Contralateral Noise Research Articles

Effect of broadband and narrowband contralateral noise on psychophysical tuning curves and otoacoustic emissions.

The relative effectiveness of narrowband and broadband noises in activating the efferent system was assessed by comparing the effect of contralateral stimulation (CS) with such sounds on psychophysical tuning curves (PTCs) determined in simultaneous masking, using signal frequencies of 1000 or 2000 Hz. To check that the CS stimuli used did activate the efferent system, distortion product otoacoustic emissions (DPOAEs) were also measured in the absence and presence of narrowband and broadband CS. The CS had no consistent effect on the masker level at the tips of the PTCs. A broadband pink noise CS consistently reduced the masker level required for threshold on both the low- and high-frequency sides of the PTCs for the 2000-Hz signal frequency. However, there were no consistent effects of the CS for any other case. The broadband pink noise CS had a greater effect in reducing DPOAE levels than the narrowband CS. The results provide psychophysical evidence supporting the idea that the efferent system is activated more effectively by a broadband than by a narrowband CS, at least for a signal frequency of 2000 Hz.

Peripheral effects of the cortico-olivocochlear efferent system

The auditory efferent system comprises descending pathways from the auditory cortex to the cochlea, allowing modulation of sensory processing even at the most peripheral level. Although the presence of descending circuits that connect the cerebral cortex with olivocochlear neurons have been reported in several species, the functional role of the cortico-olivocochlear efferent system remains largely unknown. We have been studying the influence of cortical descending pathways on cochlear responses in chinchillas. Here, we recorded cochlear microphonics and auditory-nerve compound action potentials in response to tones (1–8 kHz; 30–90 dB SPL) before, during, and after auditory-cortex lidocaine or cooling inactivation (n = 20). In addition, we recorded cochlear potentials in the presence and absence of contralateral noise, before, during, and after auditory-cortex micro-stimulation (2-50 μA, 32 Hz rate) (n = 15). Both types of auditory-cortex inactivation produced changes in the amplitude of cochlear potentials. In addition, in the microstimulation experiments, we found an increase of the suppressive effects of contralateral noise in neural responses to 2–4 kHz tones. In conclusion, we demonstrated that auditory-cortex basal activity exerts tonic influences on the olivocochlear system and that auditory-cortex electrical micro-stimulation enhances the suppressive effects of the acoustic evoked olivocochlear reflex. [Work supported by FONDECYT 1120256; FONDECYT 3130635 and Fundacion Puelma.]

Contralateral Suppression of Distortion Product Otoacoustic Emission in Children with Auditory Processing Disorders

Previous research has demonstrated that the amplitude of evoked emissions decreases in human subjects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is believed to control this phenomenon. Recent research has examined this effect in individuals with auditory processing disorders (APD), specifically with difficulty understanding speech in noise. Results showed transient evoked otoacoustic emissions (TEOAEs) were not affected by contralateral stimulation in these subjects. Much clinical research has measured the function of the MOCB through TEOAEs.This study will use an alternative technique, distortion product otoacoustic emissions (DPOAEs), to examine this phenomenon and evaluate the function of the MOCB. DPOAEs of individuals in a control group with normal hearing and no significant auditory processing difficulties were compared to the DPOAEs of children with significant auditory processing difficulties.Results showed that the suppression effect was observed in the control group at 2kHz with 3kHz of narrowband noise. For the auditory processing disorders group, no significant suppression was observed.Overall, DPOAEs showed suppression with contralateral noise, while the APD group levels increased overall.These results provide further evidence that the MOCB may have reduced function in children with APD.

Efferent-mediated reduction in cochlear gain does not alter tuning estimates from stimulus-frequency otoacoustic emission group delays

The existence of efferent feedback from cortical and subcortical brain centers to the hair cells of the cochlea has been recognized for many years, but the role that efferent neurons play in hearing is not completely known. Stimulation of medial olivocochlear (MOC) efferent neurons suppresses sound-evoked basilar membrane responses and changes the tuning of single auditory nerve fibers in animal models. Both of these effects are linked to a MOC-induced reduction in the gain of the cochlear amplification provided by outer hair cells. To non-invasively examine the link between cochlear suppression and tuning in humans, stimulus-frequency otoacoustic emissions (SFOAEs) were recorded in conditions with and without contralateral acoustic stimulation (CAS) from 28 normal-hearing participants. SFOAEs were measured using clusters of closely-spaced probe-tone frequencies centered near 1.4 and 2.0kHz. An index of cochlear tuning, QERB, was calculated based on measures of SFOAE group delay at both 1.4 and 2.0kHz. A statistically significant (p<0.01) decrease in SFOAE levels acquired during CAS was detected only for the SFOAE cluster centered at 2kHz. No statistically significant differences in QERB were found between conditions with and without CAS at 1.4 and 2.0kHz. These findings suggest that in humans, tuning based on SFOAE group delay estimates is not appreciably altered at cochlear locations with MOC efferent-induced reductions in cochlear gain.

Peripheral auditory tuning for vowels

In this study, 35 young, healthy adults were tested on whether speech-like stimuli evoke a unique response in the auditory efferent system. To this end, descending cortical influences on medial olivocochlear (MOC) activity were indirectly evaluated by studying the effects of contralateral suppression on distortion product otoacoustic emissions (DPOAEs) under four conditions: (a) in the absence of any contralateral noise (Baseline), (b) presence of contralateral broadband noise (Noise Baseline), (c) vowel discrimination-in-noise task (VDN) and (d) tone discrimination-in-noise (TDN) task. A statistically significant release from suppression was evident across all tested DPOAE frequencies (1, 1.5 and 2 kHz) only for the VDN task (p < 0.05), which yielded greater release from suppression than the TDN task. These findings indicate that during active listening in the presence of noise, the MOC activity may be differentially modulated depending on the type of stimulus (vowel vs. tone). Specifically, in the presence of background noise, vowels may show a greater release from suppression in the cochlea than frequency, intensity and duration matched tones.

Division of labor between left and right human auditory cortices during the processing of intensity and duration

Intensity and duration are important parameters for the processing of speech and music. Neuroimaging results on the processing of these parameters in tasks involving the discrimination of stimuli based on these parameters are controversial. Depending on the experimental approach, varying hypotheses on the involvement of the left and right auditory cortices (ACs) have been put forward. The aim of the present functional magnetic resonance imaging (fMRI) study was to find differences and commonalities in location and strength of brain activity during the processing of intensity and duration when the same stimuli have to be actively categorized according to these two parameters. For this we used a recently introduced method to determine lateralized processing in the AC with contralateral noise. Harmonic frequency modulated (FM) tone complexes were presented monaurally without and with contralateral noise. During categorization of the tones according to their intensity, contralateral noise increased activity mainly in the left AC, suggesting a special role for the left AC in this task. During categorization of tones according to their duration, contralateral noise increased activity in both the left and the right AC. This suggests that active categorization of FM tones according to their duration does not involve only the left AC as has been suggested, but also the right AC to a substantial degree. The area around Heschl's sulcus seems to be the most strongly involved during both intensity and duration categorization, albeit with different lateralization. Altogether the results of the present study support the view that the lateralized processing of the same stimuli in the human AC is strongly modulated by the given task (top-down effect).

Distortion-product otoacoustic emissions and contralateral suppression findings in children with Asperger's Syndrome

ObjectivesChildren with Asperger's Syndrome (AS) often demonstrate auditory behaviors such as hypersensitivity to sounds and poor performance in noisy environments. These auditory behaviors may be related to cochlear dysfunction and abnormal medial olivocochlear bundle (MOCB) activity. The objective of this study was to examine the distortion-product otoacoustic emissions (DPOAEs) with and without contralateral white noise to evaluate outer hair cell activity and MOCB activity in children with AS. MethodsA case control study where 18 boys with AS and 18 age-matched control subjects participated in the study. For both groups, DPOAEs were recorded at 4031, 2627, 1969, and 1359Hz f2 frequencies with and without contralateral white noise at 30dB SL. DPOAE SNRs and difference scores were analyzed for possible differences between both groups and age subgroups (young and old children). ResultsIn the quiet condition, there were no significant group or ear differences in DPOAEs SNR. However, DPOAEs SNR were larger at 4031Hz than at lower frequencies in both groups, mostly due to negative effect of background noise on low frequency response. Contralateral noise resulted in both suppression and enhancement of the DPOAE SNRs in 93% of the control group and 90% of the AS group. However, there were no significant differences in suppression and enhancement between the two groups or age subgroups. The young controls had right ear advantage and significantly larger suppression at all frequencies except 4031Hz than old controls. The young children with AS had slight left ear advantage and significantly larger suppression only at 2672Hz compared to the old children with AS. ConclusionsThe results, indicating minor differences in DPOAEs and contralateral suppression and enhancement of DPOAEs between both control and AS groups and age subgroups, suggest subtle differences in the function of the outer hair cells and the MOCB activity. Therefore, other central auditory processing in the temporal lobe, limbic system and autonomic nervous system may be involved in the generation of hypersensitivity to sounds and difficulty understanding in noisy environments in children with AS.

Contralateral efferent reflex effects on threshold and suprathreshold psychoacoustical tuning curves at low and high frequencies.

Medial olivocochlear efferent neurons can control cochlear frequency selectivity and may be activated in a reflexive manner by contralateral sounds. The present study investigated the significance of the contralateral medial olivocochlear reflex (MOCR) on human psychoacoustical tuning curves (PTCs), a behavioral correlate of cochlear tuning curves. PTCs were measured using forward masking in the presence and in the absence of a contralateral white noise, assumed to elicit the MOCR. To assess MOCR effects on apical and basal cochlear regions over a wide range of sound levels, PTCs were measured for probe frequencies of 500 Hz and 4 kHz and for near- and suprathreshold conditions. Results show that the contralateral noise affected the PTCs predominantly at 500 Hz. At near-threshold levels, its effect was obvious only for frequencies in the tails of the PTCs; at suprathreshold levels, its effects were obvious for all frequencies. It was verified that the effects were not due to the contralateral noise activating the middle-ear muscle reflex or changing the postmechanical rate of recovery from forward masking. A phenomenological computer model of forward masking with efferent control was used to explain the data. The model supports the hypothesis that the behavioral results were due to the contralateral noise reducing apical cochlear gain in a frequency- and level-dependent manner consistent with physiological evidence. Altogether, this shows that the contralateral MOCR may be changing apical cochlear responses in natural, binaural listening situations.

Attention-related modulation of auditory brainstem responses during contralateral noise exposure, and concentrated pitch discrimination modulates auditory brainstem responses during contralateral noise exposure

Attention-related modulation of auditory brainstem responses during contralateral noise exposure, and concentrated pitch discrimination modulates auditory brainstem responses during contralateral noise exposure

Postnatal maturation of contralateral DPOAE suppression in a precocious animal model (chinchilla) of the human neonate

Conclusion: In the neonatal chinchilla, the degree of contralateral distortion product otoacoustic emission (DPOAE) suppression and the latency and time constants of suppression are immature for 40–60 days. This suggests that olivocochlear efferent innervation of outer hair cells is not fully mature at birth in this animal model, and this may also be the case for human neonates. Objectives: To track postnatal changes in the dynamics of the olivocochlear efferent system in an animal model with cochlear development at birth similar to that in humans. Methods: Real-time measurements of contralateral DPOAE suppression were made in 79 ears of anaesthetized chinchillas, ranging in age from 1 day to 70 days. An adult control group (13 ears) was also tested. DPOAE (2f1-f2; f2 = 4.4 kHz; f2/f1 = 1.22) input/output functions were measured. Dynamics of contralateral broadband noise suppression were measured, including latency and suppression time constants. Results: DPOAE amplitude input/output functions are immature until 20–30 days postnatally. The maturation period for contralateral suppression amplitude is about 30 days. Latency of onset suppression was 40 ms at birth reducing to adult values (23 ms) at 40 days. The DPOAE suppression time constant was about 350 ms at birth and mature (230 ms) at 60 days.

Effects of chronic noise exposure on speech-in-noise perception in the presence of normal audiometry

To assess auditory processing in noise-exposed subjects with normal audiograms and compare the findings with those of non-noise-exposed normal controls. Ten noise-exposed Royal Air Force aircrew pilots were compared with 10 Royal Air Force administrators who had no history of noise exposure. Participants were matched in terms of age and sex. The subjects were assessed in terms of: pure tone audiometry, transient evoked otoacoustic emissions, suppression of transient evoked otoacoustic emissions in contralateral noise and auditory processing task performance (i.e. masking, frequency discrimination, auditory attention and speech-in-noise). All subjects had normal pure tone audiometry and transient evoked otoacoustic emissions amplitudes in both ears. The noise-exposed aircrew had similar pure tone audiometry thresholds to controls, but right ear transient evoked otoacoustic emissions were larger and speech-in-noise thresholds were elevated in the noise-exposed subjects compared to controls. The finding of poorer speech-in-noise perception may reflect noise-related impairment of auditory processing in retrocochlear pathways. Audiometry may not detect early, significant noise-induced hearing impairment.

Maturation of the human medial efferent reflex revisited

Past work applying otoacoustic emissions to gauge maturational status of the medial olivocochlear (MOC) reflex in human newborns has produced mixed results. The present study revisits the question while considering the dual nature of the 2f(1) - f(2) distortion product otoacoustic emission (DPOAE) and expanding measures of medial efferent function. Subjects included premature and term-born neonates, 6-month-old infants and young adults. The MOC reflex was elicited with contralateral acoustic stimulation (CAS) while shifts in amplitude and phase of the DPOAE, and its distortion and reflection components, were monitored. Overall, CAS-elicited reductions in DPOAE level did not differ among age groups. For all ages, the MOC reflex was strongest at frequencies below 1.5 kHz, and the reflection component of the DPOAE was most affected, showing maximally reduced amplitude and shallower phase slope when contralateral noise was presented. Results suggest that the MOC reflex likely reaches maturation prior to full-term birth. However, prematurely born neonates show markedly more episodes of CAS-induced DPOAE level enhancement. This may be due to more intrusive component mixing in this age group or disruptions in the formation of the MOC pathway or synapse in the most premature neonates.

Left auditory cortex is involved in pairwise comparisons of the direction of frequency modulated tones

Evaluating series of complex sounds like those in speech and music requires sequential comparisons to extract task-relevant relations between subsequent sounds. With the present functional magnetic resonance imaging (fMRI) study, we investigated whether sequential comparison of a specific acoustic feature within pairs of tones leads to a change in lateralized processing in the auditory cortex (AC) of humans. For this we used the active categorization of the direction (up vs. down) of slow frequency modulated (FM) tones. Several studies suggest that this task is mainly processed in the right AC. These studies, however, tested only the categorization of the FM direction of each individual tone. In the present study we ask the question whether the right lateralized processing changes when, in addition, the FM direction is compared within pairs of successive tones. For this we use an experimental approach involving contralateral noise presentation in order to explore the contributions made by the left and right AC in the completion of the auditory task. This method has already been applied to confirm the right-lateralized processing of the FM direction of individual tones. In the present study, the subjects were required to perform, in addition, a sequential comparison of the FM direction in pairs of tones. The results suggest a division of labor between the two hemispheres such that the FM direction of each individual tone is mainly processed in the right AC whereas the sequential comparison of this feature between tones in a pair is probably performed in the left AC.

Evaluation of Masking Effects on Speech Perception in Patients With Unilateral Chronic Tinnitus Using the Hearing in Noise Test

To verify that tinnitus itself could disturb speech perception and to evaluate the effects of masking noise on speech perception ability in the patients with normal hearing but unilateral chronic tinnitus using the hearing in noise test. Prospective, nonrandomized study. Between June 2009 and May 2011, we enrolled 20 patients with normal hearing and subjective unilateral tinnitus that had persisted for more than 12 months, along with 20 healthy controls of the same age. All subjects were evaluated using audiologic examinations, the tinnitus handicap inventory, and the Korean version of the Hearing in Noise Test (K-HINT) to assess characteristics of tinnitus and speech perception ability in various noisy situations. Reception threshold for speech (RTS) in a quiet environment and signal-to-noise ratio (SNR) in various conditions of noise were significantly higher in the tinnitus than in the control group, regardless of whether noise came from the front, right, or left (p < 0.05). When the tinnitus group was subdivided according to the site of noise exposure, the mean SNR of the contralateral noise group was -7.9 ± 1.4 dB, which was significantly higher than the ipsilateral noise (-9.1 ± 1.8 dB) or control group (right, -10.0 ± 0.6 dB; left, -10.1 ± 0.5 dB) (p < 0.05). In addition, there was no significant difference between ipsilateral noise and control groups. From this study, we showed that tinnitus itself could adversely affect speech perception ability by increasing both RTS and SNR in the tinnitus patients in comparison with healthy controls. In addition, we suggest that proper level of noise on the site of tinnitus might be helpful to increase speech perception in the patients who experience chronic subjective tinnitus.

Inhaled toluene can modulate the effects of anesthetics on the middle-ear acoustic reflex

Toluene (Tol) is an organic solvent widely used in the industry. It is also abused as an inhaled solvent, and can have deleterious effects on hearing. Recently, it was demonstrated that Tol has both anticholinergic and antiglutamatergic effects, and that it also inhibits voltage-dependent Ca2+ channels. This paper describes a study of the effects of inhaled Tol on rats anesthetized with isoflurane, pentobarbital, or a mixture of ketamine/xylazine. Hearing was tested using distortion product oto-acoustic emissions (DPOAEs) associated with a contralateral noise to evaluate contraction of the middle-ear muscles. This allowed us to assess the interactions between the effects of Tol and anesthesia on the central nervous system (CNS). Although both anesthetics and Tol are known to inhibit the middle-ear acoustic reflex, our data indicated that inhaled Tol counterbalances the effects of anesthetic in a dose-dependent manner. In other terms, Tol can increase the amplitude of the middle-ear reflex in anesthetized rats, whatever the nature of the anesthetic used. This indicates that inhaling Tol (a Ca2+-channel-blocking drug) modifies the potency of anesthesia, and thereby the amplitude of the middle-ear reflex.

From otoacoustic emission to late auditory potentials P300: the inhibitory effect.

This study verifies the effects of contralateral noise on otoacoustic emissions and auditory evoked potentials. Short, middle and late auditory evoked potentials as well as otoacoustic emissions with and without white noise were assessed. Twenty-five subjects, normal-hearing, both genders, aged 18 to 30 years, were tested . In general, latencies of the various auditory potentials were increased at noise conditions, whereas amplitudes were diminished at noise conditions for short, middle and late latency responses combined in the same subject. The amplitude of otoacoustic emission decreased significantly in the condition with contralateral noise in comparison to the condition without noise. Our results indicate that most subjects presented different responses between conditions (with and without noise) in all tests, thereby suggesting that the efferent system was acting at both caudal and rostral portions of the auditory system.

Effect of broadband contralateral noise on distortion product otoacoustic emissions and psychophysical tuning curves

The main purpose of this work was to describe an influence of contralateral stimulation (CS) on distortion products otoacoustic emissions (DPOAEs) and psychophysical tuning curves (PTCs). The fast method for determining PTCs was used in the study. DPOAEs and PTCs were measured in two modes: in the presence or absence of CS. The CS was a broadband noise at a level of 50 SPL. The primary tones with frequencies f1 and f2, (f2/f1 = 1.21) were presented at levels of L1 = 60 dB SPL, and L2 = 50 dB SPL. A pulsed sinusoidal signal at a sensation level (SL) of 10 dB was used in the measurements of the PTC. The signal frequency was 1 or 2 kHz. Ten normal-hearing subjects participated in this study. The CS caused a decrease in the level of the DPOAEs (suppression effect) in 90% of cases, in the whole frequency range of f2 (i.e. from 845 to 6200 Hz). The maximum suppression of the DPOAE level occurs for the f2 frequency from 1 to 2 kHz. For both signal frequencies the CS significantly reduces the sharpness of the PTCs. The CS has a significant effect on decreasing the quality factor (Q10) of PTCs.

Patient‐reported speech in noise difficulties and hyperacusis symptoms and correlation with test results

To compare self-reported symptoms of difficulty hearing speech in noise and hyperacusis in adults with auditory processing disorders (APDs) and normal controls; and to compare self-reported symptoms to objective test results (speech in babble test, transient evoked otoacoustic emission [TEOAE] suppression test using contralateral noise). A prospective case-control pilot study. Twenty-two participants were recruited in the study: 10 patients with reported hearing difficulty, normal audiometry, and a clinical diagnosis of APD; and 12 normal age-matched controls with no reported hearing difficulty. All participants completed the validated Amsterdam Inventory for Auditory Disability questionnaire, a hyperacusis questionnaire, a speech in babble test, and a TEOAE suppression test using contralateral noise. Patients had significantly worse scores than controls in all domains of the Amsterdam Inventory questionnaire (with the exception of sound detection) and the hyperacusis questionnaire (P < .005). Patients also had worse TEOAE suppression test results in both ears than controls; however, this result was not significant after Bonferroni correction. Strong correlations were observed between self-reported symptoms of difficulty hearing speech in noise and speech in babble test results in the right ear (ρ = 0.624, P = .002), and between self-reported symptoms of hyperacusis and TEOAE suppression test results in the right ear (ρ = -0.597 P = .003). There was no significant correlation between the two tests. A strong correlation was observed between right ear speech in babble and patient-reported intelligibility of speech in noise, and right ear TEOAE suppression by contralateral noise and hyperacusis questionnaire.

Contralateral-noise effects on cochlear responses in anesthetized mice are dominated by feedback from an unknown pathway

Suppression of ipsilateral distortion product otoacoustic emissions (DPOAEs) by contralateral noise is used in humans and animals to assay the strength of sound-evoked negative feedback from the medial olivocochlear (MOC) efferent pathway. However, depending on species and anesthesia, contributions of other feedback systems to the middle or inner ear can cloud the interpretation. Here, contributions of MOC and middle-ear muscle reflexes, as well as autonomic feedback, to contra-noise suppression in anesthetized mice are dissected by selectively eliminating each pathway by surgical transection, pharmacological blockade, or targeted gene deletion. When ipsilateral DPOAEs were evoked by low-level primaries, contra-noise suppression was typically ~1 dB with contra-noise levels around 95 dB SPL, and it always disappeared upon contralateral cochlear destruction. Lack of middle-ear muscle contribution was suggested by persistence of contra-noise suppression after paralysis with curare, tensor tympani cauterization, or section of the facial nerve. Contribution of cochlear sympathetics was ruled out by studying mutant mice lacking adrenergic signaling (dopamine β-hydroxylase knockouts). Surprisingly, contra-noise effects on low-level DPOAEs were also not diminished by eliminating the MOC system pharmacologically (strychnine), surgically, or by deletion of relevant cholinergic receptors (α9/α10). In contrast, when ipsilateral DPOAEs were evoked by high-level primaries, the contra-noise suppression, although comparable in magnitude, was largely eliminated by MOC blockade or section. Possible alternate pathways are discussed for the source of contra-noise-evoked effects at low ipsilateral levels.

Modeling the Anti-masking Effects of the Olivocochlear Reflex in Auditory Nerve Responses to Tones in Sustained Noise

The medial olivocochlear reflex (MOCR) has been hypothesized to provide benefit for listening in noise. Strong physiological support for an anti-masking role for the MOCR has come from the observation that auditory nerve (AN) fibers exhibit reduced firing to sustained noise and increased sensitivity to tones when the MOCR is elicited. The present study extended a well-established computational model for normal-hearing and hearing-impaired AN responses to demonstrate that these anti-masking effects can be accounted for by reducing outer hair cell (OHC) gain, which is a primary effect of the MOCR. Tone responses in noise were examined systematically as a function of tone level, noise level, and OHC gain. Signal detection theory was used to predict detection and discrimination for different spontaneous rate fiber groups. Decreasing OHC gain decreased the sustained noise response and increased maximum discharge rate to the tone, thus modeling the ability of the MOCR to decompress AN fiber rate-level functions. Comparing the present modeling results with previous data from AN fibers in decerebrate cats suggests that the ipsilateral masking noise used in the physiological study may have elicited up to 20 dB of OHC gain reduction in addition to that inferred from the contralateral noise effects. Reducing OHC gain in the model also extended the dynamic range for discrimination over a wide range of background noise levels. For each masker level, an optimal OHC gain reduction was predicted (i.e., where maximum discrimination was achieved without increased detection threshold). These optimal gain reductions increased with masker level and were physiologically realistic. Thus, reducing OHC gain can improve tone-in-noise discrimination even though it may produce a “hearing loss” in quiet. Combining MOCR effects with the sensorineural hearing loss effects already captured by this computational AN model will be beneficial for exploring the implications of their interaction for the difficulties hearing-impaired listeners have in noisy situations.