Effect Of Contralateral Noise Research Articles

Effects of contralateral noise on envelope-following responses, auditory-nerve compound action potentials, and otoacoustic emissions measured simultaneously.

This study assessed whether the effects of contralateral acoustic stimulation (CAS) are consistent with eliciting the medial olivocochlear (MOC) reflex for measurements sensitive to outer hair cell (otoacoustic emissions, OAEs), auditory-nerve (AN; compound action potential, CAP), and brainstem/cortical (envelope-following response, EFR) function. The effects of CAS were evaluated for simultaneous measurement of OAEs, CAPs, and EFRs in participants with normal hearing. Clicks were presented at 40 or 98 Hz in three ipsilateral noise conditions (no noise, 45 dB SPL, and 55 dB SPL). For the no noise condition, CAS suppressed or enhanced EFR amplitudes for 40- and 98-Hz clicks, respectively, while CAS had no significant effect on CAP amplitudes. A follow-up experiment using slower rates (4.4-22.2 Hz) assessed whether this insignificant CAS effect on CAPs was from ipsilateral MOC stimulation or AN adaptation; however, CAS effects remained insignificant despite favorable signal-to-noise ratios. CAS-related enhancements of EFR and CAP amplitudes in ipsilateral noise were not observed, contrary to the anti-masking effect of the MOC reflex. EFR and OAE suppression from CAS were not significantly correlated. Thus, the effects of CAS on EFRs may not be solely mediated by the MOC reflex and may be partially mediated by higher auditory centers.

Effect of Contralateral Noise on Speech Intelligibility

In patients with strong asymmetric hearing loss, standard clinical practice involves testing speech intelligibility in the ear with the higher hearing threshold by simultaneously presenting noise to the other ear. However, psychoacoustic and functional magnetic resonance imaging (fMRI) studies indicate that this approach may be problematic as contralateral noise has a disruptive effect on task processing. Furthermore, fMRI studies have revealed that the effect of contralateral noise on brain activity depends on the lateralization of task processing. The effect of contralateral noise is stronger when task-relevant stimuli are presented ipsilaterally to the hemisphere that is processing the task. In the present study, we tested the effect of four different levels of contralateral noise on speech intelligibility using the Oldenburg sentence test (OLSA). Cortical lateralization of speech processing was assessed upfront by using a visual speech test with fMRI. Contralateral OLSA noise of 65 or 80 dB SPL significantly reduced word intelligibility irrespective of which ear the speech was presented to. In participants with left-lateralized speech processing, 50 dB SPL contralateral OLSA noise led to a significant reduction in speech intelligibility when speech was presented to the left ear, i.e. when speech was presented ipsilaterally to the hemisphere that is mainly processing speech. Thus, contralateral noise, as used in standard clinical practice, not only prevents listeners from using the information in the better-hearing ear but may also have the unintended effect of hampering central processing of speech.

The effect of musicianship, contralateral noise, and ear of presentation on the detection of changes in temporal fine structure.

Musicians are better than non-musicians at discriminating changes in the fundamental frequency (F0) of harmonic complex tones. Such discrimination may be based on place cues derived from low resolved harmonics, envelope cues derived from high harmonics, and temporal fine structure (TFS) cues derived from both low and high harmonics. The present study compared the ability of highly trained violinists and non-musicians to discriminate changes in complex sounds that differed primarily in their TFS. The task was to discriminate harmonic (H) and frequency-shifted inharmonic (I) tones that were bandpass filtered such that the components were largely or completely unresolved. The effect of contralateral noise and ear of presentation was also investigated. It was hypothesized that contralateral noise would activate the efferent system, helping to preserve the neural representation of envelope fluctuations in the H and I stimuli, thereby improving their discrimination. Violinists were significantly better than non-musicians at discriminating the H and I tones. However, contralateral noise and ear of presentation had no effect. It is concluded that, compared to non-musicians, violinists have a superior ability to discriminate complex sounds based on their TFS, and this ability is unaffected by contralateral stimulation or ear of presentation.

Putting Research into Practice for Autism Spectrum Disorder

Putting Research into Practice for Autism Spectrum Disorder

Effects of contralateral noise on the 20-Hz auditory steady state response--magnetoencephalography study.

The auditory steady state response (ASSR) is an oscillatory brain response, which is phase locked to the rhythm of an auditory stimulus. ASSRs have been recorded in response to a wide frequency range of modulation and/or repetition, but the physiological features of the ASSRs are somewhat different depending on the modulation frequency. Recently, the 20-Hz ASSR has been emphasized in clinical examinations, especially in the area of psychiatry. However, little is known about the physiological properties of the 20-Hz ASSR, compared to those of the 40-Hz and 80-Hz ASSRs. The effects of contralateral noise on the ASSR are known to depend on the modulation frequency to evoke ASSR. However, the effects of contralateral noise on the 20-Hz ASSR are not known. Here we assessed the effects of contralateral white noise at a level of 70 dB SPL on the 20-Hz and 40-Hz ASSRs using a helmet-shaped magnetoencephalography system in 9 healthy volunteers (8 males and 1 female, mean age 31.2 years). The ASSRs were elicited by monaural 1000-Hz 5-s tone bursts amplitude-modulated at 20 and 39 Hz and presented at 80 dB SPL. Contralateral noise caused significant suppression of both the 20-Hz and 40-Hz ASSRs, although suppression was significantly smaller for the 20-Hz ASSRs than the 40-Hz ASSRs. Moreover, the greatest suppression of both 20-Hz and 40-Hz ASSRs occurred in the right hemisphere when stimuli were presented to the right ear with contralateral noise. The present study newly showed that 20-Hz ASSRs are suppressed by contralateral noise, which may be important both for characterization of the 20-Hz ASSR and for interpretation in clinical situations. Physicians must be aware that the 20-Hz ASSR is significantly suppressed by sound (e.g. masking noise or binaural stimulation) applied to the contralateral ear.

Binaural Electric-Acoustic Interactions Recorded from the Inferior Colliculus of Guinea Pigs: The Effect of Masking Observed in the Central Nucleus of the Inferior Colliculus

ObjectivesTo investigate the electric-acoustic interactions within the inferior colliculus of guinea pigs and to observe how central masking appears in invasive neural recordings of the inferior colliculus (IC).MethodsA platinum-iridium wire was inserted to scala tympani through cochleostomy with a depth no greater than 1 mm for intracochlear stimulation of electric pulse train. A 5 mm 100 µm, single-shank, thin-film, penetrating recording probe was inserted perpendicularly to the surface of the IC in the coronal plane at an angle of 30-40° off the parasagittal plane with a depth of 2.0-2.5 mm. The peripheral and central masking effects were compared using electric pulse trains to the left ear and acoustic noise to the left ear (ipsilateral) and to the right ear (contralateral). Binaural acoustic stimuli were presented with different time delays and compared with combined electric and acoustic stimuli. The averaged evoked potentials and total spike numbers were measured using thin-film electrodes inserted into the central nucleus of the IC.ResultsIpsilateral noise had more obvious effects on the electric response than did contralateral noise. Contralateral noise decreased slightly the response amplitude to the electric pulse train stimuli. Immediately after the onset of acoustic noise, the response pattern changed transiently with shorter response intervals. The effects of contralateral noise were evident at the beginning of the continuous noise. The total spike number decreased when the binaural stimuli reached the IC most simultaneously.ConclusionThese results suggest that central masking is quite different from peripheral masking and occurs within the binaural auditory system, and this study showed that the effect of masking could be observed in the IC recording. These effects are more evident and consistent with the psychophysical data from spike number analyses than with the previously reported gross potential data.

Interference in dichotic listening: the effect of contralateral noise on oscillatory brain networks

Coupling of thalamocortical networks through synchronous oscillations at gamma frequencies (30-80 Hz) has been suggested as a mechanism for binding of auditory sensory information into an object representation, which then becomes accessible for perception and cognition. This study investigated whether contralateral noise interferes with this step of central auditory processing. Neuromagnetic 40-Hz oscillations were examined in young healthy participants while they listened to amplitude-modulated sound in one ear and a multi-talker masking noise in the contralateral ear. Participants were engaged in a gap-detection task, for which their behavioural performance declined under masking. The amplitude modulation of the stimulus elicited steady 40-Hz oscillations with sources in bilateral auditory cortices. Analysis of the temporal dynamics of phase synchrony between source activity and the stimulus revealed two oscillatory components; the first was indicated by an instant onset in phase synchrony with the stimulus while the second showed a 200-ms time constant of gradual increase in phase synchrony after phase resetting by the gap. Masking abolished only the second component. This coincided with masking-related decrease of the P2 wave of the transient auditory-evoked responses whereas the N1 wave, reflecting early sensory processing, was unaffected. Given that the P2 response has been associated with object representation, we propose that the first 40-Hz component is related to representation of low-level sensory input whereas the second is related to internal auditory processing in thalamocortical networks. The observed modulation of oscillatory activity is discussed as reflecting a neural mechanism critical for speech understanding in noise.

Effects of Contralateral Noise on 40-Hz and 80-Hz Auditory Steady-State Responses

The amplitude of 40-Hz auditory steady-state response (ASSR) in response to repeated click or tone pips at levels of 45 to 60 dB SL is reduced by up to 50% by the central masking mechanism if white noise at levels of 40 to 60 dB SL is applied contralaterally. However, the effect of contralateral noise on the elevation of the threshold of ASSR is unknown. The present study investigated the effects of contralateral noise on the threshold measurements of ASSR for 40- and 80-Hz amplitude modulated tones that are widely used in clinical examinations. The effects of contralateral noise on the 40- and 80-Hz ASSRs for amplitude modulated tones at 500 Hz and 2000 Hz were examined in 11 healthy volunteers (10 men and 1 woman, mean age 26.1 years). Contralateral noise consisted of white noise low-pass filtered at 700 and 4000 Hz in the measurements of ASSR at a carrier frequency of 500 and 2000 Hz, respectively. Contralateral noise at a level of 40 dB SL caused no significant psychophysical threshold elevation, caused significant threshold elevation of the 40-Hz ASSR (average 10 to 15 dB), and caused no significant threshold elevation of the 80-Hz ASSR. The different effects on the 40- and 80-Hz ASSRs were probably related to the differences in sources because the 40-Hz ASSR contains more components from the upper auditory pathway that are affected by contralateral masking, whereas the 80-Hz ASSR contains more components from the brain stem. The present results suggest that threshold elevation of the 40-Hz ASSR may occur during clinical measurements using binaural presentation of sounds and cause a possible discrepancy between psychophysical threshold and 40-Hz ASSR measurements.

Suppression of the Pb (P1) component of the auditory middle latency response with contralateral masking

ObjectiveIn this study, the effects of contralateral noise or speech on middle latency response (MLR) components Pa and Pb (P1 or P50) were studied using high rates clicks in normal hearing awake adult subjects. MethodsOne standard (4.88Hz) and four jittered click sequences (24.4, 39.1, 58.6, 78.1Hz) at different mean rates were monaurally presented to ten subjects. The contralateral ears were stimulated with continuous pink noise, recorded speech or no stimulus for control. Overlapping MLR responses to jittered click stimuli were deconvolved using the frequency domain continuous loop averaging deconvolution (CLAD). ResultsThe recordings show that contralateral noise or speech stimulation suppresses Pb component greatly at rates around 40Hz while earlier components (ABR and Pa) are not significantly affected. The suppression of the Pb component is about 50% with some latency reduction. ConclusionsThe results show that the Pb component of the MLR is significantly affected by contralateral stimulus at resonance rates at around 40Hz. It appears that the contralateral noise obliterates the amplitude enlargement due to resonance effect. SignificanceThese findings show that the Pb is generated very differently from the Pa component and strongly inhibited by the contralateral ear. These results also explain the previously observed masking of the 40Hz auditory steady-state responses (ASSR) with contralateral noise.

Otoacoustic emission suppression testing: A clinician's window onto the auditory efferent pathway

There has been considerable progress in the last decade in understanding the role of the auditory efferent pathway. This is exemplified by the development of tests for the suppressive effect of contralateral noise on the production of otoacoustic emissions by the outer hair cells of the cochlea. Suppression of OAEs is demonstrably subserved by the auditory efferent pathway, as carried in the inferior vestibular nerve. Advances in the development of testing the suppressive effects of noise have been paralleled by application to a variety of relevant clinical scenarios, enhancing and refining the use of this test in routine clinical practice. In particular, OAE suppression testing has been proposed in the assessment of cerebello-pontine angle tumours, multiple sclerosis, myasthenia gravis, auditory neuropathy/dys-synchrony and auditory processing disorders. This review considers these advances, along with practical issues and pitfalls in testing. OAE suppression testing is the most widely accessible method ...

Effects of Contralateral Noise on the Measurement of Auditory Threshold

It is well known that sound presented in the contralateral ear can elicit the activity of the olivocochlear (OC) efferent. In the present study, the effects of the addition of contralateral noise on the psychophysical measurements of auditory thresholds were investigated in human subjects with normal hearing. The results obtained in the present study indicate that the addition of contralateral noise at a level of only 20 or 30 dB sound pressure level (SPL) may cause a significant elevation of the auditory threshold in the mid-frequency area (usually 2-3 dB). When the level of contralateral noise was elevated, the elevation of the auditory threshold tended to be larger and the affected frequency area became wider. Although other factors that elevate the auditory thresholds, such as cross-talk effects and the acoustic reflex of the middle ear muscles, may be involved in the above-mentioned paradigm, especially when higher levels of contralateral noise are used, it is important to know the degree of OC-mediated threshold elevation in usual audiometric measurement.

Effects of contralateral noise on measurement of the psychophysical tuning curve

The effects of the addition of contralateral noise on the psychophysical tuning curve (PTC) were examined in subjects with normal hearing. The masking threshold of the tail part of the PTC tended to decrease with the addition of contralateral noise, although the threshold reduction was usually less than 5 dB. On the other hand, the effects of contralateral noise were relatively small around the tip of the PTC contour. Focusing on the effects of contralateral noise on the masking threshold at the tail part of the PTC, the effects of changing the time between initiation of masking the tone and the presentation of the masked probe tone on the threshold reduction at the tail part of the PTC were also observed. The results indicate that the reduction of the masking threshold by the addition of contralateral noise tended to be larger when the presentation of the signal tone was delayed after the onset of the masker. Usually, when the signal tone was presented under conditions of the forward masking paradigm, the reduction of the threshold was most remarkable. Results obtained in the present study are discussed based on the known characteristics of the olivocochlear (OC)-efferent fibers activated by contralateral noise.

The efferent-mediated suppression of otoacoustic emissions in awake guinea pigs and its reversible blockage by gentamicin.

The physiology of the medial efferent olivocochlear system involves suppressive interactions of contralateral sounds on ipsilateral sound-evoked responses, but its role is largely unknown to date. Medial efferents act at the level of cochlear outer hair cells via cholinergic synapses and might affect their mechanical activity, thereby modulating auditory sensitivity. The aim of the present work was to obtain noninvasive measurements of distortion-product otoacoustic emissions (DPOEs), which reflect outer hair cell function, in order to establish the characteristics of medial efferent-induced suppression in awake, restrained guinea pigs. A clear suppression of DPOEs was induced by continuous contralateral white noise presented at 20-70 dB SPL, in the absence of any confounding effect of anesthesia, middle-ear muscles, or acoustic cross talk. Recently, acute injection of a high dose of the aminoglycoside antibiotic gentamicin (150 mg/kg) was reported to alter the suppressive effect of contralateral noise on eighth nerve-compound action potentials, presumably by blocking efferent synapses to outer hair cells. This hypothesis was confirmed with DPOEs for which a single injection of gentamicin at the same dose abolished suppression after about 1-2 h, whereas no change in basal levels was observed. Complete recovery was obtained after 48 h. This experiment may provide an easy, noninvasive tool for studying auditory function with and without functioning efferents.

The effect of contralateral noise on masked compound action potential in humans

The effects of contralateral noise on the masked compound action potential (CAP) were examined in human subjects. Small but significant enhancements of masked CAP amplitude (anti-masking effects) were observed in some patients with facial palsy, as well as in some subjects with healthy ears when noise was added to the contralateral ear. There were no significant differences in fractional changes of CAP by the addition of contralateral noise between subjects with healthy ears and patients with facial palsy in which acoustic reflexes of middle ear muscles (MEMs) had disappeared or were impaired. It is suggested that the anti-masking effects seen in the present study were possibly caused via the olivocochlear (OC) efferent system.

Efferent adaptation and fatigue: The effect of contralateral noise on spontaneous otoacoustic emissions

Mott etal. [Hear. Res. 38, 229–242 (1989)] have shown that both frequency and amplitude of spontaneous otoacoustic emissions (SOAEs) can be modulated by contralateral acoustic stimulation. They also examined the effects of stimulus durations up to 4 min in search of long-term adaptation, but none was found. Because the driven rate of efferent fibers declines by only about one spike per second per minute [M. C. Liberman and M. C. Brown, Hear. Res. 24, 17–36 (1986)], longer durations might be necessary to observe efferent adaptation/fatigue. In the present study, SOAEs of three subjects were measured in the presence of contralateral narrow-band noises with various frequency characteristics and with durations of up to 60 min. The hypothesized effect—an initial decline in SOAEs amplitude under contralateral stimulation followed by a return to preexposure levels with the onset of efferent adaptation—was not consistently observed. While seen in some sessions for some subjects, it could not be brought under experimental control. Thus these results were in approximate agreement with the findings of Mott etal. Some methodological and functional implications of these findings will be discussed. [Work supported by a NIDCD grant to D. McFadden.]

Sleep and active cochlear micromechanical properties in human subjects

In this paper the effect of sleep on the cochlea is studied by transiently evoked otoacoustic emissions (TEOAEs). Amplitude increases considerably (e.g., 4 dB) and the effect of a contralateral noise on the TEOAEs decreases during the night. These modifications can be related to sleep, although there is no link to electroencephalographic sleep stage. During sleep onset, the effect of contralateral noise disappears: this could correspond to a functional rest of the auditory pathway during that period.

Effect of contralateral noise on the middle components of the averaged electroencephalic response.

Middle-component AERs were obtained from normal-hearing adults to 1000-Hz tone pips at 20 and 40 dB SL and at silent control. A continuous noise at 20, 40, and 80 dB SL and at silent control was presented to the contralateral ear. When the tone pips were at 20 or 40 dB SL, five peaks were identified visually in waveforms constructed by digitally adding AERs across subject and replication. Peak latencies determined from the composite waveforms for each signal-masker condition were used as time points to measure point-to-point amplitudes in individual AERs. The masker at 20 or 40 dB SL did not alter or degrade the AER produced by the tone pip. It was concluded that clinical masking may be used in EEA when the middle components of the AER are employed as a response index.

The effects of contralateral noise on reaction time to monaural stimuli

Experiment I measured reaction time (RT) to monaural tones of six frequencies presented along with white noise to the contralateral ear. RT with the hand ipsilateral to the stimulus was an average of 9.63 msec faster than RT with the contralateral hand. Contralateral RT was significantly affected by the stimulus frequency. Experiment II measured ipsilateral and contralateral RT to monaural tones with and without contralateral noise. Noise-on results agreed with the results of Experiment I, while noise-off results showed no difference between ipsilateral and contralateral RT. No right-ear advantage was found. The ipsilateral-contralateral RT difference found with noise on is interpreted as being due to callosal transmission time as well as other factors. The finding of no right-ear advantage is discussed in relation to other studies which did report a right-ear advantage.

Effect of contralateral noise on speech detection and speech reception thresholds.

Speech detection thresholds (SDT) and speech reception thresholds (SRT) for spondee words were obtained on 20 normal hearing listeners while white or speech noise making was presented to the contralateral ear. Each masker was presented continously or pulsed simultaneously with the onset of each spondee word. Several masker sensation levels (SL) of 30, 40, 50, 60, 70, and 80 dB were employed, and the amount of masking (threshold shift) was determined for each condition. Small but consistent SDT and SRT shifts were apparent at low masker SLs (30 dB). FOR 60-80 DB masker SLs, the shifts were about 3.5 dB for each 10-dB increase in the masker. The greater threshold shifts at the higher masker SLs may have resulted from transcranial conduction and/or activation of the acoustic reflex. The pulsed masker condition had more of an effected on the SDT than on the SRT; SDT shifts were consistently larger for each masker SL when the masker was pulsed compared to continuous presentation. Overall, the average threshold shifts ranged from about 1 to 11 dB as the masker SL was increased from 30 to 80 dB. These data suggest that central masking is operating for masker SLs below 60 dB; for higher masker SLs, the increased threshold shifts probably result from a combination of central masking, transcranial conduction, and acoustic stapedius reflex action. The clinical implications of central masking are also discussed.

Observations on the effect of contralateral noise on intensive differential sensitivity.

Intensity DLs were obtained on normal hearing subjects at 500 and 4 000 Hz using two temporally different stimulus patterns in quiet and in the presence of a contralaterally presented noise. The DLI was found to be influenced by the noise, but whether the DLI became larger or smaller appeared at first to be dependent on the temporal pattern of the measurement stimulus. A second experiment, however, established that the effect of a contra-lateral noise on DLI magnitude may be more related to the proximity of background onset to increment onset than to the temporal nature of the background per se.