At the moment you're sitting looking at words on a computer screen or tablet. Reach out with one hand and touch a corner of the screen in front of you. Of course it's there because you can touch it, that's proof isn't it?
Or is it?
Where is the picture? Is the picture on the computer screen? Or is the picture a camera picture inside both your eyes? Well yes. That's how eyes work; but where does the picture go after that?
It's converted into electrical activity in over a million very fine nerve fibres in each eye, and these electrical signals are relayed to the back of your brain, the occipital lobes which are under your hands when you hold them against the back of your head and lean back.
Is the picture there?
Well, that's where the picture is being analysed. But what happens next?
Years of research published in hundreds of technical papers about visual science have shown that the visual information in the occipital lobes is processed further. If you put your hands over your ears this time, the brain underneath your palms is called the temporal lobes, and the brain underneath your fingers is called the posterior parietal lobes. Both deal with vision.
Your temporal lobes contain the library of all the imagery you have seen.
This is where the incoming picture information is dealt with so it can be recognised, or if it isn't recognised, be remembered so as to be recognised next time.
Your posterior parietal lobes deal with the picture very differently.
First off, they do it without us knowing, secondly they map the scene you are looking at in 3D.
They also map where your body is, and this allows you to reach out and touch the screen.
You may well be thinking, "All this is covered on the website. Why's he repeating it?"
The reason is a philosophical one.
The richly detailed 3D world in which we live is created entirely within our minds, yet we so compellingly see this as being out in front of us that we find this difficult to believe.
Our brains miraculously create a mental virtual reality that coincides with reality.
The brain creates the picture on three levels:
We choose what to look at and where to move, and we manage to do this within what is our own mental picture of what we are looking at in a way which coincide with the structure and identity of our surroundings.
So where is this rather complicated discussion - which I had to read through a few times to check it made sense, so I hope it does - leading?
What we all need to understand is that vision is a virtual re-creation of the world outside and around us, within our minds, which takes up a lot of brain activity throughout our brains.
So for every child with cerebral visual impairment their brains contain their own 'normal' virtual re-creation of their realities, and we cannot use what we see as a way of understanding what they see.
It is through very careful observation of their visual behaviour and by imagining ourselves to have their vision (not the other way around), that we can work to ensure that everything that we want them to learn about, whether it is social behaviour, the ability to move freely, or the information they need to learn, is made accessible.
As we've mentioned before - one cannot learn from what one can't see!
We must no longer use our internal mental images of the world around us to guide what we do to ensure that children with CVI make strides in their development; we must work toward imagining and using their mental imagery to guide how we raise them.
PS: One way of helping to understand the key idea in this Blog, is to think about the soldier who has lost a leg, who continues to feel pain in the foot that is not there. This is called phantom limb pain. Is the pain in the foot, or is it in the brain?
Similarly, when the neurosurgeon Wilder Penfield operating in the 1940s, electrically stimulated the part of the brain that deals with sensation in the thumb, a tingling sensation was felt in the thumb (see article,page 360).
So in like manner for vision, the picture we see is formed in the brain, yet is equally compellingly, cast out to clothe our environment. We see 'from inside to out'!
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