THE VISUAL DEFICIT THEORY OF DEVELOPMENTAL DYSLEXIA

Dyslexia is an impairment in reading that can result from an abnormal developmental process in the case of developmental dyslexia or cerebra l insult in the case of acquired dyslexia, It has long been known that the clinical manifestations of developmental dyslexia are varied. In addition to their reading difficulties, individuals with developmental dyslexia exhibit impairments in their ability to process the phonolog ical features of written or spoken language, Recently, it has been dem onstrated with a variety of experimental approaches that these individ uals are also impaired on a number of visual tasks involving visuomoto r, visuospatial, and visual motion processing, The results of these st udies, as well as the anatomical and physiological anomalies seen in t he brains of individuals with dyslexia, suggest that the pathophysiolo gy of developmental dyslexia is more complex than originally thought, extending beyond the classically defined language areas of the brain. Functional neuroimaging is a useful tool to more precisely delineate t he pathophysiology of this reading disorder.