It is almost impossible to know exactly ‘how’ vision works in the brain. We can begin to break down actual brain functions by studying behaviour, but nowadays technology allows us to get closer still to what is really going on. In the end, we can only ever ‘guess’ at what is happening in our brains to give rise to what we perceive. Studies have shown, however, that there are likely to be different pathways for information sharing in the brain, where ‘sight’ information combines with many other forms of information to create meaning in what we are looking at.
Visual Signal Processing (VSP) is the active process in the brain where we receive information acquired through visual signal acquisition (VSA) and then apply ‘processing rules’ to it (like cleaning up the signal, sharpening the edges, and filling in the gaps), combine that information with meaning from memory, and relate it to other body functions, like hearing and balance – all this to help us make sense of our world. It’s complicated, but thankfully it’s all quite easy to ‘use’.
In the world of reading problems, it is helpful to probe some underlying mental processes related to vision and memory. Again, what vision actually ‘is’ is debatable, but we can reasonably speak of the following visual sub-processes as elements of perception in reading:
>Visual Discrimination: Distinguishing differences between things.
>Visual Memory: How much visual information can you hold in memory, and for how long?
>Spatial Relationships: Judging distances and rotational relationships between objects.
>Form Constancy: Knowing that a shape can be constant, regardless of it’s size, or rotation, or reversal of image.
> Sequential Memory: Recall of sequences of images or visual impressions. This concerns more short-term memory, as applies in reading, as opposed to longer term visual memories of days and events past.
>Figure-Ground: The ‘Where’s Waldo’ factor. The ability to direct central vision in a deliberate fashion to find a needle in a haystack.
>Visual Closure: The ability to ‘fill in the blanks’. How much of a visual signal do you need to see before you ‘know’ what it is? For example, how much of a friend’s face, or a 7 of clubs, or the word ‘crocodile’ do you need to see before you can identify it?
>Depth/Stereopsis: The perception of depth in the visual field, and the separation of objects.
>Approximation: Pattern matching of what is coming next in the visual stream with what we think it might be. Even before we look at the next words in a sentence, we are already trying to guess what the words and punctuation will be.
We could further elaborate on this, but the real value in any measure is in how it helps us to further strengthen vision, reading, and learning. At some point, the words become more important than the solution, and while the search for understanding is worthwhile, the search for better treatment is even more so. You can read more commentary on psychoeducational tests and testing in this site and through eLVT. We generally advise minimal testing in all cases, except where required in psychiatry, vision management, and medicine. As a general rule, invasive and expensive psychoeducational assessments are not likely to reveal much more of clinical use than locally available tests, and reports from teachers and parents.