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Circuit of Communication - The pathway of human thoughts

What sets apart human beings from other animals?

Some might argue that the basic difference is our vertical spine and our ability to stand upright. But the most important feature we humans have is our ability to communicate with each other. And it is this ability that led to the most amazing inventions and discoveries in the history of this planet. So it is understandable that the art of communication is a very complex and advanced mechanism, thanks to evolution. 

Now imagine listening to a peppy song. You would want to sing along and maybe bust some moves. Or the times when you travel to the most picturesque places in the world, you would want to cherish every bit of it, maybe even write a blog about your experience. Right? Ever wondered how you are able to perform these activities with such ease? The key to this, as I would like to call, is the circuit of communication.

When you listen to a song, your mind perceives the tune, tries to comprehend the words of the song and if you like it, it directs your vocal cords to make the same sounds and words, thus enabling you to sing along.

So broadly speaking - Perception, Comprehension, Response initiation and Execution – are the 4 components of this circuit.

Needless to say, every single component is categorically governed by distinct parts of our brain. If all of them were to be taken care of by a single centre in the brain, then it would mean absolute chaos. Or should I say gross “miscommunication”?!

So let us break down this circuit and analyse it in scientific terms. The brain as we know it, is split into multiple areas called Broadmann’s areas, named after the German anatomist Korbinian Broadmann. He mapped the cerebral cortex and numbered different areas based on the architectural organisation of neurons. This type of organisation of the brain allowed us to understand that various parts of the brain have specific functions. It also gave us the ability to better locate problems in the brain based on symptoms alone. Now this article is not going to deal with specific numbers of those areas.

However, it is essential to understand that the cortex is broadly divided into primary areas, secondary areas and association areas. The secondary area is where all the off stage meticulous planning happens and this would eventually be executed by the primary areas. For example, any motor action we do is first planned by the premotor cortex which is a secondary area and it is then executed by the primary motor cortex which controls all the muscles of the body. Similar areas are present for sensory stimuli as well. These areas are strategically placed closely in such a way that relaying information among them is easy. And finally there are association areas. These connect the sensory areas to the motor areas and in turn help us to respond to all the sensory stimuli through words and actions. It has been found that all these areas are more active in the dominant hemisphere, so in a right handed person, the areas in the left hemisphere are more dominant. But that doesn't mean that all the sounds reaching the other ear fall on deaf ears. Instead all the signals received in the non dominant hemisphere are transmitted to the dominant hemisphere via the thick fibres connecting the two cerebral hemispheres, the Corpus Callosum.  Sounds a bit complicated? Okay, let us break this down further.

There are two components to communication.

The input being our sense of vision and hearing and the output is our ability to vocalise. When you read a book, the written word in the form of visual signals is received by the visual cortex which is present in the occipital lobe. Close to this within the occipital lobe is the visual association area, called the Angular gyrus. This area is required to make meaning out of the visually perceived words. Similarly the auditory cortex in the temporal lobe, like the name suggests, receives the signals of the spoken word. From here all the signals are relayed to an area called Wernicke’s area. This is the most important area in the brain because the auditory and visual signals from their respective cortices converge here. This forms the core of communication and the Wernicke’s area works tirelessly to comprehend every word and sound. 

 
 Courtesy: Guyton and Hall Textbook of Physiology

Courtesy: Guyton and Hall Textbook of Physiology

 

So far, you are able to listen to the song, make out the words, understand what it means and you seem to like it. Now all that’s left is for you to sing along and bust a move! And that brings us to the second component - the output of the communication circuit. 

All the information that is processed in the Wernicke’s area now has to be sent to the motor areas of the brain. At the heart of this, is the Broca’s area. It is present in the frontal lobe close to the Premotor and Motor area. The bunch of fibres organised like an arc designed to connect the Wernicke’s area to the Broca’s area is called Arcuate fasciculus. Now the Broca’s area in association with the premotor area consolidates the thoughts and plans the response. You now know exactly what pitch to hit, what dance move to make. This information is finally sent to the motor cortex which controls all the muscles of the body. The motor cortex wields its power – it sets the vocal cords at the optimum position, and makes you flex your arms and legs. And before you know it, you are singing along your favourite song and dancing like nobody’s watching!  

This completes the circuit of communication.

 
 Courtesy: Guyton and Hall Textbook of Physiology

Courtesy: Guyton and Hall Textbook of Physiology

 

So the next time you are having a conversation with your friend, take a moment to think about how it is possible. But the brain will of course beat you at speed and before you can get to thinking, the words would already be out!

Author: Soundarya V (Facebook)

Sources and citations

Hall, John E., and Arthur C. Guyton. "Unit XI : Chapter 57 - Cerebral Cortex, Intellectual Functions of the Brain, Learning and Memory." Guyton and Hall Textbook of Medical Physiology. 12th ed. 698-705. Print.