Pure-tone Frequency Research Articles

Delayed-X Harmonics Synthesizer algorithm for low frequency noise removal

As various technologies on noise reduction have improved their performances, slight low frequency noise has become more prominent in quiet environments. Since the traveling of low noise is difficult to be isolated by walls and earplugs, we aim an active noise control embedded in unoccluded headphones. In this case, both desired sounds (e.g., speech) and unwanted noises pass through the opened ears, so the algorithm is required to adapt only the noise separating from the speech (selective cancelation). Therefore, our selected procedure was Delayed-X Harmonics Synthesizer algorithm which produces pure tones in the opposite phase, because the generated pure tones in the low frequency can minimize the damage for the speech quality. To select the frequencies of pure tones, we focused on the fact that noise is more stationary than speech. The targets frequencies were determined by a small frame-variation on the spectra of the error signals. Our simulations demonstrated that the low noise (< 100 Hz) could be reduced by 10dB even in the slight noise condition (SNR = 5dB), while the speech intelligibility (PESQ) was maintained. When our system is embedded in the unoccluded headphones, the users will take daily conversation without any troubles of low noise.

Analysis of the efficacy of fiber laser stapes fenestration in the treatment of 58 cases of otosclerosis and ossicular malformation

Objective: To explore the surgical efficacy of conductive deafness caused by otosclerosis and ossicular malformation with 980 nm fiber laser stapedial floor fenestration. Methods: Data of 58 patients (ears) who were diagnosed with conductive deafness caused by otosclerosis (49 ears) and ossicular malformation (9 ears) treated by 980 nm Diode laser small-fenestra stapedotomy were retrospectively analyzed. Air conduction (AC) thresholds, bone conduction (BC) thresholds, and air-bone gap (ABG) at 0.5, 1, 2, 4 kHz pure tone frequencies were compared before and 3 months after surgery, and the advantages and precautions of 980 nm fiber laser were summarized. Paired t-test (SPSS 26.0 software) was use to analyze the listening data. Results: Fiber optic laser stapes fenestration and artificial stapes implantation were successfully completed in all 57 cases (ears), the hearing of another one patient (ear) with floating malformation of detachment of stapedial floor was lower than that before surgery. Preoperative at 0.5, 1, 2, 4 kHz frequencies of AC thresholds, BC thresholds, and ABG were (65.4±9.7) dB, (27.2±8.9) dB, and (38.2±9.8) dB respectively. Postoperative 3 months at the same frequency of AC thresholds, BC thresholds, and ABG were (42.1±11.3) dB, (26.9±6.6) dB, and (15.2±9.1) dB. Preoperative and postoperative of AC threshold and ABG were statistically significant at 0.5, 1, 2, 4 kHz (t value was 13.270 and13.948, both P<0.01), and yet the BC threshold was not statistically significant before and after surgery at the same frequency (t=0.418, P>0.05). Conclusions: 980 nm fiber laser stapes floor fenestration is an effective treatment for conductive deafness caused by otosclerosis and ossicular malformation.

The association between skeletal muscle mass and sensorineural hearing loss upon cisplatin-based chemoradiotherapy in patients with head and neck squamous cell carcinoma.

Patients with head and neck squamous cell carcinoma (HNSCC) treated with cisplatin-based chemoradiotherapy (CRT) frequently experience irreversible sensorineural hearing loss (SNHL). Patients with low lumbar skeletal muscle index (LSMI) may experience higher serum peak dosages of cisplatin. This study investigated whether pre-treatment low LSMI is associated with increased SNHL upon cisplatin-based CRT. LSMI was assessed using routine pre-treatment CT scans. Pure tone audiometry was performed at baseline and at follow-up to assess treatment-related SNHL. Linear mixed models were used to reveal a potential association between the continuous variable LSMI and SNHL. This retrospective cohort study included 81 patients and found a significant association between low LSMI and increased treatment-related SNHL at pure tone frequencies vital for the perception of speech (averaged of 1, 2, and 4 kHz) (p = 0.048). HNSCC patients with low LSMI suffer increased treatment-related SNHL upon cisplatin-based CRT.

Psilocybin decreases neural responsiveness and increases functional connectivity while preserving pure-tone frequency selectivity in mouse auditory cortex.

Psilocybin is a serotonergic psychedelic believed to have therapeutic potential for neuropsychiatric conditions. Despite well-documented prevalence of perceptual alterations, hallucinations, and synesthesia associated with psychedelic experiences, little is known about how psilocybin affects sensory cortex or alters the activity of neurons in awake animals. To investigate, we conducted two-photon imaging experiments in auditory cortex of awake mice and collected video of free-roaming mouse behavior, both at baseline and during psilocybin treatment. In comparison with pre-dose neural activity, a 2 mg/kg ip dose of psilocybin initially increased the amplitude of neural responses to sound. Thirty minutes post-dose, behavioral activity and neural response amplitudes decreased, yet functional connectivity increased. In contrast, control mice given intraperitoneal saline injections showed no significant changes in either neural or behavioral activity across conditions. Notably, neuronal stimulus selectivity remained stable during psilocybin treatment, for both tonotopic cortical maps and single-cell pure-tone frequency tuning curves. Our results mirror similar findings regarding the effects of serotonergic psychedelics in visual cortex and suggest that psilocybin modulates the balance of intrinsic versus stimulus-driven influences on neural activity in auditory cortex.NEW & NOTEWORTHY Recent studies have shown promising therapeutic potential for psychedelics in treating neuropsychiatric conditions. Musical experience during psilocybin-assisted therapy is predictive of treatment outcome, yet little is known about how psilocybin affects auditory processing. Here, we conducted two-photon imaging experiments in auditory cortex of awake mice that received a dose of psilocybin. Our results suggest that psilocybin modulates the roles of intrinsic neural activity versus stimulus-driven influences on auditory perception.

PSYCHOACOUSTICS-WEB: A free online tool for the estimation of auditory thresholds

PSYCHOACOUSTICS-WEB is an online tool written in JavaScript and PHP that enables the estimation of auditory sensory thresholds via adaptive threshold tracking. The toolbox implements the transformed up-down methods proposed by Levitt (Journal of the Acoustical Society of America, 49, 467-477, (1971) for a set of classic psychoacoustical tasks: frequency, intensity, and duration discrimination of pure tones; duration discrimination and gap detection of noise; and amplitude modulation detection with noise carriers. The toolbox can be used through a common web browser; it works with both fixed and mobile devices, and requires no programming skills. PSYCHOACOUSTICS-WEB is suitable for laboratory, classroom, and online testing and is designed for two main types of users: an occasional user and, above all, an experimenter using the toolbox for their own research. This latter user can create a personal account, customise existing experiments, and share them in the form of direct links to further users (e.g., the participants of a hypothetical experiment). Finally, because data storage is centralised, the toolbox offers the potential for creating a database of auditory skills.

Acoustic stimulation of the human round window by laser-induced nonlinear optoacoustics.

The feasibility of low frequency pure tone generation in the inner ear by laser-induced nonlinear optoacoustic effect at the round window was demonstrated in three human cadaveric temporal bones (TB) using an integral pulse density modulation (IPDM). Nanosecond laser pulses with a wavelength in the near-infrared (NIR) region were delivered to the round window niche by an optical fiber with two spherical lenses glued to the end and a viscous gel at the site of the laser focus. Using IPDM, acoustic tones with frequencies between 20Hz and 1kHz were generated in the inner ear. The sound pressures in scala tympani and vestibuli were recorded and the intracochlear pressure difference (ICPD) was used to calculate the equivalent sound pressure level (eq. dB SPL) as an equivalent for perceived loudness. The results demonstrate that the optoacoustic effect produced sound pressure levels ranging from 140eq. dB SPL at low frequencies ≤ 200Hz to 90eq. dB SPL at 1kHz. Therefore, the produced sound pressure level is potentially sufficient for patients requiring acoustic low frequency stimulation. Hence, the presented method offers a potentially viable solution in the future to provide the acoustic stimulus component in combined electro-acoustic stimulation with a cochlear implant.

Digits-in-Noise Test as an Assessment Tool for Hearing Loss and Hearing Aids.

The aim of this study was to examine the relationship between an American English Digits in Noise (DIN) test and commonly used audiological measures to evaluate the DIN test's ability to detect hearing loss and validate hearing aid fitting. QuickSIN and DIN tests were completed by participants with untreated hearing loss (n = 46), prescription hearing aids (n = 15), and over-the-counter (OTC) hearing aids (n = 12). Performance on the QuickSIN showed moderate positive correlations with DIN for untreated hearing loss participants and prescription hearing aid users, but not for OTC hearing aid users. For untreated hearing loss participants, both QuickSIN and DIN tests showed positive moderate to strong correlations with high frequency puretone averages. In OTC users, DIN scores did not significantly change over a 6-month time period and were better when conducted remotely compared to in-person testing. Our results suggest that the DIN test may be a feasible monitoring option for individuals with hearing loss and those fitted with hearing aids. However, due to small sample size in this pilot study, future research is needed to examine DIN test's utility for fitting and validating OTC hearing aids.

Evaluating calcium channel blockers and bisphosphonates as otoprotective agents in cochlear implantation hearing preservation candidates

Objectives Evaluate potential effects of calcium channel blockers (CCB) and bisphosphonates (BP) on residual hearing following cochlear implantation. Methods Medications of 303 adult hearing preservation (HP) candidates (low frequency pure tone average [LFPTA] of 125, 250, and 500 Hz ≤80 dB HL) were reviewed. Postimplantation LFPTA of patients taking CCBs and BPs were compared to controls matched by age and preimplantation LFPTA. Results Twenty-six HP candidates were taking a CCB (N = 14) or bisphosphonate (N = 12) at implantation. Median follow-up was 1.37 years (range 0.22–4.64y). Among subjects with initial HP, 29% (N = 2 of 7) CCB users compared to 50% (N = 2 of 4) controls subsequently lost residual hearing 3–6 months later (OR = 0.40, 95% CI = 0.04–4.32, p = 0.58). None of the four BP patients with initial HP experienced delayed loss compared to 50% (N = 2 of 4) controls with initial HP (OR = 0.00, 95% CI = 0.00–1.95, P = 0.43). Two CCB and one BP patients improved to a LFPTA <80 dB HL following initial unaided thresholds that suggested loss of residual hearing. Discussion There were no significant differences in the odds of delayed loss of residual hearing with CCBs or BPs. Conclusion Further investigation into potential otoprotective adjuvants for maintaining residual hearing following initial successful hearing preservation is warranted, with larger cohorts and additional CCB/BP agents.

Smartphone-Facilitated In-Situ Hearing Aid Audiometry for Community-Based Hearing Testing.

Hearing loss prevalence is increasing, with an estimated 2.5 billion people affected globally by 2050. Scalable service delivery models using innovative technologies and task-shifting are World Health Organization priorities to improve access to hearing care, particularly in low- and middle-income countries. Smartphone-facilitated audiometry in the community using hearing aids covered by noise-attenuating ear cups ("in-situ") could support more accessible hearing care when provided by less trained individuals such as community health workers (CHWs). This study aimed to determine the validity of this method for potential hearing aid fitting. Study objectives included determining the maximum permissible ambient noise level (MPANL), inter-device reliability, clinical threshold accuracy, reliability, and performance in real-world settings. Experiment 1: 15 normal-hearing adult participants were evaluated to determine MPANLs for circumaural Peltor 3M earcups covering Lexie Lumen hearing aids with smartphone-facilitated in-situ audiometry. MPANLs were calculated by measuring the difference in attenuation between thresholds obtained with standard headphones and in-situ hearing aids. Experiment 2: Pure-tone frequency and intensity output of 14 same-model Lexie Lumen hearing aids were measured to determine inter-device reliability. Pure-tone stimuli were measured and analyzed to determine sound pressure levels in decibels and pure-tone frequency when connected to a test box 2cc coupler. Experiment 3: 85 adult participants were tested in a sound booth to determine the accuracy of automated in-situ pure-tone audiometry (PTA) compared to clinical PTA (500, 1000, 2000, 3000, 4000, 6000 Hz) facilitated by an audiologist. The first 39 participants were tested twice to determine test-retest reliability. Experiment 4: In a community setting, 144 adult participants were tested with automated in-situ audiometry facilitated by CHWs using a smartphone app. These participants were subsequently tested with automated mobile PTA (500, 1000, 2000, 4000 Hz). An additional 44 participants were tested twice to determine test-retest reliability. Experiment 1: MPANLs of the Peltor 3M earcup-covered hearing aids were higher than standard headphones across all frequencies, ranging from 24 to 47.3 dB SPL. Experiment 2: Inter-device performance reliability was high, with all inter-device differences across all intensities and frequencies less than 3 dB. Frequency output was consistent and differed less than 0.7% between devices. Experiments 3 and 4: 85.2% and 83.3% of automated in-situ audiometry thresholds were within 10 dB of thresholds obtained in the sound booth and in a community setting, respectively. Acceptable test-retest intraclass correlation coefficient (ICC) was evident across all thresholds obtained in a sound booth (ICC = 0.85 to 0.93) and in a community setting (ICC = 0.83 to 0.97). Smartphone-facilitated in-situ audiometry allows for reliable and valid community-based testing. A simple smartphone user interface and automated in-situ audiometry allow CHWs with minimal training to facilitate the testing. With the additional capability to program hearing aids via the smartphone after the initial test, this approach would have the potential to support widespread access to personalized hearing aid fittings facilitated by CHWs in low- and middle-income countries. This approach also supports self-fitting options based on in-situ thresholds, enabling testing and fitting via over the counter hearing aids.

Predictive model for aminoglycoside induced ototoxicity.

Irreversible hearing loss is a well-known adverse effect of aminoglycosides, however, inability to accurately predict ototoxicity is a major limitation in clinical care. We addressed this limitation by developing a prediction model for aminoglycoside ototoxicity applicable to the general population. We employed a prospective non-drug-resistant tuberculosis (TB), non-HIV/AIDS cohort of 153 adults on Streptomycin based anti-TB therapy. High frequency pure-tone audiometry was done at regular intervals throughout the study. Clinical and audiological predictors of ototoxicity were collated and ototoxic threshold shift from the baseline audiogram computed. The prediction model was developed with logistic regression method by examining multiple predictors of ototoxicity. Series of models were fitted sequentially; the best model was identified using Akaike Information Criterion and likelihood ratio test. Key variables in the final model were used to develop a logit model for ototoxicity prediction. Ototoxicity occurred in 35% of participants. Age, gender, weight, cumulative Streptomycin dosage, social class, baseline pure tone average (PTA) and prior hearing symptoms were explored as predictors. Multiple logistic regression showed that models with age, cumulative dosage and baseline PTA were best for predicting ototoxicity. Regression parameters for ototoxicity prediction showed that yearly age increment raised ototoxicity risk by 5% (AOR = 1.05; CI, 1.01-1.09), and a gram increase in cumulative dosage increased ototoxicity risk by 7% (AOR = 1.05; CI, 1.05-1.12) while a unit change in baseline log (PTA) was associated 254% higher risk of ototoxicity (AOR = 3.54, CI: 1.25, 10.01). Training and validation models had area under the receiver operating characteristic curve as 0.84 (CI, 0.76-0.92) and 0.79 (CI, 0.62-0.96) respectively, showing the model has discriminatory ability. This model can predict aminoglycoside ototoxicity in the general population.

Analysis of clinical audiological characteristics of noise-induced silent hearing loss

Objective: To explore the characteristics of audiology examination of Noise-Induced Hidden Hearing Loss (NIHHL), and then explore its valuable diagnostic methods.Methods: A total of 80 young men aged between 19 and 35 were selected. They were classified into the experimental group with noise exposure history and the control group without noise exposure history, with 40 men in each group. We carried out extended high-frequency audiometry test for good ears; conducted speech in noise measurement and distortion product emission for good ears; DPOAE test, compare and analyze the results of each test.Results: The extended high frequency hearing threshold test results showed that the hearing threshold of the experimental group was larger than that of the control group at the frequency above 8kHz, with significant statistical difference (p &lt; .01). The results of speech audiometry under noise showed that the signal-to-noise ratio loss in the experimental group was greater than that in the control group, with a significant statistical difference (p &lt; .01). The results of otoacoustic emission showed that the signal-to-noise ratio of the experimental group was lower than that of the control group at the frequency of 6 kHz and above, with a statistically significant difference (p &lt; .01). There is a correlation between pure tone audiometry and DPOAE test results at high frequencies (6 kHz: p &lt;. 0001, r = -.478; 8 kHz: p &lt; .0001, r = -.491;) ; There was a correlation between speech audiometry and DPOAE test results under noise (p = .031, r = -.299).Conclusion: Compared with the control group, the extended high frequency pure tone hearing threshold increased or could not be elicited in the experimental group, speech recognition ability decreased significantly under noise, DPOAE was normally elicited but signal-to-noise ratio decreased, and there was a certain correlation between them. The above three audiological examination methods have a certain reference value for early recognition of hidden hearing loss.

Electrically evoked compound action potentials in cochlear implant users with preoperative residual hearing.

Residual hearing in cochlear implant (CI) candidates requires the functional integrity of the nerve in particular regions of the cochlea. Nerve activity can be elicited as electrically evoked compound action potentials (ECAP) after cochlear implantation. We hypothesize that ECAP thresholds depend on preoperative residual hearing ability. In a retrospective study, we analyzed 84 adult cochlear implant users who had received a Nucleus® CI632 Slim Modiolar Electrode and who preoperatively had had residual hearing. Inclusion criteria were severe to profound hearing loss with preoperative measurable hearing in the ear to receive the implant, postlingual hearing loss, German as native language and correct placement of the electrode, inserted completely into the scala tympani. Electrically evoked compound action potential (ECAP) was recorded intraoperatively. The angular insertion was measured for each electrode contact from postoperative computed tomography to estimate the corresponding spiral ganglion frequency. Pure-tone audiometry and allocated ECAP thresholds were tested to investigate possible correlation. The average of hearing thresholds, tested at 0.5, 1, 2, and 4 kHz (4FPTA) was 82 ± 18 (range 47-129) dB HL. The success rate for recording ECAP thresholds was 96.9%. For all comparable pure-tone frequencies (1, 2, 4, and 8 kHz), there was significant correlation between preoperative hearing levels and intraoperative ECAP thresholds (p < 0.001). Higher hearing thresholds are associated with increased ECAP thresholds. In CI candidates with adequate residual hearing, intraoperative electrophysiological measurement records lower thresholds. This outcome may be explained by the neural survival density of the peripheral system, with less neural degeneration.

Extending existing models of cochlear mechanics to emphasize physiological mechanisms that support innate perception of harmonic relations among pure tone frequencies

Tonotopic mapping along the basilar membrane of the cochlear organ of Corti naturally supports a consistent relationship between the physical frequency of a tone and its perception of pitch. For example, higher frequencies tend to be mapped to higher pitch perceptions. Nevertheless, a precise perception of harmonic relations among pure tone frequencies apparently lacks a strong foundation on the tonotopic mapping mechanism alone. We are presenting a supplementary hypothesis based on temporal delays and cross-correlations between delayed signals in the cochlear fluids and the surrounding structures that provide a robust mechanism to establish innate perception of applicable harmonic relations among pure tone frequencies.

The effect of smoking on hearing: The invisible part of the iceberg

Objectives Previous studies have had conflicting results regarding the potential effect of smoking on hearing. One reason for the conflicting results may be the limited number of studies evaluating extended high-frequency hearing thresholds among these studies. Therefore, this study aims to evaluate the potential effect of smoking on hearing using extended high-frequency hearing thresholds. Materials and Methods A total of 80 participants aged 20-30 with normal hearing (0.125-8 kHz hearing thresholds ≤ 15 dB HL) were included in this study. Extended high-frequency hearing thresholds in each ear of all participants were evaluated in the range of 9-20 kHz. The cigarette consumption of smokers was determined according to the Brinkman Index. Results There was a significant difference between the study and control groups in pure-tone hearing thresholds. This difference started to increase after 9 kHz in the right ear and 10 kHz in the left ear. Also, there was a highly positive correlation between Brinkman Index and hearing thresholds at all extended high-frequencies. Conclusion The present study suggests that smoking has a potential effect on hearing, especially on high-frequency hearing thresholds. Also, this is the first study to show from which frequency pure tone hearing thresholds are affected in smoking. Clinicians should not be limited to the frequency range used in the routine audiological evaluation and should not ignore extended high-frequency hearing thresholds not to overlook possible conditions that may affect hearing.

Association between nineteen dietary fatty acids and hearing thresholds: findings from a nationwide survey

IntroductionHearing loss is a prevalent health concern, and dietary factors, such as fatty acid intake, may play a role in its development. The current study aimed to investigate the association between the intake of dietary fatty acids and hearing thresholds among U.S. adults.MethodsThe researchers examined data from the National Health and Nutrition Examination Survey (NHANES), including 7,623 participants with available dietary fatty acid intake and audiometry data. Dietary fatty acid intake was assessed using dietary recalls, and hearing thresholds were measured using pure-tone audiometry. Multivariate linear regression models and smoothing curve fitting were utilized to explore the associations between dietary fatty acid intake and hearing thresholds, adjusting for relevant covariates.ResultsThis study reveals a direct association between both low and high frequency pure tone average (PTA) hearing thresholds and the dietary intake of total saturated fatty acids (SFAs) and total polyunsaturated fatty acids (PUFAs). Conversely, the intake of total monounsaturated fatty acids (MUFAs) demonstrates an inverted U-shaped correlation with low-frequency and high-frequency PTA hearing thresholds, having inflection points at 11.91 (energy (%)) and 10.88 (energy (%)), respectively.ConclusionDietary intake of certain fatty acids may influence hearing thresholds in adults.

Frequency detection, frequency discrimination, and spectro-temporal pattern perception in older and younger typically hearing adults

Elderly adults often experience difficulties in speech understanding, possibly due to age-related deficits in frequency perception. It is unclear whether age-related deficits in frequency perception differ between the apical or basal regions of the cochlea. It is also unclear how aging might differently affect frequency discrimination or detection of a change in frequency within a stimulus. In the present study, pure-tone frequency thresholds were measured in 19 older (61–74 years) and 20 younger (22–28 years) typically hearing adults. Participants were asked to discriminate between reference and probe frequencies or to detect changes in frequency within a probe stimulus. Broadband spectro-temporal pattern perception was also measured using the spectro-temporal modulated ripple test (SMRT). Frequency thresholds were significantly poorer in the basal than in the apical region of the cochlea; the deficit in the basal region was 2 times larger for the older than for the younger group. Frequency thresholds were significantly poorer in the older group, especially in the basal region where frequency detection thresholds were 3.9 times poorer for the older than for the younger group. SMRT thresholds were 1.5 times better for the younger than for the older group. Significant age effects were observed for SMRT thresholds and for frequency thresholds only in the basal region. SMRT thresholds were significantly correlated with frequency thresholds only in the older group. The poorer frequency and spectro-temporal pattern perception may contribute to age-related deficits in speech perception, even when audiometric thresholds are nearly normal.

The National Institute for Occupational Safety and Health recommended exposure level for noise needs to be revised downwards

Noise-induced hearing loss (NIHL) is caused by cumulative occupational and non-occupational noise exposure. The National Institute for Occupational Safety and Health (NIOSH) developed recommendations for occupational noise exposure in 1972, revised in 1998. Fifty years after the NIOSH 85 dBA recommended exposure level (REL) was first published, it needs to be revised downwards. In its calculations, NIOSH assumed that workers have quiet (&amp;lt;60 dBA) when not at work, something no longer true. Everyday public noise exposure now exceeds the Environmental Protection Agency's safe noise level, a time-weighted average of 70 dB for 24 hours, with multiple studies reporting average exposures near 75 dBA. Also, NIOSH calculations were based on occupational studies of material hearing loss measured by limited frequency pure tone audiometry, an insensitive measure of noise-induced auditory damage. Modern audiology techniques include extended range audiometry, speech in noise testing, diffusion product otoacoustic emissions testing, and questions about tinnitus and hyperacusis. Doing the needed research to support downward REL revision, detecting auditory damage in noise-exposed workers with these newer techniques, is a daunting task, but this is necessary both to protect workers and because the NIOSH REL forms the basis for the world's recommendations for non-occupational noise exposure.

Integrating Visual Information into the Auditory Cortex Promotes Sound Discrimination through Choice-Related Multisensory Integration.

An increasing number of studies have shown that cross-modal interaction can occur in early sensory cortices. Yet, how neurons in sensory cortices integrate multisensory cues in perceptual tasks and to what extent this influences behavior is largely unclear. To investigate, we examined visual modulation of auditory responses in the primary auditory cortex (A1) in a two-alternative forced-choice task. During the task, male rats were required to make a behavioral choice based on the pure tone frequency (low vs high) of the self-triggered stimulus to get a water reward. The result showed that the presence of a noninformative visual cue did not uniformly influence auditory response, with frequently enhancing just one of them. Closely correlated with behavioral choice, the visual cue mainly enhanced responsiveness to the auditory cue indicating a movement direction contralateral to A1 being recorded. Operating in this fashion provided A1 neurons a superior capability to discriminate sound during multisensory trials. Concomitantly, behavioral data and decoding analysis revealed that visual cue presence could speed the process of sound discrimination. We also observed this differential multisensory integration effect in well-trained rats when tested with passive stimulation and under anesthesia, albeit to a much lesser extent. We did not see this differentially integrative effect while recording in A1 in another similar group of rats performing a free-choice task. These data suggest that auditory cortex can engage in meaningful audiovisual processing, and perceptual learning can modify its multisensory integration mechanism to meet task requirements.SIGNIFICANCE STATEMENT In the natural environment, visual stimuli are frequently accompanied by auditory cues. Although multisensory integration has traditionally been seen as a feature of associational cortices, recent studies have shown that cross-modal inputs can also influence neuronal activity in primary sensory cortices. However, exactly how neurons in sensory cortices integrate multisensory cues to guide behavioral choice is still unclear. Here, we describe a novel model of multisensory integration used by A1 neurons to shape auditory representations when rats performed a cue-guided task. We found that a task-irrelevant visual cue could specifically enhance the response of neurons in sound guiding to the contralateral choice. This differentially integrative model facilitated sound discrimination and behavioral choice. This result indicates that task engagement can modulate multisensory integration.

Computer-based musical interval training program for Cochlear implant users and listeners with no known hearing loss.

A musical interval is the difference in pitch between two sounds. The way that musical intervals are used in melodies relative to the tonal center of a key can strongly affect the emotion conveyed by the melody. The present study examines musical interval identification in people with no known hearing loss and in cochlear implant users. Pitch resolution varies widely among cochlear implant users with average resolution an order of magnitude worse than in normal hearing. The present study considers the effect of training on musical interval identification and tests for correlations between low-level psychophysics and higher-level musical abilities. The overarching hypothesis is that cochlear implant users are limited in their ability to identify musical intervals both by low-level access to frequency cues for pitch as well as higher-level mapping of the novel encoding of pitch that implants provide. Participants completed a 2-week, online interval identification training. The benchmark tests considered before and after interval identification training were pure tone detection thresholds, pure tone frequency discrimination, fundamental frequency discrimination, tonal and rhythm comparisons, and interval identification. The results indicate strong correlations between measures of pitch resolution with interval identification; however, only a small effect of training on interval identification was observed for the cochlear implant users. Discussion focuses on improving access to pitch cues for cochlear implant users and on improving auditory training for musical intervals.

Computational Modeling of Synchrony in the Auditory Nerve in Response to Acoustic and Electric Stimulation.

Cochlear implants are medical devices that provide hearing to nearly one million people around the world. Outcomes are impressive with most recipients learning to understand speech through this new way of hearing. Music perception and speech reception in noise, however, are notably poor. These aspects of hearing critically depend on sensitivity to pitch, whether the musical pitch of an instrument or the vocal pitch of speech. The present article examines cues for pitch perception in the auditory nerve based on computational models. Modeled neural synchrony for pure and complex tones is examined for three different electric stimulation strategies including Continuous Interleaved Sampling (CIS), High-Fidelity CIS (HDCIS), and Peak-Derived Timing (PDT). Computational modeling of current spread and neuronal response are used to predict neural activity to electric and acoustic stimulation. It is shown that CIS does not provide neural synchrony to the frequency of pure tones nor to the fundamental component of complex tones. The newer HDCIS and PDT strategies restore synchrony to both the frequency of pure tones and to the fundamental component of complex tones. Current spread reduces spatial specificity of excitation as well as the temporal fidelity of neural synchrony, but modeled neural excitation restores precision of these cues. Overall, modeled neural excitation to electric stimulation that incorporates temporal fine structure (e.g., HDCIS and PDT) indicates neural synchrony comparable to that provided by acoustic stimulation. Discussion considers the importance of stimulation rate and long-term rehabilitation to provide temporal cues for pitch perception.