akram pourbakht

Auditory Brainstem Response (ABR) is crucial for evaluating auditory pathway function in pediatric patients. However, obtaining reliable ABR measurements in young children can be challenging due to their inability to stay still and quiet during the test. Sedation is frequently used to facilitate ABR testing in this population, but the most practically effective sedation method and its impact are still uncertain. This systematic review aimed to thoroughly investigate the success rates (completion of ABR in both ears) associated with different sedation techniques.

In recent review (2000-2022), Ten studies, identified through a comprehensive search of electronic databases, were included in the analysis. The studies reported significant variation in success rates for ABR testing with sedation, ranging from 70% to 100%. This suggests that the effectiveness of sedation may not be uniform across all situations. The included studies employed a wide variety of sedation techniques, highlighting the lack of a standardized approach in this area.

These findings highlight the heterogeneity in sedation practices and success rates for pediatric ABR testing. This emphasizes the importance of tailoring the sedation approach to the specific needs of each child while carefully considering the potential risks associated with each sedation method. Further research is warranted to establish standardized protocols for sedation in pediatric ABR , ensuring optimal test efficacy while prioritizing patient safety. 

Timbre perception is a multidimensional feature of music perception and hearing loss may deteriorate timbre and instrument recognition. Deficits in timbre recognition may originate from poor temporal or spectral coding of musical notes subsequent to hearing loss However, it is not well understood which of these features are more dominant in instrument recognition with normal hearing and hearing loss. This study aimed to evaluate the relative importance of temporal and spectral cues instrument recognition in people with and without nearing loss.

Two groups of adults with normal-hearing and hearing loss were tested with the timbre subtest of the Clinical Assessment of Music Perception (CAMP). Originally, a series of notes is played with eight musical instruments and participants were asked to identify the played instrument among them. In two other conditions, either the rise time or spectral cues of the same notes were masked using a special masking technique. Among eight instruments.

Instrument recognition scores were not significantly different between the original and spectral-manipulated conditions but were lower at the temporal-manipulated condition. The difference between the two groups was significant (p<0.05), where the normal-hearing group recognized the musical instruments significantly better than participants with hearing loss group (p<0.05).

Temporal cues may have greater importance on timbre recognition regardless of hearing status. This suggests that the interventions and assistive devices which are designed to improve timbre recognition for people with hearing loss should prioritize improvement in temporal coding.

The objective assessment tests overcome the variability of subjective methods. Cortical recordings with gap pre-pulse inhibition of the acoustic startle reflex stimulus have been used as objective tinnitus assessments in humans. This study aims to investigate this possible objective tinnitus test and compare gap-induced inhibition in different stimulus parameters and brain regions.

Twenty People (18-50 years old) without hearing loss and tinnitus were included. The sound stimuli consisted of continuous background noise with a loud startle tone preceded by a silent gap (20 and 40 ms duration, 120 and 150 ms distance from the startle). The N1-P2 complex amplitude and topoplot maps were extracted in 27-channel cortical response recording after signal processing. Four brain regions of interest (ROI) of anterio-frontal, centro-frontal, right, and left temporal were investigated.

The results showed that the maximum inhibition occurred in a 40 ms gap duration and 150 ms distance in all 4 ROIs. In comparing ROIs, the centro-frontal and left temporal regions revealed the most inhibition (p<0.05). The decrease in the amplitude of the N1 and P2 in that region could also be traced in the 100 and 200 ms topoplots.

Gap-induced inhibition was observed in all gap-embedded stimuli and all ROIs. However, the 40-150 mode and centro-frontal and left temporal regions had maximum inhibition in normal subjects. It provides a promising tool for objectively assessing tinnitus in humans with particular implications in children

Evidence-based practice improves the quality of clinical performance. Attitude affects the implementation of research findings into practice. The Evidence-Based Practice Attitude Scale (EBPAS-36) evaluates the attitude of therapists toward evidence-based practice. The present study aimed to provide a validated Persian translation of the EBPAS-36 for audiologists.

The original EBPAS-36 was translated by using the international quality of life assessment protocol. The validity of translated version was surveyed by an expert panel and the Persian version with 35 questions was yielded. A demographic questionnaire and EBPAS P-35 were given to 182 audiologists to evaluate the psychometric properties. The reliability was evaluated by completing the EBPAS P-35 after 2 weeks by 30 of the participants and Cronbach’s alpha and Intra-Class Correlation (ICC) were calculated. Confirmatory Factor Analyses (CFA) were also conducted.

The content validity ratio was above 0.33 for all except item 10 which was removed from the Persian version. The mean(SD) total score was 2.38(0.46). A significant relationship was observed between the total score and all subscales (p<0.05). The original factor structure showed an acceptable model fit (CMIN/DF=1.39, GFI=0.84, CFI=0.94, IFI=0.94, RMSEA=0.04) confirming the 12-factor structure of the EBPAS-36. The internal consistency was very good for the total score (α=0.88) and adequate to very good for the subscales (0.65–0.84), indicating high reliability. The ICC showed good agreement in the score of test-retest (total ICC=0.65).

This study confirms good psychometric properties and validity of the EBPAS P-35 in a sample of audiologists.

Tinnitus is a complex condition that varies in loudness, quality, location, and distress. Different definitions, heterogeneity, and lack of objective measuring have challenged the understanding the mechanisms involved and definitive cure. The integrative model correlates each of these characteristics to separate parallel and overlapping subnetworks that process tinnitus’s perception and emotional reaction. Many of these networks are common with the gap pre-pulse inhibition of acoustic startle (GPIAS) neural circuity. GPIAS, which measures tinnitus in animals, has recently been used for humans with various recording methods. The present study aimed to review the evidence achieved with gap stimuli in patients with tinnitus to support the potential of cortical responses recorded with the GPIAS stimulus and to objectively detect tinnitus in humans. 

Studies were identified by searching electronic databases with relevant keywords.

The role of the auditory cortex in processing short gaps, the possibility of evaluating the gap detection ability with GPIAS, and the advantage of cortical responses in reflecting both stimulus properties and different aspects of tinnitus emphasize the importance of this issue. The results of most studies have proven the gap detection deficiency in tinnitus. However, the validity of the auditory startle reflex still needs to be verified due to the inherent variability and different methods. 

Further human studies are recommended because the perception of tinnitus can be controlled. An appealing research line in this area is multi-channel cortical evoked potentials. Defects of GPIAS with cortical recording can indicate tinnitus.

High-level sounds in recreational activities are known as one of the leading causes of developing noise-induced hearing loss, particularly in adolescents and young adults. Thus, this study aimed to explore the practicality of a hearing preservation education program in modifying listening behaviors concerning recreational noise exposure and Personal Listening Device (PLD) use in adolescents and young adults.

Two hundred students, both male and female (n=100, each) between 15 and 18 years old were chosen to participate. These students engaged in the hearing preservation education program and filled in pre-education, post-education, and follow-up questionnaires. The questionnaire assessed the students’ awareness, intention, attitudes, and motivation concerning recreational noise exposure and safe PLD usage. The materials were prepared by an expert panel of audiologists and then remarked as comprehensible by teachers of the target age group.

There were significant differences in preferred volume levels and preferred listening levels of PLD, as well as the duration of PLD usage among pre-education, post-education, and follow-up questionnaire measurements (p<0.001). Notably, education significantly altered the students’ awareness, intention, attitudes, and motivation concerning recreational noise exposure among the three experimental conditions (p<0.001).

Providing a fundamental guide and effective education to adolescents and young adults will help them to use PLD safely, expand their awareness and knowledge, and consequently revise their attitudes and listening behaviors.

Caffeine intake enhances concentration through affecting brain functions. It also improves attention to the signal which is believed to be associated with increased noise tolerance and improved speech perception. This study aimed to evaluate the long-term effects of caffeine intake on simultaneous speech and sound perception in people with normal hearing.

This double-blind study was conducted on 90 people aged 18-34 years (45 males and 45 females), randomly assigned to two intervention groups (receiving 3 and 5 mg/kg caffeine) and a control group (receiving placebo). The acceptable noise level (ANL) test was conducted before and five hours after intervention.

Comparison of ANL scores before and after intervention showed a significant difference in the 3 mg/kg caffeine group (p=0.002), but not in the placebo (p=0.497) and 5 mg/kg caffeine (p=0.146) groups. Between-group analysis showed a significant difference between the placebo and 3 mg/kg caffeine groups in the ANL five hours after (p=0.005), while the difference was not significant between the placebo and the 5 mg/kg caffeine groups (p=0.139). Moreover, there was no significant difference in the ANL between the 3 and 5 mg/kg caffeine groups (p=0.148).

Caffeine intake affects noise tolerance, depending on the dose of caffeine. The ANL and speech tolerance improve five hours after consuming 3 mg/kg of caffeine.

Cochlear synaptopathy is a common cause of auditory disorders in which glutamate over-activation occurs. Modulating glutamatergic pathways has been proposed to down-regulate post-synaptic excitation. 12-guinea pigs as  sham and test groups were exposed to a 4-kHz noise at 104 dB SPL, for 2 hr. Pre-exposure intra-tympanic injection with LY354740 and normal saline 9% was applied in the test and sham groups. The amplitude growth of ABR-wave-I and wave-III latency shift with noise were considered in pre- and post-exposure times. The synapses were observed by transmission electron-microscopy. ABR thresholds recovered 1-week post-exposure in both groups. The reduction of wave-I amplitude at 4, 6, and 8 kHz were statistically different between pre- and 1- day post-exposure and recovered mostly in the sham group. The amount of latency shift in masked ABR was different between pre- and all post-exposure, and the response could not be detected at higher than 50 dB SL noise. However, the response detectability increased to 60 dB SL noise, and the significance of differences between pre- and post-exposure persisted only at the high level of noise in the test group. In electron-microscopy of sham samples, the size of the ribbon was larger, spherical with an irregularity, and hollow. The post-synaptic density was thicker and missed its flat orientation. The higher slope of the ABR-wave I amplitude, the more tolerance of noise in masked ABR, concomitant with the histological finding that revealed less synaptic damage, confirmed the therapeutic effect of LY354740 in cochlear synaptopathy.

Ischemic injury is a major cause of hearing loss and oxidative stress is an important part of ischemic injury. The goal of this study was to evaluate the cochlear oxidative stress effect on auditory responses in male rats.

Cochlear oxidative stress was induced by bilateral carotid artery occlusion for 20 minutes. The rats were evaluated by biochemical inflammatory factors tumor necrosis factor-α [TNF-α] and C-reactive protein (CRP) in the day before and 1st, 4th, and 7th days following surgery. The auditory brainstem response (ABR) and electrocochleography (ECochG) were evaluated on the day before surgery and 14th, 21th and 28th days after surgery.

TNF-α and CRP levels concentrations increased one day after ischemia and subsequently decreased on the 7th day. The click and tone burst evoked ABR showed increased thresholds on day14th, 21th, and 28th. The highest threshold was recorded on day14th. The ECochG results also were abnormal for 55%, 70%, and 45% of cases on day 14th, 21th, and 28th, respectively.

Cochlear oxidative stress affects hearing sensitivity. The ABR shows elevated thresholds and abnormal ECochG was found in many cases.

Tinnitus is defined a phantom sound percept. Few studies have examined the occurrence of synaptopathy in tinnitus patients utilizing a battery of tests that indicate synaptopathy. This study aimed to investigate the role of synaptopathy in tinnitus production and compare the various characteristics of the auditory brainstem response (ABR) test and electrocochleography (ECochG) in normal-hearing people with and without tinnitus.

This cross-sectional study was conducted on 34 normal-hearing individuals, 20 without tinnitus as controls (11 females and 9 males) and 14 with tinnitus (8 females and 6 men). The test components (amplitude, growth and slope of wave I, V/I ratio, action potential (AP) amplitude, and summating potential (SP)/AP) ratio were recorded during the ABR and ECochG tests for each subject.

The control group had higher mean values of amplitude, growth and slope of wave I, and AP amplitude compared to the tinnitus group, and this difference was statistically significant (p<0.05). The mean V/I ratio and SP/AP ratio were lower in the control group than in the tinnitus group, and this difference was statistically significant (p<0.05).

The significant difference in the parameters of ABR and ECochG tests between normal-hearing people with and without tinnitus indicates that these parameters can be used to evaluate the presence of synaptopathy in tinnitus patients. These findings suggest the need for proper interpretation of the results of ABR and ECochG tests in tinnitus patients with a focus on the parameters indicating synaptopathy.

Early detection of auditory processing disorders (APD) is essential for preventing learning and educational problems in school-aged children. It is crucial to take into account the comorbidity with APD, as well. The goal of APD screening is to obtain the basic information about those with auditory disorders to be referred for further evaluation. This study aimed to identify the elementary school students at risk of APD in Tehran, Iran.

Participants were the parents of 536 children selected from 11 elementary schools in four districts of Tehran city. The schools in each district were selected by a random clustering method. The auditory system of students was first evaluated. The parents were then asked to complete the Persian version of the auditory processing domain questionnaire (APDQ).

The prevalence of APD was 3.3% in girls and 8.3% in boys and the difference between them was statistically significant (p=0.021). The overall prevalence of APD was 4.6% based on the cut-off points of four APDQ domains, with a male-to-female ratio of 2.6.

It is necessary to screen APD in school-aged children to minimize learning and educational problems in them. Moreover, there is a need for developing screening methods to provide timely detection and appropriate intervention for those at risk of APD.

It is easier for a listener to detect a brief tonal signal presented in a longer masking noise by increasing the delay between the signal and the masker. This phenomenon (overshoot) is influenced by a reduction in cochlear amplification and to date, there is no objective tool to investigate it. Therefore, a different paradigm of the auditory brainstem response (ABR) was utilized to measure auditory overshoot. It was assumed that increasing the delay onset time (DOT) between a signal and a masker reduces the latencies of waves I and III.

Sixteen normal young male guinea pigs were tested. A tone burst stimulus (signal: 16 kHz, 5ms in duration) and wide-band noise (masker: 0.1-8.0 kHz, 100ms in duration) at three DOTs were used. To diminish the effect of the noise on waves, waveforms were subtracted from those derived from the noise burst alone. The absolute latency of the waves I and III, inter-peak latency of the waves I-III, and amplitude ratio of the waves III/I were compared for the 0, 30, and 100ms DOTs and five signal-to-noise ratios.

The latencies of increased from the 0 to 30ms DOT and then decreased from the 30 to 100ms DOT (p < 0.001). No significant changes were observed in the latency waves at the 100ms DOT compared to the 0ms DOT (p > 0.005). Moreover, there were no significant differences between the three DOTs regarding the inter-peak latency and amplitude ratio of the waves (p <0.005).

The study results showed an overshoot-like electrophysiological effect using ABR. Therefore, an objective test was used to investigate auditory cochlear gain.

This study aimed to evaluate the effects of bilateral carotid artery occlusion on cochlear oxidative stress and hearing status in rats.

The rats were divided into two sets. The first set was used for electrophysiological recording (click and 4 kHz tone burst auditory brainstem responses and electrocochleography) on the day before surgery and then on the first, fourth, and seventh days after surgery. Animals of the second set were used for biochemical analysis. The cochlea of animals in the second set was collected on the first, fourth, and seventh days after carotids occlusion for biochemical analysis. For the control groups, no carotids occlusion was done. For ischemia induction, both common carotid arteries were occluded for 20 minutes.

 Electrophysiological analysis showed that burst auditory brainstem thresholds significantly elevated after common carotid arteries occlusion on the first, fourth, and seventh days after surgery with abnormal electrocochleography results at 75%, 70%, and 85% on the first, fourth, and seventh days after surgery, respectively. The electrophysiological finding confirmed by biochemical results that showed malondialdehyde and nitric oxide levels increased and superoxide dismutase and catalase activities decreased after occlusion in cochlea tissue.

This study showed that bilateral common carotid artery occlusion increases cochlear oxidative stress and induces hearing loss in rats.

One of the major causes of sensorineural hearing loss is Noise-induced hearing loss. Cochlear damage following noise exposure occurs through two major mechanisms: direct mechanical damage and biochemical pathways. Direct mechanical damage causes hair cell loss through mechanical damage of sterreocilia and direct damage of sensory and protective cells. Cochlear damage following noise exposure through biochemical pathway result in cell death through apoptosis or necrosis. The reason for this is Oxidative Stress and generation of reactive oxygen species following noise exposure. This may remain in the cochlea long after noise exposure has been terminated.

In order to review the relationship between Cell death, Oxidative Stress and Noise induce hearing loss, all of the articles in this field published between 1990-2017 in Ovid, ProQuest, and Google Scholar databases were searched.

 This fact shows the importance of preventing apoptosis even after exposure to noise. Understanding noise-induced cochlear damage, especially the importance of free radical expression in the cochlea, can lead to advancements in preserving the hearing.

Cisplatin is one of the most commonly used antineoplastic drugs; nonetheless, its ototoxic dose-limiting side effects have remained a significant challenge in clinical practice. The recognition of the exact template of hearing loss induced by multiple low doses of cisplatin could be of great help in managing the treatment process. The present study aimed to investigate the effects of multiple doses of this drug on the auditory system.

The present study was performed using an experimental guinea pig model in four groups as follows: 1- 0.9% sodium chloride solution, 2- total dose of 7.5 mg/kg Cisplatin, 3- total dose of 10 mg/kg Cisplatin, and 4- total dose of 12.5 mg/kg cisplatin. The drugs were injected as 2.5 mg/kg/daily IP access in all groups. The auditory brainstem response (ABR) test was performed before the treatment and after every injection on a daily basis up to 72 h after the last injection.

There was dose-dependent significant hearing loss in all evaluated frequencies in three cisplatin groups. The general template of induced hearing loss during experimental days was almost the same in groups Cis7.5 and Cis10. In Cis 12.5 group, there was a jump in the threshold shift on the 5th day of the experiment and an upward trend in the function.  

As evidenced by the obtained results, the monitoring of hearing loss after every injection in patients who receive the drug and detecting the exact dose-dependent pattern of the induced hearing loss is of great help in controlling its undesirable destructive side effects on the auditory system.

Electrocochleography is one of the most practically used tests in approaching Meniere's disease (MD). To record reliable response components, the type of applied electrode is of particular importance. The TIP-trode is an appropriate electrode due to its user-friendliness. Gutter electrode can be used in more than 100 subject. This study aimed to compare the results of the Electrocochleography (ECochG) test responses using TIP-trode and the Gutter electrode.

This cross-sectional study was performed on 20 normal subjects and 20 patients with MD, who referred to the Audiology Clinic of Iran University of Medical Sciences. The ECochG response components were randomly recorded with TIP-trode and Gutter-electrode consecutively, and then statistical analysis was accomplished.

The mean impedance, action potential, and summation potential amplitudes were not significantly different between normal subjects and people with MD by using two types of electrodes. Moreover, the mean scores of summation potential/action potential (SP/AP) ratio of the Gutter electrode were higher than that of the TIP-trod. The mean SP/AP ratio between two types of electrodes was statistically significant differences in normal subjects (p = 0.027) and in MD group (p = 0.009).

We demonstrated that the utilization of the Gutter electrode in ECochG assessments was considerably effective and beneficial. It can significantly reduce expenses and be applied in clinical settings. It’s also recommended that 47.22% mean SP/AP amplitude ratio to be considered as upper limit of normality by using the Gutter electrode.

Children with Autism Spectrum Disorder (ASD) and deficits in sensory and cognitive processes (sensory skills, perceptual communication) fail to precept the whole environment in a coherent and meaningful way with a clear definition of coping with it. Therefore, recognizing the components of architecture affecting the behavioral problems of these children seems crucial for architects. The current study aimed to present an environmental design model, i.e., appropriate to the specific sensory and cognitive characteristics of children with ASDs. Such a design could help to facilitate the process of perceiving and proper understanding of the environment in this group.

Considering the research objective, we used a practical approach in this study; the relevant results could serve as models for designing the environment for children with ASDs. Additionally, this was a descriptive-analytical survey in terms of nature. Accordingly, the basis and theories of the target society were used for analyzing and extracting the effective features in introducing environmental design models; consequently, the research model was presented based on it. It is also called a surveying research method because we examined the characteristics of case studies. We collected the required data in two steps. First, the library resources and observed samples were used, and the theoretical model of the research was presented; therefore, after conducting the initial stages of research and recognizing the main characteristics, the required concepts were extracted and extended. These data were applied in the next step. Accordingly, an appropriate manner for the architectural design discussions was established, leading to the architectural design solution. In the second stage, the relevant studies of this model were evaluated by field research method in 3 different case studies of specified schools in Qazvin Province, Iran, to provide a relative understanding of their adaptation to the designed model.

The present study findings revealed that the behavioral disorders of children with ASDs could be explained in 3 areas of sensory–motion, socio–communicational, and cognitive–perceptual. Accordingly, 3 patterns of designing a multisensory environment, spatial modeling, and spatial sequence were presented in the environment of a sensory–diverse model. Furthermore, due to the limited number of specified centers for children with ASDs in Qazvin, 3 relevant schools were evaluated. Regarding the multisensory" pattern, there seems to be no consensus in the previous case studies concerning the design criteria. Therefore, sensory modulation and simulation cannot be observed together in any of them. Applying facilities and materials, visual, tactile, and deep–seated senses have been further provoked; multisensory environments, including provoking and controlling all senses that could not be entirely reached in all these environments were considered. The same was true about environmental modeling. The explored case studies failed to completely meet the design criteria of real–world simulation and functions per daily routines. Respecting creating functions–appropriate behavioral patterns, only one case study has provided relatively more favorable outcomes. The last pattern, spatial sequence, provided a relatively better condition among all investigated case studies. In other words, in the case of spatial hierarchy criteria, 33% of samples reported appropriate situations. Besides, concerning clarity criteria, 33% were evaluated as desirable, and 33% as relatively profitable. The philosophy of these criteria is to define and limit the sensory space of each activity and organize a classroom or even a building in different parts.

Paying attention to the proposed architectural patterns seems to be effective on the central processing system, leading to correcting the behavioral problems of children with ASDs by affecting the sense of environment and its perception process of the environment.

Tinnitus is a common disorder with a considerable amount of distress that affects the patient`s daily life. No objective tools were approved for measuring tinnitus distress. It can be estimated only by subjective scales and questionnaires, albeit, the Electroencephalography (EEG) studies have reported some alterations regarding tinnitus distress network. This study aimed to investigate the correlation between Tinnitus Handicap Inventory (THI) and the recorded EEG data. 

A total of 33 chronic tinnitus cases (9 females) with the mean age of 42.67 years were recruited. Their THI scores were collected, and a 3-minute EEG recorded with eye closed at resting-state. The correlation analysis was performed on THI scores and the current density in the selected Region of Interests (ROIs) concerning the distress network for the eight frequency bands. The patients grouped depending on the THI cutoff point of 56 into low and high THI groups, and then the groups were compared for source analysis and functional connectivity between ROIs using standardized low-resolution brain electromagnetic tomography.

A significant positive correlation was seen between THI scores and the electrical activity in the Anterior Cingulate Cortex (ACC), the prefrontal cortex, and the parahippocampus for an alpha band (P<0.05) and in the ACC for beta (P<0.01). Source analysis showed significant differences with increased activity in the high THI group for alpha, beta and gamma bands. Functional connectivity was also elevated in the high THI group between the ROIs in alpha and beta bands.

THI can be a useful tool for measuring tinnitus distress, and it has a high correlation with EEG data.

The auditory brainstem response (ABR) is one of the most common objective hearing tests conducting in animal and human. The purpose of this study was evaluating the morphology variations of ABR waveforms in rats with low and high rate click stimuli. First, rats with ABR thresholds higher than 55 dB SPL were excluded and total 81 ears remained in study. Absolute and interpeak latencies of wave I, II, IV were evaluated at low (17.7 Hz) and high rate (88.7 Hz) for click stimuli at 120 dB SPL. At low rate stimuli, ABR waveforms showed different morphologies. The most common complex for waves II to IV was wave III placed on downward slope of wave II (71% of cases). Almost the same morphologies were seen at higher rate; but in some waves, it rounded and decreased amplitude. For waves IV-V, the most common morphology was equal amplitude of wave IV and V in low and high rates (35% vs 56%, respectively). Generally, the high rate stimuli didn’t severely change morphology patterns except for later waves. Normal click-evoked ABR could result in different waveforms. Using click stimuli at low and high rate result in different morphology patterns. Recognizing morphology variations of ABR waveforms are essential for detecting any pathological conditions. The high rate stimuli increased latencies, especially for later waves.

Tinnitus, the phantom perception of sound, in which many cortical and subcortical areas are involved has become one of the popular subjects of neuroscience research. Neuroimaging studies have introduced the tinnitus network model to explain the involvement of auditory and non-auditory areas in this perception. In such a model, the cognitive and emotional aspects of tinnitus can be interpreted conveniently. Therefore, this paper aimed to review the neural basis of tinnitus networks, including data from neuroimaging studies, and discuss the clinical implication of this concept, as well. The data from neuroimaging studies were reviewed and discussed in order to complete the overall image of tinnitus network and its correlates such as the distress network, attentional network and other cognitive mechanisms. In addition to the auditory system, the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC) were considered to be important hubs in tinnitus distress network, especially for having important connectivity with the other networks like attention and salience networks. Moreover, the top-down control of DLPFC over the other brain areas was regarded as the most important brain area to be targeted using the non-invasive interventions and the results were compelling. Understanding the network model has helped in optimizing the neuromodulation protocols like electrical stimulation techniques. Thus, the clinical implications of this model can be generalized to the other types of treatments and the outcomes might be satisfying

People might simultaneously be exposed to noise and carbon monoxide in occupational settings. The previous studies revealed that the inhalation of molecular hydrogen (H2) exerts some healing effects on multiple diseases including hearing loss. The levels of free radicals have been shown to increase due to the exposure to noise plus carbon monoxide. This study examined the possible protective effects of hydrogen inhalation following simultaneous exposure to noise and carbon monoxide in Guinea pigs. Twelve Guinea pigs were randomly divided into two different groups: (1) Exposed to noise plus carbon monoxide and (2) exposed to noise plus carbon monoxide along with the inhalation of hydrogen. Auditory brainstem responses (ABRs) at different frequencies of 2, 4, 8, and 16 kHz were measured before and immediately after the exposure. The ABR thresholds measured immediately after the simultaneous exposure to noise and carbon monoxide significantly increased at all frequencies in group 1 while in group 2, the ABR thresholds measured immediately after the inhalation of hydrogen significantly reduced at 4, 8, and 16 kHz (P values < 0.05). This finding indicates that there is a protective effect associated with the inhalation of 2% hydrogen on the development of hearing loss after the simultaneous exposure to noise and carbon monoxide and this effect was fairly significant at higher frequencies.

Caffeine consumes targeted attention to the signal, which is expected to lead to increased noise tolerance and ultimately improved speech perception. In the current study, the effect of short-term caffeine consumption on speech and noise simultaneous reception function was evaluated using acceptable noise level (ANL) test. In this interventional double-blind study, 90 cases (45 male, 45 female) aged 18−34 years were randomly assigned into three groups: the test groups, 3 and 5 mg/kg caffeine, and the control group, just placebo. The ANL test was recorded before and one hour after intervention. The results were compared before and after taking caffeine in three groups. The statistical analysis revealed that there was significant difference in ANL result in dose 3 mg/kg caffeine before and one hour after intervention (p=0.043) and there was a significant difference in ANL result in dose 5 mg/kg caffeine before and one hour after intervention (p=0.001). Also, there was a significant difference in ANL before and one hour after taking caffeine between the group receiving 3 mg/kg dose of caffeine and the 5 mg/kg dose of caffeine (p=0.015). According to the findings of the study, after an hour of caffeine consumption, the ANL decreases. In other words, the individuals tolerate higher levels of speech noise. This is also dependent on the dose of caffeine.

Recent epidemiological evidence indicates that the fetal environment can influence susceptibility to later disease during the lifespan. Prenatal stress exposure alters the programming of the metabolic and endocrine balance of various organs, including the auditory system. The current study aimed at evaluating how prenatal stress influences Auditory Brainstem Responses. Eighteen pregnant Wistar rats were stressed during a one-month gestation by chronic mild stress (CMS, a variable schedule of different stressors). After birth, the offspring’s hearing thresholds and latencies were evaluated and compared with the control group. The hearing thresholds were assessed by recording auditory evoked brainstem responses to 4, 8,12, and 16 kHz tone burst. The results showed that although CMS caused a significant increase in corticosterone in pregnant mothers, the offspring with CMS experience had significantly lower body weight than control animals (P < 0.00) yet there was no difference between hearing sensitivity of prenatally stressed offspring and the control group. However, ABRs showed a marked prolongation in wave II and IV latencies in prenatally stressed rats (P < 0.05). The current data confirmed that prenatal exposure to mild stress is not detrimental to hearing sensitivity. However, these data suggest that prenatal stress can affect the temporal processing of auditory stimuli in the brainstem.

Acceptable noise level (ANL) measures the amount of accepted background noise while listening to the story. In the current study, ANL was carried out in chil­dren with learning disability (LD) and compared with the results of normal children by using examiner- and self-adjusted methods.
Forty seven (25 male, 22 female) normal children with good and better educational background and 46 (27 male, 19 female) LD children ranging in age from 7-12 years old were participated. ANL was assessed using an ear-level loudspeaker in front of children. The differences of ANL, most comfortable level (MCL), and background noise level (BNL) between groups and their relationship between examiner- and self-adjusted procedures were investigated.
Mean ANLs of LD children either in examiner- or self-adjusted methods (8.91±4.66 and 11.00±5.38, respectively) were worse than those of normal children (7.19±3.63 and 9.61±3.41, respectively). The difference between mean ANL of normal and LD children was statistically significant only for examiner-adjusted method (p=0.05). There were also significant differences in BNL between groups for examiner- and self-adjusted method (p ANL is clinically applicable in LD children. Moreover, LD children accept lower background noise; therefore modification of their listening environment is recommended. Because of a strong positive relationship between ANL in examiner- and self-adjusted pro­cedures, both methods can be implemented in different situations.

Cochlear microphonic (CM) is a cochlear AC electric field, recorded within, around, and remote from its sources. Nowadays it can contribute to the differential diagnosis of different auditory pathologies such as auditory neuropathy spectrum disorder (ANSD). The aim of this study was to compare CM waveforms (CMWs) and amplitudes with broad and narrow band stimuli in 25 healthy male young adult Wistar rats.
Using an extratympanic technique in ECochG (Electrocochleography) recording, CMWs in response to click and tonal stimuli with different octave frequencies were recorded at a high intensity level in subjects. The CMW amplitudes were calculated by a graphical user interface (GUI) designed in MATLAB. The data was analyzed by One-way ANOVA test.
The CMW magnitude increased upon an increase in band width stimulation. Across tonal stimuli, the CMW amplitudes at lower frequency tones were larger than those at higher frequency tones. Those findings were statistically significant (P This study found that CMW most likely is a reflection of spatial summation of voltage drops generated by hair cell groups in response to acoustic stimulation. In order to production nature of CM potentials as well as their very small magnitudes especially with tonal stimuli, thus, we recommend using click stimulation for CM potential recording especially in patient with ANSD that CM plays an important role in its differential diagnosis and follow up