Auditory processing disorders are on our minds because we'll be giving a 3 hr seminar on central auditory processing disorders next week at the Washington Speech & Hearing Association.
Auditory processing disorders are extremely common in the school age population, and the parents and teachers should be aware of them as causes of inappropriate diagnoses of attention disorders or underachievement.
Peripheral hearing problems are a significant problem particularly in the preschool population because of the high incidence of ear infections and a short Eustachian tube in young children. An average elementary school child has 7 ear infections per year, and the average ear infection takes 40 days to drain. The average amount of hearing loss from an ear infection is 20 dB, and children with this degree of hearing loss will miss 30-50% of what a teacher says.
Central auditory processing disorders have been thought to be only 5% of the population, but is certainly much higher. 10% of children less than 8 years old have auditory discrimination problems (phonology / dyslexia), and auditory processing disorders are the most common learning disorders in children who had a premature birth (now 1 in 8 births).
The biology of CAPDs is very exciting in terms of what is now able to show objectively in specific research studies, but parents and teachers should be aware there is a significant lag between the research lab and the testing suite or classroom. Current CAPD conundrums include (but are not limited to):
1. Inability of available testing to address the full range of patient symptoms.
2. Lack of simple and direct correspondence between symptoms, tests, and treatments
3. Lack of standardization in terminology/nomenclature, and test batteries.
4. Difficulty communicating with non-specialist clinicians, educators, and parents.
5. Lack of specific/targeted interventions to solve physiological deficits.
6. Inadequate understanding of boundaries between normal development and disease.
7. Incomplete adoption of CAPD by the medical and educational establishments.
But we don't share this to be despairing. The basic research is extraordinarly promising in terms of the trainability of CAPDs and the capacity for the hearing brain to 'reorganize'. Even relatively unselective training or education programs have been shown to improve students' ability to discriminate sounds and pitch contours, distinguish speaking from background noise, improve auditory attention adn memory, and improve sound localization. What we don't have yet, though, is a way to efficiently recognize and prioritize auditory processing needs on a population basis, or provide appropriate therapeutic or educational solutions based on these needs.
The figure below shows the finding by McMaster researchers that Suzuki training in young children already showed that they had much more auditory cortex activated to instruments than non-Suzuki trained children. In adult musician studies, more definite patterns of instruments can be seen (trumpeters have more auditory cortex devoted to trumpets, violinists, to violins, etc).
Suzuki Music Enhances Auditory Cortical Development