Silent Gap Research Articles

Comparison of Silent Gap in Noise Cortical Auditory Evoked Potentials in Matched Tinnitus and No-Tinnitus Control Subjects.

Purpose Previous research suggests the existence of gap detection impairments because of tinnitus. The current study aimed to determine whether there was objective evidence of gap impairment in individuals with tinnitus by recording silent gap in white noise cortical auditory evoked potentials (CAEPs) in a chronic tinnitus group and a no-tinnitus group. The results were compared to previous gap-evoked potential and behavioral gap detection studies. Method Chronic tinnitus and no-tinnitus groups were formed by matching pairs of subjects ( n = 26) based on age, gender, and hearing thresholds. Behaviorally determined gap detection thresholds were used to define the electrophysiological gap duration conditions of subthreshold, threshold, and suprathreshold gaps in white noise. Amplitude, latency, and area of the CAEP were analyzed by group and condition using mixed-model analyses of variance. Results Across all participants, as the duration of the gap increased, amplitude and area of the CAEP increased. There were no significant differences by tinnitus status between groups for any outcome measures, except for a significant interaction between group and gap duration for P1 latency. Conclusions Silent gap-evoked CAEPs can be recorded in adults with and without tinnitus. Amplitude and area were sensitive to gap duration across groups; latency was not. Contrary to hypotheses, there was little evidence supporting differences in gap-evoked CAEPs between the tinnitus and control groups. Stimulus and other factors that may have contributed to the lack of a group difference in the current study are discussed, as well as implications for future studies of objective measures of tinnitus perception. Supplemental Material https://doi.org/10.23641/asha.7822601.

Study on Acoustic Characteristics of Plug in Taijinaar Dialect of Qinghai Province

This paper is based on “Qinghai Taijinaar words voice acoustic parameter database”, according to the Chinese academy of social sciences nation national language experimental research team developed the Chinese minority language speech acoustics parameters of unified platform, the principle of using the theory and method of experimental phonetics, mainly explores the plosive pattern of acoustic characteristic;The following conclusions are drawn: in the acoustic pattern with VOT-GAP as the two-dimensional coordinate, the seychelles of Qinghai Taijinaar dialect can form a relatively stable “triangular pattern”, which are: (1) the tip of the tongue /t/, the root of the tongue /k/ gather in one side, and the position in the pattern is more to the left; (2) the tip of the tongue plosive/th/ tonguebase, plosive/k/gathered on one side, the positions of the pattern in figure than unaspirated sound/t/, /k/ relative right; (3) lips plosive/p/ and /ph/ together in one place.Contrast with the tip of the tongue, tongue root plosive, /p/ and /ph/ consonant position right; The aspirated consonant is located to the right of the unaspirated consonant. Therefore, it can be shown that the silent GAP (GAP for short) of the plug is correlated with the location of the sound, and the distribution in the acoustic pattern has a certain stability and regularity.

Neural Switch Asymmetry in Feature-Based Auditory Attention Tasks.

Active listening involves dynamically switching attention between competing talkers and is essential to following conversations in everyday environments. Previous investigations in human listeners have examined the neural mechanisms that support switching auditory attention within the acoustic featural cues of pitch and auditory space. Here, we explored the cortical circuitry underlying endogenous switching of auditory attention between pitch and spatial cues necessary to discern target from masker words. Because these tasks are of unequal difficulty, we expected an asymmetry in behavioral switch costs for hard-to-easy versus easy-to-hard switches, mirroring prior evidence from vision-based cognitive task-switching paradigms. We investigated the neural correlates of this behavioral switch asymmetry and associated cognitive control operations in the present auditory paradigm. Behaviorally, we observed no switch-cost asymmetry, i.e., no performance difference for switching from the more difficult attend-pitch to the easier attend-space condition (P→S) versus switching from easy-to-hard (S→P). However, left lateral prefrontal cortex activity, correlated with improved performance, was observed during a silent gap period when listeners switched attention from P→S, relative to switching within pitch cues. No such differential activity was seen for the analogous easy-to-hard switch. We hypothesize that this neural switch asymmetry reflects proactive cognitive control mechanisms that successfully reconfigured neurally-specified task parameters and resolved competition from other such "task sets," thereby obviating the expected behavioral switch-cost asymmetry. The neural switch activity observed was generally consistent with that seen in cognitive paradigms, suggesting that established cognitive models of attention switching may be productively applied to better understand similar processes in audition.

Jittered echo-delay resolution in bottlenose dolphins (Tursiops truncatus)

Psychophysical methods similar to those employed with bats were used to examine jittered echo-delay resolution in bottlenose dolphins (Tursiops truncatus). Two dolphins were trained to produce echolocation clicks and report a change from electronic echoes with a fixed delay of ~ 12.6 ms (~ 9.4 m simulated range) to echoes with delays that alternated (jittered) between successive emitted signals. Jitter delays varied from 0 to 50 µs. Jittered echo-delay thresholds were between 1 and 2 µs—the lowest achievable (non-zero) values with the hardware configuration. Error functions matched the click autocorrelation function near zero jitter delay, and were well within the envelope of the autocorrelation function; however, measured jitter delay thresholds were larger than predictions for a coherent or semicoherent receiver at comparable signal-to-noise ratios. When one of the two alternating jittered echoes was inverted in polarity, both dolphins reliably discriminated echoes at all jittered echo delays, including 0 µs (i.e., only jittering in polarity, not delay). Finally, both dolphins used unusual patterns of click emissions, where groups of echolocation clicks were interspersed with silent gaps. Further tests with sub-microsecond jitter values and various echo signal-to-noise ratios would be necessary for proper direct comparison with jitter detection values obtained for bats.

Auditory gap detection: psychometric functions and insights into the underlying neural activity.

The detection of a silent interval or gap provides important insight into temporal processing by the auditory system. Previous research has uncovered a multitude of empirical findings leaving the mechanism of gap detection poorly understood and key issues unresolved. Here, we expand the findings by measuring psychometric functions for a number of conditions including both across-frequency and across-intensity gap detection as a first study of its kind. A model is presented which not only accounts for our findings in a quantitative manner, but also helps frame the body of work on auditory gap research. The model is based on the peripheral response and postulates that the identification of gap requires the detection of activity associated with silence.

The possible role of brain rhythms in perceiving fast speech: Evidence from adult aging.

The rhythms of speech and the time scales of linguistic units (e.g., syllables) correspond remarkably to cortical oscillations. Previous research has demonstrated that in young adults, the intelligibility of time-compressed speech can be rescued by "repackaging" the speech signal through the regular insertion of silent gaps to restore correspondence to the theta oscillator. This experiment tested whether this same phenomenon can be demonstrated in older adults, who show age-related changes in cortical oscillations. The results demonstrated a similar phenomenon for older adults, but that the "rescue point" of repackaging is shifted, consistent with a slowing of theta oscillations.

Loss of the Cochlear Amplifier Prestin Reduces Temporal Processing Efficacy in the Central Auditory System.

Active mechanical amplification of sound occurs in cochlear outer hair cells (OHCs) that change their length with oscillations of their membrane potential. Such length changes are the proposed cellular source of the cochlear amplifier, and prestin is the motor protein responsible for OHC electromotility. Previous findings have shown that mice lacking prestin displayed a loss of OHC electromotility, subsequent loss of distortion-product otoacoustic emissions, and a 40–60 dB increase in hearing thresholds. In this study we were interested in studying the functional consequences of the complete loss of cochlear amplification on neural coding of frequency selectivity, tuning, and temporal processing in the auditory midbrain. We recorded near-field auditory evoked potentials and multi-unit activity from the inferior colliculus (IC) of prestin (−/−) null and prestin (+/+) wild-type control mice and determined frequency response areas (FRAs), tuning sharpness, and gap detection to tone bursts and silent gaps embedded in broadband noise. We were interested in determining if the moderate to severe sensorineural hearing loss associated with the loss of motor protein prestin would also impair auditory midbrain temporal-processing measures, or if compensatory mechanisms within the brainstem could compensate for the loss of prestin. In prestin knockout mice we observed that there are severe impairments in midbrain tuning, thresholds, excitatory drive, and gap detection suggesting that brainstem and midbrain processing could not overcome the auditory processing deficits afforded by the loss of OHC electromotility mediated by the prestin protein.

Changes in spontaneous movement in response to silent gaps are not robust enough to indicate the perception of tinnitus in mice.

Approaches to identify the perception of tinnitus in various animal models have been difficult to apply to mouse. As a result, mice have been underutilized to investigate the cellular, molecular, and genetic mechanisms underlying tinnitus. A recent study in guinea pigs identified a novel spontaneous behavior (unconditioned response), changes in movement during silent gaps, that identified a subgroup of animals presumably with tinnitus. Guinea pigs identified with tinnitus failed to “freeze” in response to silent gaps in sound. In the hope of developing a rapid and reliable assay for mice, we used a similar approach. C57BL/6J mice underwent three trials in which spontaneous movement was video recorded in the presence of white noise interrupted with six silent gaps. Movement metrics included velocity and body movement. Before the third trial, mice underwent either sham or noise exposure to induce hearing loss and tinnitus. Auditory brainstem responses before and after noise trauma confirmed normal hearing in sham-treated animals and hearing loss in the noise-exposed cohort. No differences in the various movement metrics were detected during the silent gaps either before or after sham/noise exposure. Variability in spontaneous movement both before and after sham/noise exposure was substantially greater in mice compared to guinea pigs. Thus, this assay is not sufficiently statistically powerful to identify changes in movement that might indicate tinnitus perception in mice. Previous observations also reported increased movement overall in guinea pigs identified as suffering tinnitus. In contrast, mice showed no statistically significant differences in movement between the three trials. Despite our results, other unconditioned (as well as conditioned) behaviors should be examined in mice to test their utility to detect changes that indicate the perception of tinnitus. Such assays are essential to accelerate the use of mouse models in tinnitus research.

Towards an objective test of chronic tinnitus: Properties of auditory cortical potentials evoked by silent gaps in tinnitus-like sounds

A common method designed to identify if an animal hears tinnitus assumes that tinnitus “fills-in” silent gaps in background sound. This phenomenon has not been reliably demonstrated in humans. One test of the gap-filling hypothesis would be to determine if gap-evoked cortical potentials are absent or attenuated when measured within background sound matched to the tinnitus sensation. However the tinnitus sensation is usually of low intensity and of high frequency, and it is unknown if cortical responses can be measured with such “weak” stimulus properties. Therefore the aim of the present study was to test the plausibility of observing these responses in the EEG in humans without tinnitus. Twelve non-tinnitus participants heard narrowband noises centered at sound frequencies of 5 or 10 kHz at sensation levels of either 5, 15, or 30 dB. Silent gaps of 20 ms duration were randomly inserted into noise stimuli, and cortical potentials evoked by these gaps were measured by 64-channel EEG. Gap-evoked cortical responses were statistically identifiable in all conditions for all but one participant. Responses were not significantly different between noise frequencies or levels. Results suggest that cortical responses can be measured when evoked by gaps in sounds that mirror acoustic properties of tinnitus. This design can validate the animal model and be used as a tinnitus diagnosis test in humans.

Consonant and Vowel Identification in Cochlear Implant Users Measured by Nonsense Words: A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to establish a baseline of the vowel and consonant identification scores in prelingually and postlingually deaf users of multichannel cochlear implants (CIs) tested with consonant-vowel-consonant and vowel-consonant-vowel nonsense syllables. Six electronic databases were searched for peer-reviewed articles reporting consonant and vowel identification scores in CI users measured by nonsense words. Relevant studies were independently assessed and screened by 2 reviewers. Consonant and vowel identification scores were presented in forest plots and compared between studies in a meta-analysis. Forty-seven articles with 50 studies, including 647 participants, thereof 581 postlingually deaf and 66 prelingually deaf, met the inclusion criteria of this study. The mean performance on vowel identification tasks for the postlingually deaf CI users was 76.8% (N = 5), which was higher than the mean performance for the prelingually deaf CI users (67.7%; N = 1). The mean performance on consonant identification tasks for the postlingually deaf CI users was higher (58.4%; N = 44) than for the prelingually deaf CI users (46.7%; N = 6). The most common consonant confusions were found between those with same manner of articulation (/k/ as /t/, /m/ as /n/, and /p/ as /t/). The mean performance on consonant identification tasks for the prelingually and postlingually deaf CI users was found. There were no statistically significant differences between the scores for prelingually and postlingually deaf CI users. The consonants that were incorrectly identified were typically confused with other consonants with the same acoustic properties, namely, voicing, duration, nasality, and silent gaps. A univariate metaregression model, although not statistically significant, indicated that duration of implant use in postlingually deaf adults predict a substantial portion of their consonant identification ability. As there is no ceiling effect, a nonsense syllable identification test may be a useful addition to the standard test battery in audiology clinics when assessing the speech perception of CI users.

Electrophysiological response during auditory gap detection: Biomarker for sensory and communication alterations in autism spectrum disorder?

ABSTRACTSensory symptoms, including auditory processing deficits, are common in autism spectrum disorder (ASD). Processing of temporal aspects of auditory input is understudied; yet, deficits in this domain could contribute to language-related impairments. In children with ASD and well-matched controls, this study examined electrophysiological response to silent gaps in auditory stimuli. Results revealed attenuated amplitude of the P2 event-related potential (ERP) component in ASD. The P2 amplitude reduction was also associated with sensory, language, and diagnostic features. These results suggest that neural response during auditory gap detection is a promising ASD biomarker that could be useful for stratifying subgroups and evaluating treatment response.

Dynamic phase alignment of ongoing auditory cortex oscillations

Neural oscillations can synchronize to external rhythmic stimuli, as for example in speech and music. While previous studies have mainly focused on elucidating the fundamental concept of neural entrainment, less is known about the time course of entrainment. In this human electroencephalography (EEG) study, we unravel the temporal evolution of neural entrainment by contrasting short and long periods of rhythmic stimulation. Listeners had to detect short silent gaps that were systematically distributed with respect to the phase of a 3 Hz frequency-modulated tone. We found that gap detection performance was modulated by the stimulus stream with a consistent stimulus phase across participants for short and long stimulation. Electrophysiological analysis confirmed neural entrainment effects at 3 Hz and the 6 Hz harmonic for both short and long stimulation lengths. 3 Hz source level analysis revealed that longer stimulation resulted in a phase shift of a participant's neural phase relative to the stimulus phase. Phase coupling increased over the first second of stimulation, but no effects for phase coupling strength were observed over time. The dynamic evolution of phase alignment suggests that the brain attunes to external rhythmic stimulation by adapting the brain's internal representation of incoming environmental stimuli.

Auditory processing enhancements in the TS2-neo mouse model of Timothy Syndrome, a rare genetic disorder associated with autism spectrum disorders.

Timothy syndrome (TS) is a rare genetic disorder caused by a single de novo missense mutation to the 8A exon of CACNA1C gene, which codes for the voltage-gated L-type Ca2+ channel (Cav1.2). TS is strongly associated with cardiac arrthytmias, autism spectrum disorders (ASDs), and neurological dysfunction such as language impairments, seizures, and intellectual disability. A genetically engineered knock-in mouse with a heterogeneous TS2 (G406R) mutation in the L-type calcium channel containing a neomycin resistance cassette was developed to study ASD-like behaviors. This mouse model (TS2-neo) provides us with a platform to investigate the role of calcium channel inactivation and calcium signaling related to brain development and ASD. The purpose of the current study was to behaviorally characterize TS2-neo mice by assessing their performance on a wide variety of behavioral paradigms, including replication of findings that support the TS2-neo as a valid platform for studying ASD-like behavior. In addition to examining core social and repetitive anomalies, we sought to focus on basic perceptual processing in the auditory domain. Results indicate that the loss of Cav1.2 inactivation in this mouse model results in deviant social and repetitive behaviors as well as poor sensorimotor learning. Additionally, TS2-neo mice display superior performance on both an embedded tone and silent gap discrimination task for short-duration acoustic stimuli. These findings parallel the low-level auditory enhancements observed within the ASD clinical population. Additionally, structural anomalies were seen for mutant mice in some white matter tracts and in the medial geniculate nucleus (MGN). Co-occurrence of these findings suggests that aberrant MGN morphology may be related to enhanced auditory processing phenotype as seen in ASD.

A probabilistic Poisson-based model accounts for an extensive set of absolute auditory threshold measurements

Thresholds for detecting sounds in quiet decrease with increasing sound duration in every species studied. The neural mechanisms underlying this trade-off, often referred to as temporal integration, are not fully understood. Here, we probe the human auditory system with a large set of tone stimuli differing in duration, shape of the temporal amplitude envelope, duration of silent gaps between bursts, and frequency. Duration was varied by varying the plateau duration of plateau-burst (PB) stimuli, the duration of the onsets and offsets of onset-offset (OO) stimuli, and the number of identical bursts of multiple-burst (MB) stimuli. Absolute thresholds for a large number of ears (>230) were measured using a 3-interval-3-alternative forced choice (3I-3AFC) procedure. Thresholds decreased with increasing sound duration in a manner that depended on the temporal envelope. Most commonly, thresholds for MB stimuli were highest followed by thresholds for OO and PB stimuli of corresponding durations. Differences in the thresholds for MB and OO stimuli and in the thresholds for MB and PB stimuli, however, varied widely across ears, were negative in some ears, and were tightly correlated. We show that the variation and correlation of MB-OO and MB-PB threshold differences are linked to threshold microstructure, which affects the relative detectability of the sidebands of the MB stimuli and affects estimates of the bandwidth of auditory filters. We also found that thresholds for MB stimuli increased with increasing duration of the silent gaps between bursts. We propose a new model and show that it accurately accounts for our results and does so considerably better than a leaky-integrator-of-intensity model and a probabilistic model proposed by others. Our model is based on the assumption that sensory events are generated by a Poisson point process with a low rate in the absence of stimulation and higher, time-varying rates in the presence of stimulation. A subject in a 3I-3AFC task is assumed to choose the interval in which the greatest number of events occurred or randomly chooses among intervals which are tied for the greatest number of events. The subject is further assumed to count events over the duration of an evaluation interval that has the same timing and duration as the expected stimulus. The increase in the rate of the events caused by stimulation is proportional to the time-varying amplitude envelope of the bandpass-filtered signal raised to an exponent. We find the exponent to be about 3, consistent with our previous studies. This challenges models that are based on the assumption of the integration of a neural response that is directly proportional to the stimulus amplitude or proportional to its square (i.e., proportional to the stimulus intensity or power).

Spectral and temporal auditory processing in the superior colliculus of aged rats

Presbyacusis reflects dysfunctions present along the central auditory pathway. Given that the topographic representation of the auditory directional spatial map is deteriorated in the superior colliculus of aged animals, therefore, are spectral and temporal auditory processes altered with aging in the rat's superior colliculus? Extracellular single-unit recordings were conducted in the superior colliculus of anesthetized Sprague-Dawley adult (10 months) and aged (22 months) rats. In the spectral domain, level thresholds in aged rats were significantly increased when superior colliculus auditory neurons were stimulated with pure tones or Gaussian noise bursts. The sharpness of the frequency response tuning curve at 10 dB SPL above threshold was also significantly broader among the aged rats. Furthermore, in the temporal domain, the minimal silent gap thresholds to Gaussian noises were significantly longer in aged rats. Hence, these results highlight that spectral and temporal auditory processing in the superior colliculus are impaired during aging.

Spike Timing Matters in Novel Neuronal Code Involved in Vibrotactile Frequency Perception

Skin vibrations sensed by tactile receptors contribute significantly to the perception of object properties during tactile exploration [1-4] and to sensorimotor control during object manipulation [5]. Sustained low-frequency skin vibration (<60Hz) evokes a distinct tactile sensation referred to as flutter whose frequency can be clearly perceived [6]. How afferent spiking activity translates into the perception of frequency is still unknown. Measures based on mean spike rates of neurons in the primary somatosensory cortex are sufficient to explain performance in some frequency discrimination tasks [7-11]; however, thereis emerging evidence that stimuli can be distinguished based also on temporal features of neural activity [12, 13]. Our study's advance is to demonstrate that temporal features are fundamental for vibrotactile frequency perception. Pulsatile mechanical stimuli were used to elicit specified temporal spike train patterns in tactile afferents, and subsequently psychophysical methods were employed to characterize human frequency perception. Remarkably, the most salient temporal feature determining vibrotactile frequency was not the underlying periodicity but, rather, the duration of the silent gap between successive bursts of neural activity. This burst gap code for frequency represents a previously unknown form ofneural coding in the tactile sensory system, whichparallels auditory pitch perception mechanisms based on purely temporal information where longer inter-pulse intervals receive higher perceptual weights than short intervals [14]. Our study also demonstrates that human perception of stimuli can be determined exclusively by temporal features of spike trains independent of the mean spike rate and without contribution from population response factors.

Comparison of perceptual properties of auditory streaming between spectral and amplitude modulation domains

The two-tone sequence (ABA_), which comprises two different sounds (A and B) and a silent gap, has been used to investigate how the auditory system organizes sequential sounds depending on various stimulus conditions or brain states. Auditory streaming can be evoked by differences not only in the tone frequency (“spectral cue”: ΔFTONE, TONE condition) but also in the amplitude modulation rate (“AM cue”: ΔFAM, AM condition). The aim of the present study was to explore the relationship between the perceptual properties of auditory streaming for the TONE and AM conditions. A sequence with a long duration (400 repetitions of ABA_) was used to examine the property of the bistability of streaming. The ratio of feature differences that evoked an equivalent probability of the segregated percept was close to the ratio of the Q-values of the auditory and modulation filters, consistent with a “channeling theory” of auditory streaming. On the other hand, for values of ΔFAM and ΔFTONE evoking equal probabilities of the segregated percept, the number of perceptual switches was larger for the TONE condition than for the AM condition, indicating that the mechanism(s) that determine the bistability of auditory streaming are different between or sensitive to the two domains. Nevertheless, the number of switches for individual listeners was positively correlated between the spectral and AM domains. The results suggest a possibility that the neural substrates for spectral and AM processes share a common switching mechanism but differ in location and/or in the properties of neural activity or the strength of internal noise at each level.

Sounds can boost the awareness of visual events through attention without cross-modal integration

Cross-modal interactions can lead to enhancement of visual perception, even for visual events below awareness. However, the underlying mechanism is still unclear. Can purely bottom-up cross-modal integration break through the threshold of awareness? We used a binocular rivalry paradigm to measure perceptual switches after brief flashes or sounds which, sometimes, co-occurred. When flashes at the suppressed eye coincided with sounds, perceptual switches occurred the earliest. Yet, contrary to the hypothesis of cross-modal integration, this facilitation never surpassed the assumption of probability summation of independent sensory signals. A follow-up experiment replicated the same pattern of results using silent gaps embedded in continuous noise, instead of sounds. This manipulation should weaken putative sound-flash integration, although keep them salient as bottom-up attention cues. Additional results showed that spatial congruency between flashes and sounds did not determine the effectiveness of cross-modal facilitation, which was again not better than probability summation. Thus, the present findings fail to fully support the hypothesis of bottom-up cross-modal integration, above and beyond the independent contribution of two transient signals, as an account for cross-modal enhancement of visual events below level of awareness.

Let silence speak about aphasia: possible associations between pause and language related cognitive processes

Let silence speak about aphasia: possible associations between pause and language related cognitive processes

Auditory evoked fields elicited by repetitive gaps embedded within a continuous tone

The N1m response, which is a prominent auditory evoked component with a latency of around 100 ms, elicited by sound onset is known to decrease with the repetition of identical sound stimuli. Previous studies demonstrated that a silent gap embedded within a continuous sound could also elicit the N1m responses; however, it remains elusive whether the N1m decrement occurs with a repetition of silent gaps. In the present study, we investigated the decrement of N1m responses elicited by five repetitive pure tones presented in silence and by five repetitive silent gaps embedded within a continuous tone using magnetoencephalography. The results obtained demonstrated that the N1m responses elicited by the repetitive pure tones decreased from the 1st to the 2nd and remained constant from the 2nd to the 5th, whereas those elicited by the repetitive gaps in a continuous tone gradually decreased from the 1st to the 5th. Those results indicate that neural refractoriness appears to mainly contribute to the decrement of the N1m responses elicited by repetitive pure tones, while habituation may play an additional role in the decrement of the N1m responses elicited by repetitive gaps in a continuous tone.