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Thread: How does brain differentiate different stimuli?

  1. #1 How does brain differentiate different stimuli? 
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    Our eyes perceive light, ear senses sound etc., but when it goes to the brain, it's in the form of electro-chemical signal.Is the signal carried to the brain same in both cases?

    Does the signal which is originally sound-wave differ from the signal originally perceived in the form of light? If so, how does the brain differentiate them?
    Or does it not?


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    The nature of the signal is the same. They are both merely electrical impulses propagated through the action potential, essentially a chemical process.

    What happens is the signal is coming from different areas on the body and traveling different paths. Then, those signals arrive in different parts of the brain.

    So, there are two primary aspects which dictate how the signal gets interpreted. One is where the signal comes from, the other is what part of the brain receives the signal. After that, it's just a matter of interpreting the signal itself.


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    Then how does brain differentiate what we hear from what we see?

    Neuroplasticity of the brain allows it to use areas for vision for processing sound in blind people.

    http://www.sciencedaily.com/releases...1006131203.htm

    http://www.sciencedaily.com/releases...1010133604.htm

    So the stimulus is different, the signal it's converted to is the same, but the area in brain for processing one stimulus can process the other and still perceive it in correct (relative term) way.

    Where is the demarcation made between the two sensory inputs?
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    As I said, the signal follows different pathways from different sources to different areas for interpretation and processing. I'm not sure I fully understand the nature of the confusion, so maybe it would help to explore links at sites like this:

    http://www.dls.ym.edu.tw/chudler/introb.html#sense

    http://faculty.washington.edu/chudler/introb.html
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  6. #5  
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    Thanks for the links.

    Though I would like to make my query more clear-
    Light fall on the retina , gets converted to electro-chemical signal, passes via nerve to the visual processing area in the brain.
    Sound hits the ear drum, converts to electro-chemical signal, goes to brain for processing, and perception occurs.

    Now a blind person, hears a sound which is taken to the sound processing part, but also the visual cortex is utilized. What I mean to say is, that here, sound has its identity in the environment as sound wave. When it goes through nerve, it become electro-chemical signal. It loses it's identity as a sound wave. So inside the nerve, both light and sound are electro-chemical signal- non-differentiable.

    So you told me that it's the part of the brain where the processing is done which determines how we perceive the particular stimulus (I hope I got that right).

    But then I see an article when shows that areas of brain meant for visual stimulus processing can be utilized for processing of sound. So we see that the neurons meant for vision can process sound(details, I don't know). So how do we perceive the same electro-chemical signal as different?

    I hope you understand the query better now!
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    Quote Originally Posted by mhima_88
    So you told me that it's the part of the brain where the processing is done which determines how we perceive the particular stimulus (I hope I got that right).
    Well, that's certainly part of it, especially when we are considering a non-blind or non-deaf member of the population. The average individual will have different parts of the brain dedicated to processing different stimuli (occipital lobe for vision and temporal for sound, etc.). Those who are blind or deaf simply adapt a bit, and commandeer those areas of the brain normally dedicated to vision or hearing. Those are still vision and hearing areas, but they are often borrowed when not in use for those... such as with deaf and blind people.

    In addition to just where in the brain the processing takes place, another key factor is where the signal comes from. If the signal comes from our eyes and retinas, it's different from a signal which comes from our ears (a different source), which is also a different source from the signal which comes from our skin, our nose, and our tongue.

    So, there are two key pieces. Where the signal is sent and where it originates. I'd try to avoid understanding basic neurophysiology by looking at how blind and deaf people do it since they are the exception, not the rule.
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    Deleting for privacy purposes.
    Last edited by Azereiah; November 13th, 2019 at 09:46 PM.
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  9. #8  
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    Quote Originally Posted by Azereiah
    Electromagnetic Radiation vs. Mechanical Movement. Sound is a pressure wave moving through a medium, to your ear.

    Retina = Light sensor. Eardrum = Pressure sensor.

    Different type of signal.
    Would go more in depth but I've gotta go, will come back later.
    I'm not too sure that really helps with the question, though, Azereiah, since once these phenomenon strike the receptor, they are both converted into equal neuochemical signals. The question pertains to the signals that the body creates, and how the different stimuli are... differentiated... not to how those stimuli differ in the physical environment.

    It doesn't so much matter what they were in the environment... whether pressure wave, electromagnetic radiation, scent, or otherwise. What matters is which part of our bodies receive that information, and ultimately where and how the neurochemical response which is generated from those signals gets directed and interpreted.
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  10. #9  
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    Which part receives the signal may matter but now that notion may be challenged in certain cases. As the following article suggests-

    http://discovermagazine.com/2008/jul...ugh-his-tongue

    To quote from the article- "Paul Bach-y-Rita, the cocreator of the system Weihenmayer is testing, challenged conventional wisdom when he proposed that “we see with the brain, not with the eyes.”
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  11. #10  
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    That rebuts nothing I've said, nor is it contrary to any of the information shared thus far.
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  12. #11  
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    If you think about it, it does add something to it though.
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