Research Projects Funded by IDA 

Summary: 

Functional MRI Studies of the Pathophysiology of Dyslexia

Developmental dyslexia is formally defined as an unexpected reading failure that cannot be explained by low intelligence quotient (IQ) or environmental circumstances, such as teaching methods or social environment. In this decade, estimates of the incidence of reading disability vary between 5% and 15% and its familial aggregation suggests a genetic basis. Claims concerning the mechanisms responsible for dyslexia have been as numerous and varied as proposals for its remediation. One possibility is that the failure to fully understand the pathophysiology of dyslexia may have resulted from the complexity of its behavioral manifestations. The work supported by the International Dyslexia Association involves behavioral testing and functional magnetic resonance imaging (fMRI) to characterize sensory and cognitive processing in individuals with and without developmental dyslexia. These studies include examinations of rapid visual and auditory processing as well as phonological awareness. Although these processes have been previously shown to be impaired in dyslexics, the nature of their shared contribution and questions concerning a common neocortical etiology are being investigated for the first time. Our approach is to perform analogous behavioral and functional studies in the visual and auditory system and to relate them to phonological awareness skills in dyslexics and controls. Integration of the resulting behavioral, anatomical and physiological information into structure/function correlations is a principal goal of our research program. Using these techniques we will examine the degree to which these physiological changes correlate with the observed behavioral deficits. Comparison of results across modalities will reveal to what degree dyslexics exhibit functional deficits common to vision and audition, and may suggest the neuroanatomical localization of a common neural substrate. The results of these experiments will provide new information concerning the neural substrates responsible for the visual, auditory and phonological abnormalities characteristic of developmental dyslexia. The project is currently ongoing and the final results will further delineate the relationship between psychophysical performance and neuronal processing mechanisms in dyslexia and may suggest new strategies for remediation.