Sensory Gating Networks in Normal-Hearing Adults With Minimal Tinnitus.

PURPOSE: The goal of this study was to observe sensory gating-related networks underlying cortical auditory evoked potential (CAEP) peak components in individuals with and without minimal tinnitus, as measured using the Tinnitus Handicap Inventory (THI). This analysis was performed on previously published sensory gating responses in normal-hearing adults with and without minimal tinnitus. METHOD: Independent component analysis was performed for each individual CAEP gating component (Pa, P50, N1, and P2). Significant components were retained for source localization analyses within the following groups: no tinnitus, tinnitus with a THI score ≤ 6, and tinnitus with a THI score > 6. Brain source localization was performed on the gating difference wave for each component using standardized low-resolution brain electromagnetic tomography. RESULTS: Gating-related networks were identified within each group. Different regional sources were observed between groups, with parietal sources underlying the Pa and P50 components as tinnitus severity increased. A larger prefrontal regional activation was also shown for the N1 gating component as tinnitus severity increased. These results expand upon the functional gating responses via CAEP waveforms in a previously published study. CONCLUSIONS: The auditory gating response, as measured via CAEPs, has previously been shown to significantly correlate with an increase in tinnitus severity in adults with normal hearing. The corresponding changes in the gating response appear to be supported by different cortical regions in those without tinnitus, those with a THI score ≤ 6, and those with a THI score > 6. Next, functional differences between localized cortical regions should be tested.

EEG Alpha Band Responses Reveal Amplification Benefits in Infants with Hearing Loss.

Our objective was to examine the effects of hearing aid amplification on auditory detection and discrimination in infants who were hard of hearing (IHH) using a physiological measure of auditory perception. We recorded EEG from 41 sleeping IHH aged 1.04 to 5.62 months while presenting auditory stimuli in a mismatch response paradigm. Responses were recorded during two listening conditions for each participant: aided and unaided. Temporal envelopes of the mismatch response in the EEG alpha band (6-12 Hz) were extracted from the latent, time-frequency transformed data. Aided alpha band responses were greater than unaided responses for the deviant trials but were not different for the standard trials. Responses to the deviant trials were greater than responses to the standard trials for the aided conditions but were not different for the unaided conditions. These results suggest that the alpha band mismatch can be used to examine both detection and discrimination of speech and non-speech sounds in IHH. With further study, the alpha band mismatch could expand and refine our abilities to validate hearing aid fittings at younger ages than current clinical protocols allow.

Relationship between Behavioral Infant Speech Perception and Hearing Age for Children with Hearing Loss.

(1) Background: Research has demonstrated that early intervention for children who are hard-of-hearing (CHH) facilitates improved language development. Early speech perception abilities may impact CHH outcomes and guide future intervention. The objective of this study was to examine the use of a conditioned head turn (CHT) task as a measure of speech discrimination in CHH using a clinically feasible protocol. (2) Methods: Speech perception was assessed for a consonant and vowel contrast among 57 CHH and 70 children with normal hearing (CNH) aged 5-17 months using a CHT paradigm. (3) Results: Regardless of hearing status, 74% of CHH and 77% of CNH could discriminate /a-i/, and 55% of CHH and 56% of CNH could discriminate /ba-da/. Regression models revealed that both CHH and CNH performed better on /ba-da/ at 70 dBA compared to 50 dBA. Performance by hearing age showed no speech perception differences for CNH and children with mild hearing loss for either contrast. However, children with hearing losses ≥ 41 dB HL performed significantly poorer than CNH for /a-i/. (4) Conclusions: This study demonstrates the clinical feasibility of assessing early speech perception in infants with hearing loss and replicates previous findings of speech perception abilities among CHH and CNH.

Reading Proficiency Trends Following Newborn Hearing Screening Implementation.

OBJECTIVES: To investigate trends in population-level school-aged reading scores among students with hearing loss in an urban Colorado school district after implementation of universal newborn hearing screening (UNHS) and Early Hearing Detection and Intervention. METHODS: The final sample included 1422 assessments conducted during the 2000-2001 through 2013-2014 school years for 321 children with hearing loss in grades 3 through 10. Longitudinal hierarchical linear modeling analyses were used to examine reading proficiency (controlling for birth year, grade in school, free and reduced lunch status, additional disability services, and English not spoken in the home). The Colorado Student Assessment Program was administered to students in third through 10th grades throughout the state. The test years chosen included children born before and after implementation of UNHS. RESULTS: After implementation of UNHS, significant longitudinal reading proficiency improvements were observed by birth year and grade overall and for all subgroups. However, gains in reading proficiency were substantially less for children eligible for free and reduced lunch and those with moderate-severe to profound hearing loss. With each succeeding birth cohort and grade, increased numbers of children participated in testing because of improved language skills, with higher proportions identified as proficient or advanced readers. CONCLUSIONS: Notable improvements in reading proficiency after Early Hearing Detection and Intervention implementation were demonstrated, as all groups of children with hearing loss became more likely to achieve proficient and advanced reading levels. On the other hand, some disparities increased, with greater improvements in reading proficiency for children in economically advantaged families.

Mismatched response predicts behavioral speech discrimination outcomes in infants with hearing loss and normal hearing.

Children with hearing loss (HL) remain at risk for poorer language abilities than normal hearing (NH) children despite targeted interventions; reasons for these differences remain unclear. In NH children, research suggests speech discrimination is related to language outcomes, yet we know little about it in children with HL under the age of 2 years. We utilized a vowel contrast, /a-i/, and a consonant-vowel contrast, /ba-da/, to examine speech discrimination in 47 NH infants and 40 infants with HL. At Mean age =3 months, EEG recorded from 11 scalp electrodes was used to compute the time-frequency mismatched response (TF-MMRSE ) to the contrasts; at Mean age =9 months, behavioral discrimination was assessed using a head turn task. A machine learning (ML) classifier was used to predict behavioral discrimination when given an arbitrary TF-MMRSE as input, achieving accuracies of 73% for exact classification and 92% for classification within a distance of one class. Linear fits revealed a robust relationship regardless of hearing status or speech contrast. TF-MMRSE responses in the delta (1-3.5 Hz), theta (3.5-8 Hz), and alpha (8-12 Hz) bands explained the most variance in behavioral task performance. Our findings demonstrate the feasibility of using TF-MMRSE to predict later behavioral speech discrimination.

The relationship between mismatch response and the acoustic change complex in normal hearing infants.

OBJECTIVE: To examine the utility of the mismatch response (MMR) and acoustic change complex (ACC) for assessing speech discrimination in infants. METHODS: Continuous EEG was recorded during sleep from 48 (24 male, 20 female) normally hearing aged 1.77 to -4.57 months in response to two auditory discrimination tasks. ACC was recorded in response to a three-vowel sequence (/i/-/a/-/i/). MMR was recorded in response to a standard vowel, /a/, (probability 85%), and to a deviant vowel, /i/, (probability of 15%). A priori comparisons included: age, sex, and sleep state. These were conducted separately for each of the three bandpass filter settings were compared (1-18, 1-30, and 1-40 Hz). RESULTS: A priori tests revealed no differences in MMR or ACC for age, sex, or sleep state for any of the three filter settings. ACC and MMR responses were prominently observed in all 44 sleeping infants (data from four infants were excluded). Significant differences observed for ACC were to the onset and offset of stimuli. However, neither group nor individual differences were observed to changes in speech stimuli in the ACC. MMR revealed two prominent peaks occurring at the stimulus onset and at the stimulus offset. Permutation t-tests revealed significant differences between the standard and deviant stimuli for both the onset and offset MMR peaks (p < 0.01). The 1-18 Hz filter setting revealed significant differences for all participants in the MMR paradigm. CONCLUSION: Both ACC and MMR responses were observed to auditory stimulation suggesting that infants perceive and process speech information even during sleep. Significant differences between the standard and deviant responses were observed in the MMR, but not ACC paradigm. These findings suggest that the MMR is sensitive to detecting auditory/speech discrimination processing. SIGNIFICANCE: This paper identified that MMR can be used to identify discrimination in normal hearing infants. This suggests that MMR has potential for use in infants with hearing loss to validate hearing aid fittings.

Spectral-temporal EEG dynamics of speech discrimination processing in infants during sleep.

BACKGROUND: Oddball paradigms are frequently used to study auditory discrimination by comparing event-related potential (ERP) responses from a standard, high probability sound and to a deviant, low probability sound. Previous research has established that such paradigms, such as the mismatch response or mismatch negativity, are useful for examining auditory processes in young children and infants across various sleep and attention states. The extent to which oddball ERP responses may reflect subtle discrimination effects, such as speech discrimination, is largely unknown, especially in infants that have not yet acquired speech and language. RESULTS: Mismatch responses for three contrasts (non-speech, vowel, and consonant) were computed as a spectral-temporal probability function in 24 infants, and analyzed at the group level by a modified multidimensional scaling. Immediately following an onset gamma response (30-50 Hz), the emergence of a beta oscillation (12-30 Hz) was temporally coupled with a lower frequency theta oscillation (2-8 Hz). The spectral-temporal probability of this coupling effect relative to a subsequent theta modulation corresponds with discrimination difficulty for non-speech, vowel, and consonant contrast features. DISCUSSION: The theta modulation effect suggests that unexpected sounds are encoded as a probabilistic measure of surprise. These results support the notion that auditory discrimination is driven by the development of brain networks for predictive processing, and can be measured in infants during sleep. The results presented here have implications for the interpretation of discrimination as a probabilistic process, and may provide a basis for the development of single-subject and single-trial classification in a clinically useful context. CONCLUSION: An infant's brain is processing information about the environment and performing computations, even during sleep. These computations reflect subtle differences in acoustic feature processing that are necessary for language-learning. Results from this study suggest that brain responses to deviant sounds in an oddball paradigm follow a cascade of oscillatory modulations. This cascade begins with a gamma response that later emerges as a beta synchronization, which is temporally coupled with a theta modulation, and followed by a second, subsequent theta modulation. The difference in frequency and timing of the theta modulations appears to reflect a measure of surprise. These insights into the neurophysiological mechanisms of auditory discrimination provide a basis for exploring the clinically utility of the MMR TF and other auditory oddball responses.

Oscillatory decoupling differentiates auditory encoding deficits in children with listening problems.

OBJECTIVE: We sought to examine whether oscillatory EEG responses to a speech stimulus in both quiet and noise were different in children with listening problems than in children with normal hearing. METHODS: We employed a high-resolution spectral-temporal analysis of the cortical auditory evoked potential in response to a 150 ms speech sound /da/ in quiet and 3 dB SNR in 21 typically developing children (mean age=10.7 years, standard deviation=1.7) and 44 children with reported listening problems (LP) with absence of hearing loss (mean age=10.3 years, standard deviation=1.6). Children with LP were assessed for auditory processing disorder (APD) by which 24 children had APD, and 20 children did not. Peak latencies, magnitudes, and frequencies were compared between these groups. RESULTS: Children with LP had frequency shifts in the theta, and alpha bands (p<0.05), and children with LP+APD had additional frequency (p<0.01) and latency shifts (p<0.05) in the upper beta and in the lower gamma bands. CONCLUSIONS: These results provide evidence for differences in higher level modulatory processing in children with LP, and that APD is driven by differences in early auditory encoding. SIGNIFICANCE: These findings may better guide future research toward improving the differential diagnosis and treatment of listening problems in this population of children.

Neural mechanisms of rapid sensitivity to syntactic anomaly.

Recent psycholinguistic models hypothesize that anticipatory processing can speed the response to linguistic input during language comprehension by pre-activating representations necessary for word recognition. We investigated the neurocognitive mechanisms of anticipatory processing by recording event-related potentials (ERPs) to syntactically anomalous (The thief was caught by for police) and well-formed (e.g., The thief was caught by the police) sentences. One group of participants saw anomalies elicited by the same word in every instance (e.g., for; low-variability stimuli), providing high affordances for predictions about the word-form appearing in the critical position. A second group saw anomalies elicited by seven different prepositions (at, of, on, for, from, over, with; high-variability stimuli) across the study, creating a more difficult prediction task. Syntactic category anomalies enhanced the occipital-temporal N170 component of the ERP, indicating rapid sensitivity - within 200 ms of word-onset - to syntactic anomaly. For low-variability but not the high-variability stimuli, syntactic anomaly also enhanced the earlier occipital-temporal P1 component, around 130 ms after word-onset, indicating that affordances for prediction engendered earlier sensitivity to syntactic anomaly. Independent components analysis revealed three sources within the ERP signal whose functional dynamics were consistent with predictive processing and early responses to syntactic anomaly. Distributed neural source modeling (sLORETA) of these early active sources produced a candidate network for early responses to words during reading in the right posterior occipital, left occipital-temporal, and medial parietal cortex.

Innovative technology for the assisted delivery of intensive voice treatment (LSVT®LOUD) for Parkinson disease.

PURPOSE: To assess the feasibility and effectiveness of a newly developed assistive technology system, Lee Silverman Voice Treatment Companion (LSVT(®) Companion™, hereafter referred to as "Companion"), to support the delivery of LSVT(®)LOUD, an efficacious speech intervention for individuals with Parkinson disease (PD). METHOD: Sixteen individuals with PD were randomized to an immediate (n = 8) or a delayed (n = 8) treatment group. They participated in 9 LSVT LOUD sessions and 7 Companion sessions, independently administered at home. Acoustic, listener perception, and voice and speech rating data were obtained immediately before (pre), immediately after (post), and at 6 months post treatment (follow-up). System usability ratings were collected immediately post treatment. Changes in vocal sound pressure level were compared to data from a historical treatment group of individuals with PD treated with standard, in-person LSVT LOUD. RESULTS: All 16 participants were able to independently use the Companion. These individuals had therapeutic gains in sound pressure level, pre to post and pre to follow-up, similar to those of the historical treatment group. CONCLUSIONS: This study supports the use of the Companion as an aid in treatment of hypokinetic dysarthria in individuals with PD. Advantages and disadvantages of the Companion, as well as limitations of the present study and directions for future studies, are discussed.

The influence of a sensitive period for auditory-visual integration in children with cochlear implants.

PURPOSE: Children who experience long periods of auditory deprivation are susceptible to large-scale reorganization of auditory cortical areas responsible for the perception of speech and language. One consequence of this reorganization is that integration of combined auditory and visual information may be altered after hearing is restored with a cochlear implant. Our goal was to investigate the effects of reorganization in a task that examines performance during multisensory integration. METHODS: Reaction times to the detection of basic auditory (A), visual (V), and combined auditory-visual (AV) stimuli were examined in a group of normally hearing children, and in two groups of cochlear implanted children: (1) early implanted children in whom cortical auditory evoked potentials (CAEPs) fell within normal developmental limits, and (2) late implanted children in whom CAEPs were outside of normal developmental limits. Miller's test of the race model inequality was performed for each group in order to examine the effects of auditory deprivation on multisensory integration abilities after implantation. RESULTS: Results revealed a significant violation of the race model inequality in the normally hearing and early implanted children, but not in the group of late implanted children. CONCLUSION: These results suggest that coactivation to multi-modal sensory input cannot explain the decreased reaction times to multi-modal input in late implanted children. These results are discussed in regards to current models for coactivation to redundant sensory information.

Cortical reorganization in children with cochlear implants.

Congenital deafness leads to atypical organization of the auditory nervous system. However, the extent to which auditory pathways reorganize during deafness is not well understood. We recorded cortical auditory evoked potentials in normal hearing children and in congenitally deaf children fitted with cochlear implants. High-density EEG and source modeling revealed principal activity from auditory cortex in normal hearing and early implanted children. However, children implanted after a critical period of seven years revealed activity from parietotemporal cortex in response to auditory stimulation, demonstrating reorganized cortical pathways. Reorganization of central auditory pathways is limited by the age at which implantation occurs, and may help explain the benefits and limitations of implantation in congenitally deaf children.

Deprivation-induced cortical reorganization in children with cochlear implants.

A basic finding in developmental neurophysiology is that some areas of the cortex cortical areas will reorganize following a period of stimulus deprivation. In this review, we discuss mainly electroencephalography (EEG) studies of normal and deprivation-induced abnormal development of the central auditory pathways in children and in animal models. We describe age cut-off for sensitive periods for central auditory development in congenitally deaf children who are fitted with a cochlear implant. We speculate on mechanisms of decoupling and reorganization which may underlie the end of the sensitive period. Finally, we describe new magentoencephalography (MEG) evidence of somatosensory cross-modal plasticity following long-term auditory deprivation.

Central auditory development: evidence from CAEP measurements in children fit with cochlear implants.

UNLABELLED: In normal-hearing children the latency of the P1 component of the cortical evoked response to sound varies as a function of age and, thus, can be used as a biomarker for maturation of central auditory pathways. We assessed P1 latency in 245 congenitally deaf children fit with cochlear implants following various periods of auditory deprivation. If children experience less than 3.5 years of auditory deprivation before implantation, P1 latencies fall into the range of normal following 3-6 months of electrical stimulation. Children who experience greater than 7 years of deprivation, however, generally do not develop normal P1 latencies even after years of stimulation. Moreover, the waveforms for these patients can be markedly abnormal. Cortical reorganization stimulated by deprivation is likely to be a significant factor in both variation in the latency and morphology of the cortical evoked response to sound for children fit with a cochlear implant and variation in the development of oral speech and language function. LEARNING OUTCOMES: The reader will be introduced to research using cortical evoked responses (CAEPs), positron emission tomography (PET) scans and in-depth recording from the auditory cortex of congenitally deaf cats that converges on the existence of a sensitive period for the development of central auditory pathways in children. The reader will also be provided with two case studies that illustrate the use of the P1 response as biomarker for development of central auditory pathways. Finally, suggestions for future research will be provided.

Abnormalities in central auditory maturation in children with language-based learning problems.

OBJECTIVE: To examine maturation of the central auditory pathways in children with language-based learning problems (LP). METHODS: Cortical auditory evoked potentials (CAEPs) recorded from 26 children with LP were compared to CAEPs recorded from 38 typical children. CAEP responses were recorded in response to a speech sound, /uh/, which was presented in a stimulus train with decreasing inter-stimulus intervals (ISIs) of 2000, 1000, 560, and 360 ms. RESULTS: We identified three atypical morphological categories of CAEP responses in the LP group. Category 1 responses revealed delayed P1 latencies and absent N1/P2 components. Category 2 responses revealed typical P1 responses, but delayed N1 and P2 responses. Category 3 responses revealed generally low-amplitude CAEP responses. A fourth sub-group of LP children had normal CAEP responses. CONCLUSIONS: Overall, the majority of children with LP had abnormal CAEP responses. These children fell into distinct categories based on the abnormalities in maturational patterns of their CAEP responses. SIGNIFICANCE: We describe a rate sensitive stimulation paradigm which may be used to identify and categorize LP children who exhibit abnormal patterns of central auditory maturation.

Minimization of cochlear implant stimulus artifact in cortical auditory evoked potentials.

OBJECTIVE: To compare two methods of minimizing cochlear implant artifact in cortical auditory evoked potential (CAEP) recordings. METHODS: Two experiments were conducted. In the first, we assessed the use of independent component analysis (ICA) as a pre-processing filter. In the second, we explored the use of an optimized differential reference (ODR) for minimizing artifacts. RESULTS: Both ICA and the ODR can minimize the artifact and allow measurement of CAEP responses. CONCLUSIONS: When using a large number of recording electrodes ICA can be used to minimize the implant artifact. When using a single electrode montage an optimized differential reference is adequate to minimize the artifact. SIGNIFICANCE: The use of an optimized differential reference could allow cortical evoked potentials to be used in routine clinical assessment of auditory pathway development in children and adults fit with cochlear implants.

P1 latency as a biomarker for central auditory development in children with hearing impairment.

We used the latency of the P1 cortical auditory-evoked potential (CAEP) as a biomarker for the development of central auditory pathways in three children who received intervention through hearing aids and/or cochlear implants. Our goal was to examine the clinical feasibility of using the latency of the P1 CAEP as an objective tool to evaluate whether acoustic amplification for hearing-impaired children has provided sufficient stimulation for normal development of central auditory pathways. If clinicians have such a marker, then they can more confidently make a decision about whether to provide a child with a cochlear implant following an appropriate hearing-aid trial. Using the same marker, clinicians will also be able to monitor the maturation of central auditory pathways once electrical stimulation is initiated.

Developmental changes in refractoriness of the cortical auditory evoked potential.

OBJECTIVE: This study examined morphological changes in the cortical auditory evoked potential (CAEP) waveform as a function of varying stimulation rate. Stimuli were presented in a paradigm which indirectly assesses the refractory properties of the underlying neuronal generators. METHODS: CAEPs were recorded in 50 normal-hearing children (3-12 years) and 10 young adults (24-26 years). A speech sound was presented in a stimulus train with sequentially decreasing inter-stimulus intervals (ISIs) of 2000, 1000, 560, and 360ms. Latencies and amplitudes of the P1, N1, and P2 components at the Cz electrode were examined as a function of stimulus rate and age. RESULTS: Results revealed significant changes in the CAEP as a function of age and stimulation rate. At younger ages the N1-P2 component was elicited only at the slowest stimulation rates, and was more clearly apparent at successively faster stimulation rates as age increased. CONCLUSIONS: We have described a stimulus paradigm that allows examination of the development of refractoriness by highlighting the interaction between age and rate on CAEP morphology. SIGNIFICANCE: Complex maturational patterns of CAEP components are best understood when the effects of both age and stimulus rate on the CAEP waveform are considered.

Central auditory maturation and babbling development in infants with cochlear implants.

OBJECTIVE: To examine the relationship between the maturation of central auditory pathways and the development of canonical (speechlike) babbling in infants with cochlear implants. DESIGN: Comparison of the latencies of the P1 cortical auditory evoked potential and vocalizations produced by subjects before they were fitted with a cochlear implant and at several time points within the first year after implantation. SUBJECTS: Two congenitally deaf children who were implanted with a multichannel cochlear implant at ages 13 and 14 months. INTERVENTIONS: P1 response latencies were recorded in response to a /ba/ stimulus before implantation and at several time points following implantation. Vocalizations produced by the subjects while interacting with their caregiver were audiorecorded twice before implantation and at monthly sessions following implantation. RESULTS: Subjects showed a rapid decrease in P1 latencies resulting in normal P1 latencies within about 3 months after implantation. Before implantation, the vocalizations were primarily of a precanonical nature. After 3 months' experience with the implants, the proportion of canonical vocalizations increased dramatically relative to the number of precanonical utterances. CONCLUSIONS: Results of this study suggest that the development of P1 response latencies and the development of early communicative behaviors may follow a similar developmental trajectory in children implanted early. Although preliminary, these findings indicate that the development of early communicative behaviors following implantation may be positively influenced by the rate of plastic changes in central auditory pathways.