glia had two major impacts on the brains of the mice.
First, they increased the speed and distance at which a signal travels to and amongst adjacent astrocytes within the brains — a phenomenon known as the calcium wave.
Second, the transplanted mice developed more rapid and sustained long-term potentiation (LTP), which affects how long neurons are affected by brief electrical stimulations. That indicates that the transplanted cells improved the rodents´ learning capabilities.
“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 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.”