Effects of an Auditory Lateralization Training in Children Suspected to Central Auditory Processing Disorder

BACKGROUND AND OBJECTIVES: Central auditory processing disorder [(C)APD] refers to a deficit in auditory stimuli processing in nervous system that is not due to higher-order language or cognitive factors. One of the problems in children with (C)APD is spatial difficulties which have been overlooked despite their significance. Localization is an auditory ability to detect sound sources in space and can help to differentiate between the desired speech from other simultaneous sound sources. Aim of this research was investigating effects of an auditory lateralization training on speech perception in presence of noise/competing signals in children suspected to (C)APD. SUBJECTS AND METHODS: In this analytical interventional study, 60 children suspected to (C)APD were selected based on multiple auditory processing assessment subtests. They were randomly divided into two groups: control (mean age 9.07) and training groups (mean age 9.00). Training program consisted of detection and pointing to sound sources delivered with interaural time differences under headphones for 12 formal sessions (6 weeks). Spatial word recognition score (WRS) and monaural selective auditory attention test (mSAAT) were used to follow the auditory lateralization training effects. RESULTS: This study showed that in the training group, mSAAT score and spatial WRS in noise (p value≤0.001) improved significantly after the auditory lateralization training. CONCLUSIONS: We used auditory lateralization training for 6 weeks and showed that auditory lateralization can improve speech understanding in noise significantly. The generalization of this results needs further researches.

Relation between working memory capacity and auditory stream segregation in children with auditory processing disorder

Background: This study assessed the relationship between working memory capacity and auditory stream segregation by using the concurrent minimum audible angle in children with a diagnosed auditory processing disorder [APD]

Methods: The participants in this cross-sectional, comparative study were 20 typically developing children and 15 children with a diagnosed APD [age, 9-11 years] according to the subtests of multiple-processing auditory assessment. Auditory stream segregation was investigated using the concurrent minimum audible angle. Working memory capacity was evaluated using the non-word repetition and forward and backward digit span tasks. Nonparametric statistics were utilized to compare the between-group differences. The Pearson correlation was employed to measure the degree of association between working memory capacity and the localization tests between the 2 groups

Results: The group with APD had significantly lower scores than did the typically developing subjects in auditory stream segregation and working memory capacity. There were significant negative correlations between working memory capacity and the concurrent minimum audible angle in the most frontal reference location [0[degree sign] azimuth] and lower negative correlations in the most lateral reference location [60[degree sign] azimuth] in the children with APD

Conclusion: The study revealed a relationship between working memory capacity and auditory stream segregation in children with APD. The research suggests that lower working memory capacity in children with APD may be the possible cause of the inability to segregate and group incoming information

Normalization and reliability evaluation of persian version of two-pair dichotic digits in 8 to 12-year-old children

Objectives: All subjects suspected of Central Auditory Processing Disorder [CAPD] were previously tested by free recall dichotic digits test [DDT]

The study objective was normalization and reliability evaluation of two-pair DDT in 750 native Persian subjects aged 8 to 12 years

Materials: A total of 750 subjects were divided into five age groups varying between 8 years and 12 years and 11 months old. Each age group had 150 subjects. DDT was tested in free recall condition. For evaluating DDT test-retest reliability, 300 participants [60 subjects in each age group] were tested again after one month

Results: Right and left ear mean score increased from 71.68[+/-2.19] and 58.51[+/-1.71] in the 8-year-old group to 90.26[+/-1.96] and 88.38[+/-1.36] in 12-year-old group, respectively

The mean Right Ear Advantage [REA] decreased from 13.16[+/-2.58] in the 8-year-old group to 1.88[+/-2.49] in the 12-year-old group. A high stability was observed between test-retest results [P0.0001]

Discussion: Persian version of two-pair dichotic digits exhibited proper reliability for evaluating 8 to 12-year-old subjects, and the study results can be used for evaluating the dichotic hearing function in subjects of the same age group

Auditory Brainstem Response Improvements in Hyperbillirubinemic Infants

BACKGROUND AND OBJECTIVES: Hyperbillirubinemia in infants have been associated with neuronal damage including in the auditory system. Some researchers have suggested that the bilirubin-induced auditory neuronal damages may be temporary and reversible. This study was aimed at investigating the auditory neuropathy and reversibility of auditory abnormalities in hyperbillirubinemic infants. SUBJECTS AND METHODS: The study participants included 41 full term hyperbilirubinemic infants (mean age 39.24 days) with normal birth weight (3,200-3,700 grams) that admitted in hospital for hyperbillirubinemia and 39 normal infants (mean age 35.54 days) without any hyperbillirubinemia or other hearing loss risk factors for ruling out maturational changes. All infants in hyperbilirubinemic group had serum bilirubin level more than 20 milligram per deciliter and undergone one blood exchange transfusion. Hearing evaluation for each infant was conducted twice: the first one after hyperbilirubinemia treatment and before leaving hospital and the second one three months after the first hearing evaluation. Hearing evaluations included transient evoked otoacoustic emission (TEOAE) screening and auditory brainstem response (ABR) threshold tracing. RESULTS: The TEOAE and ABR results of control group and TEOAE results of the hyperbilirubinemic group did not change significantly from the first to the second evaluation. However, the ABR results of the hyperbilirubinemic group improved significantly from the first to the second assessment (p=0.025). CONCLUSIONS: The results suggest that the bilirubin induced auditory neuronal damage can be reversible over time so we suggest that infants with hyperbilirubinemia who fail the first hearing tests should be reevaluated after 3 months of treatment.

effect of working memory training on auditory stream segregation in auditory processing disorders children

This study investigated the efficacy of working memory training for improving working memory capacity and related auditory stream segregation in auditory processing disorders children. Fifteen subjects [9-11 years], clinically diagnosed with auditory processing disorder participated in this non-randomized case-controlled trial. Working memory abilities and auditory stream segregation were evaluated prior to beginning and six weeks after completing the training program. Ten control subjects, who did not participate in training program, underwent the same battery of tests at time intervals equivalent to the trained subjects. Differences between the two groups were measured using a repeated measures analysis of variance. The results of this study indicated children who received auditory working memory training performed significantly better on working memory abilities and auditory stream segregation task than children do not received training program. Results from this case-control study support the benefits of working memory training for children with auditory processing disorders and indicate that training of auditory working memory is especially important for this population

[Developing and evaluating validity and reliability of Persian version of [dichotic fused rhymed word test]]

Objective: The aim of the present study is to develope and evaluate validity and reliability of Persian version of Dichotic Fused Rhymed Words Test in 18-25 years old normal population

Materials and Methods: The Persian version of Dichotic Fused Rhymed Words Test consisted of 15 pairs of monosyllable rhymed words. These paired words are set in 4 lists of 30 items that simultaneously were presented one to the left and another to the right ear so that they lead to perception of a single fusion concept. After selecting the test material from Moin Persian dictionary according to the intended criteria and pairing the rhymed words, content validity was assessed through lawshe method by 10 expert persons, words with high validity were selected and lists were set. Then, the words of each list were recorded on CD in a dichotic mode. Thereafter, the study was performed in 124 normal individuals [68 females and 56 males] within ages ranging from 18 to 25 years and the scores were recorded on a designed scoring form. To examine reliability of test, the test was performed on 15 individuals again two weeks after the initial test and the Pearson correlation was assessed

Results: There are significant differences between mean scores of right and left ears [P<0.001]. Content Validity Ratio was 0.8-1 for every item. Pearson correlation was 0.83 for test-retest [P<0.001]. Cronbach's alpha and Intra Class Correlation [ICC] was 0.81 and 0.84 for internal correlation between scores of lists of test. The result showed that there is significant correlation between the lists

Conclusion: Based on the obtained results, the Persian version of Dichotic Fused Rhymed Words Test has a good content validity and reliability. It can be used in detecting function of corpus callosum, lateralization of the cerebral hemispheres and assessment of central auditory processing

Evaluation of Saccular Function Pre-Post Cochlear Implant Surgery Using VEMPs

Objectives: The aim of present study was evaluation of saccular function in cochlear implant candidates with severe to profound sensory neural hearing loss. Before and after cochlear implantation

Methods: In this study 35 Cochlear Implant [CI] candidates with bilateral severe to profound sensory neural hearing loss before and about 30 days after cochlear implantation and 20 normal-hearing cases as a control group underwent VEMP test. Both groups were matched based on gender and age.

Results: VEMP responses were absent bilaterally in 10 out of 35 patients. 4 patients were excluded from the study because they did not receive CI during present study. From 21 remaining patients, 5 cases lost VEMP response in their implanted ear after surgery. In control group, VEMP responses were present bilaterally.

Discussion: The results of present study show that saccular dysfunction in CI candidates is extremely probable and this is possible that saccule get impaired after CI.

Auditory lateralization ability in children with [central] auditory processing disorder

The aim of the present study was to assess the auditory lateralization ability in children with [central] auditory processing disorder. Participants were divided in two groups: 15 children with Central Auditory Processing Disorder [8-10 years] and 80 normal children [8-11 years] from both genders with pure-tone air-conduction thresholds better than 20 dB HL bilaterally and interaural pure tone threshold difference better than 5 dB . All subjects had normal IQ and normal otoscopy: In the present study 9 imaginary positions were simulated in horizontal plane by Interaural Time Difference [ITD] and Interaural Intensity Difference [IID] to evaluate the auditory lateralization performance in normal and children with [central] Auditory Processing Disorder [C] APD. Lateralization performance were determined by ITD ranging from -880 to +880 microsecond and IID ranging from -10 to +10 dB for high pass and low pass noise[2 kHz cut off point]. Boltzmann function was used to describe the auditory lateralization performance and Independent Samples T-test was used to compare the two groups. According to Boltzmann function two major types of abnormalities were revealed in the lateralization performances: 1- completely disoriented, 2- side-oriented. 86.6% of [C] APD children showed significant increase in mean of test errors compared with normal ones [p<0.001]. The study supports the hypothesis that most children with [C] APD have poor auditory lateralization and abnormal processing of binaural cues