Some children with certain language disorders may not properly process the sounds they hear,
resulting in language impairments. The purpose of this study is to determine if deficits in
auditory temporal processing the way the brain analyzes the timing and patterns of sounds are
an inherited trait.
Families with auditory temporal processing deficits are sought in order to identify the genes
responsible for auditory temporal processing deficits. Children and adults with a diagnosis
or history of language impairment in the family and their family members both affected and
non-affected are eligible for this two-part study. In Part 1, participants undergo a series
of language tests and listening tests to measure various characteristics of how they perceive
sound. In Part 2, they are interviewed about language disorders, learning disabilities, and
other medical problems of family members. This information is used to construct a pedigree
(family tree diagram) showing the pattern of inheritance of family traits. Study subjects
whose pedigree indicates that language disorders may be hereditary in their family will
provide either a small blood sample (1 to 2 tablespoons) or a tissue specimen obtained from a
cheek swab (rubbing the inside of the cheek with a small brush or cotton swabs). The sample
will be used to isolate DNA for genetic analysis.
Recent research implicates auditory processing deficits in the etiology of language
impairments, but no standard methodology has been employed to determine whether auditory
processing deficits are heritable traits. We will investigate whether auditory processing
skills and auditory processing disorders (APDs) are hereditary.
We will study same-sex twins (healthy volunteers) and individuals who score in the top or
bottom 10th percentile on auditory processing tests and their first-degree family members.
Design: A Two-Phase, Staged Study
Our approach uses the two classical methods of demonstrating heritability: comparison of
monozygotic (MZ) to dizygotic (DZ) concordance rates in twins and measuring familial
aggregation of a trait. While there are a variety of auditory processing tests in common use,
there is no standard battery of tests for the diagnosis of APD.
Moreover, the normal variation in performance on many of these tests is not known. We will
systematically evaluate tests of auditory processing for variation in the general population
and for evidence of heritability.
Phase 1 Twin study
We will evaluate a variety of auditory processing tests in MZ and same-sex DZ twins. This
initial phase of the study is designed to provide data so that the performance of MZ twin
pairs can be compared to the performance of DZ twin pairs. Statistical modeling will be used
to estimate the relative contributions of heredity and environment to auditory processing
skills. In addition, we will examine variation in auditory processing skills in the general
population of twins. This will allow us to identify auditory processing skills and tests that
have the greatest heritable components, and to establish normative data for the tests we
Phase 2 Family aggregation study
Based on the outcomes of Phase 1, auditory processing tests of skills with the highest
heritable component will be selected for evaluation of probands. Those who score in the top
and bottom 10th percentile will be eligible for participation as probands in this phase of
the study. Variation of these skills in the general population, as determined by the twin
data (Phase 1) or published norms, when they are available, will be used to determine the top
and bottom 10th percentiles. This same test set will be administered to probands and at least
two first-degree relatives allowing us to determine whether traits related to auditory
processing occur within the family at a rate greater than chance.
Phase 1 outcome measures will be individual performance on tests of auditory processing
skills and comparative performance of MZ and DZ co-twin pairs on these tests. Phase II
outcome measures will be the performance on auditory processing measures of probands and
their family members, and affectance rates observed in these families.<TAB>
- INCLUSION CRITERIA:
6-85 years of age
Native English speaker, with English as the first language
Phase 1 Same sex twins (MZ or DZ) and both willing and able to participate in test
Phase 2 Score in the top or bottom 10th percentile on tests of auditory processing or are a
first-degree relative of someone who scores in the top or bottom 10th percentile and are
willing and able to participate in the test procedures.
Hearing loss, defined as air conduction pure tone thresholds (250-8000 Hz) exceeding 20
dBHL; air-bone gaps, even in the presence of normal hearing sensitivity, exceeding 10 dBHL;
and/or abnormal tympanometry.
History of chronic (fluid in middle ear for more than 4 months) or recurrent otitis media
(more than 4 episodes of acute otitis media in one year)
History of ear surgery.
History or diagnosis of a central nervous system disorder, including but not limited to:
- Intracranial tumors
- Cerebrovascular disease
- Degenerative CNS disorder
- CNS trauma
- Auditory neuropathy
- Attention deficit hyperactivity disorder (ADHD)
- Attention deficit disorder (ADD)
Currently taking medications capable of altering CNS function (e.g. antidepressants,
anxiolytics, or a psychostimulant drugs such as ritalin).
History of treatment with ototoxic medications that may affect ultrahigh frequency hearing
(e.g. cisplatin, aminoglycoside antibiotics).
Unable to provide consent or assent