What makes humans different from the rats?

According to the researchers, there is a type of brain cell that has long been overlooked in one of the aspects that make the human brain fundamentally different from that of a mouse or rats. They published their findings on the March 11 issue of Neuroscience.

Scientists at Rochester Medical Center University found that human astrocytes (cells thought to support only glowing brain cells, or those that transmit electrical signals), much faster and more complex than a star cell in the brain of mice and rats.

The author and doctor Nancy Ann Oberheim, a medical student who has just completed a doctoral thesis on astrocytes, said: 'There is not much between the brain between the brain and the rodent's brain. But we found big differences in astrocytes. Our astrocytes are faster, bigger and more complex. This has great implications for the way our brain processes information '.

Research is one of the most extensive surveys of stellar brain cells. Oberheim and colleagues discovered a previously unknown form of a star cell found only in the human brain, not in the brain of mice. The team also found that the most common form of stellar cells - protozoan cells, is about 2.6 times larger than the same cells in mice. Meanwhile, human cells have 10 times more processes or structures related to other cells than mice.

Neuroscience expert Maiken Nedergaard, who led the study, said : 'We still can't really understand why the human brain is more capable than the brains of other animals. Some people think that simply the larger human brain is more versatile, but the elephant's brain is bigger than our brain but it is not really resourceful. So size is not the answer '.

Nedergaard, who spoke last week at Gordon Research Conference, added: 'It is possible that the human brain is more likely than our star cells to be more complex and have higher processing power. . Rodent studies show that non-neuronal cells also participate in information processing, and our study suggests that it is the star cells that carry the high cognitive function specified. we are human. '

Astrocytes have long been thought to be passive support cells, a way to bind brain cells together like glue. Many medical students may take only a few minutes to consider astrocytes before switching to their relatives - it is the neurons that transmit electrical signals that are of great importance to most of us. do. It is the activity of neurons that makes what most scientists think is the activity of the brain. And it's the neurons that are the object of the existing drugs aimed at brain cells. If star cells are really important, the reason may be that they help create a healthier environment for neurons.

It turns out that astrocytes are 10 times more massive than neurons, they are pushed to the boundaries of neuroscience because of the tools used in brain research. Scientists identify signals between brain cells primarily by observing electrical activity. Non-luminous star cells are like neurons, so conventional techniques cannot record their activity. When scientists use conventional techniques, they cannot see anything.

In addition to recognizing the tool's imperfections, scientists also claim that star cells are quite quiet. So Nedergaard created a new way of detecting stellar activity, thereby developing a complex laser system to observe activity by determining the amount of calcium inside the cell. Her research team discovered what could be called the mysterious life of a stellar cell, while also providing a series of startling findings. Star cells use calcium to transmit signals to neurons, and neurons respond to this signal. Neurons and stellar cells transmit signals back and forth, indicating that astrocytes are partners in the brain's basic 'transaction' , they are the center of conditions such as stroke, Alzheimer's, epilepsy and spinal cord injury.

In the photo of brain tissue, astrocytes are yellow. (Photo: Image courtesy of University of Rochester Medical Center)

Oberheim said: 'The doctrine of faith is very difficult to change, and one of the dogmatic beliefs of glass science is that astrocytes are just supporting cells that do not fulfill the task. This view will take some time to change, but scientists are becoming aware. Star cells are now considered active members of brain functions as well as sensor processing '.

Two brain signaling systems - one including neurons, and the other including astrocytes - have complementary effects. Neurons transmit signals extremely fast over a long distance - for example, our hands touch the heater, the brain detects danger and drives the hand away immediately. Astrocytes, on the other hand, transmit signals more slowly. Their function is still being studied by scientists.

Nedergaard said: 'The brain contains two information networks that use different languages. A sophisticated electrical network consists of instantaneous neurons. The much slower second network consists of astrocytes at a rate of about 10,000 times slower, but can process information at a more refined level with reminiscent memory. "

Nedergaard added: 'No other tissue in the cell is made up of a mixture of two complete cell types such as the distribution of astrocytes and neurons in the brain. Both create extensive signal networks. Where and how they interact makes the brain a charismatic topic. '

To conduct the study, the team of scientists investigated brain tissue taken from 30 people who underwent surgery mostly to treat epilepsy or brain tumors. They compared astrocytes in the human brain and stellar cells in the brains of mice and rats. In addition to the above findings, the group also found other differences: The human cells transmit signals five times faster than the speed in mice.

Human star cells are organized into more complex units called regions compared to rodent star cells. On average, a rodent animal has tens of thousands of synapses, while the team found that a human area may contain up to 2 million joints. These regions are highly organized cell groups, seemingly positioned correctly, like molecules in crystals. According to Nedergaard, this organization is very important for information processing. She also stressed that brain damage is related to the lack of regional organization of astrocytes and cognitive function is impaired.

For humans, the so-called new astrocytes have a structural support function that is generally twice as large as the same cells in mice and rats. In addition, humans have another type of cell called interstellar astrocytes, which are not found in mice. Another difference is related to the end point of primitive astrocytes, which surround the blood vessels in the brain and are thought to play a role in blood circulation in the brain. These end points in humans surround the blood vessel wall more completely than mice. Perhaps this phenomenon plays an important role in preventing blood agents from invading the brain as well as regulating blood circulation.

The main authors include: Professor Dr. Steven Goldman and Chair of Neurology Department; Master Webster Pilcher and lecturer and chair of neurosurgeon; Jeffrey Wyatt - professor and chairman of the Department of Comparative Medicine; along with assistant professors: Dr. Takahiro Takano, Dr. Xiaoning Han, Dr. Wei He, and Dr. Fushun Wang.

Also participating in the study were Qiwu Xu and Dr. Jane Lin of the New York School of Medicine; Master Jeffrey Ojemann, and Dr. Bruce Ransom of the University of Washington where Oberheim completed her doctoral dissertation under Nedergaard's supervision.

The study received support from the G. Harold and Leila Y. Mathers Charitable Foundation and the National Institute of Stroke and Neurological Disorders.

Refer:
Nancy Ann Oberheim, Takahiro Takano, Xiaoning Han, Wei He, Jane HC Lin, Wang Fushun, Qiwu Xu, Jeffrey D. Wyatt, Webster Pilcher, Jeffrey G. Ojemann, Bruce Ransom, Steven A. Goldman, and Maiken Nedergaard.Uniquely Hominid Features of Adult Human Astrocytes.Journal of Neuroscience, 2009;29 (10): 3276 DOI: 10.1523 / JNEUROSCI.4707-08.2009