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OBJECTIVES To compare the effects of Narrow band CE-Chirps (NB CE-Chirps) and tone bursts (TBs) at 500 Hz and 1000 Hz on the amplitudes and latencies in cervical vestibular evoked myogenic potentials (cVEMPs). DESIGN Thirty-one healthy adult volunteers of varying ages were tested by air conduction at 95 dB nHL. Recording conditions were randomized for each participant and each modality was tested twice. RESULTS NB CE-Chirps showed larger corrected amplitudes than TBs at 500 Hz (p < 0.001) which were themselves larger than NB CE-Chirps and TBs at 1000 Hz (p < 0.001). In older volunteers, NB CE-Chirps 500 and 1000 Hz had significantly higher response rates than TBs 500 Hz (p = 0.039). A negative correlation was observed between the corrected amplitudes and the age of the participants regardless of the stimulus and the frequency studied. The p13 and n23 latencies were not correlated with the age of the subjects. CONCLUSIONS NB CE-Chirps at 500 Hz improved the corrected amplitudes of waveforms in cVEMPs as a result of a better frequency specificity compared with TBs. In the elderly, eliciting cVEMPs at a frequency of 1000 Hz might not be necessary to improve response rates with NB CE-Chirps. Additional studies including a higher number of healthy participants and patients with vestibular disorders are required to confirm these observations.

Discrimination for sound frequency is essential for auditory communications in animals. Here, by combiningin vivocalcium imaging and behavioral assay, we found thatDrosophilalarvae can sense a wide range of sound frequency and the behavioral specificity is mediated with the selectivity of the lch5 chordotonal organ neurons to sounds that forms a combinatorial coding of frequency. We also disclosed that Brivido1 (Brv1) and Piezo-like (Pzl), each expresses in a subset of lch5 neurons and mediate hearing sensation to certain frequency ranges. Intriguingly, mouse Piezo2 can rescuepzl-mutant’s phenotypes, suggesting a conserved role of the Piezo family proteins in high-frequency hearing.

BackgroundDepression induces an early onset of Parkinson’s disease (PD), aggravates dyskinesia and cognitive impairment, and accelerates disease progression. However, it is very difficult to identify and diagnose PD with depression (PDD) in the early clinical stage. Few studies have suggested that the changes in neural networks are associated with PDD, while degree centrality (DC) has been documented to be effective in detecting brain network changes.ObjectivesThe objectives of this study are to explore DC changes between patients with PDD and without depression (PDND) and to find the key brain hubs involved with depression in PD patients.MethodsOne hundred and four PD patients and 54 healthy controls (HCs) underwent brain resting-state functional magnetic resonance imaging. The Data Processing and Analysis of Brain Imaging and Resting-State Functional Magnetic Resonance Data Analysis Toolkit were used for processing and statistical analysis. The DC value of each frequency band was calculated. One-way analysis of variance and a two-sample t-test for post hoc comparison were used to compare the differences of the DC values in different frequency bands among PDD, PDND, and healthy control group. Gaussian random field was used for multiple comparison correction. Pearson correlation analysis was performed between each individual’s DC map and clinical indicators.ResultsThe DC value of different brain regions changed in PDD and PDND in different frequency bands. The prefrontal lobe, limbic system, and basal ganglia were the main brain regions involved. PDD patients showed a wider range and more abnormal brain areas in the slow-4 frequency band (0.027–0.073 Hz) compared to the HCs. PDD showed a decreased DC value in the medial frontal gyrus, bilateral cuneus gyrus, right lingual gyrus, bilateral supplementary motor area (SMA), bilateral superior frontal gyrus, and left paracentral lobule, but an increased DC value in the bilateral brainstem, midbrain, bilateral parahippocampal gyrus, cerebellum, left superior temporal gyrus, bilateral insula, left fusiform gyrus, and left caudate nucleus in the traditional frequency band (0.01–0.08 Hz) compared to PDND patients. PDND patients displayed more abnormal functions in the basal ganglia in the slow-4 frequency band.ConclusionThe DC changes in PDD and PDND are frequency dependent and frequency specific. The medial frontal gyrus, SMA, and limbic system may be the key hubs for depression in PD.

We examined the frequency specificity of amplitude envelope patterns in 4 frequency bands, which universally appeared through factor analyses applied to power fluctuations of critical-band filtered speech sounds in 8 different languages/dialects [Ueda and Nakajima (2017). Sci. Rep., 7 (42468)]. A series of 3 perceptual experiments with noise-vocoded speech of Japanese sentences was conducted. Nearly perfect (92–94%) mora recognition was achieved, without any extensive training, in a control condition in which 4-band noise-vocoded speech was employed (Experiments 1–3). Blending amplitude envelope patterns of the frequency bands, which resulted in reducing the number of amplitude envelope patterns while keeping the average spectral levels unchanged, revealed a clear deteriorating effect on intelligibility (Experiment 1). Exchanging amplitude envelope patterns brought generally detrimental effects on intelligibility, especially when involving the 2 lowest bands ( ≲ 1850 Hz; Experiment 2). Exchanging spectral levels averaged in time had a small but significant deteriorating effect on intelligibility in a few conditions (Experiment 3). Frequency specificity in low-frequency-band envelope patterns thus turned out to be conspicuous in speech perception.

Goal: Functional connectivity (FC) is an important indicator of the brain's state in different conditions, such as rest/task or health/pathology. Here we used high-density electroencephalography coupled to source reconstruction to assess frequency-specific changes of FC during resting state. Specifically, we computed the Small-World Propensity (SWP) index to characterize network small-world architecture across frequencies. Methods: We collected resting state data from healthy participants and built connectivity matrices maintaining the heterogeneity of connection strengths. For a subsample of participants, we also investigated whether the SWP captured FC changes after the execution of a working memory (WM) task. Results: We found that SWP demonstrates a selective increase in the alpha and low beta bands. Moreover, SWP was modulated by a cognitive task and showed increased values in the bands entrained by the WM task. Conclusions: SWP is a valid metric to characterize the frequency-specific behavior of resting state networks. ispartof: IEEE Open Journal of Engineering in Medicine and Biology vol:1 pages:57-64 ispartof: location:United States status: published

Hearing sensitivity has been extensively investigated, often by measuring the auditory brainstem response (ABR). ABR measurements are relatively non-invasive, easy to reproduce, and allow the assessment of sensitivity when psychophysical data are difficult to obtain. However, the experimental methods differ greatly in respect to stimulation, which may result in different audiograms. We used three different methods in the same individual frogs: Stimulating with brief tone bursts (tABR), long-duration tones (ltABR), and masked ABR (mABR) where transients are masked by a long-duration sinusoid, and the sensitivity is assessed by the difference between unmasked and masked ABR. We measured sensitivity in a range from 100 to 3500 Hz, and the resulting audiograms show two sensitivity peaks at 400-600 Hz and 1500-1600 Hz (both sensitive down to 30 dB re. 20 µPa). We found similar results below 1000 Hz, but when stimulating with long-duration tones, the sensitivity decreased more rapidly above this frequency. We showed that the frequency specificity of tone bursts becomes poorly defined with shorter duration at low frequencies. Comparisons between subjectively (visual inspection by researchers) and objectively (thresholds defined by SNR) defined audiograms showed very little variation. In conclusion the mABR method gave the most sensitive audiograms. The tABR method showed a similar audiogram, when using relatively long-duration tone bursts (25 ms). The ltABR method is not a good choice for studying hearing thresholds above 1000 Hz, because of the bias introduced by spike rate saturation in the nerve fibers and their inability to phase lock.

Envelope following responses (EFRs) evoked by the periodicity of voicing in vowels are elicited at the fundamental frequency of voice (f0), irrespective of the harmonics that initiate it. One approach of improving the frequency specificity of vowel stimuli without increasing test-time is by altering the f0 selectively in one or more formants. The harmonics contributing to an EFR can then be differentiated by the unique f0 at which the EFRs are elicited. The advantages of using such an approach would be increased frequency specificity and efficiency, given that multiple EFRs can be evaluated in a certain test-time. However, multiple EFRs elicited simultaneously could interact and lead to altered amplitudes and outcomes. To this end, the present study aimed to evaluate: (i) if simultaneous recording of two EFRs, one elicited by harmonics in the first formant (F1) and one elicited by harmonics in the second and higher formants (F2+), leads to attenuation or enhancement of EFR amplitude, and (ii) if simultaneous measurement of two EFRs affects its accuracy and anticipated efficiency. In a group of 22 young adults with normal hearing, EFRs were elicited by F1 and F2+ bands of /u/, /a/ and /i/ when F1 and F2+ were presented independently (individual), when F1 and F2+ were presented simultaneously (dual), and when F1 or F2+ was presented with spectrally matched Gaussian noise of the other (noise). Repeated-measures analysis of variance indicated no significant group differences in EFR amplitudes between any of the conditions, suggesting minimal between-EFR interactions. Between-participant variability was evident, however, significant changes were evident only in a third of the participants for the stimulus /u/ F1. For the majority of stimuli, the change between individual and dual conditions was positively correlated with the change between individual and noise conditions, suggesting that interaction-based changes in EFR amplitude, when present, were likely due to the restriction of cochlear regions of excitation in the presence of a competing stimulus. The amplitude of residual noise was significantly higher in the dual or noise relative to the individual conditions, although the mean differences were very small (

The cochlea behaves like a bank of band-pass filters, segregating information into different frequency channels. Some aspects of perception reflect processing within individual channels, but others involve the integration of information across them. One instance of this is sound localization, which improves with increasing bandwidth. The processing of binaural cues for sound location has been studied extensively. However, although the advantage conferred by bandwidth is clear, we currently know little about how this additional information is combined to form our percept of space. We investigated the ability of cells in the auditory system of guinea pigs to compare interaural level differences (ILDs), a key localization cue, between tones of disparate frequencies in each ear. Cells in auditory cortex believed to be integral to ILD processing (excitatory from one ear, inhibitory from the other: EI cells) compare ILDs separately over restricted frequency ranges which are not consistent with their monaural tuning. In contrast, cells that are excitatory from both ears (EE cells) show no evidence of frequency-specific processing. Both cell types are explained by a model in which ILDs are computed within separate frequency channels and subsequently combined in a single cortical cell. Interestingly, ILD processing in all inferior colliculus cell types (EE and EI) is largely consistent with processing within single, matched-frequency channels from each ear. Our data suggest a clear constraint on the way that localization cues are integrated: cortical ILD tuning to broadband sounds is a composite of separate, frequency-specific, binaurally sensitive channels. This frequency-specific processing appears after the level of the midbrain. SIGNIFICANCE STATEMENT For some sensory modalities (e.g., somatosensation, vision), the spatial arrangement of the outside world is inherited by the brain from the periphery. The auditory periphery is arranged spatially by frequency, not spatial location. Therefore, our auditory perception of location must be synthesized from physical cues in separate frequency channels. There are multiple cues (e.g., timing, level, spectral cues), but even single cues (e.g., level differences) are frequency dependent. The synthesis of location must account for this frequency dependence, but it is not known how this might occur. Here, we investigated how interaural-level differences are combined across frequency along the ascending auditory system. We found that the integration in auditory cortex preserves the independence of the different-level cues in different frequency regions.

The topological organization underlying the human brain was extensively investigated using resting-state functional magnetic resonance imaging, focusing on a low frequency of signal oscillation from 0.01 to 0.1 Hz. However, the frequency specificities with regard to the topological properties of the brain networks have not been fully revealed. In this study, a novel complementary ensemble empirical mode decomposition (CEEMD) method was used to separate the fMRI time series into five characteristic oscillations with distinct frequencies. Then, the small world properties of brain networks were analyzed for each of these five oscillations in patients (n = 67) with depressed Parkinson’s disease (DPD, n = 20) , non-depressed Parkinson’s disease (NDPD, n = 47) and healthy controls (HC, n = 46). Compared with HC, the results showed decreased network efficiency in characteristic oscillations from 0.05 to 0.12 Hz and from 0.02 to 0.05 Hz for the DPD and NDPD patients, respectively. Furthermore, compared with HC, the most significant inter-group difference across five brain oscillations was found in the basal ganglia (0.01 to 0.05 Hz) and paralimbic-limbic network (0.02 to 0.22 Hz) for the DPD patients, and in the visual cortex (0.02 to 0.05 Hz) for the NDPD patients. Compared with NDPD, the DPD patients showed reduced efficiency of nodes in the basal ganglia network (0.01 to 0.05 Hz). Our results demonstrated that DPD is characterized by a disrupted topological organization in large-scale brain functional networks. Moreover, the CEEMD analysis suggested a prominent dissociation in the topological organization of brain networks between DPD and NDPD in both space and frequency domains. Our findings indicated that these characteristic oscillatory activities in different functional circuits may contribute to distinct motor and non-motor components of clinical impairments in Parkinson’s disease. Electronic supplementary material The online version of this article (doi:10.1007/s11682-016-9514-9) contains supplementary material, which is available to authorized users.

The right anterior insula (rAI) plays a crucial role in generating adaptive behavior by orchestrating multiple brain networks. Based on functional separation findings of the insula and spectral fingerprints theory of cognitive functions, we hypothesize that the hub role of the rAI is region and frequency dependent. Using the Human Connectome Project dataset and backtracking approach, we segregate the rAI into dorsal and ventral parts at frequency bands from slow 6 to slow 3, indicating the frequency dependent functional separation of the rAI. Functional connectivity analysis shows that, within lower than 0.198 Hz frequency range, the dorsal and ventral parts of rAI form a complementary system to synchronize with externally and internally-oriented networks. Moreover, the relationship between the dorsal and ventral rAIs predicts the relationship between anti-correlated networks associated with the dorsal rAI at slow 6 and slow 5, suggesting a frequency dependent regulation of the rAI to brain networks. These findings could improve our understanding of the rAI by supporting the region and frequency dependent function of rAI and its essential role in coordinating brain systems relevant to internal and external environments.

We investigated how physiologically observed forward suppression interacts with stimulus frequency in neuronal responses in the guinea pig auditory cortex. The temporal order and frequency proximity of sounds influence both their perception and neuronal responses. Psychophysically, preceding sounds (conditioners) can make successive sounds (probes) harder to hear. These effects are larger when the two sounds are spectrally similar. Physiological forward suppression is usually maximal for conditioner tones near to a unit's characteristic frequency (CF), the frequency to which a neuron is most sensitive. However, in most physiological studies, the frequency of the probe tone and CF are identical, so the role of unit CF and probe frequency cannot be distinguished. Here, we systemically varied the frequency of the probe tone, and found that the tuning of suppression was often more closely related to the frequency of the probe tone than to the unit's CF, i.e. suppressed tuning was specific to probe frequency. This relationship was maintained for all measured gaps between the conditioner and the probe tones. However, when the probe frequency and CF were similar, CF tended to determine suppressed tuning. In addition, the bandwidth of suppression was slightly wider for off-CF probes. Changes in tuning were also reflected in the firing rate in response to probe tones, which was maximally reduced when probe and conditioner tones were matched in frequency. These data are consistent with the idea that cortical neurons receive convergent inputs with a wide range of tuning properties that can adapt independently.

We investigated how physiologically observed forward suppression interacts with stimulus frequency in neuronal responses in the guinea pig auditory cortex. The temporal order and frequency proximity of sounds influence both their perception and neuronal responses. Psychophysically, preceding sounds (conditioners) can make successive sounds (probes) harder to hear. These effects are larger when the two sounds are spectrally similar. Physiological forward suppression is usually maximal for conditioner tones near to a unit’s characteristic frequency (CF), the frequency to which a neuron is most sensitive. However, in most physiological studies, the frequency of the probe tone and CF are identical, so the role of unit CF and probe frequency cannot be distinguished. Here, we systemically varied the frequency of the probe tone, and found that the tuning of suppression was often more closely related to the frequency of the probe tone than to the unit’s CF, i.e. suppressed tuning was specific to probe frequency. This relationship was maintained for all measured gaps between the conditioner and the probe tones. However, when the probe frequency and CF were similar, CF tended to determine suppressed tuning. In addition, the bandwidth of suppression was slightly wider for off-CF probes. Changes in tuning were also reflected in the firing rate in response to probe tones, which was maximally reduced when probe and conditioner tones were matched in frequency. These data are consistent with the idea that cortical neurons receive convergent inputs with a wide range of tuning properties that can adapt independently.

Cochlear gain reduction via efferent feedback from the medial olivocochlear bundle is frequency specific (Guinan, Curr Opin Otolaryngol Head Neck Surg 18:447-453, 2010). The present study with humans used the Fixed Duration Masking Curve psychoacoustical method (Yasin et al., J Acoust Soc Am 133:4145-4155, 2013a; Yasin et al., Basic aspects of hearing: physiology and perception, pp 39-46, 2013b; Yasin et al., J Neurosci 34:15319-15326, 2014) to estimate the frequency specificity of the efferent effect at the cochlear level. The combined duration of the masker-plus-signal stimulus was 25 ms, within the efferent onset delay of about 31-43 ms (James et al., Clin Otolaryngol 27:106-112, 2002). Masker level (4.0 or 1.8 kHz) at threshold was obtained for a 4-kHz signal in the absence or presence of an ipsilateral 60 dB SPL, 160-ms precursor (200-Hz bandwidth) centred at frequencies between 2.5 and 5.5 kHz. Efferent-mediated cochlear gain reduction was greatest for precursors with frequencies the same as, or close to that of, the signal (gain was reduced by about 20 dB), and least for precursors with frequencies well removed from that of the signal (gain remained at around 40 dB). The tuning of the efferent effect filter (tuning extending 0.5-0.7 octaves above and below the signal frequency) is within the range obtained in humans using otoacoustic emissions (Lilaonitkul and Guinan, J Assoc Res Otolaryngol 10:459-470, 2009; Zhao and Dhar, J Neurophysiol 108:25-30, 2012). The 10 dB bandwidth of the efferent-effect filter at 4000 Hz was about 1300 Hz (Q(10) of 3.1). The FDMC method can be used to provide an unbiased measure of the bandwidth of the efferent effect filter using ipsilateral efferent stimulation.

A method was developed to deliver tonebursts ranging in frequency from 1 to 32 kHz for frequency-specific assessment of the canine cochlea. Brainstem auditory-evoked responses (early latency responses, 0-10 ms) to a click (CS) and to 1-, 2-, 4-, 8-, 12-, 16-, 24-, and 32-kHz toneburst stimulations (TS) were compared at 80-dB sound pressure level stimulus (SPL) intensity in 10 adult dogs. All stimulations yielded a 5-7 positive wave pattern, with the exception of the 1-kHz TS, which evoked a frequency-following response (FFR). Thresholds were lowest for the CS and the 12- and 16-kHz TS. All individual peak latencies for TS were significantly (P < or = .05) longer than for CS. Peak I latencies were significantly (P < or = .05) shorter for the 12- and 16-kHz TS than for the other TS. Interpeak latencies I-V were significantly (P < or = .05) longer for the 4- to 32-kHz TS than for CS. Differences in interpeak latencies I-III were not significant. Amplitudes of waves I and V were significantly (P < or = .05) lower for TS than for CS, except for higher wave V amplitude (P < or = .05) at 2- and 32-kHz TS. Peak I-V amplitude ratios were significantly (P < or = .05) higher for the 2-, 4-, 16-, 24-, and 32-kHz TS and lower for the 8- and 12-kHz TS, compared to CS. We conclude that reproducible information on frequency specificity of the canine cochlea can be obtained by TS. This report provides a normative database for parameters needed to evaluate frequency-specific hearing loss in dogs.

This study examines the usefulness of the upward chirp stimulus developed by Dau et al. [J. Acoust. Soc. Am. 107, 1530-1540 (2000)] for retrieving frequency-specific information. The chirp was designed to produce simultaneous displacement maxima along the cochlear partition by compensating for frequency-dependent traveling-time differences. In the first experiment, auditory brainstem responses (ABR) elicited by the click and the broadband chirp were obtained in the presence of high-pass masking noise, with cutoff frequencies of 0.5, 1, 2, 4, and 8 kHz. Results revealed a larger wave-V amplitude for chirp than for click stimulation in all masking conditions. Wave-V amplitude for the chirp increased continuously with increasing high-pass cutoff frequency while it remains nearly constant for the click for cutoff frequencies greater than 1 kHz. The same two stimuli were tested in the presence of a notched-noise masker with one-octave wide spectral notches corresponding to the cutoff frequencies used in the first experiment. The recordings were compared with derived responses, calculated offline, from the high-pass masking conditions. No significant difference in response amplitude between click and chirp stimulation was found for the notched-noise responses as well as for the derived responses. In the second experiment, responses were obtained using narrow-band stimuli. A low-frequency chirp and a 250-Hz tone pulse with comparable duration and magnitude spectrum were used as stimuli. The narrow-band chirp elicited a larger response amplitude than the tone pulse at low and medium stimulation levels. Overall, the results of the present study further demonstrate the importance of considering peripheral processing for the formation of ABR. The chirp might be of particular interest for assessing low-frequency information.

On a variety of visual tasks, improvement in perceptual discrimination with practice (perceptual learning) has been found to be specific to features of the training stimulus, including retinal location. This specificity has been interpreted as evidence that the learning reflects changes in neuronal tuning at relatively early processing stages. The aim of the present study was to examine the frequency specificity of human auditory perceptual learning in a frequency discrimination task. Difference limens for frequency (DLFs) were determined at 5 and 8 kHz, using a three-alternative forced choice method, for two groups of eight subjects before and after extensive training at one or the other frequency. Both groups showed substantial improvement at the training frequency, and much of this improvement generalized to the nontrained frequency. However, a small but statistically significant component of the improvement was specific to the training frequency. Whether this specificity reflects changes in neural frequency tuning or attentional changes remains unclear.

Whether click-evoked otoacoustic emissions (CEOAEs) have frequency specificity is an issue still subject to debate. In order to resolve this issue, changes in the frequency components of the CEOAE power spectrum, together with changes in compound action potential (CAP) thresholds before and after pure-tone exposure in guinea pigs, were examined. Changes in CAP thresholds immediately before and 1 h after exposure were compared with changes in the frequency components in the CEOAE power spectrum before and 1 h after exposure. The ILO 88 was used for measurement of CEOAEs. Total echo energy in the CEOAE power spectrum was converted into frequency bands of 1000 Hz. Shifts in filtered echo power (FEP) levels correlated maximally with those in CAP thresholds at 0.5 kHz above the same frequency. Stepwise regression indicated that only one step could be entered in a linear regression model using the variable of CAP threshold shifts at 0.5 kHz above the same frequency for all FEP shifts except FEP4.5. The remaining variables played a negligible role, since variance no longer changed when they were included in the regression equation. From these results, it was concluded that CEOAEs display frequency specificity. Influence on CEOAEs from higher frequencies is negligible.

In this study, a preparation was developed which continuously monitored the f2−f1, 2 f1−f2, and 3f1−2 f2 distortion products in guinea pigs, in response to various contralateral and ipsilateral tones and broadband noise. A consistent decline over time in the quadratic distortion product, f2−f1, with continuous ipsilateral stimulation was observed, confirming previous findings by Kirk and Johnstone [Hearing Res. 67, 20–34 (1993)]. Broadband noise applied to the contralateral ear simultaneously increased both the magnitude and the rate of decline. This effect was shown for primaries across all frequencies tested (f2 from 2–16 kHz, f2/f1 ratio of 1.26), though a maximal effect was found for f2 of 4 kHz. Experiments using contralateral tones demonstrated a half-octave shift in the frequency specificity of this effect. A more “immediate” suppression effect on 2 f1−f2 (0.6 dB) was found in animals awakening from anesthesia, though this was even larger for f2−f1 (5.1 dB). Extended ipsilateral stimulation with co...

Both distortion product emissions and transiently evoked emissions typically exhibit an individual fine structure, which seems to be linked to the fine structure of threshold in quiet observable in many normal hearing subjects. However, the recording paradigm for both experiments is rather different. Narrow‐band distortion product emissions are detectable during continuous stimulation with two sinusoids. They represent the nonlinear interaction of the two tones in a stationary condition. Transient evoked emissions on the other hand may be interpreted as a type of impulse response of a nonlinear system. The frequency specificity is comparatively low. The interrelation of both types of emissions is not completely understood until now. To test the hypothesis of a common origin, patterns of spectral fine structure of DPOAE and TEOAE results from normal hearing subjects are compared. In addition, the influence of suppressor tones is investigated in both experiments. Results will be discussed in connection to c...

Auditory brainstem response (ABR) is a useful method in evaluating auditory function in human. To investigate the ABR threshold is more effective than to pursue the trends in each component of ABR. In this study, tone burst sound stimuli were employed and the ABR threshold shift caused by kanamycin administration was investigated in dogs. In a series of monitoring of ABR against short-period auditory lesions, changes in the ABR waveform after intravenous administration of kanamycin were detected. These changes returned gradually and were reversible. The changes in ABR against long-period auditory function disorder were perceived by an increase in the ABR threshold. The ABR threshold shift occurred earlier in the high frequency sounds than in the lower frequency sounds. This is why amino glycoside antibiotics damage the cochlear hair cells in the basal layer and lead to the loss of hearing selectively for high frequency tones. These findings suggest that tracing of the ABR threshold by tone bursts could provide information that has a specificity for frequency in hearing tests and is a useful method in clinical veterinary medicine or/and toxicological tests.

Transiently evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), and spontaneous otoacoustic emission (SOAE) were measured in 45 full-term neonates (68 ears) and 12 preterm neonates (20 ears) with ILO88 & 92. Measurements were performed in the nursery of the obstetrics ward or NICU (not sound proof room) under natural sleeping condition after nursing. No sedating agent was used. TEOAEs were rated “good response” in 61 (89.7%) of 68 full-term neonate ears. DPOAEs were rated “good response” in 40 (71.4%) of 56 full-term neonate ears. SOAEs were detectable in 25 (62.5%) of 40 full-term neonate ears. Considering the high positive rate of TEOAE in full-term neonates and the easy and noninvasive method of measurement, we concluded that TEOAE is useful for auditory screening in neonates. There was failure to detect TEOAEs in 7 ears and the measurements were all performed within 6 days after birth. Some reports claim that residual amnion in the external auditory canal or the middle ear in the first few days after birth causes slight hearing loss. Thus, we expected that making the measurements more than 7 days after birth might yield higher “good response” rates. We sometimes found that the Total Echo Powers of TEOAEs were reduced by the poor condition of the ear probe. Thus, we must be very careful in regard to this technical problem in order to perform accurate examinations. Because of its lower “good response” rate, DPOAE was not as useful for screening as TEOAE. Because of the movements or respiratory noises of the newborn infants, it was hard to detect reliable DPOAEs, particularly in the low frequency range. On the other hand, because of its frequency specificity, particurally at high frequencies, DPOAE will be useful for detecting the partial hearing impairment such as congenital high-tone hearing impairment. It would be difficult to use SOAE as a clinical test. Because it is not an evoked response, its mechanism of generation is not well understood. We expect that following longitudinal changes in SOAE in neonates may yield some information about it.We measured mainly TEOAE in preterm neonates because we had to complete the measurements as soon as possible. High Total Echo Powers of TEOAEs were recorded in most infants over 38 weeks of PCA (post-conceptional age). The earliest case showed reliable TEOAE at 35 weeks PCA. In most cases that could be measured twice on different days, the Total Echo Powers of TEOAE, were higher in the second time. We therefore concluded that TEOAE might serve as an examination for monitoring the maturation of preterm neonate hearing.

Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1-4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3-10 kHz, 95-105 dB SPL, 1-10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r = 0.69, p0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.

Clinical applications of otoacoustic emissions (OAEs) have long been studied since the discovery of this surprising phenomenon by D. T. Kemp in 1978. Although there are at least 4 classes of OAEs, i. e., transiently evoked OAE (EOAE), spontaneous OAE, synchronously evoked OAE and distortion product OAE (DPOAE), most researchers have attempted to evaluate EOAE as a possible measure of cochlear pathology. However, the results only indicate that the EOAE does not provide much information about the fine distribution of cochlear lesions. On the other hand, the measurement of the DPOAE has recently become available as another possible indicator of cochlear function, and has great advantages over EOAE measurement. The results of DPOAE measurement in sensorineural hearing-impaired patients clearly indicate that the DPOAE has excellent frequency specificity. In most cases, the DP-audiogram, a plot of DPOAE level against stimulus frequency, exactly reflects the longitudinally distributed integrity of the cochlear partition. This method may become the most powerful non-invasive tool for the evaluation of cochlear function.

This study examined the neural basis of auditory selective attention using functional magnetic resonance imaging. The main hypothesis stated that attending to a particular sound frequency would significantly enhance the neural response within those tonotopic regions of the auditory cortex sensitive to that frequency. To test this prediction, low- and high-frequency sound sequences were interleaved to produce two concurrent auditory streams. Six normally hearing participants either performed a task which required them to attend to one or the other stream or listened passively to the sounds while functional images were acquired using a high-resolution (1.5 mm × 1.5 mm × 2.5 mm) sequence. Two statistical comparisons identified the attention-specific and general effects of enhancement. The first controlled for task-related processes, while the second did not. Results demonstrated frequency-specific, attention-specific enhancement in the response to the attended frequency, but no response suppression for the unattended frequency. Instead, a general effect of suppression was found in several posterior sites, possibly related to resting-state processes. Furthermore, there was widespread general enhancement across auditory cortex when performing the task compared to passive listening. This enhancement did include frequency-sensitive regions, but was not restricted to them. In conclusion, our results show partial support for frequency-specific enhancement. © 2009 Elsevier B.V. All rights reserved.

Background. Tone-burst otoacoustic emissions (TBOAEs) have not been routinely studied in pediatric populations, although tone burst stimuli have greater frequency specificity compared with click sound stimuli. The present study aimed (1) to determine an appropriate stimulus level for neonatal TBOAE measurements when the stimulus center frequency was 1 kHz, (2) to explore the characteristics of 1 kHz TBOAEs in a neonatal population. Methods. A total of 395 normal neonates (745 ears) were recruited. The study consisted of two parts, reflecting the two study aims. Part I included 40 normal neonatal ears, and TBOAE measurement was performed at five stimulus levels in the range 60-80 dB peSPL, with 5 dB incremental steps. Part II investigated the characteristics of the 1 kHz TBOAE response in a large group of 705 neonatal ears, and provided clinical reference criteria based on these characteristics. Results. The study provided a series of reference parameters for 1 kHz TBOAE measurement in neonates. Based on the results, a suggested stimulus level and reference criteria for 1 kHz TBOAE measures with neonates were established. In addition, time-frequency analysis of the data gave new insight into the energy distribution of the neonatal TBOAE response. Conclusion. TBOAE measures may be a useful method for investigating cochlear function at specific frequency ranges in neonates. However, further studies of both TBOAE time-frequency analysis and measurements in newborns are needed. © 2008 Zhang et al; licensee BioMed Central Ltd., published_or_final_version

Automatic threshold detection techniques are described for auditory steady-state response (ASSR) elicited with a sinusoidally amplitude-modulated tone. The reliability and frequency specificity of ASSR are discussed. When applied to awake adults and detected by phase spectral analysis, 40-Hz ASSR threshold patterns closely resemble their corresponding audiograms. However, 40-Hz ASSR is insufficiently reliable for determining hearing thresholds in young children during sleep. On the other hand, 80-Hz ASSR is detected clearly in sleeping children. Moreover, 80-Hz ASSR threshold patterns also closely resemble the corresponding audiograms. Therefore, 80-Hz ASSR appears to be useful for objective audiometry in children.

When trying to detect a tonal signal in a continuous broadband noise, listeners attend selectively to both the frequency and the duration of the expected signal. However, it is not known whether they monitor separate or combined representations of these two attributes. To investigate this question, a probe-signal method was used to measure the detectability of signals of expected and unexpected durations at two expected frequencies. The four listeners expected only one of two signals to be presented at random: a brief tone at one frequency or a long tone at another frequency. For each signal frequency, the detectability of the signals of unexpected duration decreased to near chance as the difference between the expected and unexpected duration, at that frequency, increased. The frequency specificity of this duration tuning indicates that both the frequency and the duration of an expected stimulus are represented in a single template.

Distortion product otoacoustic emissions (DPOAEs) are thought to stem from the outer hair cells (OHCs) around the normally narrow place tuned to the primary tone stimuli. They are thus said to be frequency-specific: their local absence should accurately pinpoint local OHC damage. Yet the influence of impaired tuning on DPOAE frequency specificity is poorly documented. Mice with local damage to OHCs were examined. Their DPOAEs were frequency-specific in that audiometric notches were accurately tracked. The same cochleae were further impaired by ischemia or furosemide injection inducing strial dysfunction with flat loss of sensitivity and tuning, while the preexisting pattern of damaged OHCs remained unaltered. Despite the loss of cochlear activity, DPOAEs produced by high-level (or =70 dB SPL) primaries remained large in about the same interval where they had been initially normal, i.e., that with nondamaged OHCs, albeit with a slight frequency shift, of -1.1 kHz on average. Thus, the ability of DPOAEs to map structurally intact OHCs cannot be a mere consequence of cochlear tuning as it largely persists in its absence. The key element for this correct mapping is likely part of intact OHC structures (e.g., stereocilia bundles) and must have some tuning of its own.

This study investigated the frequency specificity of the auditory brainstem and middle latency responses to 80 and 90 dB ppe SPL 500-Hz and 90 dB ppe SPL 2000-Hz tonebursts. The stimuli were brief (2-1-2 cycle) linear-gated tonebursts. ABR/MLRs were recorded using two electrode montages: (1) Cz-nape of neck and (2) Cz-ipsilateral earlobe. Cochlear contributions to ABR wave V-Na and MLR waves Na-Pa and Pa-Nb were assessed by plotting notched noise tuning curves which showed amplitudes and latencies as a function of center frequency of the noise masker [Abdala and Folsom, J. Acoust. Soc. Am. 97, 2394 (1995); ibid. 98, 921 (1995)]. Maxima in the response amplitude profiles for the ABR and MLR to 80 dB ppe SPL tonebursts occurred within one-half octave of the nominal stimulus frequency, with minimal contributions to the responses from frequencies greater than one octave away. At 90 dB ppe SPL, contributions came from a slightly broader frequency region for both stimulus frequencies. Thus, the ABR/MLR to 80 dB ppe SPL tonebursts shows good frequency specificity which decreases at 90 dB ppe SPL. No significant differences exist in frequency specificity of: (1) ABR wave V-Na versus MLR waves Na-Pa and Pa- Nb at either stimulus frequency or intensity; and (2) ABR/MLRs recorded using the two electrode montages.

This study investigated the frequency specificity of the auditory brainstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz brief tones using high-pass noise masking. Stimuli were linear- (2-1-2 cycles) and exact-Blackman- (5 cycles) gated tones presented at 80 dB peak-to-peak equivalent (ppe) SPL. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by the effects of high-pass noise masking on response amplitudes and latencies. The high-pass noise results demonstrate that the ABR and the MLR to the 80 dB ppe SPL brief tones show good frequency and place specificity. Changes in ABR or MLR amplitude and latency with high-pass noise masking did not occur as the masker cutoff was decreased from 2 to 3 octaves above the stimulus nominal frequency until it was within one-half octave of this frequency, below which amplitudes rapidly decreased (500- and 2000-Hz tones) and latencies increased (500-Hz tones). No significant differences existed in the frequency specificity of the ABR versus MLR, or in these evoked potentials to exact-Blackman- versus linear-gated tones.

This study investigated the frequency specificity of the auditory brainstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz brief tones using narrow-band derived response analyses of the responses recorded in high-pass masking noise [Oates and Stapells, J. Acoust. Soc. Am. 102, 3597-3608 (1997)]. Stimuli were linear- and exact-Blackman-gated tones presented at 80 dB ppe SPI. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by response amplitude profiles as a function of derived band center frequency. The largest amplitudes of waves V and Na-Pa occurred in the 500- and 707-Hz derived bands in response to the exact-Blackman- and linear-gated 500-Hz tones. The peak in the response amplitude profiles for wave V to both 2000-Hz stimuli was seen in the 2000-Hz derived band. For wave Na-Pa, the maxima in the amplitude profiles occurred in the 2000- and 1410-Hz derived bands for the exact-Blackman- and linear-gated tones. Smaller cochlear contributions to the ABR/MLR were also present at 0.5-1 octave above and below the nominal stimulus frequencies. The ABR/MLR to 500- and 2000-Hz 80 dB ppe SPL tones thus shows good frequency specificity, with no significant differences in the frequency specificity of: (1) ABR versus MLR; (2) these evoked potentials to 500-versus 2000-Hz tones; and (3) responses to exact-Blackman- versus linear-gated tones.

The reliability and frequency specificity of 80‐Hz auditory steady‐state response (80‐Hz ASSR) elicited by sinusoidally amplitude‐modulated (SAM tones) tones and detected by phase coherence were evaluated as a measure of the hearing level in young children. The 80‐Hz ASSR at a carrier frequency of 1000 Hz was monitored in 169 ears of 125 hearing‐impaired children and auditory brainstem response (ABR) elicited by tone pips was examined in 93 ears. Both responses were examined during sleep, and the thresholds were compared with the behavioral hearing threshold, which was determined by standard pure‐tone audiometry or play audiometry. In 24 ears with various patterns of audiogram, 80‐Hz ASSRs were examined at different carrier frequencies, and the threshold patterns were compared with the audiograms to investigate the frequency specificity of ASSR. The correlation coefficient between the threshold of 80‐Hz ASSR and pure‐tone threshold (r=0.863) was higher than that for ABR (r=0.828). The threshold patterns of 80‐Hz ASSR clearly followed the corresponding audiogram patterns in all types of hearing impairment. These findings suggest that 80‐Hz ASSR elicited by SAM tones and detected by phase coherence is a useful audiometric device for the determination of hearing level in a frequency‐specific manner in children.

A tone on tone simultaneous masking paradigm was used to determine tuning curves of ABR in rats. Probe stimuli were 0.5, 0.8, 1.0, 2.0, 4.0-kHz short tone bursts. ABR tuning curves were constructed to define masker intensity that resulted in a 50% reduction in probe-elicited wave-V amplitude. The frequency specificity of each probe stimulus was evaluated by Q10 and the maximum masker frequency (MMF) calculated for the tuning curves.Q10's were gradually increased with the increase in rise time. However, a prolongation of the rise time beyond 2 cycles of probe frequency yielded little improvement in Q10. Maximum masker frequencies (MMF) of the tuning curves were not necessarily equal to the frequency of probe without the 2.0-kHz. For the 0.5, 0.8, 1.0-kHz probe, the MMF of the tuning curves showed higher values than the frequency of probe. For the 4.0-kHz probe, the MMF of the tuning curves showed lower values than the frequency of probe.These rusults indicate that the short tone burst stimuli may enable to assess certain auditory function at different frequencies, and they have wider frequencies' spread of the cochlear area around stimulus frequencies.

In order to establish the application of action potentials (AP) of the cochlear nerve and brain stem auditory evoked response (BSR) in clinical audiology, the frequency specificity of them was studied using the special masking techniques.The change of AP and BSR latencies and amplitudes of white noise evoked responses were observed using the high and low pass filtered masking noise. Secondaly the band stop (reject) noise was produced during the tone pip stimuli by the frequency selective masking.According to the first examination, AP responses depended on the frequency range of cochlear partitions higher than 2kHz, while those responsive for BSR extended to a octave lower range.It is considered that the latencies of responses are dependent to the most basal part of the cochlear partition, which is stimulated when the stimulus conditions are held constant. The amplitudes of AP are decided by the length of the stimulated cochlear partition, when the stimlus conditions areheld constant and the lower frequency bands of masking are changed.The following results were obtained from the second examination. The thresholds of responses were 5dB above subjective ones to the 4kHz and 81kHz tone pip stimuli.On the other hand AP and BSR thresholds to the 2kHz tone pips were 20dB and 15dB above subjective threshold respectively. The AP responses were not obtained and BSR were unstable to the the tone pips at 1kHz.The intensity-latency curves of AP and BSR were shifted in parallel with the frequency from high to low.It is concluded that the effective frequency of the tone pips were 4kHz or higher for AP, and 2kHz or higher for BSR in clinical application. The frequency selective masking of the band stop noise is necessary for us to obtain the responses from more restricted part of the cochlear partition.

The auditory fields in the cortex of the guinea pig were investigated with microelectrode mapping techniques. Pure tones of varying frequencies and amplitudes were used as acoustic stimuli. Mainly, multiunit activity was recorded. A large tonotopic area is found in the anterior half of the auditory cortex. This area is named the anterior field (field A). Frequency tuning curves of multiunits in field A are generally narrow. Responses to tone stimuli are strong, and latencies are short. Low best frequencies are represented rostrally, high best frequencies caudally. The tonotopy is continuous and quite regular. Field A is narrow dorsally and becomes gradually broader ventrally. Correspondingly, the isofrequency lines slightly diverge from dorsal to ventral. Caudal to the first field, there is a second, smaller tonotopic area. It lies in the dorsal half of the posterior auditory cortex and is therefore named the dorsocaudal field (field DC). The frequency specificity of the cell clusters in this area is as strong as in field A, but the tonotopy is discontinuous: In the dorsal half of field DC, high best frequencies (16-32 kHz) are represented rostrally; the low frequencies (0.5-2.8 kHz) are represented immediately caudal to the high frequencies, while the intermediate frequencies are missing. Ventrally in field DC, the frequency representation is more complete. Except for this discontinuous map, we did not notice any differences between fields A and DC. A third tonotopic field was found rostral to field A. This field extends over a surface of less than 1 mm2 and was named the small field (field S). It contains a complete representation of the frequency range; high best frequencies are located rostrally, low frequencies caudally. The response latencies are slightly longer in field S than in fields A or DC, and the tuning curves are broader. A broad strip of nontonotopic cortex (auditory belt) surrounds fields A and DC caudally. We subdivided this area into the dorsocaudal and the ventrocaudal belt region. In both areas, tuning curves are often broad, and response latencies are longer than in the tonotopic cortex. In the dorsocaudal belt, most multiunits react with a phasic on-response to pure tones; in the ventrocaudal belt, tonic responses occur more frequently. Another nontonotopic region is located in the anterior auditory cortex, rostral to the tonotopic fields, and was therefore named the rostral belt. Tuning curves in this area are broad, latencies are short, and reponse thresholds are often high. In the discussion, the guinea pig is compared with other mammalian species. Species-specific features in the organization of the tonotopic cortex of the guinea pig are revealed.

BSR audiometry was administered to 20 normal and 44 hearing impaired subjects. The hearing impaired group consisted of 15 subjects with flat loss, 17 high tone loss and 12 low tone loss. One-and-a-half cycles of a 500Hz sinusoidal wave (500Hz click) and one cycle of a 3kHz sinusoidal wave (3kHz click) were used as stimuli. Intensities of these stimuli were calibrated by the averaged subjective threshold from 20 normal hearing ears. (dBHL)In normal subjects, the averaged threshold of the BSR evoked by a 500Hz click was 13.1dBHL and by a 3kHz click, 4.2dBHL.BSR frequency specificity was determined by measuring the BSR (to 500Hz and 3kHz clicks) in hearing impaired subjects. The 500Hz click evoked a BSR in subjects whose pure tone audiograms were impaired above 500Hz. Also, in cases of low tone hearing loss, the BSR was evoked at the best-hearing frequency above 500Hz. The 3kHz click evoked a BSR in subjects with hearing impairment above 1kHz.These results indicate that the BSR provide information regarding hearing ability as low frequency as 500Hz.