[Dynamics of blood flow velocity in middle cerebral arteries in dyslexic persons]

The aim of our study was to investigate the blood flow in middle cerebral arteries during the different forms of cognitive activity in dyslectic persons. Two group of subjects were tested. The first group consisted of 10 students with school difficulties, diagnosed neuropsychologically as having a particular form of dyslexia, i.e. dysgraphy or dysorthography. 6 of them were right lateralized and 4--left lateralized. The second contained 10 students without such problems. 7 of them were right lateralized and 3--left lateralized. We used four kinds of cognitive tasks, during which the blood flow velocity in MCA in left and right hemisphere was measured with the Transcranial Doppler method. The analysis of the results showed differences between the groups of blood flow velocity levels, without a difference in performance profile. The dysgraphic persons had significantly higher blood flow velocity in the right hemisphere compared to the reference group. The results suggest particularly important role of right hemisphere in dyslexic persons, which is consistent with results obtained by other authors. The analysis of lateralization showed that this factor influences significantly the blood flow velocity level--the left lateralized persons showed lower rise of blood flow velocity than the right lateralized, regardless of the kind of task and measured hemisphere.