Regional Cerebral Blood Flow (rCBF) in Developmental Dyslexia

Abstract

This exploratory study examined the patterns of regional cerebral blood flow (rCBF) in a surface and deep dyslexic during reading. Two rCBF studies (at rest, activated) were completed with each developmental dyslexic adult and their age- and sex-matched control. During the activated study, each subject read silently a controlled narrative passage. Comprehension tests verified reading activity. 133 Xenon activity after a 1-minute inhalation period and a 10-minute desaturation period was followed using 20 collumated sodium-iodide detectors. An analysis of gray matter blood flow indicated that for the controls, significant right central-posterior activation resulted from reading a narrative text. Also, differences existed between the surface and deep dyslexic in the distribution of cortical perfusion during the activated study. Compared to the matched controls, less brain activation was noted during reading bilaterally in the deep dyslexic and in the right hemisphere in the surface dyslexic. These results are discussed as they relate to neurolinguistic models of brain functioning implicated in fluent and dysfluent reading.