Asymmetric Flankers in Comodulation Masking Release

BACKGROUND AND OBJECTIVES: Detection of auditory signals may be improved when maskers far from the frequency of the target signal are coherently amplitude-modulated. This improvement of signal detection is called comodulation masking release (CMR). In the CMR experiments, flankers have been usually arranged symmetrically. In practice, we will be confronted with a problem by using symmetric flankers due to the limited output of clinical audiometers, especially at high-frequency. We aimed to check whether flanker arrangement has any effect on the amount of CMR, especially when there is no flankers with a frequency higher than the signal. SUBJECTS AND METHODS: Eighteen normal hearing listeners ranging in age from 20 to 46 years old participated. Symmetric (2-2) and asymmetric (3-1 and 4-0) flankers were used and then the amount of CMR compared among them. RESULTS: Our results showed in the same numbers of flankers, there were no statistically CMR differences between symmetric and asymmetric arrangement. Also when we did not have a flanker at a frequency higher than the signal and all flankers were placed below the signal, there was no statistically difference with the symmetric arrangement. CONCLUSIONS: The asymmetry of the flankers and also omitting the flankers with a frequency higher than the signal, have no effect on CMR results. We concluded that CMR can be considered by using clinical audiometer.

The Effects of the Vestibular Rehabilitation on the Benign Paroxysmal Positional Vertigo Recurrence Rate in Patients with Otolith Dysfunction

BACKGROUND AND OBJECTIVES: Although repositioning maneuvers have shown remarkable success rate in treatments of benign paroxysmal positional vertigo (BPPV), the high recurrence rate of BPPV has been an important issue. The aims of present study were to examine the effects of otolith dysfunction on BPPV recurrence rate and to describe the effect of vestibular rehabilitation exercises on BPPV recurrence in BPPV patients with concomitant otolith dysfunction. SUBJECTS AND METHODS: Forty-five BPPV patients included in this study (three groups). Patients in group 1 had no otolith dysfunction and patients in groups 2 and 3 had concomitant otolith dysfunction. Otolith dysfunction was determined with ocular/cervical vestibular evoked myogenic potential (oVEMP and cVEMP) abnormalities. Epley’s maneuver was performed for the patients in all groups but patients in group 3 also received a 2-month vestibular rehabilitation program (habituation and otolith exercises). RESULTS: This study showed that BPPV recurrent rate was significantly higher in patients with otolith dysfunction in comparison to the group 1 (p < 0.05). Vestibular rehabilitation resulted in BPPV recurrence rate reduction. Utricular dysfunction showed significant correlation with BPPV recurrence rate. CONCLUSIONS: Otolith dysfunction can increase BPPV recurrence rate. Utricular dysfunction in comparison to saccular dysfunction leads to more BPPV recurrence rate. Vestibular rehabilitation program including habituation and otolith exercises may reduce the chance of BPPV recurrence.

Comparison of the Minimum Plateau Width by Plateau and a New Method in People with Conductive Hearing Loss

BACKGROUND AND OBJECTIVES: In clinical masking, the plateau is a state in which the non-test ear (NTE) is completely masked by the noise and tone is heard only by the test ear (TE). At least 15 to 20 dB of plateau width is needed to obtain valid threshold. In the study, a part of plateau after initial masking level known as the minimum plateau width (mPW) was determined and compared by a new formula and the plateau searching method. SUBJECTS AND METHODS: Minimum plateau widths of air conduction were obtained in 29 participants with unilateral and 30 participants with bilateral conductive hearing loss (CHL) aged 20 to 45 years old by using step by step plateau method and mPW estimation by the formula between two points of masking diagram [mPW=(N2-N1)-(T2-T1)] and then the mPW of two methods was compared for each frequency. RESULTS: There was no significant difference between the minimum plateau width obtained by the plateau and formula methods for two given point of masking diagram in people with unilateral and bilateral CHL at octave frequencies from 500 Hz to 4,000 Hz. CONCLUSIONS: Threshold obtaining of TE by two tones for two noise levels delivered to the NTE is enough to estimate the mPW between these two noise points and it is not necessary that for clinicians to know the actual values of masking diagram components.

novel approach for extracting important cues in complex auditory brainstem response to /da/ using fuzzy model

Gathering an insight into brainstem task in generating auditory response to complex stimuli and its nonlinear behavior can be an important base in auditory system modelling, but no study has been done to demonstrate the nonlinear dynamic behavior of auditory systems considering cABR. This study attends the dynamic modeling of auditory brainstem response to consonant-vowel syllable /da/ using fuzzy logic as nonlinear mapping of the input and output of the system. We recorded cABR to /da/ from 40 normal Farsi speaking subjects in response to /da/ with 40ms duration. This data set was divided to train and validation sets. We implemented a fuzzy logic based model for the dynamic extraction of cABR to /da/ for data set. This model includes singltone fuzzifier, product inference engine and weighted center of average defuzzifier. Rule base representing dynamic of signal was generated and, then, firing rate of each rule was calculated and a histogram of rule firing rate was plotted. We selected the important regions of the histogram regarding to firing pattern of the rule. By choosing an appropriate threshold, a secondary rule reduction was done to generate a simplified model; remaining rules were best rules related to important cues of cABR. This model represents the input-output behavior of the brainstem in generating cABR to consonant-vowel /da/. The total error achieved by cross-validation of the model after an important rule selection is 0.1329 with a variance of 7.08×10-4. Nonlinear fuzzy based dynamic extraction of cABR signal is a valid approach for generating important features of cABR and a remarkable evidence of these signals can be represented by some spatial rules

Saccular function in otosclerosis patients: bone conducted-vestibular evoked myogenic potential analysis

Vestibular involvements have long been observed in otosclerotic patients. Among vestibular structures saccule has the closest anatomical proximity to the sclerotic foci, so it is the most prone vestibular structure to be affected during the otosclerosis process. The aim of this study was to investigate the saccular function in patients suffering from otosclerosis, by means of Vestibular Evoked Myogenic Potential [VEMP]. The material consisted of 30 otosclerosis patients and 20 control subjects. All participants underwent audiometric and VEMP testing. Analysis of tests results revealed that the mean values of Air-Conducted Pure Tone Average [AC-PTA] and Bone-Conducted Pure Tone Average [BC-PTA] in patients were 45.28 +/- 15.57 and 19.68 +/- 10.91, respectively and calculated 4 frequencies Air Bone Gap [ABG] was 25.64 +/- 9.95. The VEMP response was absent in 14 [28.57%] otosclerotic ears. A statistically significant increase in latency of the p13 was found in the affected ears [P=0.004], differences in n23 latency did not reach a statistically significant level [P=0.112]. Disparities in amplitude of p13-n23 in between two study groups was statistically meaningful [P=0.009], indicating that the patients with otosclerosis had lower amplitudes. This study tends to suggest that due to the direct biotoxic effect of the materials released from the otosclerosis foci on saccular receptors, there might be a possibility of vestibular dysfunction in otosclerotic patients

[Protection against noise-induced cochlear hair cell loss in conditioned guinea pigs]

Since noise-induced hearing loss is a common problem and its prevention is important, we aimed to evaluate whether previous exposure to moderate level of noise could prevent subsequent high level noise-induced cochlear damage. This study was conducted on 10 guinea pigs randomly divided into two groups [n=5, each]. Animals in control group exposed to 4 kHz, 105 dB SPL octave band noise for 4 hours, while in conditioned group animals exposed to 85 dB SPL, 4 kHz octave band noise, 6 hours/day for 5 days before exposing to 105 dB noise. One week later, the subjects euthanized for histological evaluation and the remaining and lost outer hair, inner hair and supporting cells were compared. Our results showed that outer hair cells row 1 was injured the most. A massive damage around the second turn of the cochlea was observed in control group. Conditioning significantly reduced the amount of hair cell loss. In conditioned group, the amount of hair cell loss was significantly reduced when compared to control [p<0/05]. Our findings confirmed that conditioning protects against noise-induced cochlear hair cell loss

protective effect of conditioning on noise-induced hearing loss is frequency-dependent

We compared the extent of temporary threshold shift [TTS] and hair cell loss following high level 4 kHz noise exposure with those preconditioned with moderate level 1 and 4 kHz octave band noise. Fifteen Male albino guinea pigs [300- 350 g in weight] were randomly allocated into three groups: those exposed to 4 kHz octave band noise at 102 dB SPL [group 1, n=5]; those conditioned with 1 kHz octave band noise at 85 dB SPL, 6 hours per day for 5 days, then exposed to noise [group 2, n=5]; those conditioned with 4 kHz octave band noise at 85 dB SPL, then exposed to noise [group 3, n=5]. An hour and one week after noise exposure, threshold shifts were evaluated by auditory-evoked brainstem response [ABR] and then animals were euthanized for histological evaluation. We found that TTS and cochlear damage caused by noise exposure were significantly reduced by 1 kHz and 4 kHz conditioning [P<0.001]. We also showed that 4 kHz protocol attenuates noise- induced TTS but no significant TTS reduction occurred by 1 kHz conditioning. Both protocol protected noise-induced cochlear damage. We concluded that lower tone conditioning could not protect against higher tone temporary noise-induced hearing loss, thus conditioning is a local acting and frequency-dependent phenomenon

[Comparison acoustically evoked short latency negative response with vestibular evoked myogenic potential in adults with profound hearing loss]

A negative deflection with a 3-4 ms latency period has been reported to exist within the auditory brainstem response of some patients with profound hearing loss following a strong acoustic stimulus. This deflection, namingly the n3 or the acoustically evoked short latency negative response is assumed to be a vestibular-evoked potential, especially of saccular origin. Since the myogenic potential is also saccular in origin, the purpose of the present study was to investigate the relationship between these two tests in adults with profound hearing loss. The present cross sectional study was performed on 20 profoundly deaf volunteers[39 ears] who aged between 18-40 years old, randomly selected from available deaf adults in Tehran. The auditory brainstem response of all subjects was recorded following a 1000 Hz tone burst in 70-100dB nHL. Subjects were also tested for vestibular evoked myogenic potential. Only 34 of 39 ears recorded myogenic potential that negative response was recorded in 27 of 34 ears with normal p13 and n23. In seven ears with normal p13 and n23, the negative response was absent. In 3 ears with no p13 and n23, the negative response was observed, and two none. In view of the high prevalence of the negative response in profoundly deaf ears with normal p13 and n23, it could be concluded that the negative response can be used when for any reason, it is not possible to record myogenic potential and be considered as a new test in vestibular test battery

[Auditory brainstem responses in children treated with cisplatin]

In view of improvement in therapeutic outcome of cancer treatment in children resulting in increased survival rates and the importance of hearing in speech and language development, this research project was intended to assess the effects of cisplatin group on hearing ability in children aged 6 months to 12 years. In this cross-sectional study, hearing of 10 children on cisplatin group medication for cancer who met the inclusion criteria was examined by recording auditory brainstem responses [ABR] using the three stimulants of click and 4 and 8 kHz tone bursts. All children were examined twice: before drug administration and within 72 hours after receiving the last dose. Then the results were compared with each other. There was a significant difference between hearing thresholds before and after drug administration [p<0.05]. Right and left ear threshold comparison revealed no significant difference. Ototoxic effects of cisplatin group were confirmed in this study. Insignificant difference observed in comparing right and left ear hearing thresholds could be due to small sample size. auditory brainstem responses test especially with frequency specificity proved to be a useful method in assessing cisplatin ototoxicity

[Ocular vestibular evoked myogenic potentials in normal-hearing adults]

Ocular vestibular-evoked myogenic potential [oVEMP] is a novel vestibular function test. This short-latency response can be recorded through contracting extraocular muscles by high-intensity acoustic stimulation and can be used to evaluate contralateral ocular-vestibular reflex. The aim of this study was to record and compare the amplitude, latency, asymmetry ratio and occurrence percentage of oVEMP [n10] and cervical VEMP [p13] responses in a group of normal adult subjects. We carried out a cross-sectional study on 20 adult subjects' mean age 22.18 years, SD=2.19 with normal hearing sensitivity and no history of vestibular diseases. oVEMP and cVEMP responses in both ears were recorded using air conducted stimuli 500 Hz short tone burst, 95 dB nHL via insert earphone and compared. cVEMP was recorded in all subjects but oVEMP was absent in two subjects. Mean amplitude and latency were 140.77 microv and 15.56 ms in p13; and 3.18 microv and 9.32 ms in n10. There were statistically significant differences between p13 and n10 amplitudes [p<0.001]. This study showed that occurrence percentage and amplitude of oVEMP were less than those of cVEMP. Since these two tests originate from different sections of vestibular nerve, we can consider them as parallel vestibular function tests and utilize them for evaluation of vestibular disorders.

[Effect of sound conditioning on click auditory brainstem response threshold shifts in guinea pigs]

Sound conditioning is exposure to a non-traumatic, moderate level of sound which increases inner ear resistance against further severe noise. In this study, we aimed to survey the effect of sound conditioning on auditory brainstem response [ABR] threshold shifts using click stimulus, and the effect of the frequency of conditioning on hearing protection. Fifteen guinea pigs were randomly divided into 3 groups. Two conditioned groups were exposed to 1 kHz, and 4 kHz octave band noise at 85 dB SPL, 6 hours per day for 5 days, respectively. On the sixth day, the animals were exposed to 4 kHz octave band noise at 105 dB SPL, for 4 hours. The control group was exposed to intense noise, 4 kHz at 105 Db SPL for 4 hours [without conditioning]. After exposure, ABR thresholds using click were recorded an hour, and 7 days after noise exposure. The results of the ABR with click stimulus showed less thresold shifts in conditioned groups than control [p 0.05]. Electrophysiological data of our study showed that sound conditioning has a protective effect against subsequent intensive noise exposure, and the frequency of conditioning does not have significant effect on ABR threshold shifts when using click stimulus

[Effect of N-acetylcysteine in protecting from simultaneous noise and carbon monoxide induced hair cell loss]

N-acetylcysteine, a glutathione precursor and reactive oxygen species scavenger, is reported to be effective in reducing noise-induced hearing loss. Many workers in industry are exposed simultaneously to noise and chemical pollutants such as carbon monoxide. We investigated effectiveness of N-acetylcysteine in protecting the cochlea from simultaneous noise and carbon monoxide damages. Twelve rabbits were exposed simultaneously to 100 dB sound pressure level of broad band noise and carbon monoxide 8 hours a day for 5 days. One hour before exposure, experimental group received 325 mg/kg of N-acetylcysteine while normal saline was administered for the control group. The protective effect of N-acetylcysteine was evaluated 3 weeks after exposure by histological assessment of the hair cells. Simultaneous exposure to noise and carbon monoxide resulted in a considerable damage to the outer hair cells; however, the inner hair cells and the pillar cells remained intact. Use of N-acdetylcysteine in the experimental group significantly reduced the extent of outer hair cell loss. N-acetylcysteine attenuates simultaneous noise and carbon monoxide induced hair cell damage in rabbits

[ effects of auditory selective attention on contralateral suppression of stimulus-frequency otoacoustic emissions]

To date, the function of auditory efferent system remains unclear. There is evidence that medial olivocochlear bundle receives input from the cortex. In this study, the effect of auditory selective attention on stimulus-frequency otoacoustic emissions [SFOAE] was analyzed to investigate the modification of peripheral auditory system by auditory cortex activity in frequency specific mode. Thirty-six normal hearing adult subjects with their age ranging from 18 to 30 years [mean age: 21.9 years] participated in this cross-sectional study. Contralateral suppression of stimulus-frequency otoacoustic emissions was recorded in the right ear at 2 KHz. In order to eliminate the auditory attention, subjects were instructed to read a text. Besides, in order to evaluate the effect of auditory attention on contralateral suppression, subjects were instructed to detect target tones in background noise at 1000, 2000, and 4000 KHz. A significant increase at contralateral suppression of stimulus-frequency otoacoustic emissions was observed in auditory selective attention conditions [p