Neurogenesis

What is it?

Neurogenesis is the creation of new brain cells.

For more than a century, researchers firmly believed that the brain is an irreparable organ and most new brain cells were created during the pre-natal development. But this belief has modified now. Research conducted over the last two decades has produced growing evidence that new brain cells are born both in childhood and throughout adult life in both vertebrate and invertebrate organisms.

Neurogenesis is thought to be an important mechanism underlying brain plasticity, facilitating organisms to become acclimatized to environmental changes and influencing learning and memory all through their lives.

This is a hot research topic right now, with scientist working on the key questions, like: where neurogenesis happens, how it happens, why it happens, and, more importantly for stroke recovery, how it might help the brain to heal itself.

What does latest research suggest?

Recent research shows that many new neurons survive and integrate themselves into the working brain, suggesting the capability for a self-healing brain. The onus lies on the researchers now to find a way to leverage this knowledge and improve treatments for stroke, as well as for disorders like Alzheimer's, epilepsy and traumatic brain injury using the brain's own restorative potential.

It usually takes over a month for a new neuron to be able to send and receive messages, showing that neurogenesis is a controlled process. To live and become part of the working brain, a new neuron needs not only support from neighbouring glial cells and nutrients from blood, but more importantly from the connections with other neurons. Without these connections, neurons waste away and die.

Areas of the brain involved

The areas of the brain where this has been observed to be most evident include the hippocampus, caudate nucleus, and olfactory bulb. Research conducted so far indicates that the most active area of brain cell generation is the hippocampus, the region of the brain involved in learning and memory.

Refer to the diagram below, produced by the Society for Neuroscience.

Research has revealed that thousands of new cells are produced in the hippocampus every day, although many die within weeks of their birth. One of the main objectives of researchers is to develop drugs to stimulate these areas of the brain to repair itself by replacing its own cells. Obviously, this research is of tremendous interest to stroke survivors.

Influencing factors

Animal studies have shown a link between learning and survival of new neurons in the hippocampus. The scientists found that the more the animal learned, the more neurons survived in the hippocampus. This put forth that cells that were born before the learning experience were more likely to survive to become neurons, but only if the animals actually learned.

There is sufficient evidence to show that physical activity is good for the brain. Research conducted using mice has found that the animals that used a running wheel had double the quantity of new hippocampal neurons as those that didn't exercise.

Stress has been observed to work against the production of new neurons and on the other hand, antidepressant therapy has been found to be a stimulating factor in adult animals.

Hormones such as testosterone in vertebrates and ecdysone in invertebrates have also been found to influence the rate of brain cell creation. Serotonin is believed to play a vital role in neurogenesis in a number of organisms.

All these new discoveries in the field of neurogenesis are opening up many exciting opportunities of research for scientists as they increase their understanding of how our brains work.