Principles and clinical applications of auditory evoked potentials in the geriatric population

Study of aged central auditory function using the auditory middle latency response

OBJECTIVE

Investigate the auditory function of the elderly using the middle latency potentials.

METHODOLOGY

Group 1 (G1): 20 healthy individuals of both genders, older than 60 years, without hearing loss. Group 2 (G2): 20 healthy individuals of both sexes, older than 60 years, with hearing loss in frequencies from 4 to 8 kHz. Potential recording was performed with unilateral and bilateral stimulation and the Binaural Interaction Component was calculated.

RESULTS

Na latency in C3A1 was greater in the stimulation of the right ear in G2 and the amplitude of Na-Pa was greater in the stimulation of the right ear and recording in C3A1 in G1. The latency of the Pa component was higher in the stimulation of the right ear recorded in C4A2. The Pb component in G2 by bilateral stimulation and recorded in C4A2 had higher latency. The first and second negative and positive peaks presented greater amplitude in G1. In C3A1, the 1^st negative peak was more negative in G1 and the 2^nd positive peak showed greater amplitude in C4A2 in both groups.

CONCLUSION

The transmission of auditory information to the primary auditory cortex is impaired with aging, especially in unilateral stimulation, reinforced by losses in elderly people with peripheral hearing loss, such as in the binaural interaction at the cortical and subcortical levels. Thus, the AMLR has shown to be a sensitive examination to investigate neuroauditory disorders in the elderly, especially related to high-frequency hearing loss and primary auditory cortex dysfunctions caused by the aging process.

Effects of Signal Type and Noise Background on Auditory Evoked Potential N1, P2, and P3 Measurements in Blast-Exposed Veterans

OBJECTIVES

Veterans who have been exposed to high-intensity blast waves frequently report persistent auditory difficulties such as problems with speech-in-noise (SIN) understanding, even when hearing sensitivity remains normal. However, these subjective reports have proven challenging to corroborate objectively. Here, we sought to determine whether use of complex stimuli and challenging signal contrasts in auditory evoked potential (AEP) paradigms rather than traditional use of simple stimuli and easy signal contrasts improved the ability of these measures to (1) distinguish between blast-exposed Veterans with auditory complaints and neurologically normal control participants, and (2) predict behavioral measures of SIN perception.

DESIGN

A total of 33 adults (aged 19-56 years) took part in this study, including 17 Veterans exposed to high-intensity blast waves within the past 10 years and 16 neurologically normal control participants matched for age and hearing status with the Veteran participants. All participants completed the following test measures: (1) a questionnaire probing perceived hearing abilities; (2) behavioral measures of SIN understanding including the BKB-SIN, the AzBio presented in 0 and +5 dB signal to noise ratios (SNRs), and a word-level consonant-vowel-consonant test presented at +5 dB SNR; and (3) electrophysiological tasks involving oddball paradigms in response to simple tones (500 Hz standard, 1000 Hz deviant) and complex speech syllables (/ba/ standard, /da/ deviant) presented in quiet and in four-talker speech babble at a SNR of +5 dB.

RESULTS

Blast-exposed Veterans reported significantly greater auditory difficulties compared to control participants. Behavioral performance on tests of SIN perception was generally, but not significantly, poorer among the groups. Latencies of P3 responses to tone signals were significantly longer among blast-exposed participants compared to control participants regardless of background condition, though responses to speech signals were similar across groups. For cortical AEPs, no significant interactions were found between group membership and either stimulus type or background. P3 amplitudes measured in response to signals in background babble accounted for 30.9% of the variance in subjective auditory reports. Behavioral SIN performance was best predicted by a combination of N1 and P2 responses to signals in quiet which accounted for 69.6% and 57.4% of the variance on the AzBio at 0 dB SNR and the BKB-SIN, respectively.

CONCLUSIONS

Although blast-exposed participants reported far more auditory difficulties compared to controls, use of complex stimuli and challenging signal contrasts in cortical and cognitive AEP measures failed to reveal larger group differences than responses to simple stimuli and easy signal contrasts. Despite this, only P3 responses to signals presented in background babble were predictive of subjective auditory complaints. In contrast, cortical N1 and P2 responses were predictive of behavioral SIN performance but not subjective auditory complaints, and use of challenging background babble generally did not improve performance predictions. These results suggest that challenging stimulus protocols are more likely to tap into perceived auditory deficits, but may not be beneficial for predicting performance on clinical measures of SIN understanding. Finally, these results should be interpreted with caution since blast-exposed participants did not perform significantly poorer on tests of SIN perception.

Tinnitus and event related potentials: a systematic review

Introduction

Tinnitus is sound perception in the absence of a sound source. Changes in parameters of latency and amplitude on the auditory event related potentials or long latency potentials waves have been cited in tinnitus patients when compared to a control group.

Objective

To perform an assessment of scientific evidence that verifies the possibility of alterations in latency or amplitude of the waves of event related potentials in individuals with tinnitus.

Methods

By using SciELO, Lilacs, ISI Web and PubMed, scientific databases, a review was performed. Articles published in English, Portuguese, French and Spanish that correlated tinnitus with changes in event related potentials were included in this review.

Results

Twelve articles were located, however only eight fulfilled the criteria for inclusion.

Conclusion

The sample of selected studies demonstrate that the long latency auditory evoked potentials related to events between the control and tinnitus patients showed some changes in latency and or amplitude in tinnitus patients. There are changes in event-related potentials when comparing patients with tinnitus and the control group. These changes take place considering the severity of tinnitus, tinnitus site of lesion, and capacity for changes after interventions. The event related potentials can help to determine the neurotransmitter involved in tinnitus generation and evaluate tinnitus treatments.

The Age-Related Central Auditory Processing Disorder: Silent Impairment of the Cognitive Ear

Age-related hearing loss (ARHL), also called presbycusis, is a progressive disorder affecting hearing functions and among the elderly has been recognized as the third most frequent condition. Among ARHL components, the age-related central auditory processing disorder (CAPD) refers to changes in the auditory network, negatively impacting auditory perception and/or the speech communication performance. The relationship between auditory-perception and speech communication difficulties in age-related CAPD is difficult to establish, mainly because many older subjects have concomitant peripheral ARHL and age-related cognitive changes. In the last two decades, the association between cognitive impairment and ARHL has received great attention. Peripheral ARHL has recently been defined as the modifiable risk factor with the greatest impact on the development of dementia. Even if very few studies have analyzed the relationship between cognitive decline and age-related CAPD, a strong association was highlighted. Therefore, age-related CAPD could be a specific process related to neurodegeneration. Since these two disorders can be concomitant, drawing causal inferences is difficult. The assumption that ARHL, particularly age-related CAPD, may increase the risk of cognitive impairment in the elderly remains unchallenged. This review aims to summarize the evidence of associations between age-related CAPD and cognitive disorders and to define the diagnostic procedure of CAPD in the elderly. Finally, we highlight the importance of tailoring the rehabilitation strategy to this relationship. Future longitudinal studies with larger sample sizes and the use of adequate assessment tools that can disentangle cognitive dysfunction from sensory impairments are warranted.

Overview of Central Auditory Processing Deficits in Older Adults

Although there are many reported age-related declines in the human body, the notion that a central auditory processing deficit exists in older adults has not always been clear. Hearing loss and both structural and functional central nervous system changes with advancing age are contributors to how we listen, hear, and process auditory information. Even older adults with normal or near normal hearing sensitivity may exhibit age-related central auditory processing deficits as measured behaviorally and/or electrophysiologically. The purpose of this article is to provide an overview of assessment and rehabilitative approaches for central auditory processing deficits in older adults. It is hoped that the outcome of the information presented here will help clinicians with older adult patients who do not exhibit the typical auditory processing behaviors exhibited by others at the same age and with comparable hearing sensitivity all in the absence of other health-related conditions.

Age-associated reduction of asymmetry in human central auditory function: a 1H-magnetic resonance spectroscopy study

The aim of this study was to investigate the effects of age on hemispheric asymmetry in the auditory cortex after pure tone stimulation. Ten young and 8 older healthy volunteers took part in this study. Two-dimensional multivoxel 1H-magnetic resonance spectroscopy scans were performed before and after stimulation. The ratios of N-acetylaspartate (NAA), glutamate/glutamine (Glx), and γ-amino butyric acid (GABA) to creatine (Cr) were determined and compared between the two groups. The distribution of metabolites between the left and right auditory cortex was also determined. Before stimulation, left and right side NAA/Cr and right side GABA/Cr were significantly lower, whereas right side Glx/Cr was significantly higher in the older group compared with the young group. After stimulation, left and right side NAA/Cr and GABA/Cr were significantly lower, whereas left side Glx/Cr was significantly higher in the older group compared with the young group. There was obvious asymmetry in right side Glx/Cr and left side GABA/Cr after stimulation in young group, but not in older group. In summary, there is marked hemispheric asymmetry in auditory cortical metabolites following pure tone stimulation in young, but not older adults. This reduced asymmetry in older adults may at least in part underlie the speech perception difficulties/presbycusis experienced by aging adults.

Auditory-cognitive interactions underlying interaural asymmetry in an adult listener: a case study

OBJECTIVE

Abnormal interaural asymmetry on tests of dichotic listening is commonly observed in individuals suspected of auditory processing disorder (APD). Although a structural basis for the abnormality has been widely accepted, the influence of cognitive variables on the degree of observed asymmetry has gained increasing attention. To study this issue, we manipulated cognitive influences on interaural asymmetry in an adult with the auditory complaints typically associated with APD.

STUDY SAMPLE

A 55 year-old woman with complaints of difficulty understanding speech in noisy environments despite normal audiometric levels.

DESIGN

Several experimental dichotic procedures were administered. Each procedure was characterized by the manipulation of cognitive task demands.

RESULTS

Interaural asymmetry was greatest when the demands on attention and/or memory were maximal. Electrophysiological data revealed interaural asymmetry on later stages of information processing.

CONCLUSIONS

Results are discussed in relation to auditory-specific outcomes on clinical tests for APD.

Hemispheric differences in auditory oddball responses during monaural versus binaural stimulation

Hemispheric lateralization of early event-related potentials (ERPs; e.g. N1) is largely based on anatomy of the afferent pathway; lateralization of later auditory ERPs (P2/N2, P250, P3b) is less clear. Using 257-channel EEG, the present study examined hemispheric laterality of auditory ERPs by comparing binaural and monaural versions of an auditory oddball task. N1 showed a contralateral bias over auditory cortex in both hemispheres as a function of ear of stimulation, although right hemisphere sources were activated regardless of which ear received input. Beginning around N1 and continuing through the time of P3b, right hemisphere temporal-parietal and frontal areas were more activated than their left hemisphere counterparts for stimulus evaluation/comparison and target detection. P250 and P3b component amplitudes, topographies, and source estimations were significantly influenced by ear of stimulation, with right hemisphere activity being stronger. This was particularly true for anterior temporal and inferior frontal sources which were more strongly associated with the later, more cognitive components (P250, P3b). Results are consistent with theories of a right hemisphere network that is prominently involved in sustained attention, stimulus evaluation, target detection, and working memory/context updating.

P300 em sujeitos com perda auditiva

TEMA: as avaliações comportamentais e eletrofisiológicas contribuem para o entendimento do sistema auditivo e do processo de intervenção. OBJETIVO: estudar P300 em sujeitos com perda auditiva neurossensorial congênita, segundo as variáveis gênero, idade e grau da perda auditiva. MÉTODO: a presente investigação consiste em um estudo descritivo, transversal. Foram examinados 29 sujeitos, sendo 15 do gênero masculino e 14 do gênero feminino, com idade entre 11 a 42 anos. Os critérios de elegibilidade para composição da amostra foram: idade superior a 11 anos e inferior a 45 anos; ser portador de deficiência auditiva congênita severa ou profunda; não apresentar outro tipo de distúrbio; não apresentar perda auditiva central e/ou comprometimento condutivo. A primeira etapa caracterizou-se por avaliação comportamental auditiva e fisiológica que incluiu: audiometria tonal limiar (via aérea e via óssea), logoaudiometria - LDV e medidas do ganho funcional para os sujeitos que faziam uso de próteses auditivas, Imitanciometria: curva timpanométrica e pesquisa dos reflexos ipsi e contra-laterais, registro das emissões otoacústicas (EOA) - emissões otoacústicas transitórias (EOAT) e emissões otoacústicas por produto de distorção (EOAPD). A avaliação eletrofisiológica constituiu a quarta etapa do procedimento de coleta de dados e incluiu: potenciais auditivos evocados de tronco encefálico (PEATE) e de longa latência (P300). RESULTADOS: o P300 foi registrado em 17 sujeitos, com latência e amplitude média de 326,97ms e 3,76V, respectivamente. Apresentou diferenças significantes da latência em relação à idade (p < 0,03 para derivação CzA2 e p < 0,02 para derivação CzA1) e da amplitude, segundo o grau da perda auditiva (p < 0,0015). CONCLUSÃO: o P300 pode ser registrado em sujeitos com perda auditiva.

Potenciais evocados auditivos em indivíduos acima de 50 anos de idade

TEMA: potenciais evocados auditivos. OBJETIVO: descrever os resultados dos potenciais evocados auditivos de tronco encefálico (PEATE), potenciais evocados auditivos de média latência (PEAML) e potencial cognitivo (P300) em indivíduos acima de 50 anos de idade. MÉTODO: este estudo foi desenvolvido no Laboratório de Investigação Fonoaudiológica em Potenciais Evocados Auditivos do Curso de Fonoaudiologia, do Departamento de Fisioterapia, Fonoaudiologia e Terapia Ocupacional da FMUSP. Foram avaliados 24 pacientes (45 orelhas) por meio do PEATE e do P300, sendo que apenas 18 destes pacientes (36 orelhas) foram avaliados por meio do PEAML. Todos os indivíduos encontravam-se na faixa etária de 51 a 74 anos de idade, divididos em três grupos:GI (50 - 59 anos), GII (60 - 69 anos) e GIII (70 a 79 anos) e apresentavam audição normal ou até perda auditiva neurossensorial de grau moderadamente severo no PEATE e de grau moderado no PEAML e no P300. A faixa de frequências avaliadas no PEATE e no PEAML abrangeu 3000 a 6000 Hz, enquanto que no P300 a faixa foi de 1000 a 1500Hz. Para a análise estatística dos dados foram utilizados os testes estatísticos de Kruskal-Wallis, Mann-Whitney e igualdade de duas proporções. RESULTADOS: observaram-se diferenças estatisticamente significantes entre os grupos simultaneamente para o interpico I -V no PEATE e para a latência da onda Na no PEAML, sendo que no PEATE foi o GIII que provocou a diferença e no PEAML foi o GI. Evidenciou-se diferença estatisticamente significante entre os grupos simultaneamente para a latência do componente P300. Verificou-se, também, alterações consideráveis em relação à qualidade dos traçados dos potenciais evocados auditivos, indicando uma forte correlação entre piora na qualidade do traçado e aumento da idade. CONCLUSÃO: o processo de envelhecimento do sistema auditivo afeta progressivamente as vias auditivas ao longo do tronco encefálico e lobo temporal.

The effect of aging on event-related potentials and behavioral responses: Comparison of tonal, phonologic and semantic targets

OBJECTIVE

To investigate age-related changes in speech perception by measuring event-related potentials (ERPs) elicited by auditory stimuli varying in their linguistic characteristics from pure tones to words.

METHODS

ERPs were recorded from 64 subjects in three age groups (young, middle age and elderly) to auditory target stimuli, using an oddball paradigm. Three different tasks and stimuli were used: tonal, phonological and semantic.

RESULTS

N100 latency to tonal targets was significantly shorter than to both types of speech targets. P300 latency to tonal targets was significantly shorter than to phonological targets, which in turn was shorter than to semantic targets. P300 amplitude recorded to the speech targets was significantly larger over the left hemisphere than over the right hemisphere in the young subjects. However, the reverse pattern of asymmetry, favoring the right hemisphere was found in the elderly subjects. The pattern of the hemispheric distribution for the middle aged was somewhere in between the young and elderly.

CONCLUSIONS

The data indicate possible progressive changes in left-right asymmetry in language processing with aging.

SIGNIFICANCE

Findings may indicate an increased use of compensatory mechanisms for speech processing, or alternatively, an increased use of different generators as individuals age.

Complementing behavioral measures with electrophysiological measures in diagnostic evaluation: a case study in two languages

This case study focuses on a bilingual, older man who spoke Polish and English and showed weaknesses on clinical measures of dichotic listening in English. It was unclear whether these test results were influenced by the participant's facility with his second language or by other nonauditory factors. To elucidate the nature of this deficit, the authors examined behavioral and electrophysiological responses during dichotic-listening tasks involving linguistic processing in both languages. A diotic (control) condition was included to examine whether nonauditory factors, such as language familiarity, memory, or decline in speed of mental processing, might explain the dichotic results. The results from this participant were compared with those obtained from a bilingual young adult who also spoke both Polish and English. Results showed a substantial left-ear deficit for the older individual on both behavioral and electrophysiological measures of dichotic listening. The pattern of results is consistent with previous findings in demonstrating that the left-ear deficit in this patient derived from an auditory-specific defect rather than from any of the extra-auditory factors associated with language facility or cognitive decline.