Visual Magnocellular Deficits In Dyslexia : Are These Deficits Due To Co-morbidity With ADHD?

Some cases of dyslexia may be accounted for by a visual problem involving the magnocellular pathways. Research on dyslexia and problems in the magnocellular pathway has been controversial. Some studies indicate that individuals with dyslexia have problems in this pathway whereas other studies have not. It may be that only the individuals with both dyslexia and ADHD have problems in this pathway while individuals with dyslexia only are spared. In support of this, research has shown that individuals with schizophrenia have attention deficits (similar to those seen in individuals with ADHD) and problems in the magnocellular pathway. In the present study, controls, participants with dyslexia only, participants with both dyslexia and ADHD, and participants with ADHD only completed central and peripheral backward masking experiments. It was predicted that the two groups of participants with ADHD would have problems in the magnocellular pathway. Some evidence was found in support of this.