Neuroaudiological Considerations for the Auditory Brainstem Response and Middle Latency Response Revisited: Back to the Future.

The auditory brainstem response (ABR) and middle latency response (MLR) are two sets of evoked potentials that have made major contributions to the field of diagnostic audiology. Many of these contributions were guided by clinical research audiologists. Though many of these auditory evoked potentials (AEPs) are still being used diagnostically by audiologists, there has been a steep decline in their popularity both clinically and in the research laboratory. This is indeed most unfortunate because these AEPs could and should be advancing our field and benefitting many patients. In this article, some critical research is overviewed that addresses some of the reasons why these AEPs (ABR and MLR) are not being utilized as frequently as they should be for neuroauditory assessments. Reflecting on our past when ABR and MLR were more commonly used can serve as a model for our future. Multiple applications and the diagnostic value of these AEPs are presented in an effort to convince audiologists that these electrophysiologic procedures should be revisited and reapplied in the clinic and research settings. It is argued that the dwindling use of ABR and MLR (and AEPs in general) in the field of audiology is not only remarkably premature but also lacks good scientific grounding. While on the other hand, if applied clinically, the value of these AEPs is both substantial and promising.

The Effects of Musical Training on Speech Detection in the Presence of Informational and Energetic Masking.

Recent research has suggested that musicians have an advantage in some speech-in-noise paradigms, but not all. Whether musicians outperform nonmusicians on a given speech-in-noise task may well depend on the type of noise involved. To date, few groups have specifically studied the role that informational masking plays in the observation of a musician advantage. The current study investigated the effect of musicianship on listeners' ability to overcome informational versus energetic masking of speech. Monosyllabic words were presented in four conditions that created similar energetic masking but either high or low informational masking. Two of these conditions used noise-vocoded target and masking stimuli to determine whether the absence of natural fine structure and spectral variations influenced any musician advantage. Forty young normal-hearing listeners (20 musicians and 20 nonmusicians) completed the study. There was a significant overall effect of participant group collapsing across the four conditions; however, planned comparisons showed musicians' thresholds were only significantly better in the high informational masking natural speech condition, where the musician advantage was approximately 3 dB. These results add to the mounting evidence that informational masking plays a role in the presence and amount of musician benefit.

Gaps-in-noise (GIN©) test results in children with and without reading disabilities and phonological processing deficits.

OBJECTIVE: To determine if the gaps-in-noise (GIN(©)) test could differentiate children with dyslexia and significant phonological awareness deficits from a group of children with normal reading skills. DESIGN: A prospective study of GIN test performance in two groups of children. Participants were administered routine audiological tests, a phonological processing test, and an auditory temporal resolution test (GIN test). Statistical testing was completed to determine if significant differences existed between groups on GIN test results and phonological processing measures, and to examine potential relationships between these test measures. Routine clinical analysis procedures examined the performance of the two groups from a clinical perspective. STUDY SAMPLE: Participants included 61 children between the ages of 8 years, 1 month and 9 years, 11 months, separated into two groups: children with dyslexia and significant phonological deficits (Group I); normal-reading peers with age-appropriate phonological skills (Group II). RESULTS: Children in Group I showed longer gap detection (GD) thresholds and lower gap identification scores than did the children in Group II. Results of statistical and clinical testing revealed significant differences between the groups. CONCLUSION: An auditory temporal processing deficit is a factor to be considered in children presenting with dyslexia and phonological processing disorders.

[Performance of normal young adults in two temporal resolution tests]. / Desempenho de adultos jovens normais em dois testes de resolução temporal.

BACKGROUND: temporal auditory processing is defined as the perception of sound or of sound alteration within a restricted time interval and is considered a fundamental ability for the auditory perception of verbal and non verbal sounds, for the perception of music, rhythm, periodicity and in the discrimination of pitch, duration and of phonemes. AIM: to compare the performance of normal Brazilian adults in two temporal resolution tests: the Gaps-in-Noise Test (GIN) and the Random Gap Detection Test (RGDT), and to analyze potential differences of performance in these two tests. METHOD: twenty-five college students with normal hearing (11 males and 14 females) and no history of educational, neurological and/or language problems, underwent the GIN and RGDT at 40dB SL. RESULTS: statistically significant gender effects for both tests were found, with female participants showing poorer performance on both temporal processing tests. In addition, a comparative analysis of the results obtained in the GIN and RGDT revealed significant differences in the threshold measures derived for these two tests. In general, significantly better gap detection thresholds were observed for both male and female participants on the GIN test when compared to the results obtained for the RGDT. CONCLUSION: male participants presented better performances on both RGDT and GIN, when compared to the females. There were no differences in performance between right and left ears on the GIN test. Participants of the present investigation, males and females, performed better on the GIN when compared to the RGDT. The GIN presented advantages over the RGDT, not only in terms of clinical validity and sensibility, but also in terms of application and scoring.

Desempenho de adultos jovens normais em dois testes de resolução temporal / Performance of normal young adults in two temporal resolution tests

TEMA: o processamento auditivo temporal se refere a percepção de um evento sonoro ou de uma alteração no mesmo, dentro de um intervalo definido de tempo e é considerado uma habilidade fundamental na percepção auditiva de sons verbais e não verbais, na percepção de música, ritmo e pontuação e na discriminação de pitch, de duração e de fonemas. OBJETIVO: realizar um estudo comparativo do desempenho de adultos jovens normais nos testes de resolução temporal, Random Gap Detection Test (RGDT) e Gaps-in-Noise (GIN) e analisar diferenças entre esses dois métodos de avaliação. MÉTODO: 25 universitários, 11 homens e 14 mulheres, com audição normal e sem histórico de alterações educacionais, neurológicas e/ou linguagem, foram submetidos ao RGDT e ao GIN, a 40dB NS. RESULTADO: observou-se diferença estatisticamente significante entre os sexos sendo que as mulheres apresentaram pior desempenho nos dois testes. No estudo comparativo dos resultados do RGDT e GIN, observaram-se diferenças significativas no desempenho da amostra. De maneira geral, os limiares de detecção de gap no teste GIN foram melhores do que os limiares obtidos no RGDT. CONCLUSÃO: o sexo masculino teve melhor desempenho tanto no teste RGDT quanto no GIN, quando comparado ao feminino. Além disso, não houve diferença significante nas repostas do GIN nas orelhas direita e esquerda. Os sujeitos deste estudo tiveram melhor desempenho no teste GIN, quando comparado ao RGDT, tanto no sexo masculino quanto no feminino. Portanto, o teste GIN apresentou vantagens sobre o RGDT não apenas quanto à sua validade e sensibilidade, mas também com relação a sua aplicação e correção dos resultados.

BACKGROUND: temporal auditory processing is defined as the perception of sound or of sound alteration within a restricted time interval and is considered a fundamental ability for the auditory perception of verbal and non verbal sounds, for the perception of music, rhythm, periodicity and in the discrimination of pitch, duration and of phonemes. AIM: to compare the performance of normal Brazilian adults in two temporal resolution tests: the Gaps-in-Noise Test (GIN) and the Random Gap Detection Test (RGDT), and to analyze potential differences of performance in these two tests. METHOD: twenty-five college students with normal hearing (11 males and 14 females) and no history of educational, neurological and/or language problems, underwent the GIN and RGDT at 40dB SL. RESULTS: statistically significant gender effects for both tests were found, with female participants showing poorer performance on both temporal processing tests. In addition, a comparative analysis of the results obtained in the GIN and RGDT revealed significant differences in the threshold measures derived for these two tests. In general, significantly better gap detection thresholds were observed for both male and female participants on the GIN test when compared to the results obtained for the RGDT. CONCLUSION: male participants presented better performances on both RGDT and GIN, when compared to the females. There were no differences in performance between right and left ears on the GIN test. Participants of the present investigation, males and females, performed better on the GIN when compared to the RGDT. The GIN presented advantages over the RGDT, not only in terms of clinical validity and sensibility, but also in terms of application and scoring.

Central deafness: an audiological case study.

Cases of central deafness are rare but they can be most informative about the function and dysfunction of the central auditory nervous system. Previous information on the anatomy, physiology, and terminology related to central deafness is reviewed and a patient with central deafness is profiled. The patient suffered bilateral cerebrovascular accidents (CVAs) compromising Heschl's gyrus and some adjacent neural tissue on both sides of the brain. At 18 months post CVAs, this patient could not understand speech presented solely through the auditory modality. Environmental sounds were perceived, but rarely recognized. Pure-tone testing revealed a severe-to-profound hearing loss bilaterally, but otoacoustic emissions, acoustic reflexes, and the auditory brainstem response were essentially within normal ranges for both ears. Middle late and late auditory potentials were compromised, yielding complex modifications of the waveforms. These findings and the compromised vascular anatomy in this case are detailed in this article.

GIN (Gaps-In-Noise) test performance in subjects with confirmed central auditory nervous system involvement.

OBJECTIVE: The purpose of the present study was to investigate the value of a new gap detection procedure called Gaps-In-Noise (GIN) for assessment of temporal resolution in a clinical population. DESIGN: The test consists of 0 to 3 silent intervals ranging from 2 to 20 msec embedded in 6-sec segments of white noise. The location, number, and duration of the gaps per noise segment vary throughout the test for a total of 60 gaps presented in each of four lists. The GIN procedure was administered to 50 normal-hearing listeners (group I) and 18 subjects with confirmed neurological involvement of the central auditory nervous system (group II). RESULTS: Results showed mean approximated gap detection thresholds of 4.8 msec for the left ear and 4.9 msec for the right ear for group I. In comparison, results for group II demonstrated a statistically significant increase in gap detection thresholds, with approximated thresholds of 7.8 msec and 8.5 msec being noted for the left and right ears, respectively. Significant mean differences were also observed in the overall performance scores (i.e., the identification of the presence of the gaps within the noise segments) of the two groups of subjects. Finally, psychometric functions, although similar for short and long duration gaps, were highly different for gaps in the 4- to 10-msec range for the two groups. CONCLUSIONS: A variety of psychoacoustic procedures are available to assess temporal resolution; however, the clinical use of these procedures is minimal at best. Results of the present study show that the GIN test holds promise as a clinically useful tool in the assessment of temporal resolution in the clinical arena.

Differential attention effects on dichotic listening.

The role of attention in the differentiation of auditory processing disorders from attention deficit disorders is gaining considerable interest in both the clinical and research arenas. It has been well established that when attention is directed to one ear or the other on traditional dichotic tests, performance can be altered. However, preliminary studies in our laboratory have shown that dichotic fusion paradigms are resistant to shifts in ear performance associated with changes in attention. The purpose of this study was to assess the performance of normal listeners on a dichotic consonant-vowel and a dichotic rhyme (fusion) test. Both test procedures were administered to 20 young adults in three different listening conditions (free recall, attention directed to the left ear, and attention directed to the right ear). Results from this study supported the hypothesis that dichotic rhyme tests are resistant to alterations in the laterality of attention and have implications for the development of test paradigms that can be used to segregate attention from pure auditory deficits in the clinical domain.

Central auditory deficits associated with compromise of the primary auditory cortex.

The subject of this study was a 46-year-old female who had suffered a cerebrovascular accident (CVA). Magnetic resonance imaging revealed damage in the area of the distribution of the middle cerebral artery involving most, if not all, of the primary auditory area of the left hemisphere. No auditory problems were noted prior to the CVA; however, following the CVA, the subject reported a number of auditory difficulties. Pure-tone thresholds were normal post-CVA, and performance on speech recognition testing was good in both ears if ample time was provided between a response and the presentation of the next test item. Duration pattern, intensity discrimination, and middle latency response test results were abnormal for both ears, and right ear deficits were evident on an auditory fusion test and two dichotic speech tests (digits and rhymes). This case is significant in that it demonstrates a good correlation between damage to known key auditory regions and central auditory test results.

Assessment and remediation of an auditory processing disorder associated with head trauma.

This case study involves a 41-year-old female who had sustained a mild traumatic brain injury during a horseback riding accident. The patient was seen for medical and neuropsychological testing following this incident and was referred to a speech-language pathologist for rehabilitative services. At 13 months posttrauma, the patient, who was frustrated by a lack of significant progress, requested an audiologic work-up. Results of testing conducted at this time revealed normal peripheral hearing and significant central auditory deficits. Based on these findings, an auditory rehabilitation program was developed and implemented. The components of this patient's rehabilitation program are reviewed, and the posttherapy improvements noted in her auditory functions are detailed. The case is important in that it demonstrates (1) that auditory deficits can be a sequel to minor head injury, (2) that these deficits are often subtle and may not be detected unless central auditory testing is conducted, and (3) that these deficits may be amenable to remediation.

Central deafness associated with a midbrain lesion.

Central deafness has been linked historically to bihemispheric involvement of the temporal lobe, with more recent findings suggesting that compromise of other cortical and subcortical structures can also result in this disorder. The present investigation extends our understanding of the potential anatomical correlates to central deafness by demonstrating that bilateral involvement of an auditory structure within the midbrain can additionally result in this condition. Our subject was a 21-year-old male with a subarachnoid bleed affecting both inferior colliculi. Significant auditory deficits were noted for the middle and late auditory evoked potentials, while electrophysiologic measures of the periphery indicated normal function. The patient was enrolled in a rehabilitation program for approximately 14 weeks. Although initially unresponsive to sounds, the patient regained most of his auditory abilities during the 10 months he was followed. This case documents the range of auditory deficits that may be associated with damage to the inferior colliculi, and it profiles a hierarchical recovery of auditory function consistent with test findings.

Audiological correlates to a rupture of a pontine arteriovenous malformation.

This is a report of a female patient in her midthirties who sustained a hemorrhage secondary to an arteriovenous malformation in the region of the pons. The patient's initial symptoms included hearing loss and tinnitus, which were followed by the more characteristic symptoms of headache and loss of consciousness. Results of audiological testing at three months postaccident documented the presence of a hearing loss and a central auditory processing disorder, and the patient was provided an auditory rehabilitation program. Follow-up testing over the course of an additional year documented improvement in both pure-tone threshold and central test results; however, at 15 months postaccident, some auditory deficits remained, especially in the ear ipsilateral to the primary site of lesion. The anatomical correlates of these deficits are discussed, as are the potential contributions of both the auditory rehabilitation program and spontaneous recovery mechanisms to the documented improvements in auditory function.