A. Szkiełkowska, J Ratyńska, M. Kurkowski, A. Senderski, H Skarżyński, R. Markowska “Coherence between Tomatis test and central auditory processing audiologic tests battery in children with dyslexia” .
Dyslexia is a specific , language-based disorder, which characterises by the difficulty id words decoding, which reflects insufficient abilities of phonologic processing. Develpmental dyslexia, according to different authors, affects from 4% to 12% of school age population and is characterized by the difficulty in reading in a child with normal hearing and intelligence. Reading is a complex ability, which requires cooperation of different functions. Several studies have shown that dyslexia may be accompanied by auditory processing disturbances, such as disturbance of phonematic hearing, difficulty in sound analysis and pitch discrimination . There is no consensus whether presented auditory difficulties are related specifically with speech sounds or generally to all kinds of sound stimuli. Some theories suggest that processing disturbances affect also visual modality. The aim of the study was to evaluate time and frequency processing in children with developmental dyslexia. Material and methods The studied group were 20 children aged from 10 y.o to 14 y.o. diagnosed with confirmed dyslexia. The control group was formed by 20 children without school problems. All children have been examined by otolaryngologist and have had hearing tests performed, including pure tone audiometry and impedance audiometry. All children have been assessed by speech therapist and psychologist in order to confirm existing difficulties and to assess intelligence scores. In the studied group lowered scores of speech sound analysis and synthesis have been found. For psychological evaluation Benton, Rey and Wechsler tests have been used. All children in the studied group had normal intelligence scores , no vision defects and normal hearing thresholds. All children were right – handed. Auditory functions have been assessed with the use of Duration Pattern Test (DPD) developed by Musiek and Frequency Pattern Test (FTP) by Pinheiro. In the existing literature temporal analysis in children with dyslexia was assessed with battery of tests called temporal order judgement (TOJ). DPT and FPT tests can assess temporal aspects of sound analysis . Stimuli are presented separately to each ear at the level of 50 dB SL. Tests were performed in sound booth. In both tests, 30 sequences of 3 tones were presented. In DPT test 3 tones of 250ms and 500 ms are presented. In FPT tones of 1122 Hz and 880 Hz are presented. The child is expected to give answer reegarding pitch of the tone sequence (eg. High pitch, low pitch, high pitch) or tone duration(eg long – short – long). Scores below 80% for each test were considered as below normal. All children were tested as well with the use of Tomatis procedure, in order to assess auditory attention to external and internal sounds, pitch discrimination and auditory laterality. The results were subjected to statistical analysis with the use of t-Student test. Statistical analysis revealed significance level p<0.05 between the studied and control groups. Results In 18 children (90%) with dyslexia results in DPT and PPT were abnormal. 2 children had normal scores both on DPT and FPT. In the studied group, mean value for DPT in the right ear was 46,4% and in the left ear 42,6% of correct answers. In the control group, corresponding values were 95,4% and 96,7%.
Mean values obtained in FPT in dyslexic children were 47,4% for the right ear and 43,2 in the left ear. In control group corresponding values were 94,6% and 96,3%. Listening tests by Tomatis revealed that 18 (90%) children in the studied group had problems with pitch discrimination in frequency band 750-4000Hz. In the control group, pitch discrimination problems were present in only 2 (10%) subjects. Another major difference was high percentage of left ear laterality in the group with dyslexia (80%). In the control group, only 10% showed left-sided auditory laterality.
Discussion Results of the study show that children with developmental dyslexia often present central auditory temporal processing disturbances. Similar results were obtained by Walker et al. , however his studies showed differences in DPT test between dyslexic and non-dyslexic children, and no difference within FPT test. The results of our study are convergent with results of later studies performed by King et al. on adults with dyslexia. Observed difficulties in temporal and frequency sequential analysis may be responsible for problems with segmentation of phonic sequences, which is essential in acquisition of reading skills. In our study central auditory processing disorders have been found in 90% of children with dyslexia. This percentage is high compared to other studies. King et al have found similar abnormalities in 45% dyslexic subjects. The reason for this difference may be that the group studied by us was somehow pre-selected. The subjects were in most cases the children who were referred for hearing test due to suspection of hearing loss. Therefore it may not be representative for all dyslexic population. DPT and FPT are well-established audiological tests used to evaluate central auditory processing of time and pitch. Pitch discrimination procedure of the Tomatis listening test assesses similar features as FPT test. Results of both tests are highly coherent. The role of central auditory processing disorders in dyslexia needs further studies. However the fact is that auditory training programs (including Tomatis Method) give promising results in dyslexic children. Results of the studies confirm the presence of auditory disturbances in dyslexia, however do not confirm that auditory disturbances are the underlying problem. Based on latest studies , the magnocellular theory of dyslexia has been developed. It suggests disturbances within magnocellular system which supervises fast processing of visual, auditory and somatosensory information. Conclusions Disturbances of auditory processing are common in children with developmental dyslexia. FPT, DPT as well as Tomatis listening test are useful tools to assess central auditory processing deficits in dyslexic subjects.