The mismatch negativity responses of individuals with tinnitus with normal extended high-frequency hearing-is it possible to use mismatch negativity in the evaluation of tinnitus?

OBJECTIVE: This study uses the multi-feature paradigm to compare the MMN responses of individuals with normal hearing thresholds, including the high frequencies with and without tinnitus. METHODS: Sixteen subjects with chronic subjective idiopathic tinnitus and twenty matched healthy controls were included in the study. Participants with hearing thresholds (0.125-16 kHz) less than 20 dB HL and MoCA test scores above 21 were included in the study. MMN responses and topographical maps of the responses resulting from the multi-feature MMN paradigm were recorded from 22 surface scalp electrodes. Amplitude and latency parameters of the MMN responses of five different deviants, consisting of frequency, intensity, duration, location, and silent gap, were compared between the two groups. RESULTS: The amplitudes of MMN responses were lower in the tinnitus group than in the control group at Fz electrode for all deviant types. At the same time, there was no difference between the groups for MMN latencies and, no correlation was found between THI and MMN. CONCLUSION: According to our results, the MMN might indicate a possible impairment in pre-attentive and automatic central auditory processing for chronic tinnitus patients. Since MMN responses in the tinnitus group differ from those of healthy individuals, it might be used as a reference for evaluating the central auditory pathways of tinnitus patients.

Total GABA level in human auditory cortex is associated with speech-in-noise understanding in older age.

Speech-in-noise (SIN) understanding often becomes difficult for older adults because of impaired hearing and aging-related changes in central auditory processing. Central auditory processing depends on a fine balance between excitatory and inhibitory neural mechanisms, which may be upset in older age by a change in the level of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). In this study, we used MEGA-PRESS magnetic resonance spectroscopy (MRS) to estimate GABA levels in both the left and right auditory cortices of young and older adults. We found that total auditory GABA levels were lower in older compared to young adults. To understand the relationship between GABA and hearing function, we correlated GABA levels with hearing loss and SIN performance. In older adults, the GABA level in the right auditory cortex was correlated with age and SIN performance. The relationship between chronological age and SIN loss was partially mediated by the GABA level in the right auditory cortex. These findings support the hypothesis that inhibitory mechanisms in the auditory system are reduced in aging, and this reduction relates to functional impairments.

Central auditory processing in adults with chronic stroke without hearing loss: A magnetoencephalography study.

OBJECTIVE: Stroke lesions in non-auditory areas may affect higher-order central auditory processing. We sought to characterize auditory functions in chronic stroke survivors with unilateral arm/hand impairment using auditory evoked responses (AERs) with lesion and perception metrics. METHODS: The AERs in 29 stroke survivors and 14 controls were recorded with single tones, active and passive frequency-oddballs, and a dual-oddball with pitch-contour and time-interval deviants. Performance in speech-in-noise, mistuning detection, and moving-sound detection was assessed. Relationships between AERs, behaviour, and lesion overlap with functional networks, were examined. RESULTS: Despite their normal hearing, eight patients showed unilateral AER in the hemisphere ipsilateral to the affected hand with reduced amplitude compared to those with bilateral AERs. Both groups showed increasing attenuation of later components. Hemispheric asymmetry of AER sources was reduced in bilateral-AER patients. The N1 wave (100 ms latency) and P2 (200 ms) were delayed in individuals with lesions in the basal-ganglia and white-matter, while lesions in the attention network reduced the frequency-MMN (mismatch negativity) responses and increased the pitch-contour P3a response. Patients' impaired speech-in-noise perception was explained by AER measures and frequency-deviant detection performance with multiple regression. CONCLUSION: AERs reflect disruption of auditory functions due to damage outside of temporal lobe, and further explain complexity of neural mechanisms underlying higher-order auditory perception. SIGNIFICANCE: Stroke survivors without obvious hearing problems may benefit from rehabilitation for central auditory processing.

Keys to staying sharp: A randomized clinical trial of piano training among older adults with and without mild cognitive impairment.

BACKGROUND: The prevalence of dementia, the most expensive medical condition (Kirschstein, 2000 and Hurd et al., 2013 [1,2]), and its precursor, mild cognitive impairment (MCI) are increasing [3]. Finding effective intervention strategies to prevent or delay dementia is imperative to public health. Prior research provides compelling evidence that central auditory processing (CAP) deficits are a risk factor for dementia [4-6]. Grounded in the information degradation theory [7, 8], we hypothesize that improving brain function at early perceptual levels (i.e., CAP) may be optimal to attenuate cognitive and functional decline and potentially curb dementia prevalence. Piano training is one avenue to enhance cognition [9-13] by facilitating CAP at initial perceptual stages [14-18]. OBJECTIVES: The Keys To Staying Sharp study is a two arm, randomized clinical trial examining the efficacy of piano training relative to music listening instruction to improve CAP, cognition, and everyday function among older adults. In addition, the moderating effects of MCI status on piano training efficacy will be examined and potential mediators of intervention effects will be explored. HYPOTHESES: We hypothesize that piano training will improve CAP and cognitive performance, leading to functional improvements. We expect that enhanced CAP will mediate cognitive gains. We further hypothesize that cognitive gains will mediate functional improvements. METHOD: We plan to enroll 360 adults aged 60 years and older who will be randomized to piano training or an active control condition of music listening instruction and complete pre- and immediate post- assessments of CAP, cognition, and everyday function.

Monaural 40-Hz auditory steady-state magnetic responses can be useful for identifying epileptic focus in mesial temporal lobe epilepsy.

OBJECTIVE: Patients with mesial temporal lobe epilepsy (mTLE) often exhibit central auditory processing (CAP) dysfunction. Monaural 40-Hz auditory steady-state magnetic responses (ASSRs) were recorded to explore the pathophysiology of mTLE. METHODS: Eighteen left mTLE patients, 11 right mTLE patients and 16 healthy controls (HCs) were examined. Monaural clicks were presented at a rate of 40 Hz. Phase-locking factor (PLF) and power values were analyzed within bilateral Heschl's gyri. RESULTS: Monaural 40-Hz ASSR demonstrated temporal frequency dynamics in both PLF and power data. Symmetrical hemispheric contralaterality was revealed in HCs. However, predominant contralaterality was absent in mTLE patients. Specifically, right mTLE patients exhibited a lack of contralaterality in response to left ear but not right ear stimulation, and vice versa in left mTLE patients. CONCLUSION: This is the first study to use monaural 40-Hz ASSR with unilateral mTLE patients to clarify the relationship between CAP and epileptic focus. CAP dysfunction was characterized by a lack of contralaterality corresponding to epileptic focus. SIGNIFICANCE: Monaural 40-Hz ASSR can provide useful information for localizing epileptic focus in mTLE patients.

Multifeature Mismatch Negativity in Patients With Posttraumatic Stress Disorder.

OBJECTIVE: The mismatch negativity (MMN) component of the event-related brain potential has been used to examine auditory monitoring in various mental disorders. Previous research with posttraumatic stress disorder (PTSD) patients has revealed contradictory results. Enhanced as well as diminished MMNs have been obtained. METHOD: The multifeature protocol was employed to investigate the pattern of MMN in 17 military deployment-related PTSD patients and a group of healthy university student controls. RESULTS: Our results suggest no general effect of PTSD on the MMN involving the majority of acoustic features. There were slightly reduced MMNs in patients relative to controls for 2 of the features (duration, location). On the other hand, the N1 component was reduced in patients compared with controls. CONCLUSIONS: Choice of the stimulus protocol might be an important factor to explain inconsistent results in previous research. Differences in the auditory context between stimulus protocols and deficits in the formation of larger (auditory) contexts in PTSD might account for the results. SIGNIFICANCE: This study adds to the small number of studies on PTSD and MMN and revealed valuable information to guide future, related studies.

Bilingualism leads to greater auditory capacity.

The objective of this article is to investigate the effects of bilingualism on auditory capacity of young adults using a dichotic consonant-vowel (CV) test. Listeners were asked to identify distinct CVs dichotically presented to each ear through headphones. CV identification accuracy in both ears served as a measure of auditory capacity of listeners. Eighty normal hearing participants including 40 bilinguals (23 males and 17 females) and 40 monolinguals (11 males and 29 females) were used as study sample. Members of the bilingual group acquired their second language before entering elementary school. The bilingual listeners had higher mean both-ear-correct scores than did monolingual listeners, indicating a greater auditory capacity in the bilingual group than in the monolingual group. The finding of greater auditory capacity in bilinguals using a task requiring divided attention reflects greater ability to store and recall auditory information in bilinguals. However, the inconsistency of results across studies of bilingual advantages indicates that there is a need for further research in this area using both linguistic and non-linguistic tasks and considering age of acquisition as a possible moderating variable.

Altered neural synchronization to pure tone stimulation in patients with mesial temporal lobe epilepsy: An MEG study.

OBJECTIVE: Our previous study of monaural auditory evoked magnetic fields (AEFs) demonstrated that hippocampal sclerosis significantly modulated auditory processing in patients with mesial temporal lobe epilepsy (mTLE). However, the small sample size (n = 17) and focus on the M100 response were insufficient to elucidate the lateralization of the epileptic focus. Therefore, we increased the number of patients with mTLE (n = 39) to examine whether neural synchronization induced by monaural pure tone stimulation provides useful diagnostic information about epileptic foci in patients with unilateral mTLE. METHODS: Twenty-five patients with left mTLE, 14 patients with right mTLE, and 32 healthy controls (HCs) were recruited. Auditory stimuli of 500-Hz tone burst were monaurally presented to subjects. The AEF data were analyzed with source estimation of M100 responses in bilateral auditory cortices (ACs). Neural synchronization within ACs and between ACs was evaluated with phase-locking factor (PLF) and phase-locking value (PLV), respectively. Linear discriminant analysis was performed for diagnosis and lateralization of epileptic focus. RESULTS: The M100 amplitude revealed that patients with right mTLE exhibited smaller M100 amplitude than patients with left mTLE and HCs. Interestingly, PLF was able to differentiate the groups with mTLE, with decreased PLFs in the alpha band observed in patients with right mTLE compared with those (PLFs) in patients with left mTLE. Right hemispheric predominance was confirmed in both HCs and patients with left mTLE while patients with right mTLE showed a lack of right hemispheric predominance. Functional connectivity between bilateral ACs (PLV) was reduced in both patients with right and left mTLE compared with that of HCs. The accuracy of diagnosis and lateralization was 80%-90%. CONCLUSION: Auditory cortex subnormal function was more pronounced in patients with right mTLE compared with that in patients with left mTLE as well as HCs. Monaural AEFs can be used to reveal the pathophysiology of mTLE. Overall, our results indicate that altered neural synchronization may provide useful information about possible functional deterioration in patients with unilateral mTLE.

The MMN as a viable and objective marker of auditory development in CI users.

In the present article, we review the studies on the use of the mismatch negativity (MMN) as a tool for an objective assessment of cochlear-implant (CI) functioning after its implantation and as a function of time of CI use. The MMN indexes discrimination of different sound stimuli with a precision matching with that of behavioral discrimination and can therefore be used as its objective index. Importantly, these measurements can be reliably carried out even in the absence of attention and behavioral responses and therefore they can be extended to populations that are not capable of behaviorally reporting their perception such as infants and different clinical patient groups. In infants and small children with CI, the MMN provides the only means for assessing the adequacy of the CI functioning, its improvement as a function of time of CI use, and the efficiency of different rehabilitation procedures. Therefore, the MMN can also be used as a tool in developing and testing different novel rehabilitation procedures. Importantly, the recently developed multi-feature MMN paradigms permit the objective assessment of discrimination accuracy for all the different auditory dimensions (such as frequency, intensity, and duration) in a short recording time of about 30 min. Most recently, such stimulus paradigms have been successfully developed for an objective assessment of music perception, too.

Abnormalities in cortical auditory responses in children with central auditory processing disorder.

The main objective of the present study was to identify markers of neural deficits in children with central auditory processing disorder (CAPD) by measuring latency and amplitude of the auditory cortical responses and mismatch negativity (MMN) responses. Passive oddball paradigms were used with nonverbal and verbal stimuli to record cortical auditory-evoked potentials and MMN. Twenty-three children aged 9-12 participated in the study: 10 with normal hearing acuity as well as CAPD and 13 with normal hearing without CAPD. No significant group differences were observed for P1 latency and amplitude. Children with CAPD were observed to have significant N2 latency prolongation and amplitude reduction with nonverbal and verbal stimuli compared to children without CAPD. No significant group differences were observed for the MMN conditions. Moreover, electrode position affected the results in the same manner for both groups of children. The findings of the present study suggest that the N2 response could be a marker of neural deficits in children with CAPD. N2 results suggest that maturational factors or a different mechanism could be involved in processing auditory information at the central level for these children.

[Acoustic reflexes of children with and without central auditory processing disorders]. / Stapediusreflexe von Kindern mit und ohne auditive Verarbeitungs- und Wahrnehmungsstörungen.

BACKGROUND: According to international standards, determination of acoustic reflex thresholds (ART) is one of the established objective measurements in the diagnostic workup of central auditory processing disorders (CAPD). However, there is still no evidence for the significance of ART in CAPD diagnosis. PATIENTS AND METHODS: This study tested 57 children with proven CAPD and 50 healthy children (control group) with regard to group differences in mean ART (sine tones or bandpass-filtered noise). Additionally, it was investigated whether there were group differences between the mean dissociations of ART for sine tones or bandpass filtered noise. RESULTS: Neither ipsi- nor contralaterally were significant clinically relevant group differences (p < 0.050) between the mean ART of children with and without CAPD found. After Bonferroni correction, a significant group difference in the percentage of non-triggered reflexes was only observed with left-sided contralateral 2 kHz stimuli. Concerning the number of dissociations ≥20 dB, no significant group differences (p < 0.050) were detected either ipsi- or contralaterally (Fisher's test). CONCLUSION: The results of the study seem to indicate no clinically relevant ability of ART measurements to distinguish between children with and without CAPD. This renders the benefit of ART measurements for CAPD diagnosis questionable.

Mismatch Negativity and Ear Laterality in Alzheimer's Disease and in Mild Cognitive Impairment.

BACKGROUND: Cortical auditory event-related potentials (ERPs) were studied in order to measure mismatch negativity (MMN). Three groups of subjects were studied: patients with Alzheimer's disease (AD, n = 32), mild cognitive impairment (MCI, n = 44), and subjective memory complaints without cognitive decline (SMC, n = 27). A bottom up strategy was applied, and the right and left ears were stimulated monaurally. OBJECTIVE: To investigate MMN in AD and MCI, and in a clinical reference group. METHODS: ERPs were carried out with 500 tone pulses at 80 dBnHL. Each sequence included 80% standard tones (500 Hz) (f), and 20% deviant tones (1000 Hz) (r). MMN measurements were carried out by comparing the amplitudes of (f) and (r) recordings and to calculate the amplitude difference in µV for each group. The right and the left ears were analyzed separately. RESULTS: A left ear advantage (LEA) of MMN amplitude was demonstrated in the two groups with better cognition (the MCI and the SMC groups), but not in the AD group. DISCUSSION: The absence of MMN asymmetry in the AD group is possibly caused by a dysfunction to apprehend changes of tonal stimuli.

40-Hz oscillations underlying perceptual binding in young and older adults.

Auditory object perception requires binding of elementary features of complex stimuli. Synchronization of high-frequency oscillation in neural networks has been proposed as an effective alternative to binding via hard-wired connections because binding in an oscillatory network can be dynamically adjusted to the ever-changing sensory environment. Previously, we demonstrated in young adults that gamma oscillations are critical for sensory integration and found that they were affected by concurrent noise. Here, we aimed to support the hypothesis that stimulus evoked auditory 40-Hz responses are a component of thalamocortical gamma oscillations and examined whether this oscillatory system may become less effective in aging. In young and older adults, we recorded neuromagnetic 40-Hz oscillations, elicited by monaural amplitude-modulated sound. Comparing responses in quiet and under contralateral masking with multitalker babble noise revealed two functionally distinct components of auditory 40-Hz responses. The first component followed changes in the auditory input with high fidelity and was of similar amplitude in young and older adults. The second, significantly smaller in older adults, showed a 200-ms interval of amplitude and phase rebound and was strongly attenuated by contralateral noise. The amplitude of the second component was correlated with behavioral speech-in-noise performance. Concurrent noise also reduced the P2 wave of auditory evoked responses at 200-ms latency, but not the earlier N1 wave. P2 modulation was reduced in older adults. The results support the model of sensory binding through thalamocortical gamma oscillations. Limitation of neural resources for this process in older adults may contribute to their speech-in-noise understanding deficits.

Comprehensive auditory discrimination profiles recorded with a fast parametric musical multi-feature mismatch negativity paradigm.

OBJECTIVE: Mismatch negativity (MMN), a component of the auditory event-related potential (ERP) in response to auditory-expectancy violation, is sensitive to central auditory processing deficits associated with several clinical conditions and to auditory skills deriving from musical expertise. This sensitivity is more evident for stimuli integrated in complex sound contexts. This study tested whether increasing magnitudes of deviation (levels) entail increasing MMN amplitude (or decreasing latency), aiming to create a balanced version of the musical multi-feature paradigm towards measurement of extensive auditory discrimination profiles in auditory expertise or deficits. METHODS: Using electroencephalography, we measured MMNs in healthy young adults to six types of sound feature change (pitch, timbre, location, intensity, slide and rhythm) at three different magnitudes of deviation, embedded in a music-sounding context. We also behaviourally assessed the individual musical aptitude using the Musical Ear Test (MET). RESULTS: 16 of 18 sound feature changes elicited significant MMNs. For pitch, intensity, location, and slide, the MMN amplitude increased with increasing magnitude of feature change. We observed a ceiling effect for rhythm, and a floor effect for timbre. The slide MMN amplitude correlated positively with MET melody score and negatively with MET rhythm score. CONCLUSIONS: This novel paradigm provides an extensive, objective measure of auditory discrimination profile for different sound features embedded in a complex sound context. SIGNIFICANCE: The paradigm can be adopted to study the neurophysiology of individuals with music processing difficulties or with special musical skills, and may be a useful tool for investigating development, plasticity, and deficits of auditory processing.

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.

Towards an optimal paradigm for simultaneously recording cortical and brainstem auditory evoked potentials.

BACKGROUND: Simultaneous recording of brainstem and cortical event-related brain potentials (ERPs) may offer a valuable tool for understanding the early neural transcription of behaviorally relevant sounds and the hierarchy of signal processing operating at multiple levels of the auditory system. To date, dual recordings have been challenged by technological and physiological limitations including different optimal parameters necessary to elicit each class of ERP (e.g., differential adaptation/habitation effects and number of trials to obtain adequate response signal-to-noise ratio). NEW METHOD: We investigated a new stimulus paradigm for concurrent recording of the auditory brainstem frequency-following response (FFR) and cortical ERPs. The paradigm is "optimal" in that it uses a clustered stimulus presentation and variable interstimulus interval (ISI) to (i) achieve the most ideal acquisition parameters for eliciting subcortical and cortical responses, (ii) obtain an adequate number of trials to detect each class of response, and (iii) minimize neural adaptation/habituation effects. RESULTS AND COMPARISON WITH EXISTING METHOD: Comparison between clustered and traditional (fixed, slow ISI) stimulus paradigms revealed minimal change in amplitude or latencies of either the brainstem FFR or cortical ERP. The clustered paradigm offered over a 3× increase in recording efficiency compared to conventional (fixed ISI presentation) and thus, a more rapid protocol for obtaining dual brainstem-cortical recordings in individual listeners. CONCLUSIONS: We infer that faster recording of subcortical and cortical potentials might allow more complete and sensitive testing of neurophysiological function and aid in the differential assessment of auditory function.

Auditory temporal-organization abilities in school-age children with peripheral hearing loss.

PURPOSE: The objective was to assess auditory sequential organization (ASO) ability in children with and without hearing loss. METHOD: Forty children 9 to 12 years old participated in the study: 12 with sensory hearing loss (HL), 12 with central auditory processing disorder (CAPD), and 16 with normal hearing. They performed an ASO task in which they were asked to recall 2, 3, and 5 verbal and nonverbal stimuli with an interstimulus interval (ISI) of 425 ms as well as sequences of 2 elements with an ISI of 20 or 1,000 ms. RESULTS: No significant difference was found between the group of children with HL and the 2 other groups on nonverbal stimuli in all testing conditions. Regardless of ISI duration or number of elements in the sequence, children with HL had significantly fewer correct responses than children with normal hearing and children with CAPD for the verbal stimuli /ba/-/da/. Children with HL had significantly better performance than children with CAPD for the verbal a/-/da/ when the number of elements in the sequence varied. CONCLUSIONS: Children with sensory HL showed impaired ASO ability when recalling verbal /ba/-/da/. Results suggest that hearing loss can induce a specific signature when processing these verbal stimuli.