A Spectral Network Model of Pitch Perception

A model of pitch perception, called the Spatial Pitch Network or SPINET model, is developed and analyzed. The model neurally instantiates ideas front the spectral pitch modeling literature and joins them to basic neural network signal processing designs to simulate a broader range of perceptual pitch data than previous spectral models. The components of the model arc interpreted as peripheral mechanical and neural processing stages, which arc capable of being incorporated into a larger network architecture for separating multiple sound sources in the environment. The core of the new model transforms a spectral representation of an acoustic source into a spatial distribution of pitch strengths. The SPINET model uses a weighted "harmonic sieve" whereby the strength of activation of a given pitch depends upon a weighted sum of narrow regions around the harmonics of the nominal pitch value, and higher harmonics contribute less to a pitch than lower ones. Suitably chosen harmonic weighting functions enable computer simulations of pitch perception data involving mistuned components, shifted harmonics, and various types of continuous spectra including rippled noise. It is shown how the weighting functions produce the dominance region, how they lead to octave shifts of pitch in response to ambiguous stimuli, and how they lead to a pitch region in response to the octave-spaced Shepard tone complexes and Deutsch tritones without the use of attentional mechanisms to limit pitch choices. An on-center off-surround network in the model helps to produce noise suppression, partial masking and edge pitch. Finally, it is shown how peripheral filtering and short term energy measurements produce a model pitch estimate that is sensitive to certain component phase relationships.

Pitch perception: A dynamical-systems perspective

Two and a half millennia ago Pythagoras initiated the scientific study of the pitch of sounds; yet our understanding of the mechanisms of pitch perception remains incomplete. Physical models of pitch perception try to explain from elementary principles why certain physical characteristics of the stimulus lead to particular pitch sensations. There are two broad categories of pitch-perception models: place or spectral models consider that pitch is mainly related to the Fourier spectrum of the stimulus, whereas for periodicity or temporal models its characteristics in the time domain are more important. Current models from either class are usually computationally intensive, implementing a series of steps more or less supported by auditory physiology. However, the brain has to analyze and react in real time to an enormous amount of information from the ear and other senses. How is all this information efficiently represented and processed in the nervous system? A proposal of nonlinear and complex systems research is that dynamical attractors may form the basis of neural information processing. Because the auditory system is a complex and highly nonlinear dynamical system, it is natural to suppose that dynamical attractors may carry perceptual and functional meaning. Here we show that this idea, scarcely developed in current pitch models, can be successfully applied to pitch perception.

Development of hemispheric specialization for lexical pitch-accent in Japanese infants.

Infants' speech perception abilities change through the first year of life, from broad sensitivity to a wide range of speech contrasts to becoming more finely attuned to their native language. What remains unclear, however, is how this perceptual change relates to brain responses to native language contrasts in terms of the functional specialization of the left and right hemispheres. Here, to elucidate the developmental changes in functional lateralization accompanying this perceptual change, we conducted two experiments on Japanese infants using Japanese lexical pitch-accent, which changes word meanings with the pitch pattern within words. In the first behavioral experiment, using visual habituation, we confirmed that infants at both 4 and 10 months have sensitivities to the lexical pitch-accent pattern change embedded in disyllabic words. In the second experiment, near-infrared spectroscopy was used to measure cortical hemodynamic responses in the left and right hemispheres to the same lexical pitch-accent pattern changes and their pure tone counterparts. We found that brain responses to the pitch change within words differed between 4- and 10-month-old infants in terms of functional lateralization: Left hemisphere dominance for the perception of the pitch change embedded in words was seen only in the 10-month-olds. These results suggest that the perceptual change in Japanese lexical pitch-accent may be related to a shift in functional lateralization from bilateral to left hemisphere dominance.

Auditory Imagery and the Poor-Pitch Singer

The vocal imitation of pitch by singing requires one to plan laryngeal movements on the basis of anticipated target pitch events. This process may rely on auditory imagery, which has been shown to activate motor planning areas. As such, we hypothesized that poor-pitch singing, although not typically associated with deficient pitch perception, may be associated with deficient auditory imagery. Participants vocally imitated simple pitch sequences by singing, discriminated pitch pairs on the basis of pitch height, and completed an auditory imagery self-report questionnaire (the Bucknell Auditory Imagery Scale). The percentage of trials participants sung in tune correlated significantly with self-reports of vividness for auditory imagery, although not with the ability to control auditory imagery. Pitch discrimination was not predicted by auditory imagery scores. The results thus support a link between auditory imagery and vocal imitation.

AIRSTREAM: A Neural Network Model of Auditory Scene Analysis and Source Segregation

Multiple sound sources often contain harmonics that overlap and may be degraded by environmental noise. The auditory system is capable of teasing apart these sources into distinct mental objects, or streams. Such an "auditory scene analysis" enables the brain to solve the cocktail party problem. A neural network model of auditory scene analysis, called the AIRSTREAM model, is presented to propose how the brain accomplishes this feat. The model clarifies how the frequency components that correspond to a give acoustic source may be coherently grouped together into distinct streams based on pitch and spatial cues. The model also clarifies how multiple streams may be distinguishes and seperated by the brain. Streams are formed as spectral-pitch resonances that emerge through feedback interactions between frequency-specific spectral representaion of a sound source and its pitch. First, the model transforms a sound into a spatial pattern of frequency-specific activation across a spectral stream layer. The sound has multiple parallel representations at this layer. A sound's spectral representation activates a bottom-up filter that is sensitive to harmonics of the sound's pitch. The filter activates a pitch category which, in turn, activate a top-down expectation that allows one voice or instrument to be tracked through a noisy multiple source environment. Spectral components are suppressed if they do not match harmonics of the top-down expectation that is read-out by the selected pitch, thereby allowing another stream to capture these components, as in the "old-plus-new-heuristic" of Bregman. Multiple simultaneously occuring spectral-pitch resonances can hereby emerge. These resonance and matching mechanisms are specialized versions of Adaptive Resonance Theory, or ART, which clarifies how pitch representations can self-organize durin learning of harmonic bottom-up filters and top-down expectations. The model also clarifies how spatial location cues can help to disambiguate two sources with similar spectral cures. Data are simulated from psychophysical grouping experiments, such as how a tone sweeping upwards in frequency creates a bounce percept by grouping with a downward sweeping tone due to proximity in frequency, even if noise replaces the tones at their interection point. Illusory auditory percepts are also simulated, such as the auditory continuity illusion of a tone continuing through a noise burst even if the tone is not present during the noise, and the scale illusion of Deutsch whereby downward and upward scales presented alternately to the two ears are regrouped based on frequency proximity, leading to a bounce percept. Since related sorts of resonances have been used to quantitatively simulate psychophysical data about speech perception, the model strengthens the hypothesis the ART-like mechanisms are used at multiple levels of the auditory system. Proposals for developing the model to explain more complex streaming data are also provided.

The prevalence of congenital amusia

L’amusie congénitale est un trouble neurogénétique qui se caractérise par une inhabileté à acquérir des habiletés musicales de base, telles que la perception musicale et la reconnaissance musicale normales, malgré une audition, un développement du langage et une intelligence normaux (Ayotte, Peretz & Hyde, 2002). Récemment, une éude d’aggrégation familiale a démontré que 39% des membres de familles d’individus amusiques démontrent le trouble, comparativement à 3% des membres de familles d’individus normaux (Peretz et al., 2007). Cette conclusion est intéressante puisqu’elle démontre une prévalence de l’amusie congénitale dans la population normale. Kalmus et Fry (1980) ont évalué cette prévalence à 4%, en utilisant le Distorted Tunes Test (DTT). Par contre, ce test présente certaines lacunes méthodologiques et statistiques, telles un effet plafond important, ainsi que l’usage de mélodies folkloriques, désavantageant les amusiques puisque ceux-ci ne peuvent pas assimiler ces mélodies correctement. L’étude présente visait à réévaluer la prévalence de l’amusie congénitale en utilisant un test en ligne récemment validé par Peretz et ses collègues (2008). Mille cent participants, d’un échantillon homogène, ont complété le test en ligne. Les résultats démontrent une prévalence globale de 11.6%, ainsi que quatre profiles de performance distincts: pitch deafness (1.5%), pitch memory amusia (3.2%), pitch perception amusia (3.3%), et beat deafness (3.3%). La variabilité des résultats obtenus avec le test en ligne démontre l’existence de quatre types d’amusies avec chacune une prévalence individuelle, indiquant une hétérogénéité dans l’expression de l’amusie congénitale qui devra être explorée ultérieurement.

Bases génétiques de l'amusie congénitale : une étude de jumeaux

L’amusie congénitale est un trouble neuro-développemental se définissant par des difficultés à percevoir la musique, et ce malgré une ouïe et une intelligence normales. Un déficit de discrimination fine des hauteurs serait à l’origine de ce trouble, qui se traduit notamment par une incapacité à détecter les fausses notes. afin de mieux comprendre les facteurs génétiques contribuant à la manifestation de l’amusie congénitale, la présente étude avait pour objectif: (a) de déterminer si la performance sur diverses tâches musicales et auditives était plus similaire chez les jumeaux identiques (monozygotes ; MZ) que chez les jumeaux non-identiques (dizygotes ; DZ) et (b) d’explorer les variables relatives à l’environnement musical des jumeaux, afin de mieux comprendre les contributions de l’environnement et de la génétique dans les différences sous-tendant les habiletés musicales. De plus, le profil des sujets amusiques a été analysé afin de vérifier s’il correspondait à celui décrit dans la littérature, faisant état de difficultés tonales, mais non rythmiques. Huit paires de jumeaux MZ et six paires de jumeaux DZ, parmi lesquelles au moins un des co-jumeaux était potentiellement amusique, ont pris part à cette étude. Les tâches consistaient en un test en ligne de perception mélodique et rythmique, un test de détection des différences de hauteurs, ainsi qu’un test de chant. L’analyse de la performance et de l’environnement musical des jumeaux MZ et DZ ne révèle aucune distinction comportementale entre ces deux groupes en ce qui concerne les habiletés musicales. Cela suggère que celles-ci puissent être davantage influencées par l’environnement partagé que par les facteurs génétiques. Enfin, les jumeaux amusiques ont le profil habituel d’habiletés musicales. En effet, ils commettent des erreurs de perception et de production musicale au niveau mélodique, mais ont une perception rythmique préservée. D’autres études, notamment avec de plus grands échantillons de jumeaux, seront nécessaires afin d’élucider la possible étiologie génétique sous-tendant l’amusie congénitale.

Le chant des amusiques : prédictions d'une dissociation entre les habiletés perceptives et vocales

L’objectif de cette étude était d’évaluer l’influence des habiletés perceptives sur les capacités de production vocale dans l’amusie congénitale. Treize amusiques et douze contrôles appariés ont réalisé quatre tâches : deux tâches de discrimination perceptive et deux tâches de production vocale. Les stimuli utilisés pour les tâches étaient des enregistrements vocaux provenant des participants, rendant les tâches plus écologiques et enlevant le besoin pour les participants de modifier le timbre des stimuli lorsqu’ils chantent. Les résultats ont démontré que, malgré le fait que les contrôles aient surpassé la performance des amusiques dans toutes les tâches, il y avait beaucoup plus de variabilité dans les performances des amusiques que prévu. La moitié des amusiques avaient des performances égales à celles des contrôles sur les deux tâches perceptives. D’autres amusiques montraient des performances égales ou semblables à celles des contrôles sur au moins une des tâches d’imitation vocale. Ces résultats mènent à croire qu’il serait possible que ces deux types d’habiletés musicales soient dissociables.

Pre-attentive auditory sensory processing in autistic spectrum disorder:are electromagnetic measurements telling us a coherent story?

Sensory processing is a crucial underpinning of the development of social cognition, a function which is compromised in variable degree in patients with pervasive developmental disorders (PDD). In this manuscript, we review some of the most recent and relevant contributions, which have looked at auditory sensory processing derangement in PDD. The variability in the clinical characteristics of the samples studied so far, in terms of severity of the associated cognitive deficits and associated limited compliance, underlying aetiology and demographic features makes a univocal interpretation arduous. We hypothesise that, in patients with severe mental deficits, the presence of impaired auditory sensory memory as expressed by the mismatch negativity could be a non-specific indicator of more diffuse cortical deficits rather than causally related to the clinical symptomatology. More consistent findings seem to emerge from studies on less severely impaired patients, in whom increased pitch perception has been interpreted as an indicator of increased local processing, probably as compensatory mechanism for the lack of global processing (central coherence). This latter hypothesis seems extremely attractive and future trials in larger cohorts of patients, possibly standardising the characteristics of the stimuli are a much-needed development. Finally, specificity of the role of the auditory derangement as opposed to other sensory channels needs to be assessed more systematically using multimodal stimuli in the same patient group. (c) 2006 Elsevier B.V. All rights reserved.

The role of musical aptitude in the pronunciation of English vowels among Polish learners of English

It has long been held that people who have musical training or talent acquire L2 pronunciation more successfully than those that do not. Indeed, there have been empirical studies to support this hypothesis (Pastuszek-Lipińska 2003, Fonseca-Mora et al. 2011, Zatorre and Baum 2012). However, in many of such studies, musical abilities in subjects were mostly verified through questionnaires rather than tested in a reliable, empirical manner. Therefore, we run three different musical hearing tests, i.e. pitch perception test, musical memory test, and rhythm perception test (Mandell 2009) to measure the actual musical aptitude in our subjects. The main research question is whether a better musical ear correlates with a higher rate of acquisition of English vowels in Polish EFL learners. Our group consists of 40 Polish university students studying English as their major who learn the British pronunciation model during an intense pronunciation course. 10 male and 30 female subjects with mean age of 20.1 were recorded in a recording studio. The procedure comprised spontaneous conversations, reading passages and reading words in isolation. Vowel measurements were conducted in Praat in all three speech styles and several consonantal contexts. The assumption was that participants who performed better in musical tests would produce vowels that are closer to the Southern British English model. We plotted them onto vowel charts and calculated the Euclidean distances. Preliminary results show that there is potential correlation between specific aspects of musical hearing and different elements of pronunciation. The study is a longitudinal project and will encompass two more years, during which we will repeat the recording procedure twice to measure the participants’ progress in mastering the English pronunciation and comparing it with their musical aptitude.

A BACKING DEVICE BASED ON AN EMBEDDED STIFFENER AND RETRACTABLE INSERTION TOOL FOR THIN-FILM COCHLEAR ARRAYS

Intracochlear trauma from surgical insertion of bulky electrode arrays and inadequate pitch perception are areas of concern with current hand-assembled commercial cochlear implants. Parylene thin-film arrays with higher electrode densities and lower profiles are a potential solution, but lack rigidity and hence depend on manually fabricated permanently attached polyethylene terephthalate (PET) tubing based bulky backing devices. As a solution, we investigated a new backing device with two sub-systems. The first sub-system is a thin poly(lactic acid) (PLA) stiffener that will be embedded in the parylene array. The second sub-system is an attaching and detaching mechanism, utilizing a poly(N-vinylpyrrolidone)-block-poly(d,l-lactide) (PVP-b-PDLLA) copolymer-based biodegradable and water soluble adhesive, that will help to retract the PET insertion tool after implantation. As a proof-of-concept of sub-system one, a microfabrication process for patterning PLA stiffeners embedded in parylene has been developed. Conventional hotembossing, mechanical micromachining, and standard cleanroom processes were integrated for patterning fully released and discrete stiffeners coated with parylene. The released embedded stiffeners were thermoformed to demonstrate that imparting perimodiolar shapes to stiffener-embedded arrays will be possible. The developed process when integrated with the array fabrication process will allow fabrication of stiffener-embedded arrays in a single process. As a proof-of-concept of sub-system two, the feasibility of the attaching and detaching mechanism was demonstrated by adhering 1x and 1.5x scale PET tube-based insertion tools and PLA stiffeners embedded in parylene using the copolymer adhesive. The attached devices survived qualitative adhesion tests, thermoforming, and flexing. The viability of the detaching mechanism was tested by aging the assemblies in-vitro in phosphate buffer solution. The average detachment times, 2.6 minutes and 10 minutes for 1x and 1.5x scale devices respectively, were found to be clinically relevant with respect to the reported array insertion times during surgical implantation. Eventually, the stiffener-embedded arrays would not need to be permanently attached to current insertion tools which are left behind after implantation and congest the cochlear scala tympani chamber. Finally, a simulation-based approach for accelerated failure analysis of PLA stiffeners and characterization of PVP-b-PDLLA copolymer adhesive has been explored. The residual functional life of embedded PLA stiffeners exposed to body-fluid and thereby subjected to degradation and erosion has been estimated by simulating PLA stiffeners with different parylene coating failure types and different PLA types for a given parylene coating failure type. For characterizing the PVP-b-PDLLA copolymer adhesive, several formulations of the copolymer adhesive were simulated and compared based on the insertion tool detachment times that were predicted from the dissolution, degradation, and erosion behavior of the simulated adhesive formulations. Results indicate that the simulation-based approaches could be used to reduce the total number of time consuming and expensive in-vitro tests that must be conducted.

Issues in the development of pitch labelling skill

Pitch discrimination skills are important for general musicianship. The ability to name musical notes or produce orally any named note without the benefit of a known reference is called Absolute Pitch (AP) and is comparatively rare. Relative Pitch (RP) is the ability to name notes when a known reference is available. AP has historically been regarded as being innate. This paper will examine the notion that pitch discrimination skill is based on knowledge constructed through a suite of experiences. That is, it is learnt. In particular, it will be argued that early experiences promote the development of AP. Second it will argue that AP and RP represent different types of knowledge, and that this knowledge emerges from different experiences. AP is a unique research phenomenon because it spans the fields of cognition and perception, in that it links verbal labels with physiological sensations, and because of its rarity. It may provide a vantage for investigating the nature/nurture of musicianship; expertise; knowledge structure development; and the role of knowledge in perception. The study of AP may inform educational practice and curriculum design both in music and cross-curriculur. This paper will report an initial investigation into the similarities and differences between the musical experiences of AP possessors and the manifestation of their AP skill. Interview and questionnaire data will be used for the development and proposal of a preliminary model for AP development.