New research suggests visual problems have a role in dyslexia
The first record of dyslexia as an identifiable condition came to light in the late nineteenth century amongst the many other medical curiosities that seemed to fascinate the Victorian imagination. Of course modern scientists realise that dyslexia is in fact quite common, many people being affected to a greater or lesser degree. It's also now known that there is a strong genetic component putting children of dyslexic parents at heightened risk. However despite many years of research and several significant breakthroughs, a complete model of the processes that underlie dyslexia remains elusive.
Dr Kristen Pammer is currently leading a team of scientists trying to unravel at least one piece of this complex puzzle. "Traditionally dyslexia is seen as a phonics based problem, a difficulty in associating particular sounds with letters on a page. But whilst there is clearly a large component of photonics in dyslexia, our research has lead us to believe that there may also be subtle underlying problems in the dyslexic brain's visual processing systems."
Within the visual cortex there are two distinct processing pathways. The mangocellular pathway (also known as the dorsal stream due to its physical placement) deals with conceptualising the movement of objects and their position in space. For this reason it's sometimes nicknamed the 'where' pathway. Leading to a different part of the brain, the pavocellular or ventral pathway is concerned with detailed visual information used for the recognition of objects. And can be thought of as the 'what' pathway.
In terms of reading, the pavocellular pathway is vital for recognising letters and words but interestingly enough, it's deficiencies in the mangocellular pathway that seem to be related to reading difficulties. Dr Pammer explains "Its been known for some time that adults with dyslexia often do poorly on visual tasks designed to test the functioning of the mangocellular pathway. What we were unsure of is whether this was a partial cause of dyslexia or a consequence of failing to learn to read?"