Normal Hearing Sensitivity Research Articles

Evaluation of auditory brain-stem evoked response in middle: Aged type 2 diabetes mellitus with normal hearing subjects

Background: Diabetes mellitus (DM) is commonly metabolic disorders of carbohydrate in which blood glucose levels are abnormally high due to relative or absolute insulin deficiency. In addition, it is characterized by abnormal metabolism of fat, protein resulting from insulin deficit or insulin action, or both. There are two broad categories of DM are designated as type 1 and type 2. Type 2 diabetes is due to predominantly insulin resistance with relative insulin deficiency noninsulin-dependent DM. Type 2 diabetes is much more common than insulin-dependent DM. Objectives: The aim of this study was to assess, if there is any abnormality in neural conduction in auditory brain-stem pathway in type 2 DM patients having normal hearing sensitivity when compared to age-matched healthy populations. Materials and Methods: This study included middle - aged 25 subjects having normal hearing with diabetes type 2 mellitus. All were submitted to the full audiological history taking, otological examination, basic audiological evaluation and auditory brain-stem response audiometry which was recorded in both ears, followed by calculation of the absolute latencies of wave I, III and V, as well as interpeak latencies I-III, III-V, I-V. Results: Type 2 DM patients showed significant prolonged absolute latencies of I, III ( P = 0.001) and interpeak latencies I-III, III-V and I-V in left ear ( P = 0.001) and absolute latencies of I, V ( P = 0.001), interpeak latencies III-V was statistically significant in right ear. Conclusions: The prolonged absolute latencies and interpeak latencies suggests abnormal neural firing synchronization or in the transmission in the auditory pathways in normal hearing type 2 diabetes mellitus patients.

The effect of tinnitus on some psychoacoustical abilities in individuals with normal hearing sensitivity.

Tinnitus is the perception of a sound without an external source. It can affect auditory perception abilities in individuals with normal hearing sensitivity. The aim of the study was to determine the effect of tinnitus on psychoacoustic abilities in individuals with normal hearing sensitivity. The study was conducted on twenty subjects with tinnitus and twenty subjects without tinnitus. Tinnitus group was again divided into mild and moderate tinnitus based on the tinnitus handicap inventory. Differential limen of intensity, differential limen of frequency, gap detection test, modulation detection thresholds were done through the mlp toolbox in Matlab and speech in noise test was done with the help of Quick SIN in Kannada. RESULTS of the study showed that the clinical group performed poorly in all the tests except for differential limen of intensity. Tinnitus affects aspects of auditory perception like temporal resolution, speech perception in noise and frequency discrimination in individuals with normal hearing. This could be due to subtle changes in the central auditory system which is not reflected in the pure tone audiogram.

Chronic noise exposure: impact on the vestibular function

BackgroundNoise exposure causes permanent or temporary hearing loss. High levels of noise may stimulate the vestibular system and thereby cause disturbances in the balancing mechanism.ObjectivesThis work was designed to investigate the effect of chronic noise exposure on the vestibular system.Participants and methodsTwo groups were included in this study: control group: 20 healthy individuals with normal hearing and vestibular function and study group: 40 patients with a history of prolonged noise exposure at work. This group was further divided into two subgroups: 20 patients with noise-induced hearing loss and 20 individuals with normal hearing sensitivity. All participants in this study were subjected to combined vestibular evoked myogenic potentials (VEMPs) and videonystagmography (VNG).ResultscVEMPs were absent in 5 and 20% of participants of subgroup IIa and IIb, respectively, with significantly delayed P13 and N23 latencies in the rest of participants in subgroup IIb. In terms of P13 and N23 amplitudes, there was no statistically significant difference between the control and the study subgroups. oVEMPs were absent in 40% of participants of subgroup IIb, with normal latencies and amplitudes in the rest of the participants. For VNG, only saccades latency was significantly delayed in subgroup IIb compared with subgroup IIa. A correlation was found between the participants' complaints and the results of the vestibular function tests.ConclusionChronic noise exposure is hazardous to the inner ear structures and enhances vestibular damage, especially the sacculocollic reflex pathway. Vestibular insult is higher among patients with noise-induced hearing loss than in those with normal hearing.

Distortion product otoacoustic emission fine-structure: An insight into the ear asymmetries

Context: Use of distortion product otoacoustic emission (DPOAE) as a measure of hearing sensitivity is common in clinical practice. However, use of a more informative DPOAE fine-structure has been limited due to non-reliability of DPOAE fine-structure. Aim: The current study was aimed at testing the interaural differences between the DPOAE fine-structure across three age groups. Settings and Design: Acoustically treated room with a calibrated dual channel audiometer (Orbiter 922) along with TDH-39 headphones and B-71 bone vibrator. GSI Tympstar was used for tympanometry and acoustic reflex measurements while 'ILO V6' OAE analyzer was used for recording of DPOAE and DPOAE fine-structure. Material and Methods : A total of 98 subjects with normal peripheral hearing sensitivity were tested for DPOAE fine-structure. The three age groups consisted of young (8-18 years; n = 50), middle aged (30-40 years; n = 30), and elderly (50-60 years; n = 18). DPOAE fine-structure was studied at 8 points per octave on a total of 25 frequencies from 1000 to 8000 Hz. Statistical Analysis Used: Repeated measure analysis of variance. Results: There was a significant difference (P < 0.05) in the amplitudes at frequencies between 2000 and 3000 Hz. This was evident irrespective of the age groups. There was also a decrease in DPOAE amplitude in elderly group. Conclusions: Interaural asymmetry can be attributed as a reason to these findings and it occurred mostly in the speech perception frequencies. Reduced amplitude of DPAOE in the elderly group can be attributed to presbycusis.

Is Central Auditory Processing Disorder Present in Psychosis?

The scope of this study was to trace central auditory processing issues in patients with first-episode psychosis using a psychoacoustic test battery approach. Patients (n = 17) and volunteer control subjects (n = 17) with no personal or family history of schizophrenia were included in the study on the basis of normal hearing sensitivity. The authors implemented a central auditory processing battery consisting of monaural and binaural tests with verbal and nonverbal stimuli. Perceptual deficits in both nonverbal and verbal auditory stimuli are reported in this study, with temporal central auditory processing deficits and a mean left-ear advantage documented in the patient group. This study points to the possibility of the existence of central auditory processing deficits in first-episode psychosis leading to schizophrenia. Audiologists should be aware of the psychiatric research pointing to enhanced verbal memory as a result of auditory training, linking bottom-up remediation with top-down improvement.

Age-Dependent Changes in Temporal-Fine-Structure Processing in the Absence of Peripheral Hearing Loss

In this study, the author sought to investigate if and when the ability to process temporal-fine-structure (TFS) cues deteriorates with age in adults with audiometrically normal hearing sensitivity. Using a cross-sectional design, the author assessed TFS sensitivity in 102 normal-hearing adults sampled from across the entire range of adulthood (ages 18-90 years), using 2 psychophysical tests for the assessment of within- and across-ear TFS processing. Both types of TFS sensitivity (monaural and binaural) declined gradually starting in young adulthood, with the earliest significant deficit already apparent in early midlife (i.e., between ages 40 and 49 years). TFS sensitivity was not correlated with absolute sensitivity at the test frequency. Some suprathreshold auditory processing abilities decline throughout adulthood, even when an individual's peripheral hearing is clinically normal. These deficits are not captured by a conventional, audiometric hearing assessment but may contribute to the increasing difficulties with age to identify speech in noisy environments. From a methodological point of view, the existence of such age effects warrants the use of age-matched participant groups when comparing normal and impaired peripheral hearing.

Auditory cortical processing in noise in younger and older adults

Objective: A common clinical complaint among older adults is difficulty hearing in noise, even in those with normal or near-normal peripheral hearing sensitivity. Researchers have demonstrated behavioral hearing in noise deficits in older adults, but to date limited evidence, particularly objective, exists elucidating the effects of age on auditory cortical processing in noise. The purpose of this investigation was to explore age related differences in auditory cortical processing at multiple signal-to-noise ratios (SNRs). Study design: Twenty normal-hearing young adults and 15 normal-hearing older adults participated in the study. Late auditory evoked potential (N1 and P2) latencies and amplitudes were measured in quiet and at three signal-to-noise ratios (SNRs) (+ 20, + 10, and 0 SNR). Repeated measures analyses of variance (ANOVA) were utilized to determine if statistically significant differences existed. Results: Significant group by listening condition interactions existed for N1 and P2 amplitudes. P2 latencies were significantly longer for the older adult group compared to the younger adult group. In addition, N1 and P2 amplitudes were significantly smaller for the younger adult group compared to the older adult group. Conclusion: Results suggest a possibly greater reduction in the synchronous neuronal response from quiet to noisy conditions in older adults than in younger adults.

Comparison of 2f1-f2 DPOAE and 2f2-f1 DPOAE fine structure in young and middle-aged adults

Objective: The 2f2-f1 DPOAE is not as popular as the 2f1-f2 DPOAE in the clinical realm as it is not as robust. However, it does have an advantage of being a predominantly reflection emission. The reflection component has been found to be sensitive to cochlear damage. Our objective was to compare the two types of DPOAE to track subtle changes due to aging. Design: We used the most suitable stimulus parameters to record the fine structures of 2f2-f1 DPOAE and 2f1-f2 DPOAE for comparison in two groups of individuals. Study sample: Young adults and middle-aged adults with normal hearing sensitivity participated in the experiment. Both ears of all participants were tested. Results: Although reductions were noted in the both types of DPOAE in the middle-aged participants compared with the young adults, the decrease in amplitude of the 2f2-f1 DPOAE was found to be statistically significant. This corresponded with statistically significant reductions in the reflection component of the 2f1-f2 DPOAE. Reductions in the 2f2-f1 DPOAE were found with both, high-level and low-level primaries. Conclusions: These results highlight the advantages of analysing fine structure data of the 2f2-f1 DPOAE to track subtle cochlear changes in response to aging.

Time Course and Cost of Misdirecting Auditory Spatial Attention in Younger and Older Adults

The effects of directing, switching, and misdirecting auditory spatial attention in a complex listening situation were investigated in 8 younger and 8 older listeners with normal-hearing sensitivity below 4 kHz. In two companion experiments, a target sentence was presented from one spatial location and two competing sentences were presented simultaneously, one from each of two different locations. Pretrial, listeners were informed of the call-sign cue that identified which of the three sentences was the target and of the probability of the target sentence being presented from each of the three possible locations. Four different probability conditions varied in the likelihood of the target being presented at the left, center, and right locations. In Experiment 1, four timing conditions were tested: the original (unedited) sentences (which contained about 300 msec of filler speech between the call-sign cue and the onset of the target words), or modified (edited) sentences with silent pauses of 0, 150, or 300 msec replacing the filler speech. In Experiment 2, when the cued sentence was presented from an unlikely (side) listening location, for half of the trials the listener's task was to report target words from the cued sentence (cue condition); for the remaining trials, the listener's task was to report target words from the sentence presented from the opposite, unlikely (side) listening location (anticue condition). In Experiment 1, for targets presented from the likely (center) location, word identification was better for the unedited than for modified sentences. For targets presented from unlikely (side) locations, word identification was better when there was more time between the call-sign cue and target words. All listeners benefited similarly from the availability of more compared with less time and the presentation of continuous compared with interrupted speech. In Experiment 2, the key finding was that age-related performance deficits were observed in conditions requiring anticue but not cue responses. The findings from Experiment 1 suggest that for both age groups, stream continuity mediates the process of allocating and maintaining auditory spatial attention when the target originates at an expected location, but that time is needed for the reallocation of auditory spatial attention when the target originates at an unexpected location. The findings from Experiment 2 suggest that when attention is momentarily misdirected, difficulties disengaging attention may help explain why older adults with good hearing report difficulty communicating in multi-talker listening situations.

Gender, Music, and Distortion Product Otoacoustic Emission Components

The prevalence of personal music (PM) system use with earphones is high among young adults. Although previous research has demonstrated that the majority of these adults may not be listening at levels or for durations considered dangerous, the long-term consequences of PM system use are not fully understood. In this report the relationship between self-reported PM use (i.e., non, light, moderate, or heavy) and peripheral auditory function as assayed through distortion product otoacoustic emission (DPOAE) components and fine structure was explored. The purpose was to evaluate the relationship between PM system use and peripheral auditory function. One hundred and one (N = 101) young adults, 18 to 30 years of age, with normal hearing. Survey data were first obtained to determine PM system user status along with type of earphones used, most common listening volume, and most common listening duration. Once normal-hearing sensitivity was confirmed with a hearing screening, the DPOAE research protocol was administered. DPOAEs (2f1 to f2) were measured between 1 and 6 kHz with stimulus levels fixed at L1, L2 = 55,40 dB SPL and f2/f1 = 1.22. DPOAE level as well as fine-structure depth and spacing in 1/3rd octave (oct) bands around 1, 1.5, 2, 3, 4, and 6 kHz were compared across various PM system user groups. The ear-canal DPOAE was separated into the so-called generator and characteristic frequency (CF) components. The characteristics of the components were also compared across user groups. Almost all participants reported listening to a PM system between < 1 hr/d to 3 hr/d, and 67% of the participants reported medium/comfortable as the most common volume used during a typical day. There was no significant effect of user status on 3rd oct DPOAE data, 1/3rd oct band component data, or fine-structure spacing data. Women exhibited significantly higher DPOAE as well as generator and CF component levels in the lower half of the frequency range evaluated. There were no significant gender differences for fine-structure spacing or depth. The slope of the CF component was significantly steeper in women. In this cross-sectional study, there were no significant effects of self-reported PM use on either the ear-canal DPOAE or its constituent parts. Fine-structure depth varied across user groups in a nonsystematic manner. Women exhibited higher DPOAE and component levels in the lower portion of the frequency range evaluated. It is interesting to note that a greater proportion of men reported listening to their PM system at loud or very loud levels. The size of the effect relative to the sample size of each user group may be masking the deleterious effects of PM system use on the peripheral auditory system.

Audiologic and Vestibular Findings in Wolfram Syndrome

Assessment of auditory and vestibular function in Wolfram Syndrome (WS) patients, using a standardized protocol. Prospective cohort study of 11 patients using otoscopic inspection, tympanometry, otoacoustic emissions, pure tones, speech in noise (SIN), the Speech Intelligibility Index, and rotational chair testing. Mean SNHL diagnosis was 7.3 years with 55% prevalence. Four patients with a Speech Intelligibility Index less than 0.75 (better ear) routinely used bilateral amplification devices. Two patients with normal-hearing sensitivity exhibited abnormal SIN scores. The only patient with significant vestibular dysfunction also had a distinctive low-frequency component to her SNHL. Hearing loss may occur earlier than previously suspected, and comprehensive testing including SIN testing may reveal deficits not apparent with pure-tone testing. Particular configurations of hearing loss may indicate a need for comprehensive vestibular assessment. Because SNHL can be the first symptom of WS, audiologists and otolaryngologists should be vigilant about referring patients with hearing loss for ophthalmologic examination.

Transient evoked otoacoustic emissions and vestibular evoked myogenic potentials in cigarette and water pipe smokers

This study compared the amplitude of transient evoked otoacoustic emissions (TEOAEs) and latencies of vestibular evoked myogenic potentials (VEMPs) among non-smokers, cigarette smokers, water pipe smokers, mixed smokers and ex-smokers. A total of 50 non-smokers, 28 water pipe smokers, 34 pure cigarette smokers, 28 mixed cigarette-water pipe smokers, and 21 ex-smokers were evaluated in this study. Their age ranged from 20 to 40 years. All had normal hearing sensitivity and normal middle ear functions. TEOAEs amplitude and VEMPs were measured for all participants. Results of this study showed that smoking had deleterious effects on the hair cells in the labyrinth. Damage to the outer hair cells was evidenced by the reduced amplitude of the TEOAEs in smokers and ex-smokers when compared with control group. Harm to the saccular hair cells is detected by the increased latency of the VEMPs. Results also suggested that cessation of smoking could not change the profile of TEOAEs or VEMPs. Our results suggested that smoking could have irreversible hazardous effects on the labyrinthine hair cell functions. These effects could be attributed to the impact of nicotine on the microvascular dynamics.

Visual and Cognitive Predictors of Visual Enhancement in Noisy Listening Conditions

Researchers have demonstrated that visual and auditory cues interact, improving speech intelligibility under noisy listening conditions. For instance, recent findings demonstrated that simulated cataracts hinder the ability of listeners to utilize visual cues to understand (i.e., speechread) televised speech sentences. The purpose of this study was to determine which measures of visual, auditory, and cognitive performance predicted participants’ ability to speechread televised spoken messages in the presence of background babble. Specifically, 30 young adults with normal visual acuity and hearing sensitivity completed a battery of visual, auditory, and cognitive assessments. Speech intelligibility was tested under two conditions: auditory-only with no visual input and auditory-visual with normal viewing. Speech intelligibility scores were used to calculate average visual enhancement, or the average benefit participants gained from viewing visual information in addition to auditory information. Regression analyses demonstrated that the best predictors of visual enhancement were measures of contrast sensitivity and executive functioning, including the Digit Symbol Substitution Test and Trail Making Test, part B. These results suggest that audiovisual speech integration is dependent on both low-level sensory information and high-level cognitive processes, particularly those associated with executive functioning.

Modern prescription theory and application: realistic expectations for speech recognition with hearing AIDS.

A major decision at the time of hearing aid fitting and dispensing is the amount of amplification to provide listeners (both adult and pediatric populations) for the appropriate compensation of sensorineural hearing impairment across a range of frequencies (e.g., 160-10000 Hz) and input levels (e.g., 50-75 dB sound pressure level). This article describes modern prescription theory for hearing aids within the context of a risk versus return trade-off and efficient frontier analyses. The expected return of amplification recommendations (i.e., generic prescriptions such as National Acoustic Laboratories-Non-Linear 2, NAL-NL2, and Desired Sensation Level Multiple Input/Output, DSL m[i/o]) for the Speech Intelligibility Index (SII) and high-frequency audibility were traded against a potential risk (i.e., loudness). The modeled performance of each prescription was compared one with another and with the efficient frontier of normal hearing sensitivity (i.e., a reference point for the most return with the least risk). For the pediatric population, NAL-NL2 was more efficient for SII, while DSL m[i/o] was more efficient for high-frequency audibility. For the adult population, NAL-NL2 was more efficient for SII, while the two prescriptions were similar with regard to high-frequency audibility. In terms of absolute return (i.e., not considering the risk of loudness), however, DSL m[i/o] prescribed more outright high-frequency audibility than NAL-NL2 for either aged population, particularly, as hearing loss increased. Given the principles and demonstrated accuracy of desensitization (reduced utility of audibility with increasing hearing loss) observed at the group level, additional high-frequency audibility beyond that of NAL-NL2 is not expected to make further contributions to speech intelligibility (recognition) for the average listener.

Audiological follow-up of 24 patients affected by Williams syndrome

Williams syndrome is a neurodevelopmental disorder associated with cardiovascular problems, facial abnormalities and several behavioural and neurological disabilities. It is also characterized by some typical audiological features including abnormal sensitivity to sounds, cochlear impairment related to the outer hair cells of the basal turn of the cochlea, and sensorineural or mixed hearing loss, predominantly in the high frequency range. The aim of this report is to describe a follow-up study of auditory function in a cohort of children affected by this syndrome. 24 patients, aged 5–14 years, were tested by means of air/bone conduction pure-tone audiometry, immittance test and transient evoked otoacoustic emissions. They were evaluated again 5 years after the first assessment, and 10 of them underwent a second follow-up examination after a further 5 years. The audiometric results showed hearing loss, defined by a pure tone average >15 dB HL, in 12.5% of the participants. The incidence of hearing loss did not change over the 5-year period and increased to 30% in the patients who underwent the 10-year follow-up. Progressive sensorineural hearing loss was detected in 20% of the patients. A remarkable finding of our study regarded sensorineural hearing impairment in the high frequency range, which increased significantly from 25% to 50% of the participants over the 5-year period. The increase became even more significant in the group of patients who underwent the 10-year follow-up, by which time the majority of them (80%) had developed sensorineural hearing loss. Otoacoustic emissions were found to be absent in a high percentage of patients, thus confirming the cochlear fragility of individuals with Williams syndrome. Our study verified that most of the young Williams syndrome patients had normal hearing sensitivity within the low-middle frequency range, but showed a weakness regarding the high frequencies, the threshold of which worsened significantly over time in most patients.

Aging Degrades the Neural Encoding of Simple and Complex Sounds in the Human Brainstem

Older adults, with or without normal peripheral hearing sensitivity, have difficulty understanding speech. This impaired speech perception may, in part, be due to desynchronization affecting the neural representation of acoustic features. Here we determine if phase-locked neural activity generating the brainstem frequency-following response (FFR) exhibits age-related desynchronization and how this degradation affects the neural representation of simple and complex sounds. The objectives of this study were to (1) characterize the effects of age on the neural representation of simple tones and complex consonant-vowel stimuli, (2) determine if sustained and transient components of the FFR are differentially affected by age, and (3) determine if the inability to encode a simple signal predicts degradation in representation for complex speech signals. Correlational. Thirty four adults (aged 22-77 yr) with hearing thresholds falling within normal limits. Stimuli used to evoke FFRs were 1000 Hz tone bursts as well as a consonant-vowel /da/ sound. The neural representation of simple (tone) and complex (/da/) stimuli declines with advancing age. Tone-FFR phase coherence decreased as chronological age increased. For the consonant-vowel FFRs, transient onset and offset response amplitudes were smaller, and offset responses were delayed with age. Sustained responses at the onset of vowel periodicity were prolonged in latency and smaller in amplitude as age increased. FFT amplitude of the consonant-vowel FFR fundamental frequency did not significantly decline with increasing age. The ability to encode a simple signal was related to degradation in the neural representation of a complex, speechlike sound. Tone-FFR phase coherence was significantly related to the later vowel response components but not the earlier vowel components. FFR components representing the tone and consonant-vowel /da/ stimulus were negatively affected by age, showing age-related reductions in response synchrony and amplitude, as well as prolonged latencies. These aging effects were evident in middle age, even in the absence of significant hearing loss.

Auditory profile and high resolution CT scan in autism spectrum disorders children with auditory hypersensitivity

Autism is the third most common developmental disorder, following mental retardationand cerebral palsy. ASD children have been described more often as beingpreoccupied with or agitated by noise. The aim of this study was to evaluate theprevalence and clinical significance of semicircular canal dehiscence detected on CTimages in ASD children with intolerance to loud sounds in an attempt to find ananatomical correlate with hyperacusis.14 ASD children with auditory hypersensitivity and 15 ASD children without auditoryhypersensitivity as control group age and gender matched were submitted to historytaking, otological examination, tympanometry and acoustic reflex thresholdmeasurement. ABR was done to validate normal peripheral hearing and integrity ofauditory brain stem pathway. High resolution CT scan petrous and temporal boneimaging was performed to all participated children. All participants had normal hearingsensitivity in ABR testing. Absolute ABR peak waves of I and III showed no statisticallysignificant difference between the two groups, while absolute wave V peak andinterpeak latencies I-V and III-V were shorter in duration in study group whencompared to the control group. CT scans revealed SSCD in 4 out of 14 of the studygroup (29%), the dehiscence was bilateral in one patient and unilateral in threepatients. None of control group showed SSCD. In conclusion, we have reportedevidence that apparent hypersensitivity to auditory stimuli (short conduction time in ABR) despite the normal physiological measures in ASD children with auditoryhypersensitivity can provide a clinical clue of a possible SSCD.

Effect of Noise on Auditory Processing in the Operating Room

Effective communication is a critical component of patient care in the operative room (OR). However, the presence of loud equipment, a large number of staff members, and music can contribute to high levels of background noise. In a setting in which crucial tasks are performed continuously, distractions and barriers to communication can result in harm to both patients and OR personnel. The purpose of this investigation was to simulate OR listening conditions and evaluate the effect of operating noise on auditory function. This is a prospective investigation of 15 subjects ranging from 1 to 30 years of operative experience. All surgeons had normal peripheral hearing sensitivity. The surgeons' ability to understand and repeat words were tested using the Speech in Noise Test-Revised in 4 different conditions chosen to simulate typical OR environments. These included quiet, filtered noise through a mask and background noise both with and without music. They were tested in both a tasked and in an untasked situation. It was found that the impact of noise is considerably greater when the participant is tasked. Surgeons demonstrated substantially poorer auditory performance in music than in quiet or OR noise. Performance in both conditions was poorer when the sentences were low in predictability. Operating room noise can cause a decrease in auditory processing function, particularly in the presence of music. This becomes even more difficult when the communication involves conversations that carry critical information that is unpredictable. To avoid possible miscommunication in the OR, attempts should be made to reduce ambient noise levels.

Electrophysiological Evidence of Augmented Interaural Asymmetry in Middle-Aged Listeners

Various dimensions of auditory processing, especially the perception of speech in the presence of background competition, have been shown to deteriorate with age. A persistent problem in the assessment of these age-related changes has been the high prevalence of age-related high-frequency hearing loss in elderly persons. Some investigators have suggested that a more fruitful approach to the study of age-related decline might be to study middle-aged, rather than elderly, persons, where confounding high-frequency hearing loss is less prevalent. To determine whether an increase in the left-ear disadvantage (LED) in dichotic listening could be demonstrated in a group of middle-aged persons. The N400 component of the auditory event-related potential (AERP) was utilized to evaluate interaural asymmetry in a quasi-dichotic competing speech task. Electrophysiological responses were obtained on a word-pair semantic categorization task presented through a front loudspeaker while the listener ignored competing speech presented through either left (competition left [CL]) or right (competition right [CR]) loudspeakers. Study Samples: Twenty young (18-24 yr) and 20 middle-aged (44-57 yr) females with normal hearing sensitivity. Individual, as well as grand-averaged, AERP waveforms and scalp topographies were analyzed for the word pairs. Peak amplitude and latency measures of the N400 component were subjected to a mixed design analysis of variance (ANOVA). No significant interaural asymmetry was found in the AERP waveform for the reference word condition in either age group. In response to the second word of the pair, however, middle-aged females showed significantly greater N400 negativity in the CR condition than in the CL condition. No significant laterality effect was found in the young females. The study of young versus middle-aged participants may be an effective way of avoiding the confound of high-frequency hearing loss in elderly persons when studying age effects on auditory processing.

Switch Attention to Listen

The aim of this research was to evaluate the ability to switch attention and selectively attend to relevant information in children (10–15 years) with persistent listening difficulties in noisy environments. A wide battery of clinical tests indicated that children with complaints of listening difficulties had otherwise normal hearing sensitivity and auditory processing skills. Here we show that these children are markedly slower to switch their attention compared to their age-matched peers. The results suggest poor attention switching, lack of response inhibition and/or poor listening effort consistent with a predominantly top-down (central) information processing deficit. A deficit in the ability to switch attention across talkers would provide the basis for this otherwise hidden listening disability, especially in noisy environments involving multiple talkers such as classrooms.