The three lessons in this level (Level 9) have been written from many first-hand accounts shared by people who have a type of CVI where their posterior parietal lobes have been affected. This is therefore more subjective than our other lessons, but it is the subject of ongoing research. As the accounts have been so consistent, we wanted to share them, because the understanding they give us lets us make simple adjustments to help many people, especially those unable to communicate their challenges, as is the case for young children and those with limited communication skills.
In the previous lesson (9b) we explained the challenges faced by some with CVI in terms of the map with fewer, bigger voxels.
This is where it gets complicated, because it does not seem to be fixed.
To explain, let us return to our sliding scale on the bookshelf from the previous lesson (image below)
From many consistent descriptions, rather than a fixed point where the map is consistently reduced at the same level, it varies.
Please take a few minutes to watch the film below, where this is explained with video images. The changing window of how much there is to see is what we are trying to describe here, as the varying, or dynamic effect of this type of CVI.
So this sliding scale moves, not just for different people, but for the same person.
It can vary from moment to moment, so walking down a street, like this (below)...
Can very quickly become like this (below)...
...and often without the person being aware that their vision has altered.
What causes these incredible changes?
From the descriptions we've been given, there are two key areas that directly affect what can be seen and a third that can either help or hinder. These are:
What we are describing affects us all to a small degree, but not like this, from one moment to the next (below)
This sliding scale can go both ways, either to improve visual processing or to make it more difficult. To improve visual processing, we should optimise the things that make it easier and try to avoid, eliminate or reduce the things that make it more difficult. This is obvious!
Another strategy, is to borrow processing capacity from other parts of the brain that are working more effectively.
When vision is reduced due to the map, as in the image below...
The area covered with the grey fog represents the area that has not been mapped and therefore does not have visual attention (explained in the video)...unless
Here, we are sort of borrowing from other places in the brain where processing is not affected or less affected.
The list below gives a few examples of simple changes that can improve the visual processing of attention, making experiences easier to learn from and more enjoyable.
These are just a few examples, please review the list of what we think is needed to know about each person affected by CVI in lesson 3l.
Each person needs their own detailed specific list.
So this map we are talking about, would appear to be very dynamic. We are used to thinking of the brain as structurally and functionally 'fixed'. This is a mindset that is slowly shifting due to incredible developments in our understanding of neuroplasticity. The brain is constantly active, and it is atypical functioning of this brain activity (lesson 9b) that we think is the reason for this dynamic changing experience.
Where there are fewer fibres to map the surroundings effectively in the posterior parietal lobes, what is happening to cause this dynamic experience, when there are added challenges?
Let us return to thinking of each visual nerve fibre contributing a voxel, with lots of tiny voxels near the centre and fewer bigger ones to the side.
Importantly sound is similarly mapped in the same part of the brain.
What would appear to be happening, from the descriptions we've heard, is that as the demands of the (posterior parietal) mapping systems increase beyond their limited capacity (due to fewer fibres ), the smaller central ones still work, while the larger outer ones become unavailable for use. This leads to the experience of less and less peripheral visual information being available to the mind to 'see', to the point where a person can quickly become practically unable to see or hear anything meaningful.
This is also consistent with the challenges of trying to look and listen at the same time, described by many affected by CVI.
There is a lot of research needed in this area. We need to understand more about the connection between changing emotions and visual processing. Where memories support vision, might this mean more becomes visible. Maybe the familiarity makes the person feel more confident, and that positive emotion supports vision.
Throughout these three lessons we have repeated that we are sharing first-hand accounts. This understanding of the extremely dynamic nature of the map is an area of great interest in the research community, but as yet there are no published results. Our reason for sharing these ideas with you, is to show that the dynamic nature of this condition is something we can potentially have a great deal of control over, making life much easier, or considerably more difficult.
We are confident about the improved outcomes, because, without exception, everyone we've met who has made the changes to 'help' the map, has seen benefits. That is why we have chosen to share this information now, rather than wait for what is likely to be a number of years for the published research.
One last thing...
We started each of these three lessons (9a-c) with a highlighted text box (like this one) referring to those who are 'unable to communicate their challenges'. This presents a diagnostic problem. How can their difficulties be diagnosed, if they can't cooperate with testing?
No harm can come from making things easier. So if the above suggestions work, then it's reasonable to assume that the person helped may well have a less accurate mapping system, because in medical practice, a treatment that works often helps confirm a diagnosis.
Checklist: Before moving on, please check that you have understood:
Next lesson: To follow
Further reading is not necessary to proceed, but if interested you may enjoy the following:
Clutter - page explaining the challenges clutter creates, and how reducing clutter is essential to improve the environmental for those with CVI.
Gordon Dutton's Blog 18 where he explains parallel processing challenges, that relate to the experience when the map is overloaded.
Dorsal Stream Dysfunction CVI Experience - Page explaining the process of making the video (featured in this lesson, above) with a further explanation of the challenges we have described in this lesson.
Cerebral Auditory Impairment - Page looking at the challenges many with CVI report around processing sounds and noise, where reactions can be extremely inconsistent, with a suggested explanation.
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