How the ability to see more rapid movement is seen is impaired, that is what Dyskinetopsia means:
Seeing movement is something most of us take for granted, as part of our whole package of vision. To understand what happens when this single element of our vision is impaired, we need to look at it on its own.
What is movement?
There are lots of definitions, but in terms of vision, movement involves detecting a changing position of something you can see. For example picking up a coffee cup
Try it now, pick up something near you (cup, pen, piece of paper, anything) and think about what you are looking at just in terms of the movement.
As we explained in lesson 1d and lesson 3e, visual mapping of movement is processed in an area of the brain called MT, which stands for middle temporal (lobe).
So when you are looking at the movement of your cup or pen, this is the area of your brain being activated to process it for you. The actual movement of the cup is added to the picture created in your occipital lobes to match the movement of what you are looking at.
We explained in lesson 3a "...the visual world you see is created in your brain, and is a picture of what you are looking at."
Try to imagine, whilst lifting your cup, how that experience might be different if you still create a clear picture, but the movement is not processed to match the movement of the cup you are lifting? This is what happens with dyskinetopsia. That 'match' between the movement of the object and the movement the brain creates, is not as accurate as typical vision.
So, what is typical processing of movement?
For all of us, the faster something moves, the less clear it becomes, as was demonstrated by Gordon Dutton in the film to accompany lesson 3e. With dyskinetopsia, for most people, movement needs to be slower than typically seen, to be seen clearly.
The severity of dyskinetopsia can vary, from those only mildly affected where little things may be missed or misunderstood, like recognising someone walking past. For the more severely affected, to be seen clearly, all movement needs to be slowed down considerably.
With reduced visual attention due to simultanagnostic vision, introduced in lesson 3g, movement can help attract a person's visual attention. That movement, to be optimally helpful and meaningful, however needs to be at a pace that the person with CVI can process.
The optimal speed of movement for the individual needs to be established, then things can be slowed down accordingly. There are no generic rules, as some will need things just to be slightly slower, and others considerably slower. The approach needs to match the needs of the individual.
One way to get a sense of a comfortable viewing speed is to try different options. YouTube has a facility where speeds can be slowed down. Using a programme that is liked by the person, try showing it at reduced speed (link with instructions at the end of this page).
For the more profoundly affected person, including someone with extremely limited communication, another approach is to take a known item, maybe a favourite toy, to a clear uncluttered and quiet room. Lift the toy to the area in their visual field where they see most clearly, and starting very very slowly, move the toy, watching their face, to see if they can smoothly follow the movement of the toy (called tracking). If they can keep up with the movement of the toy, you can try moving it a little faster - the point where they are no longer able to keep up, is too fast, so go back to the optimal speed of movement.
Remember, anywhere there is noise, clutter, stress or distractions, the processing may be affected and the movement speed will need to be slowed down accordingly.
It is not just what is seen that may need to be slowed down, but sounds such as words.
Anything that is too fast to be seen or heard clearly, can't be learnt from effectively, if at all!
Akinetopsia is an extremely rare condition where movement is not seen at all.
Before you move into the next lesson, please check you understand:
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