Perspectives on dichotic listening and the corpus callosum

Dichotic listening and interhemispheric integration after callosotomy: A systematic review

The right-ear advantage (REA) for recalling dichotically presented auditory-verbal stimuli has been traditionally linked to the dominance of the left cerebral hemisphere for speech processing. Early studies on patients with callosotomy additionally found that the removal of the corpus callosum leads to a complete extinction of the left ear, and consequently the today widely used models to explain the REA assume a central role of callosal axons for recalling the left-ear stimulus in dichotic listening. However, later dichotic-listening studies on callosotomy patients challenge this interpretation, as many patients appear to be able to recall left-ear stimuli well above chance level, albeit with reduced accuracy. The aim of the present systematic review was to identify possible experimental and patient variables that explain the inconsistences found regarding the effect of split-brain surgery on dichotic listening. For this purpose, a systematic literature search was conducted (databases: Pubmed, Web of Knowledge, EBSChost, and Ovid) to identify all empirical studies on patients with surgical section of the corpus callosum (complete or partial) that used a verbal dichotic-listening paradigm. This search yielded ks = 32 publications reporting patient data either on case or group level, and the data was analysed by comparing the case-level incidence of left-ear suppression, left-ear extinction, and right-ear enhancement narratively or statistically considering possible moderator variables (i.a., extent of the callosal surgery, stimulus material, response format, selective attention). The main finding was an increased incidence of left-ear suppression (odds ratio = 7.47, CI95%: [1.21; 83.49], exact p = .02) and right-ear enhancement (odds ratio = 21.61, CI95%: [4.40; 154.11], p < .01) when rhyming as compared with non-rhyming stimuli were used. Also, an increase in left-ear reports was apparent when a response by the right hemisphere was allowed (i.e., response with the left hand). While the present review is limited by the overall small number of cases and a lack of an appropriate control sample in most of the original studies, the findings nevertheless suggest an adjustment of the classical dichotic-listening models incorporating right-hemispheric processing abilities as well as the perceptual competition of the left- and right-ear stimuli for attention.

Hearing Loss and Cognitive Decline in the Aging Population: Emerging Perspectives in Audiology

In this perspective article, the author explores the connections between hearing loss, central auditory processing, and cognitive decline, offering insights into the complex dynamics at play. Drawing upon a range of studies, the relationship between age-related central auditory processing disorders and Alzheimer's disease is discussed, with the aim of enhancing our understanding of these interconnected conditions. Highlighting the evolving significance of audiologists in the dual management of cognitive health and hearing impairments, the author focuses on their role in identifying early signs of cognitive impairment and evaluates various cognitive screening tools used in this context. The discussion extends to adaptations of hearing assessments for older adults, especially those diagnosed with dementia, and highlights the significance of objective auditory electrophysiological tests. These tests are presented as vital in assessing the influence of aging and Alzheimer's disease on auditory processing capabilities and to signal cognitive dysfunction. The article underscores the critical role of audiologists in addressing the challenges faced by the aging population. The perspective calls for further research to improve diagnostic and therapeutic strategies in audiology, and emphasizes the need for a multidisciplinary approach in tackling the nexus of hearing loss, auditory processing, and cognitive decline.

A comment on the order of report in two-pair dichotic digit testing in children assessed for auditory processing

OBJECTIVE

This clinical note aimed to 1) describe the order-of-report (OoR) strategies used by a large sample of children who completed 2pDD testing in the free-recall condition as part of an audiological assessment of auditory processing (AP), and 2) determine if use of OoR correlated with 2pDD test performance.

DESIGN

A retrospective (case-review), single observation design.

STUDY SAMPLE

A convenient sample of 77 children (50 males and 27 females aged 7.0 to 17.4 years [median = 8.8 years]) referred to audiology for an AP assessment.

RESULTS

The participating children used temporal more than ear or sequential OoR and showed decreased test scores with increased use of ear OoR.

CONCLUSIONS

These findings suggest children referred for an AP assessment could favour a temporal OoR when completing 2pDD testing for its opportunity to rehearse the first digit pair (possibly strengthening its memory trace) prior to processing the second digit pair, while their use of an ear OoR could come at the cost detrimental ear dominance effects that reduce their test performance. Future research could consider if similar results are observed in other child populations and if preferred dichotic processing strategy could inform auditory training for children with dichotic listening deficits.

Children with amblyaudia show less flexibility in auditory cortical entrainment to periodic non-speech sounds

OBJECTIVE

We investigated auditory temporal processing in children with amblyaudia (AMB), a subtype of auditory processing disorder (APD), via cortical neural entrainment.

DESIGN AND STUDY SAMPLES

Evoked responses were recorded to click-trains at slow vs. fast (8.5 vs. 14.9/s) rates in n = 14 children with AMB and n = 11 age-matched controls. Source and time-frequency analyses (TFA) decomposed EEGs into oscillations (reflecting neural entrainment) stemming from bilateral auditory cortex.

RESULTS

Phase-locking strength in AMB depended critically on the speed of auditory stimuli. In contrast to age-matched peers, AMB responses were largely insensitive to rate manipulations. This rate resistance occurred regardless of the ear of presentation and in both cortical hemispheres.

CONCLUSIONS

Children with AMB show less rate-related changes in auditory cortical entrainment. In addition to reduced capacity to integrate information between the ears, we identify more rigid tagging of external auditory stimuli. Our neurophysiological findings may account for domain-general temporal processing deficits commonly observed in AMB and related APDs behaviourally. More broadly, our findings may inform communication strategies and future rehabilitation programmes; increasing the rate of stimuli above a normal (slow) speech rate is likely to make stimulus processing more challenging for individuals with AMB/APD.

Dichotic-listening performance after complete callosotomy: No relief from left-ear extinction by selective attention

The surgical section of the corpus callosum (callosotomy) has been frequently demonstrated to result in a left-ear extinction in dichotic listening. That is, callosotomy patients report the left-ear stimulus below chance level, resulting in substantially enhanced right-ear advantage (REA) compared with controls. A small number of previous studies also suggest that callosotomy patients can overcome left-ear extinction when the instruction encourages to attend selectively to the left-ear stimulus. In the present case study, we re-examine the role of selective attention in dichotic listening in two patients with complete callosotomy and 40 age- and sex-matched controls. We used the standardised Bergen dichotic-listening paradigm which uses stop-consonant-vowel syllables as stimulus material and includes both a free-report and selective-attention condition. As was predicted, both patients showed a clear left-ear extinction. However, contrasting the earlier reports, we did not find any evidence for a relief from this extinction by selectively attending to the left-ear stimulus. We conclude that previous demonstrations of an attention-improved left-ear recall in callosotomy patients may be attributed to the use of suboptimal dichotic paradigms or residual callosal connectivity, rather than representing a genuine effect of attention.

Dichotic Sentences Test Performance of Adults with communication complaints

PURPOSE

To analyze the performance of normal-hearing adults with communication complaints in the Dichotic Sentences Test.

METHODS

We selected from the database 15 normal-hearing participants with normal results in the Digits Dichotic Test, aged between 19 and 44 years, right-handed, who reported communicative complaints. The Dichotic Sentences Test was applied using two protocols consisting of four different combinations of lists called sequences 1 and 2, in the following order: training, divided attention step, right and left directed attention steps.

RESULTS

In the first application sequence, the average performance in the divided attention step was 84.7% for the right ear and 60.67% for the left, with statistical difference between ears. The asymmetry between ears varied from -50% to 60%. In the directed attention step, the average performance was 99.33% for the right ear and 98% for the left, with no statistical difference. In the second application sequence, there was a tendency for better results, more pronounced for the left ear, with no statistical significance, with the performance variation and asymmetry between ears remaining high. In the comparison between the sequences, in the divided attention step, it was found that, for the right ear, 40% of the individuals did not vary, 33% performed worse, and 26.7% performed better; for the left ear, 6.6% did not vary, 20% performed worse, and 73.33% performed better. There was result stability in the directed attention step.

CONCLUSION

The normal-hearing adults with communication complaints presented a heterogeneous profile, especially in the divided attention step, with a marked difference between ears and response variability.

Association of Central Auditory Processing Dysfunction With Preclinical Alzheimer's Disease

OBJECTIVE

To investigate whether central auditory processing dysfunction measured by the dichotic digit test-1 digit (DDT1) is present in preclinical Alzheimer's disease (AD) individuals who are cognitively normal (CN) older adults with the cerebral beta-amyloid (Aβ) deposition and to explore the potential of the DDT1 as a screening test for preclinical AD.

STUDY DESIGN

Cross-sectional design.

SETTING

A prospective observational cohort study.

METHODS

CN older adults with a global clinical dementia rating score of 0 were included. The hearing test battery including pure-tone audiometry, speech audiometry, distortion product otoacoustic emission, and DDT1 was administered to participants.

RESULTS

Fifty CN older adults were included. Among them, 38 individuals were included in the Aβ deposition negative (AN) group and 12 were included in the Aβ deposition positive (AP) group. The DDT1 scores of both the better and worse ears were significantly lower in the AP group than in the AN group (p = .008 and p = .015, respectively). No significant differences were observed between the groups in tests of the peripheral auditory pathways. In multivariable logistic regression analysis adjusted for apolipoprotein E4 positivity, the DDT1 better ear score predicted the AP group (p = .036, odds ratio = 0.892, 95% confidence interval: 0.780-0.985) with relatively high diagnostic accuracy.

CONCLUSION

Our findings suggest that Aβ deposition may affect the central auditory pathway even before cognitive decline appears. DDT1, which can easily be applied to the old-age population, may have the potential as a screening tool for preclinical AD.

Central Auditory Processing Dysfunction in Service Members and Veterans: Treatment Considerations and Strategies

PURPOSE

Military risk factors such as blast exposure, noise exposure, head trauma, and neurotoxin exposure place Service members and Veterans at risk for deficits associated with auditory processing dysfunction. However, there is no clinical guidance specific to the treatment of auditory processing deficits in this unique population. We provide an overview of available treatments and their limited supporting evidence for use in adults, emphasizing the need for multidisciplinary case management and interdisciplinary research to support evidence-based solutions.

METHOD

We explored relevant literature to inform the treatment of auditory processing dysfunction in adults, with emphasis on findings involving active or former military personnel. We were able to identify a limited number of studies, pertaining primarily to the treatment of auditory processing deficits through the use of assistive technologies and training strategies. We assessed the current state of the science for knowledge gaps that warrant additional study.

CONCLUSIONS

Auditory processing deficits often co-occur with other military injuries and may pose significant risk in military operational and occupational settings. Research is needed to advance clinical diagnostic and rehabilitative capabilities, guide treatment planning, support effective multidisciplinary management, and inform fitness-for-duty standards. We emphasize the need for an inclusive approach to the assessment and treatment of auditory processing concerns in Service members and Veterans and for evidence-based solutions to address complex military risk factors and injuries.

Age-Related Dichotic Listening Skills in Impaired and Non-Impaired Readers: A Comparative Study

Dichotic listening is the high-level auditory process which enables the perception of different verbal stimuli delivered simultaneously to the right and left ears (binaural integration), as well as the perception of a verbal stimulus presented to one ear while ignoring a different stimulus in the other ear (binaural separation). Deficits in central auditory processing have been reported in children with learning disabilities. The present study aimed to compare dichotic listening performances in right-handed impaired readers (IR) and non-impaired readers (non-IR) according to age. For this, a cross-sectional study was conducted in 120 IR (56 males and 64 females) divided into five age groups and 120 non-IR (63 male and 57 female) matched on chronological age (8 to 9 years; 9 to 10 years; 10 to 12 years; 12 to 18 years; adult). They were tested for binaural integration and binaural separation, allowing for the calculation of dichotic aptitude (DA), ear prevalence (EP), and attentional shift index (ASI). A series of ANOVAs showed an effect of age and of the reading group for all the dichotic-related measures, except for EP. Binaural separation scores were lower in IR who also showed more intrusive responses compared to non-IR. These intrusive responses, which were more frequent on the right ear for IR, decreased with age in both groups. Overall, these results suggest that dichotic listening scores improve with age as the central auditory pathways mature. However, whatever the age, performances are lower in IR than in non-IR. This might be explained by an incomplete maturation of the auditory pathways in IR; an early start for long-term follow-up and auditory training is suggested.

Central Auditory Processing Disorder in Patients with Amnestic Mild Cognitive Impairment

Background

This study was conducted to comprehensively examine the central auditory processing (CAP) abilities of patients with amnestic mild cognitive impairment (aMCI) as well as to compare the results with cognitively normal elderly controls.

Methods

A total of 78 participants were screened through pure-tone audiometry and word recognition score in order to exclude peripheral auditory dysfunction. Forty-five people passed screening tests, and 33 people failed. Finally, 25 aMCI (mean age = 71.52 ± 4.8; male : female = 24 : 76) and 20 controls (mean age = 73.45 ± 4.32; male : female = 45 : 55) were enrolled in the study. Seven CAP tests (frequency pattern test, duration pattern test, Gap-In-Noise^© test, dichotic digits test, low-pass filtered word test, speech perception in noise test, and binaural fusion test) were conducted only after the two groups passed the screening. A linear mixed model was applied to analyze CAP tests except for the binaural fusion test. For the binaural fusion test, the independent t-test was used to compare the means of test score between two groups.

Results

The aMCI group had a decrease in the mean score of the frequency pattern test, duration pattern test, Gaps-In-Noise^© test, dichotic digits test, and speech perception in noise test compared with the control group.

Conclusion

The aMCI group's CAP abilities were significantly lower than those of the control group. Thus, if the cognitive assessment and hearing evaluation are conducted in combination, the sensitivity of the diagnostic process for aMCI will be increased.

Language lateralization in very preterm children: associating dichotic listening to interhemispheric connectivity and language performance

BACKGROUND

Language difficulties of very preterm (VPT) children might be related to weaker cerebral hemispheric lateralization of language. Language lateralization refers to the development of an expert region for language processing in the left hemisphere during the first years of life. Children born VPT might not develop such a dominant left hemisphere for language processing. A dichotic listening task may be a functional task to show the dominance of the left hemisphere during language processing. During this task, different acoustic events are simultaneously presented to both ears. Due to crossing fibers in the brain, right ear stimuli are transferred directly to the left hemisphere, and left ear stimuli are transferred first to the right hemisphere and then, through the corpus callosum (CC), to the left hemisphere. Dichotic listening typically shows a right ear advantage, assuming to reflect left hemispherical language dominance. The CC, in particular the splenium, is associated with auditory processing and is considered important for language lateralization. The objective of this work was to explore whether dichotic listening performance in school-aged VPT children are associated with language performance and interhemispheric connectivity.

METHODS

This is a cross-sectional study of 58 VPT children and 30 full term controls at age 10 years. Language performance and dichotic digit test (DDT) were assessed. In 44 VPT children, additionally diffusion weighted imaging (DWI) was performed using a 3 T MRI scanner. Fractional anisotropy (FA) and mean diffusivity (MD) values of the splenium of the CC were extracted.

RESULTS

Poorer right ear DDT scores were associated with poorer language performance in VPT children only (p = 0.015). Association between right ear DDT scores and MD of the splenium approached the level of significance (p = 0.051).

CONCLUSIONS

These results support the hypothesis that poor language performance in VPT children may be a consequence of weaker lateralized language organization, due to a poorly developed splenium of the CC. Dichotic listening may reflect the level of language lateralization in VPT children.

IMPACT

Poor language performance in VPT children may be a consequence of weaker lateralized language organization, due to a poorly developed splenium of the CC. Dichotic listening performance may reflect the level of language lateralization in VPT children and right ear scores of a dichotic listening task are associated with both the splenium of the corpus callosum and language performance. If our results could be validated in future research, it suggests that poor CC development may indicate VPT children at risk for long-term language problems.

Effect of diurnal changes on dichotic listening in younger adults with normal hearing

Background

Diurnal changes can be defined as the time of the day over an individual's performance level for different activities that involve physical and mental tasks.

Objective

The current study aimed to evaluate the effect of diurnal changes in scores obtained for the Dichotic Consonant-Vowel paradigm by young adults with normal hearing sensitivity.

Method

Based on the ‘Morningness-Eveningness questionnaire’ given by Horne & Ostberg, the subjects were divided into moderately-morning, intermediate and moderately-evening categories. The Dichotic Consonant-Vowel tests were performed during morning and evening, and the right ear, left ear and double correct scores were compared between morning and evening for each category.

Results

There was significant diurnal changes noted for moderately morning and evening categories, where morning-type individuals performed better during morning and evening-type individuals performed better during the evening. The scores of intermediate individuals remained unchanged between morning and evening test results.

Conclusion

Diurnal change is a phenomenon associated with an individual's biological clock mechanism. Hence, attention and inhibitory controls aid them in carrying out tasks that require sufficient physical and mental efforts. The current study suggests that clinicians and researchers consider diurnal changes as an extraneous variable that could affect the reliability of the Dichotic Consonant-Vowel test results.

The Intricate Web of Asymmetric Processing of Social Stimuli in Humans

Although the population-level preference for the use of the right hand is the clearest example of behavioral lateralization, it represents only the best-known instance of a variety of functional asymmetries observable in humans. What is interesting is that many of such asymmetries emerge during the processing of social stimuli, as often occurs in the case of human bodies, faces and voices. In the present paper, after reviewing previous literature about human functional asymmetries for social and emotional stimuli, we suggest some possible links among them and stress the necessity of a comprehensive account (in both ontogenetic and phylogenetic terms) for these not yet fully explained phenomena. In particular, we propose that the advantages of lateralization for emotion processing should be considered in light of previous suggestions that (i) functional hemispheric specialization enhances cognitive capacity and efficiency, and (ii) the alignment (at the population level) of the direction of behavioral asymmetries emerges, under social pressures, as an evolutionary stable strategy.

Dichotic listening deficits in amblyaudia are characterized by aberrant neural oscillations in auditory cortex

OBJECTIVE

Children diagnosed with auditory processing disorder (APD) show deficits in processing complex sounds that are associated with difficulties in higher-order language, learning, cognitive, and communicative functions. Amblyaudia (AMB) is a subcategory of APD characterized by abnormally large ear asymmetries in dichotic listening tasks.

METHODS

Here, we examined frequency-specific neural oscillations and functional connectivity via high-density electroencephalography (EEG) in children with and without AMB during passive listening of nonspeech stimuli.

RESULTS

Time-frequency maps of these "brain rhythms" revealed stronger phase-locked beta-gamma (~35 Hz) oscillations in AMB participants within bilateral auditory cortex for sounds presented to the right ear, suggesting a hypersynchronization and imbalance of auditory neural activity. Brain-behavior correlations revealed neural asymmetries in cortical responses predicted the larger than normal right-ear advantage seen in participants with AMB. Additionally, we found weaker functional connectivity in the AMB group from right to left auditory cortex, despite their stronger neural responses overall.

CONCLUSION

Our results reveal abnormally large auditory sensory encoding and an imbalance in communication between cerebral hemispheres (ipsi- to -contralateral signaling) in AMB.

SIGNIFICANCE

These neurophysiological changes might lead to the functionally poorer behavioral capacity to integrate information between the two ears in children with AMB.

Effect of a Dichotic Interaural Time Difference Program on Dichotic Listening Deficit of Children with Learning Difficulty

BACKGROUND

 Dichotic listening deficit (DLD) is a common sign in children showing learning problem and is identified during auditory processing assessment. A dichotic listening training program was developed in which the weak ear lags behind the strong ear in time and has certain practices for switching attention between the ears and auditory memory.

PURPOSE

 The aim of the present study was to evaluate the effectiveness of this treatment program on dichotic performance of primary school children showing DLD.

RESEARCH DESIGN

 A pre/post clinical trial without control study.

STUDY SAMPLE

 Twenty-five primary school children, aged 7 to 12 years (mean = 9.3 years), showing DLD.

DATA COLLECTION AND ANALYSIS

 Several primary schools referred the children with learning difficulty to us. We defined learning difficulty as a score of 2 and lower on a five-point scale in at least two primary school courses in the current semester. The children with DLD participated in listening practices three times a week for 10 weeks, each session lasting for 30 minutes. The practices started with one pair of dichotic digits and ended in practice with sentences. The weak ear lag varied from 100 to 1,000 milliseconds. In the last stage of the practices, the precued and postcued directed response aimed at strengthening auditory memory and switching attention between the ears. The results obtained by the tests of dichotic digits, competing words, and competing sentences before and after the intervention were compared using paired t-test. Hedges's g was calculated as the effect size.

RESULTS

 Comparison of the results of pretraining and those of posttraining revealed that the average dominant ear (DE) and nondominant ear (NDE) scores in dichotic listening tests improved significantly with medium-to-large effect sizes. It was also found that the mean change in the NDE score of the children was significantly greater than that of the DE score for all the tests.

CONCLUSIONS

 Dichotic interaural time difference training that employed dichotic lag phenomenon followed by directed response practices significantly improved the DE and the NDE scores of the schoolchildren with DLD.

Association Between the Right Ear Advantage in Dichotic Listening and Interaural Differences in Sensory Processing at Lower Levels of the Auditory System in Older Adults

OBJECTIVE

Current evidence suggests that an enhanced right ear advantage (REA) in dichotic listening (DL) among older adults may originate from age-related structural changes in the corpus callosum and age-related decline in cognitive processes. Less is known about the effect of information processing at lower portions of the auditory system on DL performance. The present study investigates whether interaural differences (ID) in sensory processing at lower levels of the auditory system are associated with the magnitude of the REA in DL among older adults.

DESIGN

Sixty-eight older adults participated in the study. Participants were assessed with a DL test using nonforced (NF) and forced attention paradigms. Hearing sensitivity, transient-evoked otoacoustic emission (TEOAE), contralateral suppression of TEOAE, a proxy measure of medial olivocochlear activation, and auditory brainstem response to speech stimuli (speech-ABR) were tested in both ears separately. The ID in sensory processing at lower levels of the auditory system was derived by calculating the difference between the RE and LE for each auditory measure. Bivariate and multivariate regression models were performed. One multivariate model for each DL paradigm (NF and forced attention) was independently constructed. Measures of cognitive speed of processing and cognitive flexibility were accounted for in the regression models.

RESULTS

For both multivariate regression models, ID in pure-tone thresholds and ID in MOC suppression of TEOAE were significantly associated with the magnitude of the REA for DL among older adults. Cognitive measures of speed of processing and cognitive flexibility also contributed to the magnitude of the REA.

CONCLUSION

These results suggest that ID in sensory processing at lower levels of the auditory system account, at least in part, for the increased magnitude of the REA in DL among older adults.

Development of central auditory processes in Polish children and adolescents at the age from 7 to 16 years

There are discrepancies in the literature regarding the course of central auditory processes (CAP) maturation in typically developing children and adolescents. The purpose of the study was to provide an overview of age – related improvement in CAP in Polish primary and secondary school students aged 7–16 years. 180 children/adolescents, subdivided into 9 age categories, and 20 adults (aged 18–24 years) performed the Dichotic Digit Test (DDT), Duration Pattern Test (DPT), Frequency Pattern Test (FPT), Gap Detection Test (GDT) and adaptive Speech-in-Noise (aSpN). The 12-year-olds was retested after w week. We found the age effects only for the DDT, DPT and FPT. In the right ear DDT the 7-year-olds performed more poorly than all groups ≥12. In the left ear DDT both 7- and 8-year-olds achieved less correct responses compared with the 13-, 14-, 15-year-olds and with the adults. The right ear advantage was greater in the 7-year-olds than in the 15-year-olds and adult group. At the age of 7 there was lower DPT and FPT scores than in all participants ≥13 whereas the 8-year-olds obtained less correct responses in the FPT than all age categories ≥12. Almost all groups (except for the 7-year-olds) performed better in the DPT than FPT. The test-retest reliability for all tests was satisfactory. The study demonstrated that different CAP have their own patterns of improvement with age and some of them are specific for the Polish population. The psychoacoustic battery may be useful in screening for CAP disorders in Poland.

Behavioral and Hemodynamic Changes Following Dichotic Training in Patients with Neurological Deficits of the Auditory Nervous System: A Case Series

BACKGROUND

 Dichotic listening occurs when one attends to different acoustical messages presented simultaneously to both ears. This is important for understanding speech in compromised listening situations, such as background noise. Deficits in dichotic listening can be remediated by participating in auditory training. We present two patients with binaural integration deficits who underwent dichotic interaural intensity difference (DIID) training.

PURPOSE

 The purpose of this investigation is to demonstrate improvement of dichotic listening deficits following DIID training in neurological patients seen clinically for hearing issues.

RESEARCH DESIGN

 This was a case series utilizing a pre- and posttreatment design.

STUDY SAMPLE

 This case series utilized two female participants who demonstrated binaural integration deficits during an auditory processing evaluation.

INTERVENTION

 The participants underwent a pretraining auditory processing evaluation and functional magnetic resonance imaging (fMRI). Participants then underwent 12, 30-minute DIID training sessions followed by posttreatment auditory processing evaluations and fMRI.

DATA COLLECTION AND ANALYSIS

 Data was collected at the pretreatment appointment and then immediately following the completion of the training.

RESULTS

 Each patient demonstrated varying degrees of improvement on the posttreatment assessment. Case 1 showed significant improvement on the Speech-in-Noise-Revised (SPIN-R) test. fMRI showed changes in activation patterns following training. Case 2 demonstrated improved scores on the Dichotic Digits Test and SPIN-R and increased activation of the calcarine sulcus following training.

CONCLUSION

 Dichotic training can be an efficacious treatment for binaural integration deficits and may show evidence of improving speech understanding in noise. This case series demonstrates a promising therapy to help patients improve auditory function by improving dichotic listening skills.

Dichotic sentence identification test in Portuguese: a study in young adults

Introduction

Among the currently-applied auditory processing tests, dichotic listening tests have been widely used, since they allow investigating the hemispheric and inter-hemispheric function and their respective skills to process the received auditory information.

Objective

To obtain normality reference measures with the new dichotic sentence identification test in right-handed adults with normal hearing.

Methods

Quantitative, observational, cross-sectional study. 72 subjects were assessed, aged 19–44 years, right-handed, with normal hearing, without hearing complaints. The dichotic sentence identification test consists of different lists of sentences, which were combined two by two and presented at the same time, using earphones in both ears, at 50 dB Sensation Level. The test was applied in four stages: training of the 3 stages, free attention, right and left directed attention, thus evaluating different auditory skills.

Results

In the free attention task, the average percentage of correct answers in the right ear was 93.59% and in the left ear 86.06%, with a statistically significant difference between the ears, with an advantage for the right ear. In the directed attention task, the average percentage of correct answers was 99.37% in the right ear and 98.8% in the left ear, with no statistical difference between the ears.

Conclusion

It is suggested, as a normality reference for the stage of free attention, 90%–100% for correct answers for the right ear and for the left ear, from 80% to 100%. When there is asymmetry between the ears, differences of up to 20% are expected, with an advantage for the right ear For the directed attention stage, the expected normality reference values ​​are 100% for the right ear and for the left ear, with no asymmetry between the ears; however, if it occurs, a difference of 10% is expected between the ears, with an advantage for the right ear.

The influence of oral language environment on auditory development

OBJECTIVE

The purpose of this study was to compare the auditory processing of hearing children who were immersed in an oral language environment during early childhood with that of children who were poorly exposed to oral language during the same period.

METHODS

Sixty children aged between 5 and 10 years participated in this study. They were divided in two groups. Group 1 comprised of 30 children who had deaf signer parents, and Group 2 comprised of 30 children who had hearing parents. These children underwent the following auditory processing tests: Pediatric Speech Intelligibility, Dichotic Digits, Pitch Pattern Sequence, Gaps-in-Noise, and Memory Tests for Instrumental and Verbal sounds.

RESULTS

Group 1 had significantly poorer performance than that of Group 2 in all tests. In addition, an analysis by age range revealed that the differences between groups were more pronounced in younger children (5-6 years).

CONCLUSION

The results indicate that the development of auditory skills is strongly influenced by access to oral linguistic sounds. Thus, a child's exposure to an oral language environment from birth is important to the adequate development of the auditory system functions.

The effects of aerobic exercise on corpus callosum integrity: systematic review

Objective: To evaluate the influence of exercise on the body and genu of the corpus callosum (CC), which is a critical brain structure involved in facilitating interhemispheric communication. Methods: Studies were identified using electronic databases, including PubMed, PsychInfo, Sports Discus and Google Scholar. The search terms, including their combinations, included exercise, physical activity, cardiorespiratory fitness, interhemispheric, and corpus callosum. To be eligible for inclusion in this review, studies had to be published in English; employ a cross-sectional, prospective or experimental design; include a measure of exercise as the independent variable; and the outcome variable had to include an integrity, volumetric or functional measure of the CC. Extraction parameters include study design, study population, exercise protocol, CC assessment, main findings regarding the relationship between exercise and the CC, and the evaluated or speculated mechanisms of this relationship. Results: 20 articles met the study inclusion criteria. Among these, 5 were conducted in animals and 15 were conducted in humans. Among the 5 animal studies, all provided suggestive evidence associating aerobic exercise with increased white matter integrity. Among the 15 human studies, 6 studies employed tract-based special statistics (TBSS), 4 utilized regions of interest (ROI) approach and 5 executed whole brain voxel wise analysis. Changes in the body was detected by 5 out of 6 TBSS studies and the genu by 3. Out of 4 ROI studies, three detected changes in the genu, but only one did in the body (out of 3 studies). One whole brain voxelwise study detected changes in the CC body of old adults and two found changes in the genu. Conclusion: This review provides evidence to suggest that aerobic exercise, and in turn, enhanced cardiorespiratory fitness, are associated with structural and functional outcomes increasing CC integrity.

Variability of the dichotic sentence test in the test and retest of normal hearing adults

PURPOSE

to investigate the variability of the Dichotic Sentence Test through the test and retest in normal-hearing adults.

METHOD

We evaluated thirty-six individuals aged 19 to 44 years old, right-handed and with normal hearing thresholds. We performed the basic audiological evaluation and then we applied the Dichotic Digit Test and Dichotic Sentence Test. The test and retest had two sessions, with an interval from 30 to 40 days, in the same shift.

RESULTS

In the integration task, there was an advantage of the right ear in both evaluation sessions. There was no significant difference between the measures obtained in the right ear in the two evaluation sessions, while in the left ear, we found a significant difference. In the analysis of the differences in ears between the test and the retest, we found that 64% of the individuals kept the same result in the right ear, while in the left one, only 36% of the individuals kept the same result in both stages and 44% showed a 10% difference between the two evaluations. We observed moderate positive correlation for both the right ear (r=0.420) and the left ear (r=0.550), with a tendency to improve retest scores. In the separation task, there was a small variability only in the left ear, also with improved retest scores.

CONCLUSION

There was a significant difference between the measures obtained in the test and retest only in the integration task in the left ear, but there was a moderate positive correlation between the measures obtained in the two evaluation sessions, showing a tendency to improve scores in the second evaluation session.

An optimal dichotic-listening paradigm for the assessment of hemispheric dominance for speech processing

Dichotic-listening paradigms are widely accepted as non-invasive tests of hemispheric dominance for language processing and represent a standard diagnostic tool for the assessment of developmental auditory and language disorders. Despite its popularity in research and clinical settings, dichotic paradigms show comparatively low reliability, significantly threatening the validity of conclusions drawn from the results. Thus, the aim of the present work was to design and evaluate a novel, highly reliable dichotic-listening paradigm for the assessment of hemispheric differences. Based on an extensive literature review, the paradigm was optimized to account for the main experimental variables which are known to systematically bias task performance or affect random error variance. The main design principle was to minimize the relevance of higher cognitive functions on task performance in order to obtain stimulus-driven laterality estimates. To this end, the key design features of the paradigm were the use of stop-consonant vowel (CV) syllables as stimulus material, a single stimulus pair per trial presentation mode, and a free recall (single) response instruction. Evaluating a verbal and manual response-format version of the paradigm in a sample of N = 50 healthy participants, we yielded test-retest intra-class correlations of rICC = .91 and .93 for the two response format versions. These excellent reliability estimates suggest that the optimal paradigm may offer an effective and efficient alternative to currently used paradigms both in research and diagnostic.

Auditory processing disorders in incarcerated youth: A call for early detection and treatment

BACKGROUND

Numerous reports have linked language impairment, academic underachievement, and attention disorder to misbehavior in adolescence. Recent studies have found an association between deficits in hearing and auditory processing and involvement in the juvenile justice system. In fact, the existence of an auditory processing disorder (APD) is a risk factor for adolescent delinquency even in the presence of normal hearing. The nexus between APD, low academic achievement and offending behavior in teens has prompted recommendation for early screening of school children for abnormalities in auditory processing. Using a variety of diagnostic tools, investigators have found an increase in the frequency of APD in cohorts of confined youthful offenders. The present investigation evaluates the prevalence of APD in a group of incarcerated youth residing in a detention center.

METHODS

A total of 52 incarcerated adolescents (8 females and 44 males; age range 13-20 (M = 16.0), residing at a juvenile detention center in Pittsburgh, Pennsylvania and determined to have normal auditory acuity were included in the study. All participants were screened for APD using two dichotic listening tests, the Randomized Dichotic Digits Test (RDDT) and the Dichotic Words Test (DWT), evaluative modalities to identify deficits in auditory processing. The prevalence of APD in the study group was compared to previously published normative data for non-offending age-matched youth.

RESULTS

On the RDDT, 23.1% of participants demonstrated normal auditory processing, while 77% had abnormal test results. On the DWT, 75% of subjects exhibited normal auditory processing, while the scores were abnormal for 24.9%. When the results of the RDDT and the DWT were combined to establish a pattern for the purpose of interpreting a deficit, 21.1% of the participants produced results that were within normal limits, while 17.3% qualified for a diagnosis of APD, with abnormal results on both tests. Previous studies have estimated the prevalence of auditory processing disorder in the general adolescent population as being between 2% and 7%.

CONCLUSIONS

This study found a higher prevalence of auditory processing disorder in a cohort of incarcerated youth compared with age-matched controls. Diagnostic screening protocols that identify at-risk children have been developed, as have effective therapies to improve auditory processing function. Teachers, pediatricians and psychologists should consider APD in children and adolescents with behaviors that may increase their risk for juvenile justice involvement. Studies on optimal timing and strategies for assessing and treating APD in children and adolescents are needed, including youth caught up in the juvenile justice system.

Application of diffusion tensor tractography in the surgical treatment of brain tumors located in functional areas

The present study aimed to explore the application of diffusion tensor tractography (DTT) in the preoperative planning and prognostic evaluation of tumors located in the functional areas of the brain. A total of 42 patients diagnosed with intracranial tumors were randomly assigned to either the trial or the control group. DT imaging (DTI) was performed on the basis of preoperative conventional magnetic resonance imaging (MRI) and analyzed for patients in the trial group. Patients in the control group underwent only routine MRI scans. The effect of DTT on the prognosis of patients was evaluated by tumor resection rate and quality of life evaluation using Karnofsky performance score (KPS) comparison between the trial and control groups. There were no significant differences for total tumor removal rate in the trial group (85.71%) compared with that in the control group (71.43%) (P>0.05). The rate of postoperative symptom improvement in the trial group (85.71%) was significantly higher compared with that in the control group (47.62%) (P<0.05). The KPS value of the trial group was significantly higher postoperatively (78.57±17.40) compared with that preoperatively (66.67±16.23) (P<0.05). The KPS value of the control group postoperatively (72.38±19.21) was significantly higher compared with that preoperatively (66.67±16.00) (P<0.05). The postoperative KPS improvement rate [postoperative value-preoperative value)/preoperative value] of the trial group was significantly higher compared with that in the control group. In conclusion, the use of DTT is an effective supplement to traditional MRI, with particular relevance in preoperative planning, particularly for tumors in the functional area of the brain, and can significantly improve the prognostic function of patients.

Handedness predicts Conservative-Republican preference and eliminates relations of Big Five personality to political orientation using the 48 contiguous American states as analytical units

The two present nomothetic studies focused on the period from 1996 to 2012 to determine relations between handedness and political orientation using the 48 contiguous American states as analytical units. The estimated percentage of left-handers in each state operationally defined handedness. A composite measure of Conservative-Republican preference was created from CBS/New York Times/Gallup polls of state resident conservatism and the percent in each state voting Republican in each presidential election from 1996 to 2012. Study 1 showed that state levels of left-handedness correlated to an extremely high degree with Conservative-Republican preference (r = -.80). As well, with common demographic differences between states reflected in socioeconomic status, White population percent, and urban population percent controlled through multiple regression, handedness still accounted for an additional 37.2% of the variance in Conservative-Republican preference. Study 2 found that each of the Big Five personality variables correlated significantly with handedness and with Conservative-Republican preference, but in the opposite direction. Furthermore, Study 2 demonstrated quite surprisingly that all Big Five personality relations to Conservative-Republican preference were eliminated when handedness was controlled in multiple regression equations. For all regression equations, the global Moran's I test specifically developed for detecting residual spatial autocorrelation indicated no significant spatial autocorrelation.

Dichotic training in children with auditory processing disorder

OBJECTIVES

Several test batteries have been suggested for auditory processing disorder (APD) diagnosis. One of the important tests is dichotic listening tests. Significant ear asymmetry (usually right ear advantage) can be indicative of (APD). Two main trainings have been suggested for dichotic listening disorders: Differential Interaural Intensity Difference (DIID) and Dichotic Offset Training (DOT). The aim of the present study was comparing the efficacy of these two trainings in resolving dichotic listening disorders.

METHODS

12 children in the age range of 8 to 9 years old with APD were included (mean age 8.41 years old±0.51). They all had abnormal right ear advantage based on established age-appropriate norms for Farsi dichotic digit test. Then subjects were randomly divided into two groups (each contained 6 subjects): group 1 received DIID training (8.33 years old ±0.51) and group 2 received DOT training (8.50 years old±0.54).

RESULTS

Both trainings were effective in improvement of dichotic listening. There was a significant difference between two trainings with respect to the length of treatment (P-value≤0.001). DOT needed more training sessions (12.83±0.98 sessions) than DIID (21.16±0.75 sessions) to achieve the same amount of performance improvement.

CONCLUSION

Based on the present study it can be assumed that DOT might be a good replacement for DIID training in cases that DIID is not applicable and DIID candidacy conditions are not met. To generalize the results, studies with larger sample sizes are recommended.

On the Etiology of Listening Difficulties in Noise Despite Clinically Normal Audiograms

Many people with difficulties following conversations in noisy settings have “clinically normal” audiograms, that is, tone thresholds better than 20 dB HL from 0.1 to 8 kHz. This review summarizes the possible causes of such difficulties, and examines established as well as promising new psychoacoustic and electrophysiologic approaches to differentiate between them. Deficits at the level of the auditory periphery are possible even if thresholds remain around 0 dB HL, and become probable when they reach 10 to 20 dB HL. Extending the audiogram beyond 8 kHz can identify early signs of noise-induced trauma to the vulnerable basal turn of the cochlea, and might point to “hidden” losses at lower frequencies that could compromise speech reception in noise. Listening difficulties can also be a consequence of impaired central auditory processing, resulting from lesions affecting the auditory brainstem or cortex, or from abnormal patterns of sound input during developmental sensitive periods and even in adulthood. Such auditory processing disorders should be distinguished from (cognitive) linguistic deficits, and from problems with attention or working memory that may not be specific to the auditory modality. Improved diagnosis of the causes of listening difficulties in noise should lead to better treatment outcomes, by optimizing auditory training procedures to the specific deficits of individual patients, for example.

PLP1 Gene Variation Modulates Leftward and Rightward Functional Hemispheric Asymmetries

Molecular neurobiological factors determining corpus callosum physiology and anatomy have been suggested to be one of the major factors determining functional hemispheric asymmetries. Recently, it was shown that allelic variations in two myelin-related genes, the proteolipid protein 1 gene PLP1 and the contactin 1 gene CNTN1, are associated with differences in interhemispheric integration. Here, we investigated whether three single nucleotide polymorphisms that were associated with interhemispheric integration via the corpus callosum in a previous study also are relevant for functional hemispheric asymmetries. To this end, we tested more than 900 healthy adults with the forced attention dichotic listening task, a paradigm to assess language lateralization and its modulation by cognitive control processes. Moreover, we used the line bisection task, a paradigm to assess functional hemispheric asymmetries in spatial attention. We found that a polymorphism in PLP1, but not CNTN1, was associated with performance differences in both tasks. Both functional hemispheric asymmetries and their modulation by cognitive control processes were affected. These findings suggest that both left and right hemisphere dominant cognitive functions can be modulated by allelic variation in genes affecting corpus callosum structure. Moreover, higher order cognitive processes may be relevant parameters when investigating the molecular basis of hemispheric asymmetries.

The Relationship between Types of Attention and Auditory Processing Skills: Reconsidering Auditory Processing Disorder Diagnosis

Measures of attention have been found to correlate with specific auditory processing tests in samples of children suspected of Auditory Processing Disorder (APD), but these relationships have not been adequately investigated. Despite evidence linking auditory attention and deficits/symptoms of APD, measures of attention are not routinely used in APD diagnostic protocols. The aim of the study was to examine the relationship between auditory and visual attention tests and auditory processing tests in children with APD and to assess whether a proposed diagnostic protocol for APD, including measures of attention, could provide useful information for APD management. A pilot study including 27 children, aged 7-11 years, referred for APD assessment was conducted. The validated test of everyday attention for children, with visual and auditory attention tasks, the listening in spatialized noise sentences test, the children's communication checklist questionnaire and tests from a standard APD diagnostic test battery were administered. Pearson's partial correlation analysis examining the relationship between these tests and Cochrane's Q test analysis comparing proportions of diagnosis under each proposed battery were conducted. Divided auditory and divided auditory-visual attention strongly correlated with the dichotic digits test, r = 0.68, p < 0.05, and r = 0.76, p = 0.01, respectively, in a sample of 20 children with APD diagnosis. The standard APD battery identified a larger proportion of participants as having APD, than an attention battery identified as having Attention Deficits (ADs). The proposed APD battery excluding AD cases did not have a significantly different diagnosis proportion than the standard APD battery. Finally, the newly proposed diagnostic battery, identifying an inattentive subtype of APD, identified five children who would have otherwise been considered not having ADs. The findings show that a subgroup of children with APD demonstrates underlying sustained and divided attention deficits. Attention deficits in children with APD appear to be centred around the auditory modality but further examination of types of attention in both modalities is required. Revising diagnostic criteria to incorporate attention tests and the inattentive type of APD in the test battery, provides additional useful data to clinicians to ensure careful interpretation of APD assessments.

Computerized Auditory Training in Students: Electrophysiological and Subjective Analysis of Therapeutic Effectiveness

Introduction  Computerized auditory training (CAT) has been building a good reputation in the stimulation of auditory abilities in cases of auditory processing disorder (APD).

Objective  To measure the effects of CAT in students with APD, with typical or atypical phonological acquisition, through electrophysiological and subjective measures, correlating them pre- and post-therapy.

Methods  The sample for this study includes14 children with APD, subdivided into children with APD and typical phonological acquisition (G1), and children with APD and atypical phonological acquisition (G2). Phonological evaluation of children (PEC), long latency auditory evoked potential (LLAEP) and scale of auditory behaviors (SAB) were conducted to help with the composition of the groups and with the therapeutic intervention. The therapeutic intervention was performed using the software Escuta Ativa (CTS Informática, Pato Branco, Brazil) in 12 sessions of 30 minutes, twice a week. For data analysis, the appropriate statistical tests were used.

Results  A decrease in the latency of negative wave N2 and the positive wave P3 in the left ear in G1, and a decrease of P2 in the right ear in G2 were observed. In the analysis comparing the pre- and post-CAT groups, there was a significant difference in P1 latency in the left ear and P2 latency in the right ear, pre-intervention. Furthermore, eight children had an absence of the P3 wave, pre-CAT, but after the intervention, all of them presented the P3 wave. There were changes in the SAB score pre- and post-CAT in both groups. The presence of correlation between the scale and some LLAEP components was observed.

Conclusion  The CAT produced an electrophysiological modification, which became evident in the effects of the effects of neural plasticity after CAT. The SAB proved to be useful in measuring the therapeutic effects of the intervention. Moreover, there were behavioral changes in the SAB (higher scores) and correlation with LLAEP.

Practical guidelines to minimise language and cognitive confounds in the diagnosis of CAPD: a brief tutorial

OBJECTIVE

To provide audiologists with strategies to minimise confounding cognitive and language processing variables and accurately diagnose central auditory processing disorder (CAPD).

DESIGN

Tutorial.

STUDY SAMPLE

None.

RESULTS

Strategies are reviewed to minimise confounding cognitive and language processing variables and accurately diagnose CAPD.

CONCLUSIONS

Differential diagnosis is exceedingly important and can be quite challenging. Distinguishing between two or more conditions presenting with similar symptoms or attributes requires multidisciplinary, comprehensive assessment. To ensure appropriate interventions, the audiologist is a member of the multidisciplinary team responsible for determining whether there is an auditory component to other presenting deficits or whether one condition is responsible for the symptoms seen in another. Choice of tests should be guided both by the symptoms of the affected individual, as established in an in-depth interview and case history, the individual's age and primary language, and by the specific deficits reported to be associated with specific clinical presentations. Knowing which tests are available, their strengths and limitations, the processes assessed, task and response requirements, and the areas of the central auditory nervous system (CANS) to which each test is most sensitive provides the audiologist with critical information to assist in the differential diagnostic process.

The Effect of Age and History of Recurrent Otitis Media on Dichotic Listening and Verbal Memory in Children

OBJECTIVES

To explore the possible effects of recurrent otitis media (ROM) in early childhood on binaural processing and verbal memory in school-aged children.

METHODS

Two hundred eleven children, including 31 children with and 180 children without a history of ROM, were examined. A dichotic digit test (DDT) and a forward and backward digit memory span test (DMST) were administered.

RESULTS

A significant difference was observed between age groups among ROM-free children. The ROM-positive group earned significantly poorer results than the ROM-free group in all measurements, except for the right DDT (rDDT) score. Furthermore, a significant correlation was found between the DDT and EA scores with both DMST scores in the ROM-free group. The correlation between the rDDT and forward DMST scores was not significant in the ROM-positive group, and no significant correlation was observed between the EA score and either DMST score.

CONCLUSIONS

Our findings support that a history of OM in early childhood based on a parental survey of children is associated with differences in DDT and DMST outcomes.

Dichotic listening as an index of lateralization of speech perception in familial risk children with and without dyslexia

Atypical language lateralization has been marked as one of the factors that may contribute to the development of dyslexia. Indeed, atypical lateralization of linguistic functions such as speech processing in dyslexia has been demonstrated using neuroimaging studies, but also using the behavioral dichotic listening (DL) method. However, so far, DL results have been mixed. The current study assesses lateralization of speech processing by using DL in a sample of children at familial risk (FR) for dyslexia. In order to determine whether atypical lateralization of speech processing relates to reading ability, or is a correlate of being at familial risk, the current study compares the laterality index of FR children who did and did not become dyslexic, and a control group of readers without dyslexia. DL was tested in 3rd grade and in 5/6th grade. Results indicate that at both time points, all three groups have a right ear advantage, indicative of more pronounced left-hemispheric processing. However, the FR-dyslexic children are less good at reporting from the left ear than controls and FR-nondyslexic children. This impediment relates to reading fluency.

Central auditory processing disorders in children and adults

Central auditory processing disorders (CAPD) can affect children and adults of all ages due to a wide variety of causes. CAPD is a neurobiologic deficit in the central auditory nervous system (CANS) that affects those mechanisms that underlie fundamental auditory perception, including localization and lateralization; discrimination of speech and non-speech sounds; auditory pattern recognition; temporal aspects of audition, including integration, resolution, ordering, and masking; and auditory performance with competing and/or degraded acoustic signals (American Speech-Language-Hearing Association, 2005a, b). Although it is recognized that central auditory dysfunction may coexist with other disorders, CAPD is conceptualized as a sensory-based auditory disorder. Administration of behavioral and/or electrophysiologic audiologic tests that have been shown to be sensitive and specific to dysfunction of the CANS is critical for a proper diagnosis of CAPD, in addition to assessments and collaboration with a multidisciplinary team. Intervention recommendations for CAPD diagnosis are based on the demonstrated auditory processing deficits and related listening and related complaints. This chapter provides an overview of current definitions and conceptualizations, methods of diagnosis of, and intervention for, CAPD. The chapter culminates with a case study illustrating pre- and posttreatment behavioral and electrophysiologic diagnostic findings.

Application of a multidisciplinary model to a case example of presurgical epilepsy planning

This article presents a case example which illustrates the multidisciplinary model for presurgical assessment for epilepsy patients. Nearly three million people in the United States are diagnosed with epilepsy and more than one third of this population is refractory to pharmacological treatment. Poor seizure control is associated with additional impairment in quality of life and cognitive and social functioning, and even with premature death. In accordance with these concerns, surgical intervention is increasingly recognized as a viable treatment option, which should be considered soon after drug resistance becomes apparent. Despite the widespread evidence of effectiveness surgery is often delayed, in part because of the necessity, and difficulties, of correctly applying a multidisciplinary approach to presurgical assessment. And yet, a multidisciplinary team is crucial in the evaluation of risks and benefits of possible surgical intervention and in guiding the surgical procedure to maximize seizure control and minimize risk to eloquent cortex. In the model and complex case presented, the neuropsychologist has a critical role in the presurgical evaluation, as well as in the postsurgical evaluation of outcome.

Avaliação audiológica em lactentes com agenesia de corpo caloso

Objetivo verificar a ocorrência de alterações auditivas em lactentes com alteração do corpo caloso, comparando-os a crianças sem tal malformação. Métodos estudo de coorte dividido em duas partes: retrospectivo de 2008 a 2011 e prospectivo de 2011 a 2012. O grupo estudo foi constituído por 12 lactentes com diagnóstico de agenesia de corpo caloso e o grupo controlepor12 lactentes, pareados por idade pós concepcional e sexo. Todos realizaram Emissões Otoacústicas Evocadas por Estimulo Transiente, Potencial Evocado Auditivo de Tronco Encefálico (análise da média das latências das ondas I, III e V e interpicos I-III, III-V e I-V a 80dBnNA) e Avaliação do Comportamento Auditivo. Resultados na análise da ocorrência de alteração auditiva na avaliação com Emissões Otoacústicas Transientes e Potencial Evocado Auditivo de Tronco Encefálico, houve diferença em ambos os grupos com maior percentual de resultados normais no grupo controle. Houve diferença significante entre as orelhas, nas latências da onda III e intervalo interpico I-III, menor à direita, nogrupo controle.Naavaliação comportamental, houve diferença significante entre os grupos em relação aos resultados normais e alterados, com maior ocorrência de alteração central no grupo estudo.Ainda neste grupo, a segunda avaliação mostrou maior índice de resultados alterados quando comparados à primeira avaliação, sendo estaticamente significante. Conclusão as alterações auditivas nos lactentes com alteração do corpo caloso não foram identificadas ao nascimento, tendo sido apenas a partir de seis meses de vida. A maioria das alterações ocorreram na via auditiva central, no tronco encefálico.

Sources of pathology underlying listening disorders in children

Some children referred to audiology and developmental disability services have listening difficulties, despite normal audiograms. These children may be tested for 'auditory processing disorder' (APD), a controversial construct suggesting that neural dysfunction in the central auditory system leads to impaired auditory perception. An important question, not currently tested in clinical evaluation, is whether listening difficulties result from problems with bottom-up auditory sensory processing or top-down modulating cognition. Perceptual variability and poor performance on standardized tests suggest that listening difficulties are primarily cognitive in origin. However, evidence for impaired olivocochlear function and temporal processing deficits may implicate peripheral or central auditory dysfunction in some cases. Wide-spread, top-down modulation of auditory cortical, brainstem and ear function suggests that afferent and efferent control systems may not be simple to segregate. During normal maturation, hearing appears to develop in proportion to the complexity of both stimuli and tasks. But some younger individuals have mature hearing, highlighting individual differences that suggest APD may be due to a generalized developmental delay. Recent studies have investigated specific hypotheses showing, for example, that spatial hearing and executive function are compromised in some children with listening difficulties. Using speech stimuli (e.g. consonant-vowel syllables) to examine auditory brainstem responses, and psychophysiological relations between dichotic hearing and cortical physiology, various effects of auditory experience and development point the way to promising approaches for further studies of APD. Newer technology, from genetic sequencing to MRI, may have the sensitivity to test whether and how frequently APD is associated with impaired processing in the auditory system.

Altered white matter microstructure underlies listening difficulties in children suspected of auditory processing disorders: a DTI study

INTRODUCTION

The purpose of the present study was to identify biomarkers of listening difficulties by investigating white matter microstructure in children suspected of auditory processing disorder (APD) using diffusion tensor imaging (DTI). Behavioral studies have suggested that impaired cognitive and/or attention abilities rather than a pure sensory processing deficit underlie listening difficulties and auditory processing disorder (APD) in children. However, the neural signature of listening difficulties has not been investigated.

METHODS

Twelve children with listening difficulties and atypical left ear advantage (LEA) in dichotic listening and twelve age- and gender-matched typically developing children with typical right ear advantage (REA) were tested. Using voxel-based analysis, fractional anisotropy (FA), and mean, axial and radial diffusivity (MD, AD, RD) maps were computed and contrasted between the groups.

RESULTS

Listening difficulties were associated with altered white matter microstructure, reflected by decreased FA in frontal multifocal white matter regions centered in prefrontal cortex bilaterally and left anterior cingulate. Increased RD and decreased AD accounted for the decreased FA, suggesting delayed myelination in frontal white matter tracts and disrupted fiber organization in the LEA group. Furthermore, listening difficulties were associated with increased MD (with increase in both RD and AD) in the posterior limb of the internal capsule (sublenticular part) at the auditory radiations where auditory input is transmitted between the thalamus and the auditory cortex.

CONCLUSIONS

Our results provide direct evidence that listening difficulties in children are associated with altered white matter microstructure and that both sensory and supramodal deficits underlie the differences between the groups.

The processing of chimeric and dichotic emotional stimuli by connected and disconnected cerebral hemispheres

Hemispheric asymmetries have been widely explored in both the visual and the auditory domain, but little is known about hemispheric asymmetries in audio-visual integration. We compared the performance of a partially callosotomized patient, a total split-brain patient and a control group during the evaluation of the emotional valence of chimeric faces and dichotic syllables (an emotional syllable in one ear and white noise in the other ear) presented unimodally (only faces or only syllables) or bimodally (faces and syllables presented simultaneously). Stimuli could convey happy and sad expressions and participants were asked to evaluate the emotional content of each presentation, using a 5-point Likert scale (from very sad to very happy). In unimodal presentations, the partially callosotomized patient's judgments depended on the emotional valence of the stimuli processed by the right hemisphere, whereas those of the total split-brain patient showed the opposite lateralization; in these conditions, the control group did not show asymmetries. Moreover, in bimodal presentations, results provided support for the valence hypothesis (i.e., left asymmetry for positive emotions and vice versa) in both the control group and the partially callosotomized patient, whereas the total split-brain patient showed a tendency to evaluate the emotional content of the right hemiface even when asked to focus on the acoustic modality. We conclude that partial and total hemispheric disconnections reveal opposite patterns of hemispheric asymmetry in auditory, visual and audio-visual emotion processing. These results are discussed in the light of the right-hemisphere hypothesis and the valence hypothesis.

Masking level differences--a diffusion tensor imaging and functional MRI study

In our previous study we investigated Masking Level Differences (MLD) using functional Magnetic Resonance Imaging (fMRI), but were unable to confirm neural correlations for the MLD within the auditory cortex and inferior colliculus. Here we have duplicated conditions from our previous study, but have included more participants and changed the study site to a new location with a newer scanner and presentation system. Additionally, Diffusion Tensor Imaging (DTI) is included to allow investigation of fiber tracts that may be involved with MLDs. Twenty participants were included and underwent audiometric testing and MRI scanning. The current study revealed regions of increased and decreased activity within the auditory cortex when comparing the combined noise and signal of the dichotic MLD stimuli (N0Sπ and NπS0) with N0S0. Furthermore, we found evidence of inferior colliculus involvement. Our DTI findings show strong correlations between DTI measures within the brainstem and signal detection threshold levels. Patterns of correlation when the signal was presented only to the right ear showed an extensive network in the left hemisphere; however, the opposite was not true for the signal presented only to the left ear. Our current study was able to confirm what we had previously hypothesized using fMRI, while extending our investigation of MLDs to include the characteristics of connecting neural pathways.