Brain cells have both excitatory and inhibitory roles in transmitting neural signals. Discover how they can adapt within those roles and what that could mean for treating brain disorders.
I’ve fallen off my bicycle a couple of times in my life. In one case, I broke my arm. As an adult, I got distracted, struck the curb, and flew over the handlebars, landing on my head.
My helmet was in the saddlebag (I’ve always been absent-minded), so I ended up with a nasty abrasion all over my face. I suffered a mild concussion, and to this day, I don’t remember anything about the accident.
I remember looking over my shoulder at a car that was passing me on the left. Then I remember a sympathetic cop tending to my injury and then driving me and my twisted bike home. In between, it’s just a blank.
I Couldn’t Remember the Moment of Impact
It seems to me that I knew what had happened when I went to bed that night. Even so, when I woke up in the morning, I couldn’t remember the moment of the impact.
That’s the nature of brain structures. Our brains consist of cells called neurons that send signals to one another using the gaps between them that neurologists call synapses. Neurons are connected to one another in small functional units called neural circuits.
Scientists call the neurons that send signals that cause other neurons to fire excitatory neurons. On the other hand, we also have inhibitory neurons that reduce the odds that other neurons will pass the signal on.
Neurons Interact and Balance One Another
We all need both kinds of neurons. They interact and balance one another to provide us with normal brain function.
Neurologists have linked an imbalance between neurons to conditions like epilepsy, Alzheimer’s disease and autism, and psychiatric disorders. For reasons we don’t fully understand yet, our percentage of inhibitory brain cells stays roughly the same throughout our lives, at somewhere between 15% and 30%
This piqued the interest of researchers at the Max Planck Institute for Biological Cybernetics in Germany. Dr. Anna Levina led the study and briefly explained the question behind it. “Can neural circuits with a different proportion of excitatory and inhibitory neurons still function normally?”
Grew Cultures of Brain Cells in the Lab
Brain research poses complex ethical questions, but the team used a novel approach to avoid these concerns. They grew cultures of brain cells in the lab so that no human or animal brains would have to be used.
Working this way allowed the team to produce cultures that contained very different ratios between the two kinds of neurons. Then, they measured the activities of these artificial neural networks.
The investigators found that even when the ratios were well outside the range, we would find in nature, the neural networks stayed active. Even at extreme levels like 10% or even 90%, the team didn’t see much change in brain cell activity.
Our Brains Come Equipped with a Means of Compensating
Somehow, our brains come equipped with a means of compensating for bizarre neural arrangements to carry on as best they can. The question is, how?
The team believes that neural networks have a way of adjusting the number of connections they use. If there aren’t enough inhibitory neurons, the ones that exist take up the slack by making more synapse connections with other brain cells.
When there are more inhibitory neurons than we need, the excitatory neurons make more connections to keep things in balance. Still, the mechanism behind this balancing act is poorly understood at this point.
Something Self-Organizing about Nature and our Universe
As scientists unveil more and more answers to life’s mysteries, we see a theme emerging over and over. There’s something self-organizing about Nature and our Universe.
Whether it’s how galaxies form out of clouds of gas, ecosystems establish a balanced food chain, or our brains sort themselves out despite wildly varying configurations, things have a way of forming positive patterns on their own.
Could Even Lead to Better Mental Health Medications
The scientists are hoping to find a practical application for their discovery. If they can grow working brain cell cultures in the lab and perform tests on them, why can’t scientists use them to better understand mental illness?
That kind of research could even lead to better mental health medications or treatments. As most families know, relief in this area is sorely needed.
We always have more to learn if we dare to know.
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