Continuing the discussion from Homemade solar eclipse viewer:
I have started this thread taking ahead the discussion triggered by @Arunan and @Manpreetheersskp
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@Manpreetheersskp, so you say that the eye is just a sensor and that brain combines these to give us a perception! And that this is not a passive process, and refer to neural adaptation. I must say this is wonderful. What you are referring indicates neuroplasticity.
However, recently, there appears to something more to this aspect of neural adaptation and active perception, especially questioning the role of brain as a ācentral processingā organ. And this is something that is still not entirely settled among the brain scientists, but increasingly people tend to find value in resisting this assumption about brain as a centralised processor. For example, it is difficult to explain our regular activities like walking in āsensing, processing and actingā terms. Also, there is a strange creature called Sea Squirt which eats away its own brain once it reached some place. Now that it has no brain, do they sense the environment!? We donāt know! 
To start getting a sense of it, see this interesting experiment with two kittens.
What do you think is happening here with these kittens and what do you think is the role of the brain here?
-DP
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@karnamdpdurga,In the case of sea squirt because when there larvae are born they could swim for a very short time so when they need food they not only eat their brain, they also eat notochord, tail, sense organs and nervous system, since these are no longer needed, while it feeds by wafting water into its mouth cavity, and filtering out suspended particles. Because they are going to be like corals.
In case of kittens you should see this link 
I think because the are kept in dark most of time and they become in light for only 3 hours a day so there brain has started visualizing the world as they had seen in that carousel. If this experiment was experimented on humans the result could be a little bit similar to that of kittens.
This experiment could be tested at home by watching the following video. This is just for understanding that if our eyes see something different for about 5 or 6 minutes continuously the brain will see the rest of the world like that for a short period of time.
GENIUS LEVEL OPTICAL ILLUSIONS - YouTube
at the end of first illusion you see objects shrinking. Now you tell me @karnamdpdurga why this happens.
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@Manpreetheersskp, you are doing a good job at exploring these in detail. All I was trying to do by using the Squirt and Kitten experiment was that:
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the action/motor system (muscles, hands, legs etc) in our body is key behind the neural adaptation and the plastic nature of our brain: For example in the kittenās case, though the brain+nervous system and the eyes are very similar, and the visual input was also same (as they moved in the same carousel), as the action system (legs) of the kitten is arrested, some aspects of vision are affected.
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the brain and the nervous system is perhaps not as central as we used to think it is: And in the case of the Squirt, the moment it did not have to move, the brain became redundant and is eaten away just like we bite away our nails.
So, the underlying question, that I was trying to raise is: how important is brain in our cognition? Is our thinking and so-called processing centralised or distributed across the body? We normally tell: brain does this, brain does that. Even you said, in the kittensā case " brain has started visualizing the world". Is there someone sitting inside the brain?
Let me provoke you with some statements, and see how you find them. My legs and ears move, coordinate and make me walk without falling; my hands and eyes move, coordinate and making me read and respond to your messages; the brain just connects and facilitate these. So, one may end up saying - āI think with my 
, and not 
!!ā Sounds weird!?
-DP
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Yes, this is common in many illusions. To understand this, let us play together a STEM-game 
. Let us step-by-step try to explain these illusions with the action-system explanation of human cognition. Up for it?
-DP
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When we experience a highly discomfiting sensation we react by withdrawing the area of our body away from the stimuli. Can we use this phenomenon to determine if the brain is a central processor for such sensations?
What is the speed of transmission of a nerve impulse to the brain and back to a set of muscles?
https://www.radford.edu/jkell/Reaction%20Times.pdf
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