Function of Mature Neurones in the Brain

Neurobiologist talks about neuronal migration, the value of the hippocampus and infantile amnesia

In the mammalian brain is constantly going on the formation of new neurons. And one of the important issues is figuring out what these neurons and, in fact, the brain needs. In general, the human brain has 98 billion neurons, they are all connected with each other in a complex manner with the help of contacts and processes. It turns out that in this architecture, the brain is no place for a new neurons. We have formed during the life of the individual experience, there are some new memories, we acquire new skills - all in the brain neural networks is provided. The emergence of new neurons in the brain, in theory, should lead to the fact that these formed neural network must either be modified or disrupted. That is why for a long time it was thought that a new neurons in the brain may not appear because the introduction of new neurons in the brain gives rise to some uncertainty. However, the new neurons in the brain are constantly emerging, and hence, they are for some reason needed.

For improving brain functionality there are drugs: Semax, Noopept, Picamilon and Phenotropil.

The first explanation of why we need new neurons in the brain that occur in the head - is that new neurons are necessary for the restoration process for the regeneration process. If so, then we need to detect the brain areas where the products are constantly new neurons, as occurs in the development. Such areas should be a lot, and in different parts of the brain. However, this was not entirely true. In the brain neurogenesis it is only in two areas - it subventricular zone and hippocampus. Perhaps neurogenesis in the adult brain, and is at least a few areas, but the cells can migrate in various areas of the brain. Testing this hypothesis has shown that this is not so.

Neurons, which are formed in the hippocampus, not migrate away from the layer where the stem cells, they migrate only a distance of two or three cell diameters and are practically in the same place are produced. Neurons in the subventricular zone migrate indeed a very great distance, and they migrate to the olfactory bulbs are clearly defined in a way that limits glial tube. In other regions of the subventricular zone of neurons do not migrate. It has been shown that under certain pathological processes migrating neurons from the SVZ into striatal can enter - this is one of the brain structures. But, for example, in close overlying the subventricular zone of the cortex neurons do not migrate. Thus, the second hypothesis that neurons can migrate over long distances for the recovery of some disturbances in the brain was confirmed also experimentally.

The third assertion, which would have to be verified experimentally if the new neurons are needed to restore the brain - is that new neurons, stem cells contained in the brain, should produce different types of neurons, ie, the diversity of neurons, which are in the brain. It turned out that this is not so. It was found that the cells formed in the adult brain, deterministic and their fate predetermined, they can be converted only in certain classes of neurons, which are located in certain areas of the brain. Thus, it should be said that brain reduction with new neurons likely occurs.

Then why do we need new neurons? The second explanation - they probably needed for normal functioning of the brain. Because the sense of smell in rodents is a very important sense organ and in rodents there is a very active neurogenesis is in the olfactory bulb, a human sense of smell is not as important neurogenesis he is not in the olfactory bulb, it is one of the evidence that, in fact, new neurons are needed to operation. In particular, in rodents these neurons are involved in learning, olfactory that uses keys.

One of the most studied in terms of the functional purpose area is the area of the hippocampal neurons. It was shown that new neurons we need to remember.
Generally hippocampus - structure is critical to memory formation processes, in particular for spatial memory formation. So the first thing the researchers began to check - if we take and somehow will inhibit neurogenesis, how it will affect our ability to memorize or animal space capacity? It turned out that if the decrease neurogenesis radiation or some genetic effects, that is, to create genetically modified animals, the capacity for spatial learning in animals does not suffer. However, those animals with reduced neurogenesis, suffered very subtle mechanisms of memory formation, namely the animals ceased to distinguish between similar memories. This was shown in the following experiments: if you take the mouse, place it in a specific environment and there it hit the shock - it's called the classical technique of conditioned reflex fading, the current does not create a mouse very severe pain, but makes her uncomfortable, and she remembers that this the situation is dangerous. If the animal is then put in the same situation, the animal starts to fade, it will begin to show that it is aware that this situation is dangerous. If the animal is put in a similar situation, the animals are in good neurogenesis well you will show that this new situation, though similar to the old, but it is absolutely not dangerous. But if neurogenesis in mice disrupted, they no longer distinguish a similar situation of danger.

In such experiments it was shown that new neurons are needed to similar memories are not superimposed on each other, not interfered to similar memories were located side by side, but do not overlap. One of the particular manifestations of such overlapping, seemingly memories is our ability to retraining. Perhaps, when we go to work, we have already clearly formed on the machine where it is necessary to make a connection, where it is necessary to go further. If you suddenly change jobs and have to go to another metro station, then at the first attempt, we make mistakes, leaving, for example, at the station, but after several attempts, we well remember what to do transfer to another station. Apparently, if disrupted neurogenesis in the hippocampus, this ability to retraining may start to suffer. It was shown again in animals.

If the animal train layout, a water maze, a swimming pool, where there is a hidden platform under the water, the animal gradually learns where this platform, and external spatial keys it stores location. If the mouse is trained to put into this pool, it starts to swim and, looking around, comes out onto the platform, where the keys are. Then, if the platform change to a different location, click start to quickly retrain for a new position of the platform. However, in the case of impaired neurogenesis is retraining requires a lot more attempts. That is, apparently, in the early stages still there is some overlap of similar memories, because the same pool, the same keys, only the position of the platform is different. Apparently, new neurons are also needed, not only to distinguish similar memories that differentiate them in the formation of similar memories, but also, apparently, to the forgetting process.

There is a phenomenon that is called infantile amnesia. If you ask a man when he is starting to remember, it turns out that most people remember myself since the age of four, and all that was before, as if the memory is erased. Perhaps this is due to a memory erasing early new neurons in the brain. In particular, it has been shown experimentally. Taught the same skills and young adult mice and then tested, the memory is stored in the animals for one month. And it turned out that the adult animal remembers what they were beaten shock in context throughout the month, while young animals in about two weeks to forget that they were beaten in the current environment. Moreover, it was shown that if the animals were running in the wheel - and the wheel running almost doubles neurogenesis in the brain - as the shifty animals acquired skill will forget than animals that did not run in the wheel.

The new neurons in the brain that appear to possess special properties. For example, they are hyperexcitability, and thanks to this their hyperexcitability, and they are able to somehow modify the memory.
Further elucidation of the functions of new neurons in the brain is progressively developing field of neuroscience, and an understanding of why we need new neurons in the brain, it is very important for several reasons. First of all, because people are constantly exposed to influences that may potentially reduce neurogenesis, - a diagnostic procedure when they are irradiated with radiation, it hops on aircraft where the same planes insufficiently shielded against radiation, and also in the light of future missions, long flights in space . Perhaps the astronauts who will fly to Mars, perhaps even fly, but what will happen to their cognitive functions? Will they be able to compare and easily retrained in similar problems? All of these issues now is still open.