Brain-wrapping neurons discovered in mice

Last year, scientists at the Allen Brain Institute on Seattle, WA have discovered 3 super long neurons that wrap around the entire in brain of a mouse. Usually, long neurons exist in outside of the brain and spine (what we neuroscientists call the periphery), and function to connect body parts that are far away from the brain. In humans, for example, the longest known nerve stretches from the just outside the bottom of the spine down to the big toe, with an average distance of half your full height. In adult humans, that’s about 3 feet (1 m)! Mice’s bodies are about 15 cm long, and, based on the size of mouse brains, these cells would be at least 2.5 cm long. That’s longer than most known neurons in the body!

What’s especially interesting about these “crown of thorn” neurons, as they’re called, is that they originate from a part of the brain called the claustrum. The claustrum is a region of the brain located just underneath the cortex, that is highly connected to multiple regions of the brain. Because of this connectivity, researchers have often considered the claustrum to be a potential “seat of consciousness”.

Image result for coronal slice

A depiction of the claustrum (red arrow) in a coronal slice of the brain.

This “seat of consciousness” idea is supported by a study carried out with Vietnam War veterans who had brain damage to their claustrum. Scientists measured two aspects of consciousness: wakefulness, and amount of awareness. They found that patients with more damage to their claustrum would lose consciousness (wakefulness) more frequently and for longer periods of time, than those with little or no damage. This finding is complemented by another study, published in 2014, found that electrically stimulating the claustrum in humans would lead to a temporary and reversible loss of consciousness (wakefulness).

To boot, the “town of thorns” neurons are highly connected, similar to its neighbors in the claustrum. Having super-long, super-connected neurons that communicate with far regions of the brain suggests that they work kind of like electric wires or fiber optics–transferring important electrical information to far distances. Far-reaching communication is something that would be required to manage whole-brain events like wakefulness. It could even play a role in the other side of consciousness- awareness.

Pretty neat, huh?

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