Changes In Auditory Thresholds Research Articles

Deletion of Luzp2 Does Not Cause Hearing Loss in Mice.

Deafness is the prevailing sensory impairment among humans, impacting every aspect of one's existence. Half of congenital deafness cases are attributed to genetic factors. Studies have shown that Luzp2 is expressed in hair cells (HCs) and supporting cells of the inner ear, but its specific role in hearing remains unclear. To determine the importance of Luzp2 in auditory function, we generated mice deficient in Luzp2. Our results revealed that Luzp2 has predominant expression within the HCs and pillar cells. However, the loss of Luzp2 did not result in any changes in auditory threshold. HCs or synapse number and HC stereocilia morphology in Luzp2 knockout mice did not show any notable distinctions. This was the first study of the role of Luzp2 in hearing in mice, and our results provide important guidance for the screening of deafness genes.

Transtympanic Injections of N-acetylcysteine and Dexamethasone for Prevention of Cisplatin-Induced Ototoxicity: Double Blind Randomized Clinical Trial.

Cisplatin is a potent chemotherapeutic agent that is used against a variety of tumors. The most common side effect of cisplatin is ototoxicity. This dose-related hearing impairment is high frequency, bilateral, and permanent. Unfortunately, there is no prophylactic protocol, and, in current clinical practice, the treatment of cancer with cisplatin is interrupted when ototoxicity develops or the resulting hearing impairment is tolerated as an acceptable side effect of cancer treatment. The aim of this study is to compare transtympanic injections of N-acetylcysteine and dexamethasone (both of which have shown substantial otoprotective activity) for the prevention of cisplatin-induced ototoxicity. A double blind randomised clinical trial study of 60 cisplatin-treated patients was performed in Shahid Sadoughi Hospital in 2016-2017. Transtympanic injection of N-acetylcysteine (10%) and dexamethasone was performed. Hearing acuity was evaluated by an audiologist blinded to the treated ears before each cycle with pure tone audiometry (PTA) and six months later. Altogether, 114 transtympanic infusions were performed (57 in each group). The data were analyzed by the Fisher test and chi-squared. In the ears with N-acetylcysteine, no significant changes in auditory thresholds were recorded. In the ears with dexamethasone, cisplatin induced a significant decrease of auditory thresholds at the 8000 Hz frequency band (P = 0.001). Transtympanic injections of N-acetylcysteineas a safe and inexpensive antioxidant agent seem to be an effective otoprotective strategy for the prevention of cisplatin-induced ototoxicity and for increasing the quality of life, especially in children.

Role of brainstem auditory evoked potential in Forensic Medicine

Brainstem Auditory Evoked Potential (BAEP) is an important test used in clinical practice. It is used to diagnose auditory threshold changes and to characterize the type of hearing loss as it does not depends on voluntary response from the subject. Its role in forensic medicine becomes relevant for the assessment of type of hearing loss in medicolegal cases for conductive or sensory neural. It can be used for assessing nature of injuring cases of malingering and pinpointing the neuronal pathway, hhearing loss and whether the victim had hearing loss before the injury or after the injury. This study presents latencies of wave I, II, III, IV and V, interpeak latencies of wave I‐III, I‐V, III‐V and amplitudes of waves I‐Ia, V‐Va and absolute amplitude R in 100 healthy normal hearing in medical students of same age group comprising of 50 females and 50 male for comparison of inter gender difference and for the purpose of establishing normal values. In the present study, it has been concluded that there is highly significant difference in the waves and interpeak latencies III, V and I‐V between females and males. It was also found that the duration of wave I showed statistically highly significant differences and V‐Va showed significant difference between left and right ear in females. It was also found that the duration of wave showed statistically highly significant difference in males.

Transtympanic Injections of N-acetylcysteine for the Prevention of Cisplatin-induced Ototoxicity

Ototoxicity is a common and irreversible adverse effect of cisplatin treatment with great impact on the patients' quality of life. N-acetylcysteine is a low-molecular-weight agent which has shown substantial otoprotective activity. The role of transtympanic infusions of N-acetylcysteine was examined in a cohort of patients treated with cisplatin-based regimens. Twenty cisplatin-treated patients were subjected, under local anesthesia, to transtympanic N-acetylcysteine (10%) infusions in 1 ear, during the hydration procedure preceding intravenous effusion of cisplatin. The contralateral ear was used as control. The number of transtympanic infusions was respective to the number of administered cycles. Hearing acuity was evaluated before each cycle with pure tone audiometry by an audiologist blinded to the treated ear. A total of 84 transtympanic infusions were performed. In treated ears, no significant changes in auditory thresholds were recorded. In the control ears cisplatin induced a significant decrease of auditory thresholds at the 8000 Hz frequency band (P=0.008). At the same frequency (8000 Hz), the changes in auditory thresholds were significantly larger for the control ears than the treated ones (P=0.005). An acute pain starting shortly after the injection and lasting for a few minutes seemed to be the only significant adverse effect. Transtympanic injections of N-acetylcysteine seem to be a feasible and effective otoprotective strategy for the prevention of cisplatin-induced ototoxicity. Additional studies are required to further clarify the efficiency of this treatment and determine the optimal dosage and protocol.

Transcranial Magnetic Stimulation (TMS) in the Treatment of Attention-Deficit/Hyperactivity Disorder in Adolescents and Young Adults

Transcranial magnetic stimulation (TMS) uses a medical device that applies magnetic pulses noninvasively to the cortex of the brain to depolarize neurons. We tested its safety and efficacy in young persons with a diagnosis of attention-deficit/hyperactivity disorder (ADHD). Transcranial magnetic stimulation was applied to the right prefrontal cortex at 10 Hz, at 100% of the observed motor threshold, for 2000 pulses per session, in a 10-session course over 2 weeks in a sham-controlled crossover design (n=9). There was 1 week of no TMS between the active and sham phases. Safety of TMS was assessed by means of serial audiometry, neuropsychological testing, and electroencephalogram (EEG) at baseline, midpoint, and end point of the study. Efficacy was assessed as a primary outcome by changes in the Clinical Global Impression-Improvement (CGI-I) scale and secondarily by change in the ADHD-IV scale. Transcranial magnetic stimulation was found to be safe, with no serious adverse events and no discontinuations due to adverse effects. All randomized subjects completed the full course of sessions. There were no significant changes in auditory thresholds or in electroencephalographic assessments. Neuropsychological testing showed no significant differences between active and sham groups. There was an overall significant improvement in the clinical global impression of improvement and the ADHD-IV scales across the study phases (active and sham TMS combined; P<0.01), but the change between active and sham TMS phases did not differ. Transcranial magnetic stimulation was found to be safe, with no serious adverse events observed in this pilot study. Improvement in symptoms was observed across the combined phases of the study, although there was no difference between the active and sham forms of TMS. Effects of clinical importance should be further assessed in larger controlled studies.

Effect of Surgical Technique on Electrode Impedance after Cochlear Implantation

We compare the evolution of electrode impedance values (IVs) following either conventional cochlear implantation or implantation by the soft surgery (SS) technique. We performed a retrospective chart review of 20 consecutive adult patients who underwent implantation with the Nucleus CA 24 device between 2004 and 2007. Five patients with preoperative residual hearing at the frequencies 256, 512, and 1,024 Hz underwent implantation by an SS cochlear implantation technique (SS group), and the 15 other patients underwent a conventional implantation technique (conventional cochleostomy [CC] group). The active electrodes were classified as distal (17 to 22), middle (10 to 16), or proximal (3 to 9) according to their position in relation to the tip of the electrode array. Their IVs were collected at 1, 3, 12, 24, and 36 months after implantation. Changes in auditory thresholds at 3 and 24 months were reported for patients in the SS group. The postoperative IVs of both the CC and SS groups decreased significantly between 1 and 3 months after implantation (p < 0.05) and then remained stable. The IVs after 12 months were significantly lower (p < 0.05) in the SS group than in the CC group. Patients who underwent the SS technique displayed lower long-term electrode IVs than did their counterparts in the CC group. If electrode IVs are indeed an indirect representation of cochlear fibrosis, the use of the SS technique in lieu of the CC technique could reduce fibrotic development.

Age-related Changes in Auditory Thresholds in Guinea Pigs

Age-related Changes in Auditory Thresholds in Guinea Pigs

E055 Cochlea implant care with Charge Syndrome

Partial deafness is characterised by normal or slightly elevated thresholds in the low-frequency band with nearly total deafness in higher frequencies. The aim of the study was to investigate whether the low-frequency hearing of partially deafened patients could be preserved after cochlear implant surgery applying Med-El Combi 40+ with partially inserted electrode. Cochlear implantation was performed in six partially deafened patients. Changes in auditory thresholds using pure tone audiometry recordings were measured to determine the extent of preservation of low-frequency hearing. Low-frequency hearing was preserved to the large extent in all patients. Preservation of low-frequency hearing creates the opportunity for application of electric and acoustic stimulation in the partially deafened. It could provide speech comprehension better than with either modality alone. Obtained results can be considered as the first step towards the application of cochlear implant in the treatment of partial deafness.

Anti‐intercellular adhesion molecule‐1 antibody's effect on noise damage

The purpose of this study was to investigate possible preventive effects of anti-intercellular adhesion molecule-1 antibody (anti-ICAM-1 Ab) on noise-induced cochlear damage as assessed by changes in auditory thresholds and cochlear blood flow. A controlled animal study. Pretreated rats with anti-ICAM-1 Ab or saline control, followed with exposure to 72 continuous hours of broad band noise (107 dB SPL), and 24 hours after noise exposure treated again with anti-ICAM-1 Ab or saline. Eighteen healthy male Fischer rats (200-250 g) were used. Sixteen were randomly selected to study noise-induced temporary threshold shifts. The remaining two rats were used to study cochlear blood flow (CBF), using laser Doppler flowmetry and blood pressure measurements. Rats treated with anti-ICAM-1 Ab (1.875 mg/kg, intravenously) showed attenuated temporary threshold shifts (TTS) compared to controls. Both groups showed a partial threshold recovery 72 hours following noise exposure, normal for this noise exposure paradigm. Comparisons of baseline and post-treatment measurements of CBF and mean arterial blood pressure revealed no significant changes. Anti-ICAM-1 Ab animals displayed significantly lower mean auditory threshold shifts at all five test frequencies (P < .05) when compared to control. Blocking the cascade of reactive oxygen species (ROS) generation by using anti-ICAM-Ab protects against noise-induced hearing loss.

Effects of Aging on Brainstem Responses to Toneburst Auditory Stimuli: A Cross‐Sectional and Longitudinal Study in Dogs

It is assumed that the hearing of dogs becomes impaired with advancing age, but little is known about the prevalence and electrophysiologic characteristics of presbycusis in this species. As in humans, hearing in dogs becomes impaired with aging across the entire frequency range, but primarily in the high-frequency area. This change can be assessed quantitatively by brainstem-evoked response audiometry (BERA). Three groups of 10 mixed-breed dogs with similar body weights but different mean ages were used. At the start of the study, the mean age was 1.9 years (range, 0.9-3.4) in group I, 5.7 years (3.5-7) in group II, and 12.7 years (11-14) in group III. In a cross-sectional study, the BERA audiograms obtained with toneburst stimuli were compared among the 3 groups. In a longitudinal study, changes in auditory thresholds of group II dogs were followed for 7 years. Thresholds were significantly higher in group III than in groups I and II at all frequencies tested, and higher in group II than in group I at 4 kHz. The audiograms in group II indicated a progressive increase in thresholds associated with aging starting around 8-10 years of age and most pronounced in the middle- to high-frequency region (8-32 kHz). Age-related hearing loss in these dogs started around 8-10 years of age and encompassed the entire frequency range, but started and progressed most rapidly in the middle- to high-frequency area. Its progression can be followed by BERA with frequency-specific stimulation.

Preservation of low-frequency hearing in partial deafness cochlear implantation

Partial deafness is characterised by normal or slightly elevated thresholds in the low-frequency band with nearly total deafness in higher frequencies. The aim of the study was to investigate whether the low-frequency hearing of partially deafened patients could be preserved after cochlear implant surgery applying Med-El Combi 40+ with partially inserted electrode. Cochlear implantation was performed in six partially deafened patients. Changes in auditory thresholds using pure tone audiometry recordings were measured to determine the extent of preservation of low-frequency hearing. Low-frequency hearing was preserved to the large extent in all patients. Preservation of low-frequency hearing creates the opportunity for application of electric and acoustic stimulation in the partially deafened. It could provide speech comprehension better than with either modality alone. Obtained results can be considered as the first step towards the application of cochlear implant in the treatment of partial deafness.

Loudness changes associated with the perception of an auditory after-image: Cambios en la intensidad asociados a la percepción de una imagen post-auditiva

The Zwicker tone (ZT) is an auditory sensation that occurs following the presentation of broadband noise containing a spectral notch. The present study aimed to test whether the changes in auditory thresholds that have been shown to follow the presentation of the ZT inducer are accompanied by suprathreshold effects. Using an interaural loudness-balance procedure, the loudness of probe tones presented after notched and after flat noise was compared. The results revealed small differences in the influence of the two types of noise on loudness at low intensities only. This suggests that the influence of notched noise stimulation on the auditory system is mediated by changes in the internal noise in auditory centres.

Effects of a 2- to 4-week course of repetitive transcranial magnetic stimulation (rTMS) on neuropsychologic functioning, electroencephalogram, and auditory threshold in depressed patients

Background: The safety of repetitive transcranial magnetic stimulation (rTMS) has only previously been formally studied in volunteers receiving a single session of stimulation or in a small number of depressed subjects receiving a 2-week treatment course. This study examined safety issues in depressed subjects receiving up to 4 weeks of rTMS. Efficacy results from this study have been previously reported. Methods: Eighteen subjects with DSM-IV major depression participated in a 2-week, parallel, double-blind, sham-controlled study of rTMS treatment. Twelve subjects then went on to receive 4 weeks active rTMS in an open follow-up. We examined the effects of rTMS on neuropsychologic function (up to 4 weeks), auditory threshold (up to 6 weeks exposure to rTMS noise), and an electroencephalogram (after 2 weeks). Data were analyzed by repeated measures analysis. Results: There were trends for improvement in neuropsychologic performance, probably due to practice effects. No mean changes in auditory threshold occurred, but two patients showed mild high-frequency hearing loss after several weeks of rTMS. Electroencephalograms in two patients, one of whom had sham stimulation, showed minor abnormality. Conclusions: No significant mean deficits were demonstrated in this cohort. Overall, rTMS for up to 4 weeks is safe, but individual results suggest caution and the need for further investigation of the safety of several weeks of rTMS.

Auditory perception following hair cell regeneration in European starling (Sturnus vulgaris): frequency and temporal resolution.

Behavioral detection thresholds, auditory filter widths, and temporal modulation transfer functions were obtained from four starlings before, during and after 11 days of subcutaneous injections of kanamycin, an aminoglycoside antibiotic. Birds were operantly conditioned to respond to pure tones and amplitude modulated noises ranging in frequency from 0.25 to 7 kHz using adaptive staircase procedures and were tested daily for 92 days after the first injection of aminoglycoside. All birds had threshold shifts of at least -60 dB at frequencies above 4 kHz. Lower frequencies were affected in some birds, although none of the birds had hearing loss below 3 kHz. All four birds had wider auditory filters at 5 kHz immediately after the aminoglycoside series. Any changes in frequency resolution at frequencies below 5 kHz were slight, transitory, and rarely observed. Two of the four birds had permanently wider auditory filters at 5 kHz. Temporal modulation transfer functions were briefly affected in two birds during the time of greatest threshold shift. Recovery of detection thresholds began soon after the injections ceased and continued for approximately 60 days. Recovery in frequency resolution lagged behind auditory threshold by about 10 days. Normal temporal resolution was observed in the context of impaired intensity and frequency resolution. Changes in auditory threshold and frequency resolution were closely associated for all birds at 5 kHz, but were correlated with statistical significance in only two birds. Scanning electron microscopy was performed on all four birds after 90 days of recovery and confirmed that the extent of initial damage was consistent with the pattern of observed hearing loss.

The effects of moderate and low levels of acoustic overstimulation on stereocilia and their tip links in the guinea pig

Guinea pigs were exposed to pure tones of 10 kHz at intensities between 98 and 115 dB SPL for 5–30 min, to produce varying degrees of acoustic trauma. Changes in auditory thresholds were measured electrophysiologically, and the animals were immediately fixed for scanning electron microscopy. Correlation between morphological changes to the hair bundle and losses in threshold, showed that with the smallest degrees of trauma (98 dB SPL for 15 min, mean maximum threshold loss of 22 dB), damage was confined to a small stretch of inner hair cells OHO, with only subtle changes to the stereocilia of the outer hair cells (OHC). At exposure intensities greater than 102 dB SPL (duration: 15 min) the IHC stereocilia in the centre of the lesion were always substantially disarrayed. Substantial damage to the OHC bundles was seen only with exposures above 110 dB SPL (duration: >- 5 min), producing threshold losses of 50 dB or more. Tip links were lost only where the stereocilia were disarrayed. It is concluded that the tip links are not the most vulnerable components of the cochlear hair cell, but that relatively low levels of acoustic stimulation can cause significant damage to the stereociliary bundle of the IHCs.

Salicylate‐induced changes in auditory thresholds of adolescent and adult rats

Shifts in auditory intensity thresholds after salicylate administration were examined in postweanling and adult pigmented rats at frequencies ranging from 1 to 35 kHz. A total of 132 subjects from both age levels were tested under two-way active avoidance or one-way active avoidance paradigms. Estimated thresholds were inferred from behavioral responses to presentations of descending and ascending series of intensities for each test frequency value. Reliable threshold estimates were found under both avoidance conditioning methods, and compared to controls, subjects at both age levels showed threshold shifts at selective higher frequency values after salicylate injection, and the extent of shifts was related to salicylate dose level. © 1996 John Wiley & Sons, Inc.

Salicylate-induced changes in auditory thresholds of adolescent and adult rats.

Shifts in auditory intensity thresholds after salicylate administration were examined in postweanling and adult pigmented rats at frequencies ranging from 1 to 35 kHz. A total of 132 subjects from both age levels were tested under two-way active avoidance or one-way active avoidance paradigms. Estimated thresholds were inferred from behavioral responses to presentations of descending and ascending series of intensities for each test frequency value. Reliable threshold estimates were found under both avoidance conditioning methods, and compared to controls, subjects at both age levels showed threshold shifts at selective higher frequency values after salicylate injection, and the extent of shifts was related to salicylate dose level.

Heat-Induced Pain Diminishes Vibrotactile Perception: A Touch Gate

The gate control theory of pain (Melzack and Wall, 1965) suggests that tactile stimuli can decrease the perception of pain. We have found the reverse effect: Heat at levels that induce pain can substantially suppress tactile sensitivity, independently of shifts in attention or arousal. Ten human observers were stimulated by a tonic, pain-producing heat stimulus and vibrotactile stimuli (1, 10, and 100 Hz) coincidentally presented to the right thenar eminence. Vibrotactile thresholds were assessed with the skin at a normative temperature of 31 degrees C and at higher temperatures producing pain. Increases in vibrotactile thresholds (mean change = 7.3 dB) occurred at skin temperatures just below and above those that induced pain. Furthermore, absolute-magnitude estimates of suprathreshold vibrotactile stimuli determined during the same experiments showed decreased sensitivity and psychophysical recruitment. The changes are not attributable to attentional or arousal shifts, since they were not associated with changes in auditory thresholds. Furthermore, the changes occurred just below the subjects' pain thresholds (where nociceptors are presumably activated). This over-twofold diminution of vibrotactile sensitivity suggests that heat stimuli capable of inducing pain can significantly diminish taction, perhaps through a "touch gate" in a manner similar to the gate control theory proposed for pain.

Auditory event-related dynamics of the EEG spectrum and effects of exposure to tones

A new measure of event-related brain dynamics, the event-related spectral perturbation (ERSP), is introduced to study event-related dynamics of the EEG spectrum induced by, but not phase-locked to, the onset of the auditory stimuli. The ERSP reveals aspects of event-related brain dynamics not contained in the ERP average of the same response epochs. Twenty-eight subjects participated in daily auditory evoked response experiments during a 4 day study of the effects of 24 h free-field exposure to intermittent trains of 89 dB low frequency tones. During evoked response testing, the same tones were presented through headphones in random order at 5 sec intervals. No significant changes in behavioral thresholds occurred during or after free-field exposure. ERSPs induced by target pips presented in some inter-tone intervals were larger than, but shared common features with, ERSPs induced by the tones, most prominently a ridge of augmented EEG amplitude from 11 to 18 Hz, peaking 1–1.5 sec after stimulus onset. Following 3–11 h of free-field exposure, this feature was significantly smaller in tone-induced ERSPs; target-induced ERSPs were not similarly affected. These results, therefore, document systematic effects of exposure to intermittent tones on EEG brain dynamics even in the absence of changes in auditory thresholds.

Disruption of human eyeblink conditioning after central cholinergic blockade with scopolamine.

Human (Homo sapiens) volunteers (N = 72) received saline, a low dose of oral scopolamine (0.6 mg), a high dose of oral scopolamine (1.2 mg), or a peripheral analogue (glycopyrrolate). They then underwent classical conditioning of the eyeblink response to a tone conditioned stimulus (CS) and a corneal airpuff unconditioned stimulus (UCS) in a delay conditioning paradigm. There was a dose-related decline in acquisition of the conditioned response. These drug-induced conditioning deficits were similar to those previously reported in rabbit eyeblink conditioning and could not be attributed to such nonassociative factors as changes in auditory thresholds to the tone CS, magnitude of reflexive blinks to the airpuff UCS, or to changes in spontaneous blink rates.