Conclusion: Research on the role of auditory processing in communication disorders springs from a variety of theoretical perspectives and assumptions, and this variety, combined with controversies over the interpretation of research results, makes it difficult to draw clinical implications from the literature. Neurophysiological research methods are a promising route to better understanding of auditory processing. Progress in theory development and its clinical application is most likely to be made when researchers from different disciplines and theoretical perspectives communicate clearly and combine the strengths of their approaches.
Conclusions: Audiologists are selecting AP test batteries based on the age and case history of the patient, which is in accordance with recent national guidelines. Audiologists are primarily responsible for APD diagnosis and recommending treatment/management. APD treatment is provided by speech-language pathologists, educators, and audiologists.
from the American Journal of Audiology
Lexical content of stimulus materials impacts performance characteristics for dichotic speech recognition tasks in the normal-hearing young adult population. The use of nonsense CVC syllable material may provide a way to assess dichotic speech recognition performance while potentially lessening the effects of lexical content on performance.
Preschool impairments in auditory processing and speech perception uniquely predict future reading problems
Developmental dyslexia is characterized by severe reading and spelling difficulties that are persistent and resistant to the usual didactic measures and remedial efforts. It is well established that a major cause of these problems lies in poorly specified phonological representations. Many individuals with dyslexia also present impairments in auditory temporal processing and speech perception, but it remains debated whether these more basic perceptual impairments play a role in causing the reading problem. Longitudinal studies may help clarifying this issue by assessing preschool children before they receive reading instruction and by following them up through literacy development. The current longitudinal study shows impairments in auditory frequency modulation (FM) detection, speech perception and phonological awareness in kindergarten and in grade 1 in children who receive a dyslexia diagnosis in grade 3. FM sensitivity and speech-in-noise perception in kindergarten uniquely contribute to growth in reading ability, even after controlling for letter knowledge and phonological awareness. These findings indicate that impairments in auditory processing and speech perception are not merely an epiphenomenon of reading failure. Although no specific directional relations were observed between auditory processing, speech perception and phonological awareness, the highly significant concurrent and predictive correlations between all these variables suggest a reciprocal association and corroborate the evidence for the auditory deficit theory of dyslexia.
Relationship Between Verbal Working Memory and the SCAN–C in Children With Specific Language Impairment
Conclusions: Performance on the SCAN–C may be related to working memory functioning. As a consequence, it is unclear whether difficulty on this task should be viewed as a problem with auditory processing or a problem with verbal working memory.
Electrophysiological correlates of rapid auditory and linguistic processing in adolescents with specific language impairment
Brief tonal stimuli and spoken sentences were utilized to examine whether adolescents (aged 14;3–18;1) with specific language impairments (SLI) exhibit atypical neural activity for rapid auditory processing of non-linguistic stimuli and linguistic processing of verb-agreement and semantic constraints. Further, we examined whether the behavioral and electrophysiological indices for rapid auditory processing were correlated with those for linguistic processing. Fifteen adolescents with SLI and 15 adolescents with normal language met strict criteria for displaying consistent diagnoses from kindergarten through the eighth grade. The findings provide evidence that auditory processing for non-linguistic stimuli is atypical in a significant number of adolescents with SLI compared to peers with normal language and indicate that reduced efficiency in auditory processing in SLI is more vulnerable to rapid rates (200 ms ISI) of stimuli presentation (indexed by reduced accuracy, a tendency for longer RTs, reduced N100 over right anterior sites, and reduced amplitude P300). Many adolescents with SLI displayed reduced behavioral accuracy for detecting verb-agreement violations and semantic anomalies, along with less robust P600s elicited by verb-agreement violations. The results indicate that ERPs elicited by morphosyntactic aspects of language processing are atypical in many adolescents with SLI. Additionally, correlational analyses between behavioral and electrophysiological indices of processing non-linguistic stimuli and verb-agreement violations suggest that the integrity of neural functions for auditory processing may only account for a small proportion of the variance in morphosyntactic processing in some adolescents.
from Brain and Language
Auditory Pathways and Processes: Implications for Neuropsychological Assessment and Diagnosis of Children and Adolescents
Neuroscience research on auditory processing pathways and their behavioral and electrophysiological correlates has taken place largely outside the field of clinical neuropsychology. Deviations and disruptions in auditory pathways in children and adolescents result in a well-documented range of developmental and learning impairments frequently referred for neuropsychological evaluation. This review is an introduction to research from the last decade. It describes auditory cortical and subcortical pathways and processes and relates recent research to specific conditions and questions neuropsychologists commonly encounter. Auditory processing disorders’ comorbidity with ADHD and language-based disorders and research addressing the challenges of assessment and differential diagnosis are discussed.
Effect of auditory training on the middle latency response in children with (central) auditory processing disorder
The purpose of this study was to determine the middle latency response (MLR) characteristics (latency and amplitude) in children with (central) auditory processing disorder [(C)APD], categorized as such by their performance on the central auditory test battery, and the effects of these characteristics after auditory training. Thirty children with (C)APD, 8 to 14 years of age, were tested using the MLR-evoked potential. This group was then enrolled in an 8-week auditory training program and then retested at the completion of the program. A control group of 22 children without (C)APD, composed of relatives and acquaintances of those involved in the research, underwent the same testing at equal time intervals, but were not enrolled in the auditory training program. Before auditory training, MLR results for the (C)APD group exhibited lower C3-A1 and C3-A2 wave amplitudes in comparison to the control group [C3-A1, 0.84 µV (mean), 0.39 (SD – standard deviation) for the (C)APD group and 1.18 µV (mean), 0.65 (SD) for the control group; C3-A2, 0.69 µV (mean), 0.31 (SD) for the (C)APD group and 1.00 µV (mean), 0.46 (SD) for the control group]. After training, the MLR C3-A1 [1.59 µV (mean), 0.82 (SD)] and C3-A2 [1.24 µV (mean), 0.73 (SD)] wave amplitudes of the (C)APD group significantly increased, so that there was no longer a significant difference in MLR amplitude between (C)APD and control groups. These findings suggest progress in the use of electrophysiological measurements for the diagnosis and treatment of (C)APD.
auditory training favored the improvement in the auditory processing abilities and benefited the hearing aid fitting process.
Although the relationship between auditory processing and reading-related skills has been investigated in school-age populations and in prospective studies of infants, understanding of the relationship between these variables in the period immediately preceding formal reading instruction is sparse. In this cross-sectional study, auditory processing, phonological awareness, early literacy skills, and general ability were assessed in a mixed sample of 88 three- to six-year-old children both cross-sectionally and longitudinally. Results from both cross-sectional and longitudinal analyses suggest the importance of early auditory rise time sensitivity in developing phonological awareness skills, especially in the development of rhyme awareness.
from the Journal of Learning Disabilities
Cantonese dichotic digits recognition was evaluated in free-recall, directed-attention right, and directed-attention left response conditions. All participants were right-handed and included a group of young adults with normal hearing and a group of older adults with minimal sensorineural hearing loss. In all conditions, performance by the young adults was better than performance by the older adults. A right-ear advantage was observed for both groups. Due to a greater deficit in dichotic digits recognition performance in the left ear of older subjects their right-ear advantages were larger than those for the young adults. The results support an age-related disadvantage in recognition performance for dichotic stimuli presented to the left ear of older subjects that is not entirely accounted for by differences in hearing sensitivity between subject groups but may be related to a primary cognitive deficit.
from the International Journal of Audiology
Working memory (WM) for auditory information has been thought of as a unitary system, but whether WM for verbal and tonal information relies on the same or different functional neuroarchitectures has remained unknown. This fMRI study examines verbal and tonal WM in both nonmusicians (who are trained in speech, but not in music) and highly trained musicians (who are trained in both domains). The data show that core structures of WM are involved in both tonal and verbal WM (Broca’s area, premotor cortex, pre-SMA/SMA, left insular cortex, inferior parietal lobe), although with significantly different structural weightings, in both nonmusicians and musicians. Additionally, musicians activated specific subcomponents only during verbal (right insular cortex) or only during tonal WM (right globus pallidus, right caudate nucleus, and left cerebellum). These results reveal the existence of two WM systems in musicians: A phonological loop supporting rehearsal of phonological information, and a tonal loop supporting rehearsal of tonal information. Differences between groups for tonal WM, and between verbal and tonal WM within musicians, were mainly related to structures involved in controlling, programming and planning of actions, thus presumably reflecting differences in action-related sensorimotor coding of verbal and tonal information. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc.
from Human Brain Mapping
Persons with Autism Spectrum Disorders (ASD) display atypical perceptual processing in visual and auditory tasks. In vision, Bertone et al. (2005) found that enhanced and diminished visual processing is linked to the level of neural complexity required to process stimuli, as proposed in the neural complexity hypothesis. Based on these findings, Samson et al. (2006) proposed to extend the neural complexity hypothesis to the auditory modality. They hypothesized that persons with ASD should display enhanced performance for simple tones that are processed in primary auditory cortical regions, but diminished performance for complex tones that require additional processing in associative auditory regions, in comparison to typically developing individuals. To assess this hypothesis, we designed four auditory discrimination experiments targeting pitch, non-vocal and vocal timbre, and loudness. Stimuli consisted of spectro-temporally simple and complex tones. The participants were adolescents and young adults with autism, Asperger syndrome, and typical developmental histories, all with IQs in the normal range. Consistent with the neural complexity hypothesis and enhanced perceptual functioning model of ASD (Mottron et al., 2006), the participants with autism, but not with Asperger syndrome, displayed enhanced pitch discrimination for simple tones. However, no discrimination-thresholds differences were found between the participants with ASD and the typically developing persons across spectrally and temporally complex conditions. These findings indicate that enhanced pure-tone pitch discrimination may be a cognitive correlate of speech-delay among persons with ASD. However, auditory discrimination among this group does not appear to be directly contingent on the spectro-temporal complexity of the stimuli.
The main objective of this study was to assess the influence of peripheral hearing loss (abnormal encoding of the auditory system) on auditory information processing. We examine the ability of children with and without hearing loss to correctly reproduce sequence blocks of acoustic stimuli that vary in type, number, and temporal ordering.
Twenty-six children between 8 and 12 years old, 13 with hearing loss and 13 without hearing loss, participated in the study. They performed an auditory temporal ordering task (auditory sequential organization task) by recalling two, three, and five verbal (/ba/-/da/and/a/-/da/) and nonverbal stimuli (acoustic transformation of /ba/-/da/) with a fixed interstimulus interval (ISI) of 425 ms. They also reproduced sequences of two elements with variables ISI, 20, and 1000 ms.
Children with hearing loss had significantly lower correct responses than children with normal hearing for sequences of two, three, and five verbal stimuli with similar and complex acoustic features (/ba/-/da/), for an ISI of 425 ms. There was no significant difference in performance between children with hearing loss and their peers with normal hearing on nonverbal sequences or verbal sequences with different and complex acoustic features (/a/-/da/) when ISI was 425 ms. Furthermore, children with hearing loss performed significantly lower than their peers on the three groups of stimuli when ISI was 20 ms between two stimuli.
Peripheral hearing loss can influence auditory information processing in the central auditory system.
Timing is everything: Neural response dynamics during syllable processing and its relation to higher-order cognition in schizophrenia and healthy comparison subjects
Successful linguistic processing requires efficient encoding of successively-occurring auditory input in a time-constrained manner, especially under noisy conditions. In this study we examined the early neural response dynamics to rapidly-presented successive syllables in schizophrenia participants and healthy comparison subjects, and investigated the effects of noise on these responses. We used magnetoencephalography (MEG) to reveal the time-course of stimulus-locked activity over bilateral auditory cortices during discrimination of syllable pairs that differed either in voice onset time (VOT) or place of articulation (POA), in the presence or absence of noise. We also examined the association of these early neural response patterns to higher-order cognitive functions.
The M100 response, arising from auditory cortex and its immediate environs, showed less attenuation to the second syllable in patients with schizophrenia than healthy comparison subjects during VOT-based discrimination in noise. M100 response amplitudes were similar between groups for the first syllable during all three discrimination conditions, and for the second syllable during VOT-based discrimination in quiet and POA-based discrimination in noise. Across subjects, the lack of M100 attenuation to the second syllable during VOT-based discrimination in noise was associated with poorer task accuracy, lower education and IQ, and lower scores on measures of Verbal Learning and Memory and Global Cognition.
Because the neural response to the first syllable was not significantly different between groups, nor was a schizophrenia-related difference obtained in all discrimination tasks, early linguistic processing dysfunction in schizophrenia does not appear to be due to general sensory input problems. Rather, data suggest that faulty temporal integration occurs during successive syllable processing when the signal-to-noise ratio is low. Further, the neural mechanism by which the second syllable is suppressed during noise-challenged VOT discrimination appears to be important for higher-order cognition and provides a promising target for neuroscience-guided cognitive training approaches to schizophrenia.