New nerve cells even in old age
After birth the brain looses many nerve cells and this continues throughout life – most neurons are formed before birth, after which many excess neurons degenerate. However, there are some cells that are still capable of division in old age – in the brains of mice, at least. According to scientists from the Max Planck Institute of Immunobiology in Freiburg, different types of neuronal stem cells exist that can create new neurons. While they divide continuously and create new neurons in young animals, a large proportion of the cells in older animals persist in a state of dormancy. However, the production of new cells can be reactivated, for example, through physical activity or epileptic seizures. What happens in mice could also be applicable to humans as neurons that are capable of dividing also occur in the human brain into adulthood. (Cell Stem Cell, May 7th 2010)
You can't teach an old dog new tricks.
The corresponding view that the brain loses learning and memory capacity with advancing age prevailed for a long time. However, neuronal stem cells exist in the hippocampus – a region of the brain that plays a central role in learning and memory functions –that can produce new nerve cells
throughout life.
It is known from tests on mice that the newly formed cells are integrated into the existing networks and play an important role in the learning capacity of animals. Nonetheless, the formation of new cells declines with age and the reasons for this were unknown up to now.
The scientists observed more newborn hippocampal neurons in physically active mice than in their inactive counterparts. "Consequently, running promotes the formation of new neurons," says Verdon Taylor.
Pathological brain activity,
for example that which occurs during epileptic seizures,
also triggers the division of the neuronal stem cells.
The different stem cell populations are easy to distinguish under the microscope. The first group comprises cells which lie perpendicular to the surface of the hippocampus. Most of these radial stem cells are dormant. As opposed to this, over 80% of the cells in the group of horizontal stem cells – cells whose orientation runs parallel to the hippocampus surface – continuously form new cells; the remaining 20% are dormant but sporadically become activated. The activity of genes such as Notch, RBP-J and Sox2 is common to all of the cells.
Radial and horizontal stem cells differ not only in their arrangement, apparently they also react to different stimuli. When the animals are physically active, some radial stem cells abandon their dormant state and begin to divide, while this has little influence on the horizontal stem cells. The result is that more radial stem cells divide in active mice.
The horizontal stem cells, in contrast,
are also influenced by epileptic seizures.
It would appear that neuronal stem cells are not only found in the brains of mice. The presence of
neurons that are formed over the course of life
has also been demonstrated in the human hippocamus.
Therefore, scientists suspect that different types of active and inactive stem cells also arise in the human brain. It is possible that inactive stem cells in humans can also be activated in a similar way to inactive stem cells in mice.
"There are indicators that
the excessive formation of new neurons
plays a role in epilepsy.
The use of neuronal brain stem cells in the treatment of brain injuries or degenerative diseases like Alzheimers may also be possible one day," hopes Verdon Taylor.
Source: Max-Planck-Gesellschaft
Monday, May 17, 2010
New view on developing brain
Mechanism found
that prepares the brain of a newborn
for information processing
With their French colleagues, researchers at the University of Helsinki have found a mechanism in the memory centre of newborn that adjusts the maturation of the brain for the information processing required later in life. The study was published this week in an American science magazine The Journal of Neuroscience.
The brain cells in the brain of a newborn are still quite loosely interconnected. In the middle of chaos, they are looking for contact with each other and are only later able to operate as interactive neural networks.
Many cognitive operations, such as attention, memory, learning and certain states of sleep are based on rhythmic interactions of neural networks. For a long time the researchers have been interested in finding the stage in the development of the brain in which the functional characteristics and interconnections are sufficiently developed for these subtle brain functions.
Key players in this maturation process include a type of nerve cells called interneurones, and recent research sheds light on their functional development. The researchers have noticed that the activeness of the interneurones change dramatically during early development. In the memory centre of the brain they found a mechanism which adjusts changes in the activeness of interneurones.
The interneurones nerve cells are kind of controller cells. In the nervous system of a newborn they promote the creation of nerve cell contacts, and on the other hand they prevent premature rhythmic activity of neural networks. During development the controlling role will change, and the result is that the neural network becomes more efficiently rhythmic. This can be seen, for example, in the strengthening of the EEG signal during sleep.
The mechanism adjusting the activity of the interneurones is related to the development phase which prepares the brain to process and handle information needed later in life. The finding may also offer more detailed means to intervene in the electric disorders of developing neural networks, such as epilepsy.
Source: University of Helsinki
that prepares the brain of a newborn
for information processing
With their French colleagues, researchers at the University of Helsinki have found a mechanism in the memory centre of newborn that adjusts the maturation of the brain for the information processing required later in life. The study was published this week in an American science magazine The Journal of Neuroscience.
The brain cells in the brain of a newborn are still quite loosely interconnected. In the middle of chaos, they are looking for contact with each other and are only later able to operate as interactive neural networks.
Many cognitive operations, such as attention, memory, learning and certain states of sleep are based on rhythmic interactions of neural networks. For a long time the researchers have been interested in finding the stage in the development of the brain in which the functional characteristics and interconnections are sufficiently developed for these subtle brain functions.
Key players in this maturation process include a type of nerve cells called interneurones, and recent research sheds light on their functional development. The researchers have noticed that the activeness of the interneurones change dramatically during early development. In the memory centre of the brain they found a mechanism which adjusts changes in the activeness of interneurones.
The interneurones nerve cells are kind of controller cells. In the nervous system of a newborn they promote the creation of nerve cell contacts, and on the other hand they prevent premature rhythmic activity of neural networks. During development the controlling role will change, and the result is that the neural network becomes more efficiently rhythmic. This can be seen, for example, in the strengthening of the EEG signal during sleep.
The mechanism adjusting the activity of the interneurones is related to the development phase which prepares the brain to process and handle information needed later in life. The finding may also offer more detailed means to intervene in the electric disorders of developing neural networks, such as epilepsy.
Source: University of Helsinki
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