Factors affecting sensitivity to frequency change in school-age children and adults

PURPOSE

The factors affecting frequency discrimination in school-age children are poorly understood. The goal of the present study was to evaluate developmental effects related to memory for pitch and the utilization of temporal fine structure.

METHOD

Listeners were 5.1- to 13.6-year-olds and adults, all with normal hearing. A subgroup of children had musical training. The task was a 3-alternative forced choice in which listeners identified the interval with the higher frequency tone or the tone characterized by frequency modulation (FM). The standard was 500 or 5000 Hz, and the FM rate was either 2 or 20 Hz.

RESULTS

Thresholds tended to be higher for younger children than for older children and adults for all conditions, although this age effect was smaller for FM detection than for pure-tone frequency discrimination. Neither standard frequency nor modulation rate affected the child/adult difference FM thresholds. Children with musical training performed better than their peers on pure-tone frequency discrimination at 500 Hz.

CONCLUSIONS

Testing frequency discrimination using a low-rate FM detection task may minimize effects related to cognitive factors like memory for pitch or training effects. Maturation of frequency discrimination does not appear to differ across conditions in which listeners are hypothesized to rely on temporal cues and place cues.

Perception of a sung vowel as a function of frequency-modulation rate and excursion in listeners with normal hearing and hearing impairment

PURPOSE

Frequency fluctuations in human voices can usually be described as coherent frequency modulation (FM). As listeners with hearing impairment (HI listeners) are typically less sensitive to FM than listeners with normal hearing (NH listeners), this study investigated whether hearing loss affects the perception of a sung vowel based on FM cues.

METHOD

Vibrato maps were obtained in 14 NH and 12 HI listeners with different degrees of musical experience. The FM rate and FM excursion of a synthesized vowel, to which coherent FM was applied, were adjusted until a singing voice emerged.

RESULTS

In NH listeners, adding FM to the steady vowel components produced perception of a singing voice for FM rates between 4.1 and 7.5 Hz and FM excursions between 17 and 83 cents on average. In contrast, HI listeners showed substantially broader vibrato maps. Individual differences in map boundaries were, overall, not correlated with audibility or frequency selectivity at the vowel fundamental frequency, with no clear effect of musical experience.

CONCLUSION

Overall, it was shown that hearing loss affects the perception of a sung vowel based on FM-rate and FM-excursion cues, possibly due to deficits in FM detection or discrimination or to a degraded ability to follow the rate of frequency changes.

Effects of consecutive wideband tympanometry trials on energy absorbance measures of the middle ear

PURPOSE

Wideband acoustic immittance (WAI) is a new technique for assessing middle ear transfer function. It includes energy absorbance (EA) measures and can be acquired with the ear canal pressure varied, known as wideband tympanometry (WBTymp). The authors of this study aimed to investigate effects of consecutive WBTymp testing on EA.

METHOD

Data were collected in 29 young adults with normal hearing and middle ear status. Before and after 8 successive WBTymp runs, EA was also measured at ambient pressure. Subsequently, two 226-Hz tympanometry tests were performed.

RESULTS

EA systematically changed over the WBTymp trials in a frequency-specific manner: increase for low frequencies (below 1.5 kHz) and decrease for high frequencies (around 2 kHz and 5 to 6 kHz). The changes, although small, were significant. Much larger EA changes were measured at ambient pressure. The test-retest difference of 226-Hz tympanogram measures was much smaller than previously reported.

CONCLUSION

Consecutive tympanometry testing alters EA measures of the middle ear. This phenomenon could be mainly attributed to change in stiffness at the eardrum, called tympanometric preconditioning. This also has effects on baseline WBTymp outcomes. This effect should be taken into account as a procedural variable in both research and clinical applications of WAI measurements.

Song recognition by young children with cochlear implants: comparison between unilateral, bilateral, and bimodal users

PURPOSE

To examine song identification by preschoolers with normal hearing (NH) versus preschoolers with cochlear implants (CIs).

METHOD

Participants included 45 children ages 3;8-7;3 (years;months): 12 with NH and 33 with CIs, including 10 with unilateral CI, 14 with bilateral CIs, and 9 bimodal users (CI-HA) with unilateral CI and contralateral hearing aid. Preschoolers were asked to identify children's songs presented via 5 versions: (a) full (lyrics sung with piano accompaniment); (b) a cappella (only lyrics); (c) melodic (matching main melodic contour); (d) tonal (only pitch information); and (e) rhythmic (only song's rhythm).

RESULTS

The NH group surpassed all CI groups at identifying songs via melodic and tonal versions, but no significant differences emerged between the NH group and any CI group via full, a cappella, or rhythmic versions. Among the CI groups, no significant differences emerged via melodic or rhythmic versions, but bimodal users performed significantly better than bilateral users via the tonal version. Chronological age and duration of CI use correlated significantly with identification via the rhythmic version.

CONCLUSION

Bimodal users showed an advantage in identifying songs in the tonal version through use of complementary information.

Behavioral frequency discrimination ability of partially deafened cats using cochlear implants

The aim of this study was to determine the effects of cochlear implant (CI) use on behavioral frequency discrimination ability in partially deafened cats. We hypothesized that the additional information provided by the CI would allow subjects to perform better on a frequency discrimination task. Four cats with a high frequency hearing loss induced by ototoxic drugs were first trained on a go/no-go, positive reinforcement, frequency discrimination task and reached asymptotic performance (measured by d' - detection theory). Reference frequencies (1, 4, and 7 kHz) were systematically rotated (Block design) every 9-11 days to cover the hearing range of the cats while avoiding bias arising from the order of testing. Animals were then implanted with an intracochlear electrode array connected to a CI and speech processor. They then underwent 6 months of continuous performance measurement with the CI turned on, except for one month when the stimulator was turned off. Overall, subjects performed the frequency discrimination task significantly better with their CI turned on than in the CI-off condition (3-way ANOVA, p < 0.001). The analysis showed no dependence on subject (3-way ANOVA, subject × on-off condition, p > 0.5); however, the CI only significantly improved performance for two (1 and 7 kHz) of the three reference frequencies. In this study we were able to show, for the first time, that cats can utilize information provided by a CI in performing a behavioral frequency discrimination task.

A combined model of sensory and cognitive representations underlying tonal expectations in music: from audio signals to behavior

Listeners' expectations for melodies and harmonies in tonal music are perhaps the most studied aspect of music cognition. Long debated has been whether faster response times (RTs) to more strongly primed events (in a music theoretic sense) are driven by sensory or cognitive mechanisms, such as repetition of sensory information or activation of cognitive schemata that reflect learned tonal knowledge, respectively. We analyzed over 300 stimuli from 7 priming experiments comprising a broad range of musical material, using a model that transforms raw audio signals through a series of plausible physiological and psychological representations spanning a sensory-cognitive continuum. We show that RTs are modeled, in part, by information in periodicity pitch distributions, chroma vectors, and activations of tonal space--a representation on a toroidal surface of the major/minor key relationships in Western tonal music. We show that in tonal space, melodies are grouped by their tonal rather than timbral properties, whereas the reverse is true for the periodicity pitch representation. While tonal space variables explained more of the variation in RTs than did periodicity pitch variables, suggesting a greater contribution of cognitive influences to tonal expectation, a stepwise selection model contained variables from both representations and successfully explained the pattern of RTs across stimulus categories in 4 of the 7 experiments. The addition of closure--a cognitive representation of a specific syntactic relationship--succeeded in explaining results from all 7 experiments. We conclude that multiple representational stages along a sensory-cognitive continuum combine to shape tonal expectations in music.

Cross-modal information integration in category learning

An influential theoretical perspective describes an implicit category-learning system that associates regions of perceptual space with response outputs by integrating information preattentionally and predecisionally across multiple stimulus dimensions. In this study, we tested whether this kind of implicit, information-integration category learning is possible across stimulus dimensions lying in different sensory modalities. Humans learned categories composed of conjoint visual-auditory category exemplars comprising a visual component (rectangles varying in the density of contained lit pixels) and an auditory component (in Exp. 1, auditory sequences varying in duration; in Exp. 2, pure tones varying in pitch). The categories had either a one-dimensional, rule-based solution or a two-dimensional, information-integration solution. Humans could solve the information-integration category tasks by integrating information across two stimulus modalities. The results demonstrated an important cross-modal form of sensory integration in the service of category learning, and they advance the field's knowledge about the sensory organization of systems for categorization.

The neural changes in connectivity of the voice network during voice pitch perturbation

Voice control is critical to communication. To date, studies have used behavioral, electrophysiological and functional data to investigate the neural correlates of voice control using perturbation tasks, but have yet to examine the interactions of these neural regions. The goal of this study was to use structural equation modeling of functional neuroimaging data to examine network properties of voice with and without perturbation. Results showed that the presence of a pitch shift, which was processed as an error in vocalization, altered connections between right STG and left STG. Other regions that revealed differences in connectivity during error detection and correction included bilateral inferior frontal gyrus, and the primary and pre motor cortices. Results indicated that STG plays a critical role in voice control, specifically, during error detection and correction. Additionally, pitch perturbation elicits changes in the voice network that suggest the right hemisphere is critical to pitch modulation.

On the intonation of German intonation questions: the role of the prenuclear region

German questions and statements are distinguished not only by lexical and syntactic but also by intonational means. This study revisits, for Northern Standard German, how questions are signalled intonationally in utterances that have neither lexical nor syntactic cues. Starting from natural productions of such 'intonation questions', two perception experiments were run. Experiment 1 is based on a gating paradigm, which was applied to naturally produced questions and statements. Experiment 11 includes two indirect-identification tasks. Resynthesized stimuli were judged in relation to two context utterances, each of which was compatible with only one sentence mode interpretation. Results show that utterances with a finally falling nuclear pitch-accent contour can also trigger question perception. An utterance-final rise is not mandatory. Also, question and statement cues are not restricted to the intonational nucleus. Rather, listeners can refer to shape, slope, and alignment differences of the preceding prenuclear pitch accent to identify sentence mode. These findings are in line with studies suggesting that the utterance-final rise versus fall contrast is not directly related to sentence modality, but represents a separate attitudinal meaning dimension. Moreover, the findings support that both prenuclear and nuclear fundamental frequency (F0) patterns must be taken into account in the analysis of tune meaning.

A comparative analysis of auditory perception in humans and songbirds: a modular approach

We propose that a relatively small number of perceptual skills underlie human perception of music and speech. Humans and songbirds share a number of features in the development of their auditory communication systems. These similarities invite comparisons between species in their auditory perceptual skills. Here, we summarized our experimental comparisons between humans (and other mammals) and songbirds (and other birds) in their use of pitch height and pitch chroma perception and discuss similarities and differences in other auditory perceptual abilities of these species. Specifically, we introduced a functional modular view, using pitch chroma and pitch height perception as examples, as a theoretical framework for the comparative study of auditory perception and perhaps all of the study of comparative cognition. We also contrasted phylogeny and adaptation as causal mechanisms in comparative cognition using examples from auditory perception.

The effect of interaural fluctuation rate on correlation change discrimination

While bilateral cochlear implants (CIs) provide some binaural benefits, these benefits are limited compared to those observed in normal-hearing (NH) listeners. The large frequency-to-electrode allocation bandwidths (BWs) in CIs compared to auditory filter BWs in NH listeners increases the interaural fluctuation rate available for binaural unmasking, which may limit binaural benefits. The purpose of this work was to investigate the effect of interaural fluctuation rate on correlation change discrimination and binaural masking-level differences in NH listeners presented a CI simulation using a pulsed-sine vocoder. In experiment 1, correlation-change just-noticeable differences (JNDs) and tone-in-noise thresholds were measured for narrowband noises with different BWs and center frequencies (CFs). The results suggest that the BW, CF, and/or interaural fluctuation rate are important factors for correlation change discrimination. In experiment 2, the interaural fluctuation rate was systematically varied and dissociated from changes in BW and CF by using a pulsed-sine vocoder. Results indicated that the interaural fluctuation rate did not affect correlation change JNDs for correlated reference noises; however, slow interaural fluctuations increased correlation change JNDs for uncorrelated reference noises. In experiment 3, the BW, CF, and vocoder pulse rate were varied while interaural fluctuation rate was held constant. JNDs increased for increasing BW and decreased for increasing CF. In summary, relatively fast interaural fluctuation rates are not detrimental for detecting changes in interaural correlation. Thus, limiting factors to binaural benefits in CI listeners could be a result of other temporal and/or spectral deficiencies from electrical stimulation.

Auditory processing and hallucinations in schizophrenia

The aim of this study was to investigate whether deficits in auditory processing are associated with auditory hallucinations in patients with schizophrenia. It was hypothesised that individuals with a diagnosis of schizophrenia would demonstrate deficits in processing the spectral and temporal aspects of sound and that such deficits would be more pronounced in patients with a history of auditory hallucinations (hallucinators) than those without such a history (non-hallucinators). A community sample meeting clinical criteria for schizophrenia or schizoaffective disorder (19 hallucinators, 15 non-hallucinators) and a matched healthy control group (n=17) completed a broad range of auditory processing tasks involving pitch discrimination of modulated (temporal) and unmodulated (spectral) pure tones, auditory streaming and affective prosodic identification, as well as measures assessing current psychiatric symptoms. In all experimental tasks patients were impaired compared to controls. Specifically hallucinators performed worse than non-hallucinators and controls for pitch discrimination of unmodulated tones and auditory streaming, and both hallucinators and non-hallucinators performed significantly worse than controls for discrimination of modulated tones and affective prosody. These findings suggest that impaired temporal processing may contribute to general difficulties identifying affective speech prosody in patients with schizophrenia, while spectral processing deficits may specifically compromise melodic streaming in hallucinators, which combined with deficits in temporal processing, contribute to the experience of auditory hallucinations.

Difficulties with pitch discrimination influences pitch memory performance: evidence from congenital amusia

Music processing is influenced by pitch perception and memory. Additionally these features interact, with pitch memory performance decreasing as the perceived distance between two pitches decreases. This study examined whether or not the difficulty of pitch discrimination influences pitch retention by testing individuals with congenital amusia. Pitch discrimination difficulty was equated by determining an individual’s threshold with a two down one up staircase procedure and using this to create conditions where two pitches (the standard and the comparison tones) differed by 1x, 2x, and 3x the threshold setting. For comparison with the literature a condition that employed a constant pitch difference of four semitones was also included. The results showed that pitch memory performance improved as the discrimination between the standard and the comparison tones was made easier for both amusic and control groups, and more importantly, that amusics did not show any pitch retention deficits when the discrimination difficulty was equated. In contrast, consistent with previous literature, amusics performed worse than controls when the physical pitch distance was held constant at four semitones. This impaired performance has been interpreted as evidence for pitch memory impairment in the past. However, employing a constant pitch distance always makes the difference closer to the discrimination threshold for the amusic group than for the control group. Therefore, reduced performance in this condition may simply reflect differences in the perceptual difficulty of the discrimination. The findings indicate the importance of equating the discrimination difficulty when investigating memory.

Exploring the limits of frequency lowering

PURPOSE

This study examined how frequency lowering affected sentence intelligibility and quality for adults with postlingually acquired, mild-to-moderate hearing loss.

METHOD

Listeners included adults aged 60-92 years with sloping sensorineural hearing loss and a control group of similarly aged adults with normal hearing. Sentences were presented in quiet and babble at a range of signal-to-noise ratios. Intelligibility and quality were measured with varying amounts of frequency lowering, implemented using a form of frequency compression.

RESULTS

Moderate amounts of compression, particularly with high cutoff frequencies, had minimal effects on sentence intelligibility. Listeners with the greatest high-frequency hearing loss showed the greatest benefit. Sentence intelligibility decreased with more compression. Listeners were more affected by a given set of parameters in noise than in quiet. In quiet, any amount of compression resulted in lower speech quality for most listeners, with the greatest degradation for listeners with better high-frequency hearing. Quality ratings were lower with background noise, and in noise, the effect of changing compression parameters was small.

CONCLUSIONS

The benefits of frequency lowering in adults were affected by the compression parameters as well as individual hearing thresholds. The data are consistent with the idea that frequency lowering can be viewed in terms of improved audibility versus increased distortion trade-off.

A flexible analysis tool for the quantitative acoustic assessment of infant cry

PURPOSE

In this article, the authors describe and validate the performance of a modern acoustic analyzer specifically designed for infant cry analysis.

METHOD

Utilizing known algorithms, the authors developed a method to extract acoustic parameters describing infant cries from standard digital audio files. They used a frame rate of 25 ms with a frame advance of 12.5 ms. Cepstral-based acoustic analysis proceeded in 2 phases, computing frame-level data and then organizing and summarizing this information within cry utterances. Using signal detection methods, the authors evaluated the accuracy of the automated system to determine voicing and to detect fundamental frequency (F 0) as compared to voiced segments and pitch periods manually coded from spectrogram displays.

RESULTS

The system detected F 0 with 88% to 95% accuracy, depending on tolerances set at 10 to 20 Hz. Receiver operating characteristic analyses demonstrated very high accuracy at detecting voicing characteristics in the cry samples.

CONCLUSIONS

This article describes an automated infant cry analyzer with high accuracy to detect important acoustic features of cry. A unique and important aspect of this work is the rigorous testing of the system's accuracy as compared to ground-truth manual coding. The resulting system has implications for basic and applied research on infant cry development.

The effect of instrumental timbre on interval discrimination

We tested non-musicians and musicians in an auditory psychophysical experiment to assess the effects of timbre manipulation on pitch-interval discrimination. Both groups were asked to indicate the larger of two presented intervals, comprised of four sequentially presented pitches; the second or fourth stimulus within a trial was either a sinusoidal (or “pure”), flute, piano, or synthetic voice tone, while the remaining three stimuli were all pure tones. The interval-discrimination tasks were administered parametrically to assess performance across varying pitch distances between intervals (“interval-differences”). Irrespective of timbre, musicians displayed a steady improvement across interval-differences, while non-musicians only demonstrated enhanced interval discrimination at an interval-difference of 100 cents (one semitone in Western music). Surprisingly, the best discrimination performance across both groups was observed with pure-tone intervals, followed by intervals containing a piano tone. More specifically, we observed that: 1) timbre changes within a trial affect interval discrimination; and 2) the broad spectral characteristics of an instrumental timbre may influence perceived pitch or interval magnitude and make interval discrimination more difficult.

More is less: pitch discrimination and language delays in children with optimal outcomes from autism

The autism spectrum disorders (ASD) are neurodevelopmental disorders diagnosed behaviorally but associated with differences in brain development. Individuals with ASD exhibit superior auditory perceptual skills, which may correlate with ASD symptomatology, particularly language skills. We describe findings from individuals diagnosed with ASD before age five, who now have no symptoms (e.g., having optimal outcomes). Unlike an ASD group, which shows heightened pitch discrimination, the Optimal Outcome group's abilities do not differ from those of typically developing controls. Furthermore, pitch discrimination is associated with both current autism symptomatology and early-language milestones. Findings illuminate processes associated with resolution of autism. We also discuss a specific mechanism by which heightened auditory discrimination leads to language delays in ASD.

Maintaining intelligibility at high speech intensities: evidence of lateral inhibition in the lower auditory pathway

Three experiments examined the intelligibility enhancement produced when noise bands flank high intensity narrowband speech. Enhancement was unaffected by noise gating (experiment 1), ruling out peripheral adaptation as a source, and was also unaffected by interaural decorrelation of noise bands flanking diotic speech (experiment 2), indicating that enhancement occurs prior to binaural processing. These results support previous suggestions that intelligibility loss at high intensities is reduced by lateral inhibition in the cochlear nuclei. Results from a final experiment suggest that this effect is only ipsilateral, implicating a specific population of inhibitory neurons.

Polarity effects on place pitch and loudness for three cochlear-implant designs and at different cochlear sites

Users of Advanced Bionics, MedEl, and Cochlear Corp. implants balanced the loudness of trains of asymmetric pulses of opposite polarities presented in monopolar mode. For the Advanced Bionics and MedEl users the pulses were triphasic and consisted of a 32-μs central phase flanked by two 32-μs phases of opposite polarity and half the amplitude. The central phase was either anodic (TP-A) or cathodic (TP-C). For the Cochlear Corp. users, pulses consisted of two 32-μs phases of the same polarity separated by an 8-μs gap, flanked by two 32-μs phases of the opposite polarity, each of which was separated from the central portion by a 58-μs gap. The central portion of these quadraphasic pulses was either anodic (QP-A) or cathodic (QP-C), and all phases had the same amplitude. The current needed to achieve matched loudness was lower for the anodic than for the cathodic stimuli. This polarity effect was similar across all electrode locations studied, including the most apical electrode of the MedEl device which stimulates the very apex of the cochlea. In addition, when quadraphasic pulses were presented in bipolar mode, listeners reported hearing a lower pitch when the central portion was anodic at the more apical, than at the more basal, electrode. The results replicate previous reports that, unlike the results of most animal studies, human cochlear implant listeners are more sensitive to anodic than to cathodic currents, and extend those findings to a wider range of cochlear sites, implant types, and pulse shapes.

A comparison of spectral magnitude and phase-locking value analyses of the frequency-following response to complex tones

Two experiments, both presenting diotic, harmonic tone complexes (100 Hz fundamental), were conducted to explore the envelope-related component of the frequency-following response (FFRENV), a measure of synchronous, subcortical neural activity evoked by a periodic acoustic input. Experiment 1 directly compared two common analysis methods, computing the magnitude spectrum and the phase-locking value (PLV). Bootstrapping identified which FFRENV frequency components were statistically above the noise floor for each metric and quantified the statistical power of the approaches. Across listeners and conditions, the two methods produced highly correlated results. However, PLV analysis required fewer processing stages to produce readily interpretable results. Moreover, at the fundamental frequency of the input, PLVs were farther above the metric's noise floor than spectral magnitudes. Having established the advantages of PLV analysis, the efficacy of the approach was further demonstrated by investigating how different acoustic frequencies contribute to FFRENV, analyzing responses to complex tones composed of different acoustic harmonics of 100 Hz (Experiment 2). Results show that the FFRENV response is dominated by peripheral auditory channels responding to unresolved harmonics, although low-frequency channels driven by resolved harmonics also contribute. These results demonstrate the utility of the PLV for quantifying the strength of FFRENV across conditions.

Magnetoencephalographic study on forward suppression by ipsilateral, contralateral, and binaural maskers

When two tones are presented in a short time interval, the response to the second tone is suppressed. This phenomenon is referred to as forward suppression. To address the effect of the masker laterality on forward suppression, magnetoencephalographic responses were investigated for eight subjects with normal hearing when the preceding maskers were presented ipsilaterally, contralaterally, and binaurally. We employed three masker intensity conditions: the ipsilateral-strong, left-right-balanced, and contralateral-strong conditions. Regarding the responses to the maskers without signal, the N1m amplitude evoked by the left and binaural maskers was significantly larger than that evoked by the right masker for the left-strong and left-right-balanced conditions. No significant difference was observed for the right-strong condition. Regarding the subsequent N1m amplitudes, they were attenuated by the presence of the left, binaural, and right maskers for all conditions. For the left- and right-strong conditions, the subsequent N1m amplitude in the presence of the left masker was smaller than those of the binaural and right maskers. No difference was observed between the binaural and right masker presentation. For left-right-balanced condition, the subsequent N1m amplitude decreased in the presence of the right, binaural, and left maskers in that order. If the preceding activity reflected the ability to suppress the subsequent activity, the forward suppression by the left masker would be superior to that by the right masker for the left-strong and left-right-balanced conditions. Furthermore, the forward suppression by the binaural masker would be expected to be superior to that by the left masker owing to additional afferent activity from the right ear. Thus, the current results suggest that the forward suppression by ipsilateral maskers is superior to that by contralateral maskers although both maskers evoked the N1m amplitudes to the same degree. Additional masker at the contralateral ear can attenuate the forward suppression by the ipsilateral masker.

Fronto-temporal interactions in the theta-band during auditory deviant processing

Mismatch negativity (MMN) is a negative component of event-related potential (ERP) that reflects auditory deviant detection. Previous studies repeatedly suggested that MMN is generated by the fronto-temporal network. However, it is still unclear how the frontal and temporal areas interact. To verify this, we observed the spatiotemporal pattern of inter-regional functional connectivity using phase synchrony and Granger causality, by analyzing event-related electroencephalograms (EEGs) elicited by standard and deviant tones in an oddball paradigm. Strong theta-band phase synchrony and bidirectional Granger causality were observed between the frontal and temporal areas during the processing of auditory deviants, especially at the temporal interval of MMN. Our results support the hypothesis that fronto-temporal interactions are crucial to the generation of MMN during auditory deviant processing.

Effects of various electrode configurations on music perception, intonation and speaker gender identification

Advances in speech coding strategies and electrode array designs for cochlear implants (CIs) predominantly aim at improving speech perception. Current efforts are also directed at transmitting appropriate cues of the fundamental frequency (F0) to the auditory nerve with respect to speech quality, prosody, and music perception. The aim of this study was to examine the effects of various electrode configurations and coding strategies on speech intonation identification, speaker gender identification, and music quality rating. In six MED-EL CI users electrodes were selectively deactivated in order to simulate different insertion depths and inter-electrode distances when using the high definition continuous interleaved sampling (HDCIS) and fine structure processing (FSP) speech coding strategies. Identification of intonation and speaker gender was determined and music quality rating was assessed. For intonation identification HDCIS was robust against the different electrode configurations, whereas fine structure processing showed significantly worse results when a short electrode depth was simulated. In contrast, speaker gender recognition was not affected by electrode configuration or speech coding strategy. Music quality rating was sensitive to electrode configuration. In conclusion, the three experiments revealed different outcomes, even though they all addressed the reception of F0 cues. Rapid changes in F0, as seen with intonation, were the most sensitive to electrode configurations and coding strategies. In contrast, electrode configurations and coding strategies did not show large effects when F0 information was available over a longer time period, as seen with speaker gender. Music quality relies on additional spectral cues other than F0, and was poorest when a shallow insertion was simulated.

Sensory-motor interactions for vocal pitch monitoring in non-primary human auditory cortex

The neural mechanisms underlying processing of auditory feedback during self-vocalization are poorly understood. One technique used to study the role of auditory feedback involves shifting the pitch of the feedback that a speaker receives, known as pitch-shifted feedback. We utilized a pitch shift self-vocalization and playback paradigm to investigate the underlying neural mechanisms of audio-vocal interaction. High-resolution electrocorticography (ECoG) signals were recorded directly from auditory cortex of 10 human subjects while they vocalized and received brief downward (-100 cents) pitch perturbations in their voice auditory feedback (speaking task). ECoG was also recorded when subjects passively listened to playback of their own pitch-shifted vocalizations. Feedback pitch perturbations elicited average evoked potential (AEP) and event-related band power (ERBP) responses, primarily in the high gamma (70-150 Hz) range, in focal areas of non-primary auditory cortex on superior temporal gyrus (STG). The AEPs and high gamma responses were both modulated by speaking compared with playback in a subset of STG contacts. From these contacts, a majority showed significant enhancement of high gamma power and AEP responses during speaking while the remaining contacts showed attenuated response amplitudes. The speaking-induced enhancement effect suggests that engaging the vocal motor system can modulate auditory cortical processing of self-produced sounds in such a way as to increase neural sensitivity for feedback pitch error detection. It is likely that mechanisms such as efference copies may be involved in this process, and modulation of AEP and high gamma responses imply that such modulatory effects may affect different cortical generators within distinctive functional networks that drive voice production and control.

Influence of rhythmic grouping on duration perception: a novel auditory illusion

This study investigated a potential auditory illusion in duration perception induced by rhythmic temporal contexts. Listeners with or without musical training performed a duration discrimination task for a silent period in a rhythmic auditory sequence. The critical temporal interval was presented either within a perceptual group or between two perceptual groups. We report the just-noticeable difference (difference limen, DL) for temporal intervals and the point of subjective equality (PSE) derived from individual psychometric functions based on performance of a two-alternative forced choice task. In musically untrained individuals, equal temporal intervals were perceived as significantly longer when presented between perceptual groups than within a perceptual group (109.25% versus 102.5% of the standard duration). Only the perceived duration of the between-group interval was significantly longer than its objective duration. Musically trained individuals did not show this effect. However, in both musically trained and untrained individuals, the relative difference limens for discriminating the comparison interval from the standard interval were larger in the between-groups condition than in the within-group condition (7.3% vs. 5.6% of the standard duration). Thus, rhythmic grouping affected sensitivity to duration changes in all listeners, with duration differences being harder to detect at boundaries of rhythm groups than within rhythm groups. Our results show for the first time that temporal Gestalt induces auditory duration illusions in typical listeners, but that musical experts are not susceptible to this effect of rhythmic grouping.