Introduction to Neurogenesis

Throughout history, neuroscientists have commonly believed that once the brain is damaged, there is no way to repair it. However, in the past few years, scientists have discovered that the brain does change throughout life, and can possibly repair itself as well as be enhanced by healthy activities including exercise and proper nutrition. Neurogenesis offers hope to individuals suffering from disorders including Parkinson's, Huntington's, and Alzheimer's disease. One of the main goals of researchers is to develop drugs to stimulate areas of the brain to repair itself by replacing its own cells.(7)(9)

In the 1960's and 1970's, researchers discovered that some parts of the adult brain can repair itself. A number of studies during this time found that the axons of the neurons in the brain and spinal cord can regrow to some degree after trauma. More recently, in 1998, Eriksson and colleagues studied postmortem human brain tissue and found that new neurons were generated in the human hippocampus, an area of the brain that helps regulate memory and learning.(4) Researchers have also found that neurogenesis occurs in adult mice, birds, and other primates. A 1997 study conducted by Kemperman and Gage found that adult mice given enriched living conditions showed a sixty percent increase in new cell growth in the dentate gyrus than the control animals. The animals also did better on learning tasks than the control mice. (9) Scientists are now studying how neurogenesis occurs naturally, and how it can be used to aid in various medical treatments.

New Brain Cells

An image of a brain neuron

In order for new brain cells to develop, multipotent neural stem cells divide in the brain and develop into either neurons or glia. In order to mature, the cells move away from the multipotent cells, and many die. Those that make connections with neurons survive. It takes over a month for the new neuron to be able to send and receive messages, showing that neurogenesis is a controlled process. Neurogenesis is regulated by growth factors that can lead to the development of new cells. Once the cells become either glial cells or neurons, other growth factors including brain-derived neurotrophic factor keep the cells alive.(7)

New neurons in the human brain have been found in the ventricles of the forebrain as well as the hippocampus. The cells that become neurons travel to the olfactory bulbs. Researchers have speculated that neurogenesis occurs in the hippocampus since this area is so important in memory and learning. Other researchers have attempted to discover if neurogenesis occurs in other areas of the brain and spinal cord, but have not yet found conclusive evidence to support this hypothesis. It is anticipated that new techniques will be able to direct neurogenesis in other areas of the brain. Uses of this technique would include enabling the brain to repair damage and to enhance mental functioning. (7)