Biomedical Engineering Reference
In-Depth Information
(or verifying) this hypothesis is the major focus of the present study. We will also
prove, through white matter parcellation into inner and outer compartments, that
an increment or decrement in white matter volume occurs respectively in the outer
compartment, where the communication between minicolumns takes place.
In addition to the volumetric study of white matter, the study of cortical thick-
ness, the geometrical difference in gyrification between normals and dyslexics, as
well as surface area and gray matter volume are of major importance, and will be
included in our future attempts to investigate the relationship between the MRI
and changes in minicolumnar structures. The level set representation for the gray
matter surface will play a major role in characterizing the geometry of the cortex
and analyzing the gyration window through the curvature at the different points.
Moreover, the wavelet transform will be applied on different sub-images as an
attempt to transfer the images to a different domain in which some information
about the temporal and frequency content of the images can be inferred.
3.2. Dataset Description
Sixteen right-handed dyslexic men, aged 18 to 40 years, and a group of 14
controls matched for gender, age, educational level, socioeconomic background,
handedness, and general intelligence participated in the present study. All sub-
jects were physically healthy and free of any history of neurological disease, head
injury, significant uncorrected sensory deficit, severe psychiatric disorder, and
chronic substance abuse, as determined by medical history, a physical examina-
tion, laboratory testing, and a structured psychiatric interview. Subjects currently
under treatment for attention deficit disorders were excluded. Dyslexic patients
with a childhood history of significant reading impairment were subject to inter-
vention, which ranged from tutoring to full-time special education. Despite their
significant reading disability, all had graduated from high school, several were in
college, and three had completed postdoctoral degrees. All met DSM-IV (Ameri-
can Psychiatric Association, 1994) criteria for developmental reading disorder. All
had at least average intelligence and good spoken language skills (Wechsler Full
Scale, Verbal, and Performance IQs
≥
90) but showed persistent reading deficits.
Passage (decoding) scores, reflecting a combination of reading rate and accuracy,
on the Gray Oral Reading Test, third edition (GORT-3), were 8 or lower using
norms for the ceiling of the test at a 12.9 grade level and an age of 18 years, 11
months. This cutoff score is 0.67 of an SD below average for high school seniors.
Using the GORT-3, all but one dyslexic subject read at a level that was, at the time
of study, at least 1 SD lower than his Full Scale IQ. Thus, this group generally
met both absolute and discrepancy-based criteria for dyslexia. Single-word recog-
nition scores (Wide Range Achievement Test, third edition, WRAT-3) were less
sensitive to the reading deficits. Ten out of 16 scored within an average range on
a test of single-word recognition (WRAT-3 Reading: 90-110), whereas the others
were deficient on this measure as well (range 73-88). Based on subject interviews
