First and foremost I am grateful to Peter Blythe and Sally Goddard-Blythe from INPP, Chester who promoted my contacts to the majority of the people with whom I have been working in this matter for several years.
This presentation would not have been possible without much appreciated cooperation with Håkan Carlsson and Birgitta Borthen, The Sensomotoric Centre in Mjölby, Sweden; Camilla Leslie, MRCSLT, East Lothian Department of Speech and Language Therapy, Scotland; Nina Alopaeus-Laurinsalo and Veli Laurinsalo, The Sensomotoric Centre in Helsinki in cooperation with Dr. Pirjo Korpilahti, Department of Phonetics, University of Helsinki, Finland, and the former and current staff members at A Chance To Grow’s New Vision School in Minneapolis: Kari Done, Tammy Brenitzer, Sara Cook and Kimberly Herman.
Last, but not least, I want to thank my friend, composer and music publisher Bent-Peder Holbech, ROTNA-music, Aakirkeby, Denmark for his enthusiastic work with the soundtracks SYNCRO-SOUND, that have been used in all the presented specific auditory stimulation projects (ADT, HSAS, JST).
This presentation was supported by a grant (1494-28812) from The Danish Research Council for the Humanities.
There is evidence that the difficulties in phonological processing found by many dyslexics may be related to altered cell size in the magnocellular layer of the medial geniculate nucleus of the brain which could be linked to abnormal development of the auditory system of the left hemisphere. This abnormal development may play a role in poor processing of rapid temporal transition sounds (i.e. speech sounds, in particular rapid processing of consonants and consonant blends).
The interference of processing these sounds may lead to a multitude of problems including poor auditory and reading comprehension skills, sequencing and memory skills, problem solving, speech production, as well as interaction skills.
These may be compounded when put into an environment with competing stimuli (i.e. a classroom, playground, gymnasium, or even home with a television or radio playing in the background).
For decades researchers have been aware that individuals exist who, despite apparently normal peripheral hearing sensitivity, exhibit auditory difficulties. In 1954, Helmer Myklebust, in his book Auditory Disorders in Children, discussed the presence of what he termed “central hearing loss” in the pediatric population. Today we would call it Central Auditory Processing Disorders (CAPD).
It has been found in an animal model that auditory discrimination abilities may progressively improve with practice. It has been hypothesized that similar improvements may be induced in children using special auditory stimulation techniques.
The results reported in the following seem to indicate that simple assessment techniques, such as precise determination of hearing thresholds, binaural audiometry and dichotic listening to decide auditory laterality, may contribute to the diagnosis of what is generally considered to be a central processing problem often out of reach by normally applied teaching methods.
Furthermore it is indicated that specific auditory stimulation based on such assessments may positively support remedial education by improving auditory discrimination abilities.
The projects presented here are the results of developmental work by several clinics and schools in Europe and the U.S. using specific auditory stimulation programs to support remedial education.
Most of the previous research on auditory problems in relation to specific language and reading problems focuses on central auditory processing disorders resulting from dysfunction of processes related to audition.
Brain imaging studies and postmortem examinations of individuals with dyslexia, learning disabilities, ADHD, and normal controls have revealed functional, morphologic and structural differences in auditory areas of the brain that are activated when listening to simple tonal complexes, language and music (Galaburda and Kemper, 1978; Hynd et al, 1990, 1991).
Other researchers have concluded that some children’s discrimination deficits originate in the auditory pathway before conscious perception and have implications for differential diagnosis and targeted therapeutic strategies for children with learning disabilities and attention disorders (Korpilahti, 1996; Kraus et al, 1996).
Leviton and Bellinger (1986) concluded on the basis of a meta analysis of several studies that there is a convincing association between early and persistent otitis media and later reduction in language function as measured by paraphrase quality.
Wright et al (1997) reported that children with specific language impairment have auditory perceptual difficulties in certain temporal and spectral sound contexts and are less able than controls to take advantage of a frequency separation between a tone and noise to aid detection of a tone. They conclude that the temporal and spectral specificity of the auditory perceptual deficits reported may serve to guide the search for the underlying neural bases of language disorders.
Evidence exists that weakness in the auditory identification of speech sounds is one of the causal factors in poor reading skills (Clark & Richards, 1966; Goetzinger, 1962).
Bess, Tharpe, and Gibler (1986) reported that children with unilateral, right ear impairment tended to have poorer syllable recognition scores than left ear impaired children, but found no apparent explanation for this difference.
Näslund, Johansen and Thoma (1997) reported from a study with 59 Danish subjects that dichotic listening (DL) predicts reading performance, but language laterality variations among handedness and gender groups must be considered. Analyses of separate handedness groups found that significant variance in reading measures for R-Handed subjects was explained by Age, L-ear bias in DL-reports from both ears (DL-B) and the difference between responses to left ear alone and L-ear reports in DL-B.
Variance in Non-R-Handed subjects’ reading was explained by Gender, Age, L-ear intrusions in DL when attending the R-ear (DL-R) and responses to right ear alone minus DL-R.
Tomatis (1991) has suggested an ascending hearing curve from 15-20 dB at 125 Hz to -5 --10 dB at 3000-4000 Hz with stabilization at this level and a slight drop in the higher frequencies to be the optimum curve for analysis of music and language. This optimum curve was also found by Gulick (1971).
Plasticity is now recognized as a fundamental property also of the central auditory system (Diamond, 1988).
Auditory system plasticity may result in deprived speech perception and language learning problems if hearing, especially in the right ear, has been reduced during some critical periods of early life (Jensen, J.H. et al, 1989)
On the other hand, plasticity may also be the fundamental reason for the reported improved results in auditory perception after specific auditory stimulation as suggested by Johansen (1984, 1988, 1992).
Taken together the reported research has raised these questions:
1) Is there a correlation between the total variation of the hearing curves and the optimum curve (as suggested by Tomatis) and the number of errors found by dichotic listening?
2) Can specific auditory stimulation influence hearing sensitivity and thus the variation between the hearing curve and the optimum curve?
3) Is a reduction in variation obtained by specific auditory stimulation followed by a reduction in errors registered by dichotic listening?
4) Are length of stimulation periods and reductions in errors correlated?
5) Are there any indications that specific auditory stimulation may influence other aspects of children’s behavior?
To answer these questions clinical results from four different settings in four different countries have been evaluated.