Relationship Between Cognitive Abilities and Basic Auditory Processing in Young Adults.

PURPOSE: The diagnosis of auditory processing disorder (APD) is controversial particularly due to the influence of higher order factors of language and cognition on the diagnostic APD testing. As a result, there might be a need for testing for other domains (e.g., cognition) along with conducting the diagnostic APD testing to rule out the influence of other domains. In order to make recommendations on whether cognitive testing is needed along with the auditory processing testing, as a starting point, the current study was conducted to examine the relationship between cognitive abilities and basic auditory processing in young adults. METHOD: A total of 38 young adults with normal audiometric thresholds between 250 and 8000 Hz participated in this study. They were tested on their executive function, language, processing speed, working memory, and episodic memory components of cognitive testing and tests for temporal fine structure and spectrotemporal sensitivity for auditory processing testing. RESULTS: No significant correlation was found between the cognitive tests and the tests for basic auditory processing in young adults. CONCLUSIONS: These findings present contrast to the existing findings in children and older adults where a stronger correlation between cognitive abilities and auditory processing has been found. The current findings suggest that testing for cognitive abilities may not be needed when testing for basic auditory processing in young adults.

Multi-session training in the evening schedule exhibits enhanced speech learning.

Speech learning can be influenced by a variety of factors. A growing body of literature suggests a significant influence of sleep on speech learning, i.e., those trained in the evening outperform those trained in the morning most probably due to consolidation of learning that happens during the sleep for the evening group. Since, learning, in general, may be a process that spans multiple sessions, in the current exploratory study, we aimed at investigating the effect of a multi-session training paradigm on the learning performance of the morning vs evening group. We compared young adults who were trained in the morning (8-10 am; n = 16) with those who were trained in the evening (6-8 pm; n = 16) on a Hindi dental-retroflex pseudoword-picture association training paradigm. Overall, we found that the evening group learned to a larger extent both for the identification (on trained items) and discrimination (on untrained items) tasks. The current findings, even with a multi-session paradigm, are consistent with the previous findings that support enhanced performance by training in the evening. These findings may have clinical implications toward scheduling of speech therapy.

Auditory Evoked Potentials in Communication Disorders: An Overview of Past, Present, and Future.

This article provides a brief overview of auditory evoked potentials (AEPs) and their application in the areas of research and clinics within the field of communication disorders. The article begins with providing a historical perspective within the context of the key scientific developments that led to the emergence of numerous types of AEPs. Furthermore, the article discusses the different AEP techniques in the light of their feasibility in clinics. As AEPs, because of their versatility, find their use across disciplines, this article also discusses some of the research questions that are currently being addressed using AEP techniques in the field of communication disorders and beyond. At the end, this article summarizes the shortcomings of the existing AEP techniques and provides a general perspective toward the future directions. The article is aimed at a broad readership including (but not limited to) students, clinicians, and researchers. Overall, this article may act as a brief primer for the new AEP users, and as an overview of the progress in the field of AEPs along with future directions, for those who already use AEPs on a routine basis.

Early Development of Neural Speech Encoding Depends on Age but Not Native Language Status: Evidence From Lexical Tone.

We investigated the development of early-latency and long-latency brain responses to native and non-native speech to shed light on the neurophysiological underpinnings of perceptual narrowing and early language development. Specifically, we postulated a two-level process to explain the decrease in sensitivity to non-native phonemes toward the end of infancy. Neurons at the earlier stages of the ascending auditory pathway mature rapidly during infancy facilitating the encoding of both native and non-native sounds. This growth enables neurons at the later stages of the auditory pathway to assign phonological status to speech according to the infant's native language environment. To test this hypothesis, we collected early-latency and long-latency neural responses to native and non-native lexical tones from 85 Cantonese-learning children aged between 23 days and 24 months, 16 days. As expected, a broad range of presumably subcortical early-latency neural encoding measures grew rapidly and substantially during the first two years for both native and non-native tones. By contrast, long-latency cortical electrophysiological changes occurred on a much slower scale and showed sensitivity to nativeness at around six months. Our study provided a comprehensive understanding of early language development by revealing the complementary roles of earlier and later stages of speech processing in the developing brain.

Neural Speech Encoding in Infancy Predicts Future Language and Communication Difficulties.

Purpose This study aimed to construct an objective and cost-effective prognostic tool to forecast the future language and communication abilities of individual infants. Method Speech-evoked electroencephalography (EEG) data were collected from 118 infants during the first year of life during the exposure to speech stimuli that differed principally in fundamental frequency. Language and communication outcomes, namely four subtests of the MacArthur-Bates Communicative Development Inventories (MCDI)-Chinese version, were collected between 3 and 16 months after initial EEG testing. In the two-way classification, children were classified into those with future MCDI scores below the 25th percentile for their age group and those above the same percentile, while the three-way classification classified them into < 25th, 25th-75th, and > 75th percentile groups. Machine learning (support vector machine classification) with cross validation was used for model construction. Statistical significance was assessed. Results Across the four MCDI measures of early gestures, later gestures, vocabulary comprehension, and vocabulary production, the areas under the receiver-operating characteristic curve of the predictive models were respectively .92 ± .031, .91 ± .028, .90 ± .035, and .89 ± .039 for the two-way classification, and .88 ± .041, .89 ± .033, .85 ± .047, and .85 ± .050 for the three-way classification (p < .01 for all models). Conclusions Future language and communication variability can be predicted by an objective EEG method that indicates the function of the auditory neural pathway foundational to spoken language development, with precision sufficient for individual predictions. Longer-term research is needed to assess predictability of categorical diagnostic status. Supplemental Material https://doi.org/10.23641/asha.15138546.

An Objective Approach Toward Understanding Auditory Processing Disorder.

Purpose In the field of audiology, auditory processing disorder (APD) continues to be a topic of ongoing debate for clinicians and scientists alike, both in terms of theory and clinical practice. In the current viewpoint, we first lay out the main issues that are central to the controversy surrounding APD, and then suggest a framework toward their resolution. Method The current viewpoint is informed by reviewing existing studies in the field of APD to better understand the issues contributing to the controversies in APD. Results We found that, within the current definition of APD, the two main issues that make the APD diagnosis controversial are (a) comorbidity with other disorders and (b) the lack of domain specificity. These issues remain unresolved, especially with the use of the existing behavioral APD test batteries. In this viewpoint, we shed light on how they can be mitigated by implementing the administration of an objective, physiological test battery. Conclusions By administering an objective test battery, as proposed in this viewpoint, we believe that it will be possible to achieve a higher degree of specificity to the auditory domain that will not only contribute towards clinical practice but also contribute towards strengthening APD as a theoretical construct.

Effect of Complexity on Speech Sound Development: Evidence From Meta-Analysis Review of Treatment-Based Studies.

In the current study, we aimed at understanding the effect of exposure to complex input on speech sound development, by conducting a systematic meta-analysis review of the existing treatment-based studies employing complex input in children with speech sound disorders. In the meta-analysis review, using a list of inclusion criteria, we narrowed 280 studies down to 12 studies. Data from these studies were extracted to calculate effect sizes that were plotted as forest plots to determine the efficacy of complexity-based treatment approaches. The outcome variables of interest were improvement on the treated and generalization to the untreated sounds. Meta-analysis revealed that the exposure to complex input not only promoted improvement in production of complex speech sounds (d = 1.08, CI = 0.98-1.19) but also facilitated the production of untreated simple speech sounds (d = 2.69, CI = 1.98-3.54). Overall, the current findings revealed that the exposure to complex input promotes acquisition of both complex and simple speech sounds. The current findings are in line with the models of language learnability. The current findings have implications in the treatment of speech sound disorders.

Combination of absolute pitch and tone language experience enhances lexical tone perception.

Absolute pitch (AP), a unique ability to name or produce pitch without any reference, is known to be influenced by genetic and cultural factors. AP and tone language experience are both known to promote lexical tone perception. However, the effects of the combination of AP and tone language experience on lexical tone perception are currently not known. In the current study, using behavioral (Categorical Perception) and electrophysiological (Frequency Following Response) measures, we investigated the effect of the combination of AP and tone language experience on lexical tone perception. We found that the Cantonese speakers with AP outperformed the Cantonese speakers without AP on Categorical Perception and Frequency Following Responses of lexical tones, suggesting an additive effect due to the combination of AP and tone language experience. These findings suggest a role of basic sensory pre-attentive auditory processes towards pitch encoding in AP. Further, these findings imply a common mechanism underlying pitch encoding in AP and tone language perception.

Complexity drives speech sound development: Evidence from artificial language training.

Traditionally, learning is assumed to take place with exposure to simpler elements first followed by exposure to elements with increasing levels of difficulty. Recent reports suggest that exposure to complex elements leads to more widespread changes. However, whether learning via exposure to complex or to simple elements is more beneficial is a matter of ongoing debate. In the current study, using behavioral and electrophysiological measures, we aimed at understanding this by comparing subjects trained with complex speech sounds with those trained with simple speech sounds in a 5-day pseudoword-picture training paradigm. We found that though the subjects learned both complex and simple speech sounds to similar degrees, subjects who were trained with complex stimuli demonstrated more generalizations to novel complex and simple stimuli, whereas those trained with simple stimuli exhibited generalization only to simple but not to complex stimuli (Experiment 1). Along with behavioral measures, using mismatch negativity, we found that training with complex stimuli can lead to more extensive neural changes for both complex and simple stimuli as compared with training with simple stimuli (Experiment 2). In artificial language learning, learning with complex stimuli appears to be more effective than training with simple stimuli as far as generalization is concerned. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Neural Correlates of Indicators of Sound Change in Cantonese: Evidence from Cortical and Subcortical Processes.

Across time, languages undergo changes in phonetic, syntactic, and semantic dimensions. Social, cognitive, and cultural factors contribute to sound change, a phenomenon in which the phonetics of a language undergo changes over time. Individuals who misperceive and produce speech in a slightly divergent manner (called innovators) contribute to variability in the society, eventually leading to sound change. However, the cause of variability in these individuals is still unknown. In this study, we examined whether such misperceptions are represented in neural processes of the auditory system. We investigated behavioral, subcortical (via FFR), and cortical (via P300) manifestations of sound change processing in Cantonese, a Chinese language in which several lexical tones are merging. Across the merging categories, we observed a similar gradation of speech perception abilities in both behavior and the brain (subcortical and cortical processes). Further, we also found that behavioral evidence of tone merging correlated with subjects' encoding at the subcortical and cortical levels. These findings indicate that tone-merger categories, that are indicators of sound change in Cantonese, are represented neurophysiologically with high fidelity. Using our results, we speculate that innovators encode speech in a slightly deviant neurophysiological manner, and thus produce speech divergently that eventually spreads across the community and contributes to sound change.

Brainstem encoding of speech and musical stimuli in congenital amusia: evidence from Cantonese speakers.

Congenital amusia is a neurodevelopmental disorder of musical processing that also impacts subtle aspects of speech processing. It remains debated at what stage(s) of auditory processing deficits in amusia arise. In this study, we investigated whether amusia originates from impaired subcortical encoding of speech (in quiet and noise) and musical sounds in the brainstem. Fourteen Cantonese-speaking amusics and 14 matched controls passively listened to six Cantonese lexical tones in quiet, two Cantonese tones in noise (signal-to-noise ratios at 0 and 20 dB), and two cello tones in quiet while their frequency-following responses (FFRs) to these tones were recorded. All participants also completed a behavioral lexical tone identification task. The results indicated normal brainstem encoding of pitch in speech (in quiet and noise) and musical stimuli in amusics relative to controls, as measured by FFR pitch strength, pitch error, and stimulus-to-response correlation. There was also no group difference in neural conduction time or FFR amplitudes. Both groups demonstrated better FFRs to speech (in quiet and noise) than to musical stimuli. However, a significant group difference was observed for tone identification, with amusics showing significantly lower accuracy than controls. Analysis of the tone confusion matrices suggested that amusics were more likely than controls to confuse between tones that shared similar acoustic features. Interestingly, this deficit in lexical tone identification was not coupled with brainstem abnormality for either speech or musical stimuli. Together, our results suggest that the amusic brainstem is not functioning abnormally, although higher-order linguistic pitch processing is impaired in amusia. This finding has significant implications for theories of central auditory processing, requiring further investigations into how different stages of auditory processing interact in the human brain.