Investigating Compressive Nonlinearity Using Forward Masking Auditory Brainstem Response in Humans.

To investigate whether hormone replacement therapy modifies the auditory brainstem response in postmenopausal women. Nineteen postmenopausal women received hormone replacement therapy (study group) and 25 received no treatment nor placebo (control group). In both groups, age ranged from 45 to 60 years and pure-tone sensitivity was 25 dB or better at frequencies between 500 and 2000 Hz. Auditory brainstem response was evaluated before and after 3 months of hormone use in the study group. The control group was also evaluated at the same periods. The following auditory brainstem response parameters were compared between the two groups: latencies of waves I, III, and V; I-III, III-V, and I-V interpeak intervals. Mean age did not differ between groups (study group: 51.5 ± 0.7 years; control: 52.9 ± 0.6 years). No significant differences in wave latencies, or interpeak intervals were observed between the two groups (p > 0.05).

Analysis of auditory brainstem response (ABR) in very preterm infants can be difficult owing to the poor detectability of the various components of the ABR. We evaluated the ABR morphology and tried to extend the current assessment system. Prospective cohort study. We included 28 preterm very low birth weight infants admitted to the neonatal intensive care unit of Sophia Children's Hospital. ABRs were measured between 26 and 34 weeks postconceptional age. The presence of the following ABR parameters was recorded: the ipsilateral peaks I, III and V, the contralateral peaks III and V, and the response threshold. In 82% of our population, a typical "bow tie" response pattern was present as a sign of early auditory development. This bow tie pattern is the narrowest part of the response wave and is predominantly characterized by the ipsilateral negative peak III. This effect may be emphasized by the contralateral peak III. The bow tie pattern is seen approximately 0.1 milliseconds before the ipsilateral peak III. From 30 weeks postconceptional age onward, a more extensive morphologic pattern is recorded in 90% of the infants. A flow chart was designed to analyze the ABR morphology of preterm infants in an unambiguous stepwise fashion. A typical bow tie pattern preceding peak III seems to be the earliest characteristic of the developing ABR morphology in preterm infants. As ABR characteristics will improve with increasing age, neonatal hearing screening should be postponed until after 34 weeks.

The effects of masker intensity and masker frequency on the threshold of a 1‐kHz, 20‐ms probe were assessed in forward masking, with a masker‐probe delay of 5 ms. In general, probe threshold is a power function of masker intensity, with an exponent considerably less than unity; the exponent and constant of proportionality depend upon masker frequency. For example, with a 1‐kHz masker, a 10‐dB increase in masker level increases probe threshold by only about 5 dB, over a 60‐dB range of masker intensities. The nonlinear relation between probe threshold and masker intensity is consistent with the increased “selectivity” sometimes observed in forward‐masked tuning curves as compared with those obtained in simultaneous masking. These data then emphasize the importance of nonlinear intensity effects, in addition to possible changes in true frequency selectivity, in determining the form of psychophysical tuning curves obtained in forward masking and their relation to those obtained in simultaneous masking. [Supported by NICHD, NINCDS.]

Thalamocortical abnormalities in auditory brainstem response patterns distinguish DSM-IV bipolar disorder type I from schizophrenia

The objective of the present study was to investigate the possible electrophysiological time-related changes in auditory pathway during mobile phone electromagnetic field exposure. Thirty healthy rabbits were enrolled in an experimental study of exposure to GSM-900 radiation for 60 min and auditory brainstem responses (ABRs) were recorded at regular time-intervals during exposure. The study subjects were radiated via an adjustable power and frequency radio transmitter for GSM-900 mobile phone emission simulation, designed and manufactured according to the needs of the experiment. The mean absolute latency of waves III–V showed a statistically significant delay (p < 0.05) after 60, 45 and 15 min of exposure to electromagnetic radiation of 900 MHz, respectively. Interwave latency I–III was found to be prolonged after 60 min of radiation exposure in correspondence to wave III absolute latency delay. Interwave latencies I–V and III–V were found with a statistically significant delay (p < 0.05) after 30 min of radiation. No statistically significant delay was found for the same ABR parameters in recordings from the ear contralateral to the radiation source at 60 min radiation exposure compared with baseline ABR. The ABR measurements returned to baseline recordings 24 h after the exposure to electromagnetic radiation of 900 MHz. The prolongation of interval latencies I–V and III–V indicates that exposure to electromagnetic fields emitted by mobile phone can affect the normal electrophysiological activity of the auditory system, and these findings fit the pattern of general responses to a stressor.

Vestibular migraine (VM) is a clinical condition characterized by temporal overlap between vestibular symptoms and migraine. In this study, we aimed to determine the changes in vestibular myogenic potential (cVEMP) and auditory brainstem response (ABR) in patients with VM and migraine. A total of 86 participants with no hearing loss or additional disease between the ages of 18 and 45 were enrolled in three different groups: group 1, VM; group 2, migraine without aura; and group 3, healthy controls. cVEMP and ABR were performed for all participants during attacks and attack-free periods. The differences between the right and left sides were calculated. There was no significant difference in cVEMP p13-n23 latencies between any of the groups. There were statistically significant differences related to cVEMP p13-n23 amplitudes between groups 1, 2, and 3. This significant difference originated from group 1 when compared with the other groups (p<0.05). When we compared the cVEMP results of patients with VM during attack and attack-free periods, a statistically significant decrease was determined in the p13-n23 amplitude values during the attack period (p<0.01). Additionally, when we compared group 1 and group 3, the wave V peak latencies in ABR were significantly prolonged in group 1 (p<0.05). cVEMP and ABR can be used as diagnostic criteria for patients with VM during attacks. Further studies with larger groups are needed to verify our findings.

The objective of this study was to determine the fastest and the most effective auditory brainstem response (ABR) measurement protocol for audiological diagnosis in babies up to three months of age. Twenty-two newborns (aged 0 to 63 days) who passed the newborn screening test in at least one ear were evaluated in the study. The ABR were recorded with click stimulus using two different electrode montages (1st montage: ipsilateral mastoid, contralateral mastoid, vertex. 2nd montage: nape of the neck, vertex, cheek). Latencies of waves I, III, V and duration of the test were recorded and analyzed. Wave V latencies from both electrode montages were statistically shortest at the level of 70 dBnHL and longest at the level of 20 dBnHL (p=0.00). When the duration of the test at three different intensity levels were compared between the two electrode montages, only the test durations at 50 dBnHL were significantly different (p=0.017). The test times at 70 dBnHL in the first montage were observed to be significantly different in babies aged 1 to 30 days and aged 31 to 63 days (p=0.005). In protocols to evaluate the hearing of pediatric groups, it is very important to complete the ABR, which has significant value in early diagnosis, in a short time and reliably. It is concluded that in terms of practicality, the second montage is more advantageous and comfortable for both audiologists and newborns in single channel ABR systems.

Measures of frequency selectivity from forward masking indicate sharper tuning than those from simultaneous masking (Houtgast, 1974; Moore, 1978). We show that a simple relation between forward and simultaneous masking predicts this result. Consider the masking of a 10-ms, sinusoidal signal of frequency fs = 2.0 kHz by a 200-ms, 50-Hz-wide narrow-band noise masker with center frequency fm. Let Df = fm − fs be the frequency interval between the signal and the masker, and let Dt = ts − tm be the time interval between their offsets. We may define the following three masking conditions: (1) on-frequency forward, Dt = 15 ms, Df = 0 Hz, (2) off-frequency simultaneous, Dt = 0 ms, Df = 200 Hz, and (3) off-frequency forward, Dt = 15 ms, Df = 200 Hz. Masking functions (signal intensity at masked threshold versus masker intensity) were obtained in each of these conditions. Our preliminary data indicate that the off-frequency forward masking function (F) is predicted reasonably well by the composite relation F = G(kH), where G is the on-frequency forward masking function, H is the off-frequency simultaneous masking function, and k is a constant. Predictions were equally as good for other values of Df, yielding the expected difference in tuning between simultaneous and forward measures.

ObjectiveTo investigate whether sound conditioning influences auditory system protection by activating adenylate activated kinase (AMPK), and if such adaption protects ribbon synapses from high-intensity noise exposure.Materials and methodsCBA mice (12 weeks old) were randomly divided into four groups (n = 24 mice per group): control, sound conditioning (SC), sound conditioning plus noise exposure (SC+NE), and noise exposure (NE). Hearing thresholds were assessed before testing, after sound conditioning, and 0, 3, 7, and 14 days after 110 dB noise exposure. Amplitudes and latencies of wave I at 90 dB intensity were assessed before test, after conditioning, and at 0 and 14 days after 110 dB noise exposure. One cochlea from each mouse was subjected to immunofluorescence staining to assess synapse numbers and AMPK activation, while the other cochlea was analyzed for phosphorylated adenylate activated kinase (p-AMPK) protein expression by western blot.ResultsThere was no significant difference in auditory brainstem response (ABR) threshold between SC and control mice. The degree of hearing loss of animals in the two SC groups was significantly reduced compared to the NE group after 110 dB noise exposure. Animals in the SC group showed faster recovery to normal thresholds, and 65 dB SPL sound conditioning had a stronger auditory protection effect. After sound conditioning, the amplitude of ABR I wave in the SC group was higher than that in the control group. Immediately after noise exposure (D0), the amplitudes of ABR I wave decreased significantly in all groups; the most significant decrease was in the NE group, with amplitude in 65SC+NE group significantly higher than that in the 85SC+NE group. Wave I latency in the SC group was significantly shorter than that in the control group. At D0, latency was prolonged in the NE group compared with the control group. In contrast, there was no significant difference in latency between the 65SC+NE and 85SC+NE groups. Further, at D14, there was no significant difference between the NE and control groups, while latency remained significantly shorter in the 65SC+NE and 85SC+NE groups compared with controls. Number of ribbon synapses in SC mice did not differ significantly from that in controls. After 110 dB noise exposure, there were significantly more ribbon synapses in the SC+NE group than the NE group. Ribbon synapses of all groups were recovered 14 days after the noise exposure, while the SC group had a shorter recovery time than the non-SC groups (p < 0.05). AMPK was highly activated in the SC group, and p-AMPK expression was detected; however, after 110 dB noise exposure, the strongest protein expression was detected in the NE group, followed by the SC+NE groups, and the lowest protein expression was detected in the control group.ConclusionSound conditioning animals were more noise resistant and recovered hearing faster than non-SC animals. Further, 65 dB SPL SC offered better hearing protection than 85 dB SPL SC. Early AMPK activation may protect hearing by increasing ATP storage and reducing the release of large quantities of p-AMPK, which could help to inhibit synapse damage.

Sudden infant death syndrome (SIDS)-the sudden and unexplained death of a seemingly healthy infant, < 1 year old-may be associated with abnormalities in the brain regions that underlie breathing and arousal during sleep. While post-mortem studies suggest abnormalities in SIDS infants' brainstems, there are no studies of these infants' brainstem function before death. One way to assess the function of the brainstem is with auditory brainstem response (ABR), a routine hearing-screening method that noninvasively measures the brainstem's response to sound. We hypothesized that anomalies in newborns' ABR measures may predict SIDS. We integrated two secondary datasets and examined ABRs of newborns who later died of SIDS (n = 11) compared to a normative sample (n = 198,990), using existing archived records of neonatal ABR results from a sample of newborns born in Florida. As hypothesized, infants who died from SIDS were more likely than non-SIDS infants to have abnormal ABRs as newborns. Children who died of SIDS appeared to have shorter latencies to the trough that follows peak V in the left ear than children without SIDS. However, our expert-rated data failed to replicate this finding, suggesting it is unlikely to reflect a true effect. Understanding the association between SIDS and ABR may facilitate more accurate identification of an infant's risk for SIDS at birth, enabling increased monitoring, which may facilitate interventions and improve survivorship.

Background Migraine involves complex neurovascular mechanisms with evidence of brainstem dysfunction, particularly in auditory processing. Comparative data between migraine with aura (MA) and without aura (MoA) using detailed electrophysiological and psychoacoustic assessments are limited. In this study, we aim to compare auditory brainstem function in MA and MoA patients and healthy controls and assess correlations with migraine characteristics. Methods Forty-one migraine patients (18 MA, 23 MoA) and 41 matched controls with normal peripheral hearing underwent clinical evaluation, Arabic Central Auditory Processing Disorder (CAPD) questionnaire, basic audiologic testing, masking level difference (MLD) at 500 Hz and 1000 Hz, and auditory brainstem responses (ABR) at low and high repetition rates. ABR parameters included absolute latencies (Waves I, III, V), interpeak intervals, and V/I amplitude ratios. Results Basic audiologic measures Pure-Tone Average (PTA), Speech Reception Threshold (SRT), Word Discrimination (WD) were normal in all participants. Migraineurs showed significantly higher MLD scores than controls (MLD 500: 9.3 ± 1.7 vs. 4.5 ± 1.4 dB; MLD 1000: 9.5 ± 1.7 vs. 4.6 ± 1.2 dB; p &lt; 0.001). ABR revealed prolonged latencies (LIII, LV, HI–V) and interpeak intervals (LIII–V, LI–V) in migraine ( p &lt; 0.001), indicating central auditory brainstem dysfunction. Compared to MoA, MA patients had longer LV ( p = 0.041) and greater interaural amplitude asymmetry (LHV1a, p = 0.035). In MA, ABR latencies correlated strongly with attack frequency and disability by using Migraine Disability Assessment (MIDAS) ( r = 0.78–0.84, p &lt; 0.01). Conclusion Both MA and MoA present with central auditory brainstem abnormalities despite normal peripheral hearing. MA shows subtle but significant prolongations in brainstem conduction and asymmetry, which correlate with clinical severity. These findings address a gap in migraine research by providing subtype-specific electrophysiological evidence, supporting the potential use of ABR parameters particularly latency of wave III, V, IV and interpeak interval I–V as objective biomarkers for disease monitoring and targeted intervention.

Otologic safety of intratympanic N-acetylcysteine in an animal model.

The S1P(2) receptor is a member of a family of G protein-coupled receptors that bind the extracellular sphingolipid metabolite sphingosine 1-phosphate with high affinity. The receptor is widely expressed and linked to multiple G protein signaling pathways, but its physiological function has remained elusive. Here we have demonstrated that S1P(2) receptor expression is essential for proper functioning of the auditory and vestibular systems. Auditory brainstem response analysis revealed that S1P(2) receptor-null mice were deaf by one month of age. These null mice exhibited multiple inner ear pathologies. However, some of the earliest cellular lesions in the cochlea were found within the stria vascularis, a barrier epithelium containing the primary vasculature of the inner ear. Between 2 and 4 weeks after birth, the basal and marginal epithelial cell barriers and the capillary bed within the stria vascularis of the S1P(2) receptor-null mice showed markedly disturbed structures. JTE013, an S1P(2) receptor-specific antagonist, blocked the S1P-induced vasoconstriction of the spiral modiolar artery, which supplies blood directly to the stria vascularis and protects its capillary bed from high perfusion pressure. Vascular disturbance within the stria vascularis is a potential mechanism that leads to deafness in the S1P(2) receptor-null mice.

This study examined the auditory status of females with Rett syndrome (RS) using auditory brainstem response (ABR) testing and measures of acoustic admittance. Prevalence of hearing impairment in 81 female patients (age range 1 year 3 months to 39 years 8 months; mean age 8 years 7 months, SD 6 years 4 months) was evaluated with ABR measurements. If the ABR latencies at 20dB nHL exceeded those of the normative group, a slight hearing loss was diagnosed. For ABR thresholds in the range 30 to 40dB nHL, a mild hearing loss was determined; moderate hearing loss was diagnosed for ABR thresholds in the range 50 to 60dB nHL. Bilateral hearing loss was found in 16 (19.3%) patients and unilateral hearing loss in 13 (16%) patients. Bilateral hearing loss of moderate degree was found in one patient. No patient was found with severe hearing loss (ABR threshold of 70dB nHL and above) in either ear. Slight hearing loss was found in 10.5% of ears (17 of 162), mild hearing loss in 14.2% of ears(23 of 162), and moderate hearing loss in 3.1% of ears (5 of 162). In 72.2% of ears (117 of 162), findings indicated the presence of normal peripheral auditory sensitivity. Prevalence of sensorineural hearing loss was 17.3% (28 of 162). Evidence of conductive involvement (conductive and mixed hearing loss) was observed in 9.9% of ears (16 of 162). In this cross-sectional study, the prevalence of hearing loss was increased in older RS participants and in those with seizures requiring the use of anticonvulsants. Neither the type of hearing loss nor the presence of preserved speech seemed to be correlated with the type of mutation in methyl-CpG-binding protein 2 (MeCP2) gene that is associated with RS.

Auditory brainstem responses (ABR) are used to evaluate the peripheral and central functions of the auditory tract. Air and bone-conduction auditory stimuli are used to evaluate the type and degree of hearing loss. The wave latencies and interpeak latencies (IPLs) are the important diagnostic data in ABR tests. Gender and age of the patients are some of the factors affecting these latencies. This study investigated the effects of age and gender on the wave and IPLs of bone-conduction ABR. One hundred healthy individuals (50 women and 50 men) aged between 10 and 60 years were enrolled into this study, and both ears of all subjects (200 ears total) were included in the assessments. Based on their age, the subjects were equally divided into five groups, and each group consisted of 10 men and 10 women. The findings showed a significant difference in wave latencies and IPLs between the two genders (p<0.05). Depending on stimulus intensity, wave latencies also showed statistically significant differences between the age groups (p<0.05). However, no significant difference was noted between the age groups regarding IPLs. Normative values that covered wave latencies and IPLs evoked at stimulus intensities of 50, 30, and 10 dB nHL were established for the clinical use and use as a reference for the bone-conduction ABR testing procedure.