Glial Cells and Neurogenesis

Your Brain: Neurons and Glia

Our brains are composed of two main cell types: neurons and glia. 

Neurons are nerve cells, responsible for taking up, processing, and transmitting information through electrical and chemical signals. Neurons carry stimuli, allowing you to react to your environment. When you hold your hand too close to a hot stove, for example, ascending neurons carry the sensation to your nervous system, which prompts descending neurons that trigger you to remove your hand from the heat.

Glial cells, also known as glia or neuroglia, are the non-neuronal cells in the central nervous system. They primarily function as neuron support, surrounding, protecting, and supplying nutrients and oxygen to the neurons. Glial cells also work to destroy pathogens and remove dead neurons, acting as the sort of "immune cell" of the brain. 

Glial Cells: Beyond Passive Support

The scientific study and understanding of glial cells have come a long way from their discovery in the 1800s. Initially, glia were considered secondary to neurons. The name "glia," in fact, comes from the Greek word meaning glue, as their passive work holding neurons in place was considered their most important job.

However, in the 1980s, neuroscientist Pierre Magistretti discovered evidence that neurotransmitters could trigger the release of glucose reserves in astrocytes, a type of glial cell. 

Suddenly glial cells, previously considered the supporting players of the central nervous system, had the potential to go beyond neuron support. They might even, scientists hypothesized, be able to influence neuron activity.

No Longer a Supporting Player 

Previous studies targeting only neurons may have missed the potential of the glial cells. It's not because the glial cells weren't a considerable presence, either: there are approximately 85 billion glia in the human brain, about the same number as neurons.

Glial cells are now believed to influence a wide variety of functions, including depression; appetite and metabolism; and learning and memory. Neuroscientist Andrew Koob even argued that glia might be the source of our imaginations.

Potentially the most exciting implication of all, though? Glial cells may influence neurogenesis.

What is Neurogenesis?

Neurogenesis is the growth and formation of new neurons in the central nervous system, particularly in the brain. 

Until relatively recently, neuroscientists believed that neurogenesis did not occur in adult humans. Instead, we thought that new neurons were only formed during embryonic development and very early childhood. The nervous system grows and changes rapidly in our first years; after that, it was believed, the nervous system could not produce new nerve cells. New neurons in the adult brain were simply not possible. Emerging research over the past few decades appears to contradict that belief, though.

Note: this theory is still somewhat contested. As recently as 2018, scientists still weren't convinced that adult brains could form new neurons. In 2019, though, a new study published in Nature Medicine argued that strong evidence points towards adult hippocampal neurogenesis.

Why is Neurogenesis Important?

Adult neurogenesis is believed to occur in two main regions of the brain: the hippocampus and the olfactory bulb. 

The hippocampus is a critical component of the limbic system and plays an essential role in learning, memory, spatial navigation, and emotional regulation. The olfactory bulb is involved in the sense of smell—the word "olfactory" derives from the Latin olfacere, meaning "to smell." Among other things, the olfactory bulb sends signals to the hippocampus. If a particular scent has ever transported you to a specific memory (say, lemons that smell like the tree in the backyard of your childhood home), you know that scent can play a primary role in triggering memories.

If neurogenesis does occur in these critical areas of the brain, it can make a substantial difference in the following areas:

• Improved cognition, including memory capacity and quality
• Regulating stress and reducing depression
• Neural repair, including recovery from traumatic brain injuries

If glial cells can generate neurons and spur these changes, they may have a significant and wide-ranging effect on the quality of life for many people.

How Can We Impact Neurogenesis?

There are several factors affecting neurogenesis, and many of them are within our control.

Activities

• Learning a new skill stimulates our brains and increases the production of new neurons.
• Exercise and meditation reduce stress and can boost neurogenesis in the hippocampus.
• Rest helps prevent sleep deprivation, which decreases neurogenesis. 

Diet

• Calorie restriction, including intermittent fasting, has been shown to increase neurogenesis.
• Omega-3 fatty acids and flavonoids can increase neuron production.

Supplementation

• Resveratrol appears to enhance neurogenesis in the hippocampus.
• Phosphatidylcholine (one of Ray Kurzweil's top supplements) combats aging at the cellular level.
• Curcumin's effects on human neurogenesis have so far gone unstudied. In healthy mice, though, it's been shown to increase neurogenesis.
• DHEA, also known as one of the "hormones of youth," increased new neurons in a study of healthy rats, though its effects on humans have not yet been studied.
• Pregnenolone may have specific cognitive benefits, including maintaining memory and decreasing anxiety.
• Nootropics like Excelerol are designed to enhance learning and memory while protecting the brain.

Glial Cells, Neurogenesis, and Your Longer, Healthier Life

Glial cells appear to play a central role in adult neurogenesis, but so do you. By taking an active role in maintaining and supporting the health of your central nervous system, you may be able to build new brain cells and increase your longevity.

As always, follow Step 1 of TRANSCEND and talk to your doctor before making any drastic changes to your diet or lifestyle.