Relation Between Speech Delay and Dyslexia
National Institute of Child Health and Human Development
Principal Investigators:
Bruce F. Pennington, Ph.D. and Richard Boada, Ph.D.
This longitudinal study extends our previous work on the genetics
and linguistic phenotype in familial dyslexia (see selected
annotated publications) by studying its relation to other
speech/language disorders. Specifically, this project focuses
on the relation between speech delay (SD) and dyslexia (RD)
which manifest at different ages and are typically studied
by different disciplines, two factors which may have obscured
their relation. If they share etiological and cognitive risk
factors, then a shift in their conceptualization,
diagnosis, and treatment may be indicated.
The project will answer the following questions:
- Do speech delay and dyslexia share genetic risk factors?,
- Do they share underlying cognitive risk factors?
To answer these questions, we have identified and tested
112 five-year-old probands with speech delay, 77 of their
5-7 year old siblings, and 41 five-year-old controls. All
subjects have been tested with measures of 1) speech and language
symptoms, and 2) phonological and auditory processes that
might be common to both speech delay and dyslexia. We have now
evaluated the literacy outcome of SD probands and controls at
age 8.
So far, we have found that 1) the SD group as a whole has a
phonological deficit similar to that found in dyslexia, but
differ in having worse language impairment
but better performance on rapid serial naming tasks and
2) that the entire SD group has a worse literacy outcome at age
8 than controls, but that the subgroup of SD with LI carries most
of the risk for a diagnosis of dyslexia. We are now comparing the
SD group at age 8 to other dyslexic groups at a similar age to
better define which cognitive risk factors are shared and not
shared by these two disorders.
The sibling
pair sample has been tested by our collaborator Shelley Smith
for linkage between speech delay
and candidate loci for dyslexia on chromosomes 1p, 6p, and
15q and significant linkage was found to the loci on 6p and
15q. We will conduct a whole genome scan of a larger sib-pair
sample to identify other risk loci for SD.
return to top
Current
Projects | Validity of Subtypes of
ADHD
|
