Neurogenesis in adulthood - its functions and influencing environmental factors

Neurogenesis is a process in which neurons are generated neural stem cells (NSCs) and progenitor cells. During this process, neurons are either renewed itself by neural stem cells or newly generated as newborn neurons from a type of biological stem cells called progenitor (See Fig.3). This process is highly active during prenatal development resulting to rapid growth in cranial volume. Scientists have found out that neurogenesis is still happening throughout adulthood, however, at a significantly slower rate. This process has been also shown to be predominantly occurring in two distinct cranial regions, which are: the hippocampus and the subventricular zone. For better understanding, the attached figures below (Fig.1 & Fig.2) illustrate the relative locations of these two parts in a human brain:

Figure 1: The hippocampus

Figure 2: The subventricular zone

Figure 3: Differentiating process of NTCs and progenitor cells to more specialized neural cells.

In recent years, scientists have been studying about factors that trigger neurogenesis in late adulthood and main functions of newborn neurons. Given that, the hippocampus in human are responsible for the consolidation of information from short-term memories to long-term memories, which means this region is highly related to learning processes. Meanwhile, subventricular zone is a “hot spot” for generation of self-renewing neurons, which also performs many interaction between neural cells and maintains multipotent abilities of neurons. Therefore, scientists from Princeton University have revealed that neurogenesis in adults has profound functions of learning process as adaptations to the environment. Since the environment is constantly changing and human beings are learning new things everyday by encountering different people and experience their lives differently each day. Overall, the birth of new neurons is generated due to the environmental adaptation and plays a significant role in learning processes, behavioral and cognitive tasks.

After performing many tests on humans and other mammals with different cognitive-dependent tasks, scientists have also found that stress-induced situations and anxiety such as restraint, social defeat, exposure to predator odors, inescapable foot shock, and sleep deprivation leads to a decrease in the production of neurons. In contrary, rewarding experiences such as mating, physical exercises increase the production of new neurons.

 
Furthermore, neurogenesis can be controlled in laboratories at molecular level, however, scientists are hoping for further investigation of further real world circumstances that are directly related to the generation of new neurons. 

- Posted by Phi Duong (Group A)