There is a great deal of variation in reading skill in the general population, and even within the college student population. Some individuals read quickly and comprehend well with little effort. Others struggle with word decoding, and may not achieve high levels of reading comprehension. In some cases, reading difficulties are severe enough to be diagnosed as dyslexia. But even within the nondyslexic population, there is a large range of individual differences in reading skill. We are investigating the behavioral and neuroanatomical correlates of this variation in order to understand the neural underpinnings of this important language ability.
Some of our initial findings are:
- We identified and carefully tested a mathematically talented graduate student who demonstrated a reading profile characterized by excellent comprehension and very poor phonological decoding. On divided visual field tasks, he performed very poorly on words presented to the left visual field (right hemisphere), resulting in an extreme left hemisphere behavioral asymmetry. His MRI scan revealed an unusual type of Sylvian fissure morphology and an extreme leftward asymmetry of the planum temporale. This case study suggests one type of organization that may be associated with successful compensation for dyslexia.
- Resilient readers have achieved good reading comprehension despite poor phonological ability. We have identified a group of resilient readers in the college population, and compared their reading skills and neuroanatomical features to both proficient and poor readers. This work, spearheaded by graduate student Suzanne Welcome, suggests that resilient readers compensate for phonological deficits by relying to a greater extent on semantic context during reading. In addition, their cortical anatomy can be differentiated from that seen in poor and proficient readers. Resilient readers appear to be a unique subpopulation, on that can reveal modes of compensation that may be relevant for understanding dyslexia.
This research was supported by NSF Grant SBR-9729009 and NIH grant DC006957, and was conducted in collaboration with Dr. Christiana Leonard (University of Florida, Gainesville) and Dr. Ronald Otto (CDIC, Riverside).