The Key to the Senses: Transduction

Here’s probably the most basic question in all of sensory neuroscience (the study of the senses). How does a ray of light enter our nervous system, to eventually become something that we see? How in fact does anything external (anything we touch, smell, taste, hear or see) get turned into something internal (some kind of signal in the brain that tells us to sense something).

The answer is simple, so simple in fact that it is one word:Transduction.

It's about this simple...

OK fine, it’s a simple answer if you know what transduction means. So I’m going to explain it to everyone now.

In a sentence, transduction is the conversion of one form of energy into another. Try to think back and remember the different types of energy:

They might have missed a couple out...


  • Kinetic

  • Sound

  • Chemical

  • Electrical

  • Light

  • Heat

  • Nuclear

  • Magnetic

  • Gravitational potential

  • Elastic Potential

Now lets lay these out in relevance to our 6 senses (and we do have 6, the last one is just a bit of a debated secret).

Touch:

  • Kinetic
  • Heat
  • Gravitational Potential (kind of)
  • Elastic potential (again kind of)

Taste and Smell:

  • Chemical

Sight:

  • Light

Hearing:

  • Sound

Self (our awareness of where our bodies are):

  • Elastic potential.

These are all the main types of energy that we can sense. Now here’s the problem:

The nervous system only uses one type of energy, and that is electric.

Therefore if we the brain is what allows us to sense the outside world, all of these energies we mentioned previously have to be converted into electrical energy so they can enter the brain. That is where transduction come in.

In all of our sense organs (eyes/ears/tongue etc.) there are nerve endings which contain hundreds and thousands of receptors. Each organ will have different types of receptors that will react differently to each type of energy.

In the eye there are ‘photoreceptors‘. When light touches these receptors they undergo a sudden reaction which generates electrical energy.

In a similar way there are ‘chemoreceptors‘ in the tongue and nose which will react to chemicals and generate electrical energy.

The skin and ears use ‘mechanoreceptors‘ which are physically moved, either by us touching something or by us hearing something. When they are moved these receptors open up, allowing electricity to enter.

 

As you can see all of these receptors¬†convert one form of energy into electrical energy. Thus these receptors ‘transduce‘ the energy, allowing us to sense them!

There you go, now if anyone ever asks you how we can sense things, just say: Transduction!

 

I might do another basic sense post before moving onto the specific senses themselves. Just to warn you!

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5 Comments

  1. You’ve made a wonderfully clear statement here – clear enough for me to be able to say, “Hang on – there’s a transduction step missing in all this.”

    The step I see as missing is how the electrical energy – into which all the other forms of energy are transduced by our sensory apparatus – gets transduced in the brain into the differentiated qualities of experience that we attach to the original differentiated energetic stimuli – light and sound for example.

    After the transduction of everything into electrical energy – or patterns of electrical energy – surely all the brain has is patterns of electrical energy – there are no differentiated qualities of experience.

    I know that some neuroscientists say that those patterns of electrical energy are our experiences – but they aren’t – they’re patterns of electrical energy!

    Far greater minds than mine have come to a grinding halt over this issue – but I’d be interested in your thoughts on it.

    Reply
    • I started watching quantum physics videos online which started because I had the question how does our brains store data.? What are the keys to retrieving that data? What about data that just pops up without a query? All of my senses trigger memories. We don’t just store binary it’s the whole multimedia package getting stored along with “feelings” data. The size of equivalent hard disk space is incomprehensible.
      I think that science really needs to go a lot smaller.
      So I think your lecture is leading that way.

      Reply
      • You’ve both made pretty good statements.

        Firstly, my knowledge of quantum physics is seriously malnourished. I don’t know much about it, and from what I have heard most people who study it don’t know much about it either. If anyone knows anything about it that is relevant it would be great to have a guest post!

        I have heard that data and information are stored somewhere on the quantum level. But this is really new cutting edge and ridiculously complicated stuff.

        What I am going to say is that each neuron (a single nerve fibre) is separate from the others surrounding it. As a result we get a phenomenon called ‘labelled line’ where a neuron knows what it is made for (don’t ask me how, this is where things get philosophical) so the neuron is essentially ‘labelled’ in the brain. This means that if you artificially stimulated a neuron, say from the retina in the eye, you would see something, despite that it has been stimulated by something other than light.

        Because of this the receptors on the end of the neuron turn the energy into something that the brain can interpret. But it is which neuron that this signal came from that matters when you want to determine what type of energy it is.

        Memory triggers and retrieving data is kind of a half psychological and half neurological question to do with patterns of brain activity and us retrieving associations with certain sensory stimuli. It’s part of a survival mechanism (as is everything) so that you associate something with a memory, allowing you to recognise a similar situation in the future.

        Memory is still a big part of research that we don’t know a whole lot about. But there have been some advances which I’ll come to in another post (I need to cover some more basic topics first).

  2. Re-reading that last sentence of mine, I can see that there might be a shade of implication that, if not the greatest, I might nevertheless have a great mind and you might not – neither of which I would would wish to suggest.

    Language can be very slippery!

    Reply
  1. Sight: The Science of Vision | Science Defined

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