Project description:Hearing loss is a major health problem and psychological burden in humans. Mouse models offer a possibility to elucidate genes involved in the underlying developmental and pathophysiological mechanisms of hearing impairment. To this end, large-scale mouse phenotyping programs include auditory phenotyping of single-gene knockout mouse lines. Using the auditory brainstem response (ABR) procedure, the German Mouse Clinic and similar facilities worldwide have produced large, uniform data sets of averaged ABR raw data of mutant and wildtype mice. In the course of standard ABR analysis, hearing thresholds are assessed visually by trained staff from series of signal curves of increasing sound pressure level. This is time-consuming and prone to be biased by the reader as well as the graphical display quality and scale.In an attempt to reduce workload and improve quality and reproducibility, we developed and compared two methods for automated hearing threshold identification from averaged ABR raw data: a supervised approach involving two combined neural networks trained on human-generated labels and a self-supervised approach, which exploits the signal power spectrum and combines random forest sound level estimation with a piece-wise curve fitting algorithm for threshold finding.We show that both models work well and are suitable for fast, reliable, and unbiased hearing threshold detection and quality control. In a high-throughput mouse phenotyping environment, both methods perform well as part of an automated end-to-end screening pipeline to detect candidate genes for hearing involvement. Code for both models as well as data used for this work are freely available.
Project description:ObjectivesTimely assessments are critical to providing early intervention and better hearing and spoken language outcomes for children with hearing loss. To facilitate faster diagnostic hearing assessments in infants, the authors developed the parallel auditory brainstem response (pABR), which presents randomly timed trains of tone pips at five frequencies to each ear simultaneously. The pABR yields high-quality waveforms that are similar to the standard, single-frequency serial ABR but in a fraction of the recording time. While well-documented for standard ABRs, it is yet unknown how presentation rate and level interact to affect responses collected in parallel. Furthermore, the stimuli are yet to be calibrated to perceptual thresholds. Therefore, this study aimed to determine the optimal range of parameters for the pABR and to establish the normative stimulus level correction values for the ABR stimuli.DesignTwo experiments were completed, each with a group of 20 adults (18-35 years old) with normal-hearing thresholds (≤20 dB HL) from 250 to 8000 Hz. First, pABR electroencephalographic (EEG) responses were recorded for six stimulation rates and two intensities. The changes in component wave V amplitude and latency were analyzed, as well as the time required for all responses to reach a criterion signal-to-noise ratio of 0 dB. Second, behavioral thresholds were measured for pure tones and for the pABR stimuli at each rate to determine the correction factors that relate the stimulus level in dB peSPL to perceptual thresholds in dB nHL.ResultsThe pABR showed some adaptation with increased stimulation rate. A wide range of rates yielded robust responses in under 15 minutes, but 40 Hz was the optimal singular presentation rate. Extending the analysis window to include later components of the response offered further time-saving advantages for the temporally broader responses to low-frequency tone pips. The perceptual thresholds to pABR stimuli changed subtly with rate, giving a relatively similar set of correction factors to convert the level of the pABR stimuli from dB peSPL to dB nHL.ConclusionsThe optimal stimulation rate for the pABR is 40 Hz but using multiple rates may prove useful. Perceptual thresholds that subtly change across rate allow for a testing paradigm that easily transitions between rates, which may be useful for quickly estimating thresholds for different configurations of hearing loss. These optimized parameters facilitate expediency and effectiveness of the pABR to estimate hearing thresholds in a clinical setting.
Project description:Previous studies report prolonged auditory brainstem response (ABR) in children and adults with autism spectrum disorder (ASD). Despite its promise as a biomarker, it is unclear whether healthy newborns who later develop ASD also show ABR abnormalities. In the current study, we extracted ABR data on 139,154 newborns from their Universal Newborn Hearing Screening, including 321 newborns who were later diagnosed with ASD. We found that the ASD newborns had significant prolongations of their ABR phase and V-negative latency compared with the non-ASD newborns. Newborns in the ASD group also exhibited greater variance in their latencies compared to previous studies in older ASD samples, likely due in part to the low intensity of the ABR stimulus. These findings suggest that newborns display neurophysiological variation associated with ASD at birth. Future studies with higher-intensity stimulus ABRs may allow more accurate predictions of ASD risk, which could augment the universal ABR test that currently screens millions of newborns worldwide. LAY SUMMARY: Children with autism spectrum disorder (ASD) have slow brain responses to sounds. We examined these brain responses from newborns' hearing tests and found that newborns who were later diagnosed with autism also had slower brain responses to sounds. Future studies might use these findings to better predict autism risk, with a hearing test that is already used on millions of newborns worldwide.
Project description:The frequency-specific tone-evoked auditory brainstem response (ABR) is an indispensable tool in both the audiology clinic and research laboratory. Most frequently, the toneburst ABR is used to estimate hearing thresholds in infants, toddlers, and other patients for whom behavioral testing is not feasible. Therefore, results of the ABR exam form the basis for decisions regarding interventions and hearing habilitation with implications extending far into the child's future. Currently, responses are elicited by periodic sequences of toneburst stimuli presented serially to one ear at a time, which take a long time to measure multiple frequencies and intensities, and provide incomplete information if the infant wakes up early. Here, we describe a new method, the parallel ABR (pABR), which uses randomly timed toneburst stimuli to simultaneously acquire ABR waveforms to five frequencies in both ears. Here, we describe the pABR and quantify its effectiveness in addressing the greatest drawback of current methods: test duration. We show that in adults with normal hearing the pABR yields high-quality waveforms over a range of intensities, with similar morphology to the standard ABR in a fraction of the recording time. Furthermore, longer latencies and smaller amplitudes for low frequencies at a high intensity evoked by the pABR versus serial ABR suggest that responses may have better place specificity due to the masking provided by the other simultaneous toneburst sequences. Thus, the pABR has substantial potential for facilitating faster accumulation of more diagnostic information that is important for timely identification and treatment of hearing loss.
Project description:The auditory brainstem response (ABR) is a sub-cortical evoked potential in which a series of well-defined waves occur in the first 10 ms after the onset of an auditory stimulus. Wave V of the ABR, particularly wave V latency, has been shown to be remarkably stable over time in individual listeners. However, little attention has been paid to the reliability of wave I, which reflects auditory nerve activity. This ABR component has attracted interest recently, as wave I amplitude has been identified as a possible non-invasive measure of noise-induced cochlear synaptopathy. The current study aimed to determine whether ABR wave I amplitude has sufficient test-retest reliability to detect impaired auditory nerve function in an otherwise normal-hearing listener. Thirty normal-hearing females were tested, divided equally into low- and high-noise exposure groups. The stimulus was an 80 dB nHL click. ABR recordings were made from the ipsilateral mastoid and from the ear canal (using a tiptrode). Although there was some variability between listeners, wave I amplitude had high test-retest reliability, with an intraclass correlation coefficient (ICC) comparable to that for wave V amplitude. There were slight gains in reliability for wave I amplitude when recording from the ear canal (ICC of 0.88) compared to the mastoid (ICC of 0.85). The summating potential (SP) and ratio of SP to wave I were also quantified and found to be much less reliable than measures of wave I and V amplitude. Finally, we found no significant differences in the amplitude of any wave components between low- and high-noise exposure groups. We conclude that, if the other sources of between-subject variability can be controlled, wave I amplitude is sufficiently reliable to accurately characterize individual differences in auditory nerve function.
Project description:The auditory system provides a valuable experimental model to investigate the role of sensory activity in regulating neuronal membrane properties. In this study, we have investigated the role of activity directly by measuring changes in medial nucleus of the trapezoid body (MNTB) neurons in normal hearing mice subjected to 1-h sound stimulation. Broadband (4-12 kHz) chirps were used to activate MNTB neurons tonotopically restricted to the lateral MNTB, as confirmed by c-Fos-immunoreactivity. Following 1-h sound stimulation a substantial increase in Kv3.1b-immunoreactivity was measured in the lateral region of the MNTB, which lasted for 2 h before returning to control levels. Electrophysiological patch-clamp recordings in brainstem slices revealed an increase in high-threshold potassium currents in the lateral MNTB of sound-stimulated mice. Current-clamp and dynamic-clamp experiments showed that MNTB cells from the sound-stimulated mice were able to maintain briefer action potentials during high-frequency firing than cells from control mice. These results provide evidence that acoustically driven auditory activity can selectively regulate high-threshold potassium currents in the MNTB of normal hearing mice, likely due to an increased membrane expression of Kv3.1b channels.
Project description:Auditory brainstem response (ABR) serves as an objective indication of auditory perception at a given sound level and is nowadays widely used in hearing function assessment. Despite efforts for automation over decades, ABR threshold determination by machine algorithms remains unreliable and thereby one still relies on visual identification by trained personnel. Here, we described a procedure for automatic threshold determination that can be used in both animal and human ABR tests. The method terminates level averaging of ABR recordings upon detection of time-locked waveform through cross-correlation analysis. The threshold level was then indicated by a dramatic increase in the sweep numbers required to produce "qualified" level averaging. A good match was obtained between the algorithm outcome and the human readouts. Moreover, the method varies the level averaging based on the cross-correlation, thereby adapting to the signal-to-noise ratio of sweep recordings. These features empower a robust and fully automated ABR test.
Project description:The deleterious effects of anemia on auditory nerve (AN) development have been well investigated; however, we have previously reported that significant functional consequences in the auditory brainstem response (ABR) can also occur as a consequence of marginal iron deficiency (ID). As the ABR has widespread clinical use, we evaluated the ability of this electrophysiological method to characterize the threshold of tissue ID in rats by examining the relationship between markers of tissue ID and severity of ABR latency defects. To generate various levels of ID, female Long-Evans rats were exposed to diets containing sufficient, borderline, or deficient iron (Fe) concentrations throughout gestation and offspring lifetime. We measured hematological indices of whole body iron stores in dams and offspring to assess the degree of ID. Progression of AN ID in the offspring was measured as ferritin protein levels at different times during postnatal development to complement ABR functional measurements. The severity of ABR deficits correlated with the level of Fe restriction in each diet. The sufficient Fe diet did not induce AN ID and consequently did not show an impaired ABR latency response. The borderline Fe diet, which depleted AN Fe stores but did not cause systemic anemia resulted in significantly increased ABR latency isolated to Peak I.The low Fe diet, which induced anemia and growth retardation, significantly increased ABR latencies of Peaks I to IV. Our findings indicate that changes in the ABR could be related to various degrees of ID experienced throughout development.
Project description:Specific predictions regarding the level dependence of auditory evoked responses near the detection limit were made in a companion modeling study (Lütkenhöner, J Assoc Res Otolaryngol 9:102-121, 2008). Here, these predictions are experimentally tested for auditory brainstem responses (ABR) to Gaussian-shaped 4-kHz tone pulses (full width at half maximum = 0.5 ms) that were presented at sound levels close to the subjective threshold. In the average of over about one million stimulus repetitions (repetition period = 16 ms), the amplitude of ABR wave V showed a smooth transition from a proportional to a logarithmic growth with increasing sound intensity. The latter type of growth corresponds to a linear increase with respect to sound level measured in decibels. Alternatively, the ABR amplitude near the detection limit may be considered a linear function of sound pressure, although-according to the model-this is only an approximation. Data and model are consistent with the view that a sensory threshold does not exist for the auditory modality, in accordance with signal detection theory. Even so, the model may be used to define a quasithreshold that is comparable to the subjective threshold.
Project description:Neural circuits in the auditory brainstem compute interaural time and intensity differences used to determine the locations of sound sources. These circuits display features that are specialized for these functions. The projection from the ventral cochlear nucleus (VCN) to the medial nucleus of the trapezoid (MNTB) body travels along highly myelinated fibers and terminates in the calyx of Held. This monoinnervating synapse emerges during development as multiple inputs are eliminated. We previously demonstrated that elimination of microglia with a colony stimulating factor-1 inhibitor results in impaired synaptic pruning so that multiple calyceal terminals reside on principal cells of MNTB. This inhibitor also resulted in impaired auditory brainstem responses (ABRs), with elevated thresholds and increased peak latencies. Loss of the microglial fractalkine receptor, CX3CR1, decreased peak latencies in the ABR. The mechanisms underlying these effects are not known. One prominent microglial signaling pathway involved in synaptic pruning and plasticity during development and aging is the C1q-initiated compliment cascade. Here we investigated the classical complement pathway initiator, C1q, in auditory brainstem maturation. We found that C1q expression is detected in the MNTB by the first postnatal week. C1q levels increased with age and were detected within microglia and surrounding the soma of MNTB principal neurons. Loss of C1q did not affect microglia-dependent calyceal pruning. Excitatory and inhibitory synaptic markers in the MNTB and LSO were not altered with C1q deletion. ABRs showed that C1q KO mice had normal hearing thresholds but shortened peak latencies. Altogether this study uncovers the developmental time frame of C1q expression in the sound localization pathway and shows a subtle functional consequence of C1q knockdown.