VSP, or Visual Signal Processing, can be simplified as saying: What happens to a visual signal after the eyes have locked-on to it? That is, what does the brain ‘do’ with the signal when it arrives?
Keep in mind that VSP is an ‘always on’ circuit, that is, it’s always in action waiting for the next bit of information to process. Unlike a light switch that either closes or opens the circuit, VSP sits waiting for input from VSA, and once the input is available, it is processed through a number of neural circuits in the brain. So, VSP, is more like a ‘stream’ than a circuit – it’s always flowing so long as water is present. VSP works as long as visual signals are present. There is even evidence to support that VSP in those with developed vision works even if there are NO signals coming in from the eyes.
In reading, VSP drives VSA to find the visual signals and guide the visual path along the line of text.
There are different definitions of what constitutes visual signal ‘processing’, aka ‘Visual Information Processing’, or VIP. For this discussion, we will consider seven elements that represent functions that are vital to success with language:
Visual Discrimination: Differentiating differences between two objects, especially when they have similar appearances, like a ‘d’ and a ‘b’.
Visual Memory: Remembering a visual signal and being able to identify it in a group at a later time.
Spatial Relationships:Understanding orientations and placement of objects with respect to one another.
Form Constancy: Knowing that a particular signal can appear to be larger, smaller, or rotated, but still remain the same signal. A small ‘m’ is the same as a large yellow ‘m’ you might see in front of a fast food restaurant, even though the size and colour might be different.
Sequential Memory:Remembering a sequence of visual signals (shapes, say, or letters), in sequence as they occur. Sequential memory can only be accurately assessed if VSA skills are intact.
Figure-Ground:Think of ‘Where’s Waldo’ or looking for a needle in a haystack. This is the ability to use your central visual awareness to locate specific features amidst a confusing, or busy, visual field.
Visual Closure:Filling in the blanks of a signal when the entire signal is not visible. How much of your mother’s face do you need to see before you know it’s your mother? Or what about the word ‘word’, or your name, or individual letters? Children having difficulty with Visual Closure and Figure Ground will be slow readers.
These can all be tested, measured, and with therapy, can improve. Dyslexic children will almost always show decreased VSP and VSA, which suggests a strong visual association, if not a causal relationship between visual function and reading trouble. Frequently, children will exhibit reading problems that are easily confused with dyslexia, but in the end it is a matter of laboured VSA or VSP.