Martin D. Vestergaard

Progressive associative phonagnosia: A neuropsychological analysis

There are few detailed studies of impaired voice recognition, or phonagnosia. Here we describe two patients with progressive phonagnosia in the context of frontotemporal lobar degeneration. Patient QR presented with behavioural decline and increasing difficulty recognising familiar voices, while patient KL presented with progressive prosopagnosia. In a series of neuropsychological experiments we assessed the ability of QR and KL to recognise and judge the familiarity of voices, faces and proper names, to recognise vocal emotions, to perceive and discriminate voices, and to recognise environmental sounds and musical instruments. The patients were assessed in relation to a group of healthy age-matched control subjects. QR exhibited severe impairments of voice identification and familiarity judgments with relatively preserved recognition of difficulty-matched faces and environmental sounds; recognition of musical instruments was impaired, though better than recognition of voices. In contrast, patient KL exhibited severe impairments of both voice and face recognition, with relatively preserved recognition of musical instruments and environmental sounds. Both patients demonstrated preserved ability to analyse perceptual properties of voices and to recognise vocal emotions. The voice processing deficit in both patients could be characterised as associative phonagnosia: in the case of QR, this was relatively selective for voices, while in the case of KL, there was evidence for a multimodal impairment of person knowledge. The findings have implications for current cognitive models of voice recognition.

Dead regions in the cochlea: Implications for speech recognition and applicability of articulation index theory

Dead regions in the cochlea have been suggested to be responsible for failure by hearing aid users to benefit from apparently increased audibility in terms of speech intelligibility. As an alternative to the more cumbersome psychoacoustic tuning curve measurement, threshold-equalizing noise (TEN) has been reported to enable diagnosis of dead regions. The purpose of the present study was first to assess the feasibility of the TEN test protocol, and second, to assess the ability of the procedure to reveal related functional impairment. The latter was done by a test for the recognition of low-pass-filtered speech items. Data were collected from 22 hearing-impaired subjects with moderate-to-profound sensorineural hearing losses. The results showed that 11 subjects exhibited abnormal psychoacoustic behaviour in the TEN test, indicative of a possible dead region. Estimates of audibility were used to assess the possible connection between dead-region candidacy and ability to recognize low-pass-filtered speech. Large variability was observed with regard to the ability of audibility to predict recognition scores for both dead-region and no-dead-region subjects. Furthermore, the results indicate that dead-region subjects might be better than no-dead-region subjects at recognizing speech of marginal audibility. Se ha sugerido que las regiones cocleares muertas son responsables del fracaso de algunos usuaríos de auxiliares auditivos en beneficiarse del aparente aumento de audibilidad en términos de inteligibilidad del lenguaje. Como alternativa a la medición psicoacústica de las curvas de frecuencia característica, se ha reportado que la prueba de ruido ecualizante del umbral (TEN) permite el diagnóstico de estas regiones. El propósito de este estudio, en primer lugar, fue conocer la factibilidad de un protocolo de pruebas TEN y segundo, evaluar la habilidad de este procedimiento para revelar trastornos funcionales relacionados. Esto último se logró por medio de una prueba de reconocimiento de items de lenguaje con filtrado pasa-bajo. Se colectaron datos de 22 hipoacúsicos con pérdidas sensorineurales moderadas a profundas. Los resultados demostraron que 11 sujetos mostraron un comportamiento psicoacústico anormal en la prueba TEN, lo que indica una posible muerte de la región. Se utilizaron cálculos de audibilidad para probar la posible conexión entre una probable región muerta y la habilidad para reconocer lenguaje con filtro pasa-bajo. Se observo una amplia variabilidad en la predicción de puntaje de reconocimiento tanto en sujetos con regiones muertas como en sujetos sin ellas. Además, los resultados indican que los sujetos con regiones muertas pueden reconocer mejor el lenguaje en un nivel de audibilidad marginal.

Timbre‐independent extraction of pitch in newborn infants

The ability to separate pitch from other spectral sound features, such as timbre, is an important prerequisite of veridical auditory perception underlying speech acquisition and music cognition. The current study investigated whether or not newborn infants generalize pitch across different timbres. Perceived resonator size is an aspect of timbre that informs the listener about the size of the sound source, a cue that may be important already at birth. Therefore, detection of infrequent pitch changes was tested by recording event-related brain potentials in healthy newborn infants to frequent standard and infrequent pitch-deviant sounds while the perceived resonator size of all sounds was randomly varied. The elicitation of an early negative and a later positive discriminative response by deviant sounds demonstrated that the neonate auditory system represents pitch separately from timbre, thus showing advanced pitch processing capabilities.

Evidence Accumulation in Obsessive-Compulsive Disorder: the Role of Uncertainty and Monetary Reward on Perceptual Decision-Making Thresholds

The compulsive behaviour underlying obsessive-compulsive disorder (OCD) may be related to abnormalities in decision-making. The inability to commit to ultimate decisions, for example, patients unable to decide whether their hands are sufficiently clean, may reflect failures in accumulating sufficient evidence before a decision. Here we investigate the process of evidence accumulation in OCD in perceptual discrimination, hypothesizing enhanced evidence accumulation relative to healthy volunteers. Twenty-eight OCD patients and thirty-five controls were tested with a low-level visual perceptual task (random-dot-motion task, RDMT) and two response conflict control tasks. Regression analysis across different motion coherence levels and Hierarchical Drift Diffusion Modelling (HDDM) were used to characterize response strategies between groups in the RDMT. Patients required more evidence under high uncertainty perceptual contexts, as indexed by longer response time and higher decision boundaries. HDDM, which defines a decision when accumulated noisy evidence reaches a decision boundary, further showed slower drift rate towards the decision boundary reflecting poorer quality of evidence entering the decision process in patients under low uncertainty. With monetary incentives emphasizing speed and penalty for slower responses, patients decreased the decision thresholds relative to controls, accumulating less evidence in low uncertainty. These findings were unrelated to visual perceptual deficits and response conflict. This study provides evidence for impaired decision-formation processes in OCD, with a differential influence of high and low uncertainty contexts on evidence accumulation (decision threshold) and on the quality of evidence gathered (drift rates). It further emphasizes that OCD patients are sensitive to monetary incentives heightening speed in the speed-accuracy tradeoff, improving evidence accumulation.

The interaction of vocal characteristics and audibility in the recognition of concurrent syllables

In concurrent-speech recognition, performance is enhanced when either the glottal pulse rate (GPR) or the vocal tract length (VTL) of the target speaker differs from that of the distracter, but relatively little is known about the trading relationship between the two variables, or how they interact with other cues such as signal-to-noise ratio (SNR). This paper presents a study in which listeners were asked to identify a target syllable in the presence of a distracter syllable, with carefully matched temporal envelopes. The syllables varied in GPR and VTL over a large range, and they were presented at different SNRs. The results showed that performance is particularly sensitive to the combination of GPR and VTL when the SNR is 0 dB. Equal-performance contours showed that when there are no other cues, a two-semitone difference in GPR produced the same advantage in performance as a 20% difference in VTL. This corresponds to a trading relationship between GPR and VTL of 1.6. The results illustrate that the auditory system can use any combination of differences in GPR, VTL, and SNR to segregate competing speech signals.

Self-report outcome in new hearing-aid users: Longitudinal trends and relationships between subjective measures of benefit and satisfaction

This study focussed on self-report outcome in new hearing-aid users. The objectives of the experiment were changes in self-report outcome over time, and relationships between different subjective measures of benefit and satisfaction. Four outcome inventories and a questionnaire on auditory lifestyle were administered to 25 hearing-aid users repeatedly after hearing-aid fitting, and assessments took place one week, four weeks, and 13 weeks after hearing-aid provision. The results showed that, for first-time users who used their hearing aids more than four hours per day, self-reported outcome increased over 13 weeks in some scales, although there was no change in amplification during this time. Furthermore, it was found that, for data collected immediately post-fitting, some subscales were much less face valid than for data collected later. This result indicates that the way in which hearing-aid users assess outcome changes over time. The practical consequence of the results is that early self-report outcome assessment may be misleading for some self-report outcome schemes. Sumario El estudio se enfocó en los resultados auto-reportados en nuevos usuarios de auxiliares auditivos (AA). Los objetivos del experimento fueron los cambios en los resultados auto-reportados en el tiempo y las relaciones entre las diferentes mediciones subjetivas de beneficio y satisfacción. Se aplicaron cuatro inventarios de resultados y un cuestionario sobre estilo de vida auditivo a 25 usuarios de AAdespués de la adaptación; la evaluación tuvo lugar una, cuatro y trece semanas después. Los resultados muestran que para los nuevos usuarios que utilizan su AA más de 4 horas al día, los resultados auto-reportados mejoran en algunas escalas en el curso de 13 semanas, aun cuando no hubiera cambio en la amplificación durante este tiempo. Incluso, se encontró que los datos colectados inmediatamente después de la adaptación, fueron menos válidos que los colectados posteriormente. Estos resultados indican que la forma en que los usuarios evalúan los resultados, cambia con el tiempo. La consecuencia práctica es que los resultados auto-reportados tempranamente pueden ser engañosos en algunos esquemas de resultados auto-reportados.

Adaptive Prediction Error Coding in the Human Midbrain and Striatum Facilitates Behavioral Adaptation and Learning Efficiency

Summary Effective error-driven learning benefits from scaling of prediction errors to reward variability. Such behavioral adaptation may be facilitated by neurons coding prediction errors relative to the standard deviation (SD) of reward distributions. To investigate this hypothesis, we required participants to predict the magnitude of upcoming reward drawn from distributions with different SDs. After each prediction, participants received a reward, yielding trial-by-trial prediction errors. In line with the notion of adaptive coding, BOLD response slopes in the Substantia Nigra/Ventral Tegmental Area (SN/VTA) and ventral striatum were steeper for prediction errors occurring in distributions with smaller SDs. SN/VTA adaptation was not instantaneous but developed across trials. Adaptive prediction error coding was paralleled by behavioral adaptation, as reflected by SD-dependent changes in learning rate. Crucially, increased SN/VTA and ventral striatal adaptation was related to improved task performance. These results suggest that adaptive coding facilitates behavioral adaptation and supports efficient learning.

Effects of voicing in the recognition of concurrent syllables.

This letter reports a study designed to measure the benefits of voicing in the recognition of concurrent syllables. The target and distracter syllables were either voiced or whispered, producing four combinations of vocal contrast. Results show that listeners use voicing whenever it is present either to detect a target syllable or to reject a distracter. When the predictable effects of audibility were taken into account, limited evidence remained for the harmonic cancellation mechanism thought to make rejecting distracter syllables more effective than enhancing target syllables.

Dopamine Modulates the Neural Representation of Subjective Value of Food in Hungry Subjects

Although there is a rich literature on the role of dopamine in value learning, much less is known about its role in using established value estimations to shape decision-making. Here we investigated the effect of dopaminergic modulation on value-based decision-making for food items in fasted healthy human participants. The Becker-deGroot-Marschak auction, which assesses subjective value, was examined in conjunction with pharmacological fMRI using a dopaminergic agonist and an antagonist. We found that dopamine enhanced the neural response to value in the inferior parietal gyrus/intraparietal sulcus, and that this effect predominated toward the end of the valuation process when an action was needed to record the value. Our results suggest that dopamine is involved in acting upon the decision, providing additional insight to the mechanisms underlying impaired decision-making in healthy individuals and clinical populations with reduced dopamine levels.

The mutual roles of temporal glimpsing and vocal characteristics in cocktail-party listeninga)

At a cocktail party, listeners must attend selectively to a target speaker and segregate their speech from distracting speech sounds uttered by other speakers. To solve this task, listeners can draw on a variety of vocal, spatial, and temporal cues. Recently, Vestergaard et al. [J. Acoust. Soc. Am. 125, 1114-1124 (2009)] developed a concurrent-syllable task to control temporal glimpsing within segments of concurrent speech, and this allowed them to measure the interaction of glottal pulse rate and vocal tract length and reveal how the auditory system integrates information from independent acoustic modalities to enhance recognition. The current paper shows how the interaction of these acoustic cues evolves as the temporal overlap of syllables is varied. Temporal glimpses as short as 25 ms are observed to improve syllable recognition substantially when the target and distracter have similar vocal characteristics, but not when they are dissimilar. The effect of temporal glimpsing on recognition performance is strongly affected by the form of the syllable (consonant-vowel versus vowel-consonant), but it is independent of other phonetic features such as place and manner of articulation.