Neural Circuits

The nervous system is one of the vital systems in the body. When it fails to function, other organs in the body will eventually shut down. The cells in the nervous system are called neurons.

They have a unique way of communicating with each other. Without the neurons, the brain won’t function. The neuron is the primary working unit of the brain. It is specially designed to transmit information to other nerve cells, muscles, and gland cells.

Neurons are specially and uniquely designed to transmit information to other cells. Neurons are made up of cell bodies, axons, and dendrites. The contact points where neurons communicate with each other are called synapses. The structural and functional components of the brain are all caused by interconnected neurons.

The brain of mammals has around 100 million to 100 billion neurons. If these neurons receive or send messages, they transmit electrical impulses along their axons. The majority of axons are enclosed with a layered myelin sheath. What these sheaths do is transmit electrical signals along the axon.

The myelin sheath is made by glia; a specialized cell. The glia in the brain is called oligodendrocyte and Schwann cell in the nervous system. (1)

Neurons do not function all alone. They need to form an organization or circuit so that they can process specific information. Neurons need to work cohesively. The arrangement of the neural circuit primarily depends on the intended functions. A neural circuit consists of neurons that are interconnected by synapse. Once activated, they carry a specific function. They connect forming a large scale brain network.

Neural circuits are both functional and anatomical entities. The brain primarily depends on the neural circuit to interpret the information about the world, the ability to control movements and learn from experiences.

However, it is quite difficult for scientists to pinpoint which cells are responsible for a particular task as the nerve cells are intermingled in a tight space causing to form an intricate network. (2)

Brain cells working hand-in-hand to perform a specific
set of actions

To accomplish what needs to be done, the brain cells need to work together. For actions and emotions to be possible, many brain cells need to work hand-in-hand. The research for brain actions started more than a decade ago.

Camillo Golgi, an Italian scientist, used two special chemicals to stain individual brain cells. These are potassium dichromate and silver nitrate. The staining method made it possible for scientists to fully observe neurons particularly the specialized extensions, dendrites, and axons.

The staining method discovered by Golgi has paved a way in the advancement in neuroscience. However, Golgi’s staining method is only good at showing neurons in minute numbers. Not to mention, all cells are stained using the same color. So, it is quite difficult to distinguish under a microscope which one is the axon and dendrites.

To see how the cells in the brain function, a new technique is used – complex genetic engineering technique. With such a method, scientists will be able to label the surrounding neurons in various colors. Hence, it would be easy to identify and trace the connections of different neurons.

The new technique is also called Brainbow because it creates a rainbow-like image. The method uses a mix of random colors such as red, yellow, and green fluorescent proteins into every neuron. If you combine these colors, you will be able to achieve over a hundred different hues. Scientists can easily map the connections of different neurons because every single neuron has a distinct color combination. (3)

Neural circuits can be mapped using another method – the capability of the virus to attack and spread in the brain. What the scientists did is modify the rabies virus enabling it to leave a green fluorescent protein marker in neurons as it makes its way across the junctions (synapses) between cells.

Some scientists combine genetic engineering with fiber optics to thoroughly check the neural circuits. Using this method, the neuron is activated by flashes of light and genetically modified to have a light-sensing protein. What that particular neuron does is excites the next neuron in the circuit enabling the researchers to find out what particular type of neuron communicates with each other.

This is a breakthrough in neurobiology as it assists researchers in mapping and studying neural circuits involved in a particular disease. The very same method is used to check for disease-related circuitry in studies of some types of diseases such as in the case of Parkinson’s disease. It leads to the development of deep brain stimulation treatment in people suffering from Parkinson’s disease. (4)

Human Connectome – a new imaging technology for neural circuitry

New imaging technology for neural circuitry is used to map the exact connections between individual neurons and to check the human connectome.

A noninvasive brain imaging method measures water diffusion (diffusion tensor imaging) is used to check neural circuits that connect the localized region of the brain. Checking the human connectome of healthy and diseased people enables researchers to learn how a particular disorder affects the circuit of the brain. (5)

Conclusion

The brain, itself, consists of dozens of different sections. Each section performs a specific function such as helping you move and process thoughts. For the brain to perform the way it is expected to, its different neurons and parts need to work harmoniously.

When they work hand-in-hand, they have the ability to power your thoughts and movements. The communication between different parts of the brain is made possible by neurons. Neural circuits serve as the pathway in the brain for thought and movement.

Every day, the brain changes and new neurons are wired. In the brain alone, there are billions of neurons and they have to work together to function in a normal manner. For neurons to function they need to be powered and their primary source of power is the chemicals in the brain.

The neural circuit is all about powering different neurons across all sections of the brain. There should be a coordinated movement in every neuron in the brain so that the brain can perform its vital functions.

References

1. https://www.brainfacts.org/brain-anatomy-and-function/cells-and-circuits/2019/the-short-answer-what-is-a-brain-circuit-060619
2. https://www.ncbi.nlm.nih.gov/pubmed/10845062
3. https://www.brainfacts.org/brain-anatomy-and-function/cells-and-circuits
4. https://www.jneurosci.org/content/35/41/13912
5. https://www.frontiersin.org/journals/neural-circuits