For decades scientists thought that neurons in the brain were produced only during the early stages of development and could not be supplemented. Recently, however, they found that these cells have the ability to divide and turn into new neurons in specific brain regions. The function of these neural precursor cells remains a hot area of research. Scientists from the National Institutes of Health (NIH) report that the new brain cells in the mouse olfactory system, the area that handles odors, play a crucial role in maintaining proper cell connections, The results of the study were published in the October 8, 2014 issue of Journal of Neuroscience.
The first author, NIH National Institute of neurological disorders and stroke (NINDS) scientist Dr. Belluscio Leonardo pointed out: "for the brain stem cells, this is the new role of a surprising and change how we think about the way they are."
The olfactory bulb (olfactory bulb) is located in the anterior part of the brain and receives information directly from the nose about environmental odors. The neurons in the olfactory bulb sorted the messages and relayed the signals to other parts of the brain, and then we realized the smells we were experiencing. Loss of smell is often an early symptom of various neurological disorders, including Alzheimer's disease and Parkinson's disease.
In one called neurogenesis (neurogenesis) in the process of generation of adult neural progenitor cells (adult-born), is produced in deep brain subventricular zone in, and migrate to the olfactory bulb, they think there is its final position. Once in place, they become associated with existing cells and are incorporated into the neural circuit.
Dr. Belluscio of the olfactory system, researcher Heather Cameron teamed up with the occurrence of NIH of the National Institute of mental health, the nerve, to better understand what is the effect of continuously adding loop structure of the olfactory bulb of new neurons. The researchers used two specially designed mouse types to specifically target and eliminate stem cells producing these new neurons in adults, while keeping other olfactory bulb cells intact. This specificity has not been achieved before.
In the first group of mice experiments, Dr Belluscio's team first blocked the tissue of the olfactory circuit by temporarily blocking one nostril in animals, preventing olfactory sensory information from entering the brain. Previous research in his laboratory showed that this form of sensory deprivation (sensory, deprivation) could make certain predictions in the olfactory bulb dramatically spread out and lose the precise pattern of connectivity exhibited under normal conditions. These studies also show that once sensory deprivation is reversed, this widely interrupted loop can re organize itself and restore its original accuracy.
However, in the current study, Dr. Belluscio's laboratory found that once the nose is unobstructed, the loop is still in disarray if new neurons are prevented from forming and entering the olfactory bulb. "We found that without the introduction of new neurons, the system would not recover from the state of destruction," Dr. Belluscio said."
To investigate this concept further, his team eliminated the formation of adult neurons in mice without sensory deprivation. They found that the olfactory bulb tissue began to break, similar to the pattern seen in animals that were prevented from receiving sensory information from the nose. They observed a link between the extent of stem cell loss and the number of loop disruptions, suggesting that more damage to stem cells could lead to greater levels of confusion in the olfactory bulb.
According to Dr Belluscio, it is widely believed that the loop in the adult brain is fairly stable and that the introduction of new neurons alters the existing loop and then re organization it. He said: "however, in this case, the loop seems to be inherently unstable, often need to supply new neurons, not only to restore the organization after the interruption, but also to maintain its stable or mature structure. Despite the constant replacement of cells in this olfactory loop, it has not changed in normal circumstances, which is quite alarming."
Belluscio and colleagues speculate that new neurons in the olfactory bulb may be important in maintaining or regulating the activity dependent changes in the system, which can help animals adapt to changing environments.
"We were excited to find that the new neurons affect the precise connections between neurons in the olfactory bulb," Dr. Cameron said. Because new neurons in the whole brain share many common features, it is likely that other regions (such as the sea horse, involved in memory) neurogenesis also produce similar connectivity changes."
The underlying basis for the relationship between neurological diseases and changes in the olfactory system is unknown, but it may be due to our better understanding of how olfaction works. "This is an exciting field of science," Dr. Belluscio said. I think the olfactory system is very sensitive to changes in neural activity, and in light of its association with other brain regions, we should have a better understanding of the relationship between loss of smell and many brain diseases."