Auditory System

The purpose of this paper is to present the experimental device and the work in progress performed in search for objective organic correlation of damage to hearing, examining possible acoustic otofunctional effects on the cochlear epithelium of the rat due to exposure to microwaves (900 MHz). Two experiments using male Sprague-Dawley rats were carried out with a far-field exposure in a cubic chamber. No statistically significant evidence was obtained at both specific absorption rate (SAR) values. The exposure system and the diagnostic apparatus are extremely useful to investigate a potential effect on the auditory system: however, with the parameters applied in these experiments, no evidence was observed.

Normal maturation and functioning of the central auditory system affects the development of speech perception and oral language capabilities. This study examined maturation of central auditory pathways as reflected by age-related changes in the P1/N1 components of the auditory evoked potential (AEP). A synthesized consonant-vowel syllable (ba) was used to elicit cortical AEPs in 86 normal children ranging in age from 6 to 15 years and ten normal adults. Distinct age-related changes were observed in the morphology of the AEP waveform. The adult response consists of a prominent negativity (N1) at about 100 ms, preceded by a smaller P1 component at about 50 ms. In contrast, the child response is characterized by a large P1 response at about 100 ms. This wave decreases significantly in latency and amplitude up to about 20 years of age. In children, P1 is followed by a broad negativity at about 200 ms which we term N1b. Many subjects (especially older children) also show an earlier negativity (N1a). Both N1a and N1b latencies decrease significantly with age. Amplitudes of N1a and N1b do not show significant age-related changes. All children have the N1b; however, the frequency of occurrence of N1a increases with age. Data indicate that the child P1 develops systematically into the adult response; however, the relationship of N1a and N1b to the adult N1 is unclear. These results indicate that maturational changes in the central auditory system are complex and extend well into the second decade of life.

The hearing abilities of a group of 30 elderly (67–93yr of age) subjects were compared with those of a group of 30 young (19–27yr of age) normal hearing volunteers with the aim of characterizing the changes in the peripheral and central parts of the auditory system. In elderly subjects the pure-tone thresholds were typically represented by a gradually sloping curve

Current predictors of speech intelligibility are inadequate for understanding and predicting speech confusions caused by acoustic interference. We develop a model of auditory speech processing that includes a phenomenological representation of the action of the Medial Olivocochlear efferent pathway and that is capable of predicting consonant confusions made by normal hearing listeners in speech-shaped Gaussian noise. We then use this model to predict human error patterns of initial consonants in consonant-vowelconsonant words in the context of a Dynamic Rhyme Test. In the process we demonstrate its potential for speech discrimination in noise. Our results produced performance that was robust to varying levels of stationary additive speech-shaped noise and which mimicked human performance in discrimination of synthetic speech as measured by the Chi-squared test.

This paper describes a detailed protocol for obtaining chronic, multi-site unit recordings in cerebral cortex of awake animals for periods of three months or more. The protocol includes details for making relatively simple and inexpensive implantable multichannel electrodes that consist of arrays of separate microwires. The results reported in this paper suggest that a viable implant will have discriminable unit activity on about 80% of the electrodes, resulting in, on average, the simultaneous unit recording of upwards of 60 units during a daily recording session. The active electrodes during one recording session tend to remain active in subsequent recording sessions for several weeks. Using the methods described here, implants have been constructed which incorporate several different electrode materials, coatings, sizes, and electrode separation within a single array. These microwire electrode arrays provide the basic technology for obtaining unit recordings for several months. This provides a model system for studying biocompatibility of neural implants, which is a critical component for the development of neural implants that have an indefinite working span. q

Most contemporary cochlear implants (CIs) stimulate the auditory nerve with trains of amplitude-modulated, symmetric biphasic pulses. Although both polarities of a pulse can depolarize the nerve fibers and generate action potentials, it remains unknown which of the two (positive or negative) phases has the stronger effect. Understanding the effects of pulse polarity will help to optimize the stimulation protocols and to deliver the most relevant information to the implant listeners. Animal experiments have shown that cathodic (negative) current flows are more effective than anodic (positive) ones in eliciting neural responses, and this finding has motivated the development of novel speech-processing algorithms. In this study, we show electrophysiologically and psychophysically that the human auditory system exhibits the opposite pattern, being more sensitive to anodic stimulation. We measured electrically evoked compound action potentials in CI listeners for phase-separated pulses, allowing us to tease out the responses to each of the two oppositepolarity phases. At an equal stimulus level, the anodic phase yielded the larger response. Furthermore, a measure of psychophysical masking patterns revealed that this polarity difference was still present at higher levels of the auditory system and was therefore not solely due to antidromic propagation of the neural response. This finding may relate to a particular orientation of the nerve fibers relative to the electrode or to a substantial degeneration and demyelination of the peripheral processes. Potential applications to improve CI speech-processing strategies are discussed.

recently demonstrated that place of articulation of initial voiced stops could be identified from time-varying features observed in visual displays of linear prediction smoothed spectra. The present study extends this method of analysis in several directions. First, both voiced and voiceless syllable-initial stops produced at three speaking rates-normal, fast, and slow-were examined. Second, a new rule for vocal tract size normalization was tested. Third. the earlier time-varying features were augmented in order to specify the burst and voicing as well as place of articulation. The four time-varying features were (1) an abrupt increase in energy at high frequencies, (2) the onset of a prominent low-frequency peak.

Hearing disorders are common among children with autism, ranging from peripheral and sensorineural hearing deficit or loss to auditory hypersensitivity with bizarre reactions to sounds. The auditory abnormalities and consequent sensory deprivation exacerbate the communication deficit of autism, and early auditory assessment holds an important place in the planning of intervention and the overall prognosis of patients. Physiologic, pathologic, imaging, and neurochemical studies have revealed an array of aberrations in the perception and processing of the audiologic stimuli, including (among others) maturational defects, atypical lateralization, and serotonin dysfunction. Ó

In this study, we present a binaural scene analyzer that is able to simultaneously localize, detect and identify a known number of target speakers in the presence of spatially positioned noise sources and reverberation. In contrast to many other binaural cocktail party processors, the proposed system does not require a priori knowledge about the azimuth position of the target speakers. The proposed system consists of three main building blocks: binaural localization, speech source detection, and automatic speaker identification. First, a binaural front-end is used to robustly localize relevant sound source activity. Second, a speech detection module based on missing data classification is employed to determine whether detected sound source activity corresponds to a speaker or to an interfering noise source using a binary mask that is based on spatial evidence supplied by the binaural front-end. Third, a second missing data classifier is used to recognize the speaker identities of all detected speech sources. The proposed system is systematically evaluated in simulated adverse acoustic scenarios. Compared to state-of-the art MFCC recognizers, the proposed model achieves significant speaker recognition accuracy improvements.

Existe um crescimento elevado da oferta de produtos e serviços das empresas de teleatendimento. Porém, os operadores usuários de fones de ouvido mostram-se afetados pela exposição a ruído, podendo estar sujeitos à perda auditiva permanente e irreversível devido à exposição acima dos limites permissíveis. Os métodos tradicionais de medição da exposição a ruído não são adequados quando a fonte sonora é instalada diretamente sobre o sistema auditivo externo (orelha) através do uso de fones. Neste trabalho, a norma ISO 11904 é usada para avaliar a exposição a ruído em operadores de teleatendimento, considerando duas técnicas: cabeça artificial padronizada e microfone em ouvido real. Os resultados obtidos demonstraram que os dois métodos aplicados são eficientes e efetivos, podendo contribuir na avaliação apropriada da exposição a ruído em usuários de fones de ouvido de teleatendimento.

Background and Aim: In the last few decades, the total number of preterm newborns, with ges-tational age less than 35 weeks, who survived the prematurity conditions, has increased significantly. This might lead to a high prevalence of late neurocognitive and developmental abnormalities. The neurological development is closely related to the hearing and language acquisition ; these factors play a crucial role in social and emotional growth. The present review emphasizes the consequences of preterm birth on neurodevelopment, speech-language, and auditory system. Recent Findings: The relationship between the preterm birth and neural developmental indicates that prematurity could lead to a higher risk of cerebral palsy, developmental delay, and mental retardation as compared to the birth at term. The preterm newborns would be deprived of normally enriched hearing experience during the length of hospital stay, which is markedly different from that of the typical full-term new-borns. This altered hearing ability might impede the early normal development of auditory neural pathways in preterm children, posing serious

Hearing aid amplification can be used as a model for studying the effects of auditory stimulation on the central auditory system (CAS). We examined the effects of stimulus presentation level on the physiological detection of sound in unaided and aided conditions. P1, N1, P2, and N2 cortical evoked potentials were recorded in sound field from 13 normal-hearing young adults in response to a 1000-Hz tone presented at seven stimulus intensity levels. As expected, peak amplitudes increased and peak latencies decreased with increasing intensity for unaided and aided conditions. However, there was no significant effect of amplification on latencies or amplitudes. Taken together, these results demonstrate that 20 dB of hearing aid gain affects neural responses differently than 20 dB of stimulus intensity change. Hearing aid signal processing is discussed as a possible contributor to these results. This study demonstrates (1) the importance of controlling for stimulus intensity when evoking responses in aided conditions, and (2) the need to better understand the interaction between the hearing aid and the CAS.

The effect of spatial separation on the ability of human listeners to resolve a pair of concurrent broadband sounds was examined. Stimuli were presented in a virtual auditory environment using individualized outer ear filter functions. Subjects were presented with two simultaneous noise bursts that were either spatially coincident or separated ͑horizontally or vertically͒, and responded as to whether they perceived one or two source locations. Testing was carried out at five reference locations on the audiovisual horizon ͑0°, 22.5°, 45°, 67.5°, and 90°azimuth͒. Results from experiment 1 showed that at more lateral locations, a larger horizontal separation was required for the perception of two sounds. The reverse was true for vertical separation. Furthermore, it was observed that subjects were unable to separate stimulus pairs if they delivered the same interaural differences in time ͑ITD͒ and level ͑ILD͒. These findings suggested that the auditory system exploited differences in one or both of the binaural cues to resolve the sources, and could not use monaural spectral cues effectively for the task. In experiments 2 and 3, separation of concurrent noise sources was examined upon removal of low-frequency content ͑and ITDs͒, onset/offset ITDs, both of these in conjunction, and all ITD information. While onset and offset ITDs did not appear to play a major role, differences in ongoing ITDs were robust cues for separation under these conditions, including those in the envelopes of high-frequency channels.

Objective: The aim of the present experiment was to assess the consequences of cochlear implantation at different ages on the development of the human central auditory system. Design: Our measure of the maturity of central auditory pathways was the latency of the P1 cortical auditory evoked potential. Because P1 latencies vary as a function of chronological age, they can be used to infer the maturational status of auditory pathways in congenitally deafened children who regain hearing after being fit with a cochlear implant. We examined the development of P1 response latencies in 104 congenitally deaf children who had been fit with cochlear implants at ages ranging from 1.3 yr to 17.5 yr and three congenitally deaf adults. The independent variable was the duration of deafness before cochlear implantation. The dependent variable was the latency of the P1 cortical auditory evoked potential.

Human capital (HC) represents the cumulative tacit knowledge that is embedded in the minds of people in organisations. HC is important to organisations because it serves as a source of innovation and strategic renewal. Individuals carry HC when they join an organisation and take their talent, skills and tacit knowledge with them when they leave the organisation. Thus HC is volatile in nature. Organisations are therefore keen to do what they can to foster and develop HC as a means of achieving sustainable competitive advantage. This paper argues that neuro-linguistic programming (NLP) has the potential of developing and enhancing the stock of HC in organisations. NLP emerged in the 1970s from the University of California, USA. NLP suggests that subjective experience is encoded in terms of three main representation systems: visual, auditory, and kinaesthetic (VAK). NLP practitioners claim that people tend to have one preferred representation system over another in a given context. Despite that previous research has shown that NLP can assist in facilitating knowledge and learning capabilities, very limited research is conducted using NLP in nurturing HC in organisations. This paper critically reviews the literature and theoretically argues that NLP can be used as a practical approach to develop HC in organisations. This is because NLP primarily focuses on individual internal learning and that learning likely leads to the accumulation of HC in organisations. In other words, organisational members may find it more effective to enhance their tacit knowledge, both individually and collectively, if they adopt the NLP approach in their day-to-day work. Examples on how NLP may be used to develop HC in organisations will be provided. Future research direction and limitations will also be discussed.

With the advent of image and video representation of visual scenes in digital computer, subsequent necessity of vision-substitution representation of a given image is felt. The medium for non-visual representation of an image is chosen to be sound due to well developed auditory sensing ability of human beings and wide availability of cheap audio hardware. Visionary information of an image can be conveyed to blind and partially sighted persons through auditory representation of the image within some of the known limitations of human hearing system. The research regarding image sonification has mostly evolved through last three decades. The paper also discusses in brief about the reverse mapping, termed as sound visualization. This survey approaches to summarize the methodologies and issues of the implemented and unimplemented experimental systems developed for subjective sonification of image scenes and let researchers accumulate knowledge about the previous direction of researches in this domain.

Purpose: To investigate the incidence of radiation-induced ototoxicity according to the total dose delivered to specific parts of the auditory system, fractionation, and chemotherapy. Methods and Materials: Records of 325 patients treated for primary extracranial head and neck tumors with curative intent who received radiotherapy between 1964 and 2000 (median follow-up, 5.4 years) were retrospectively reviewed. Reconstructions of the treatment plans were generated to estimate the doses received by components of the auditory system. Results: Radiotherapy-induced morbidity developed in 41.8% of patients (external ear, 33.2%; middle ear, 28.6%; and inner ear, 26.8%). Univariate/multivariate analyses indicate that total dose received by parts of the auditory system seem to be significant, though fractionation and chemoradiation may contribute to the incidence of ototoxicities. Sensorineural hearing loss (SNHL) was observed in 49 patients (15.1%). Univariate and multivariate analyses indicated that age (p ‫؍‬ 0.0177 and p ‫؍‬ 0.005) and dose to cochlea (p < 0.0001 and p < 0.0001) were significant, and chemoradiation (p ‫؍‬ 0.0281 and p ‫؍‬ 0.006) may increase the incidence of SNHL.

Sound communication is not unique to humans but rather is a trait shared with most non-mammalian vertebrates. A practical way to address questions of vocal signal encoding has been to identify mechanisms in non-mammalian model systems that use acoustic communication signals in their social behavior. Teleost fishes, the largest group of living vertebrates, include both vocal and non-vocal species that exploit a wide range of acoustic niches. Here, we focus on those vocal species where combined behavioral and neurobiological studies have recently begun to elucidate a suite of adaptations for both the production and the perception of acoustic signals essential to their reproductive success and survival. Studies of these model systems show that teleost fish have the vocal-acoustic behaviors and neural systems both necessary and sufficient to solve acoustic problems common to all vertebrates. In particular, behavioral studies demonstrate that temporal features within a call, including pulse duration, rate and number, can all be important to a call's communicative value. Neurobiological studies have begun to show how these features are produced by a vocal motor system extending from forebrain to hindbrain levels and are encoded by peripheral and central auditory neurons. The abundance and variety of vocal fish present unique opportunities for parallel investigations of neural encoding, perception, and communication across a diversity of natural, acoustic habitats. As such, investigations in teleosts contribute to our delineating the evolution of the vocal and auditory systems of both non-mammalian and mammalian species, including humans.

Objective: We measured late cortical potentials in a psychophysical procedure for binaural unmasking of a dichotically-embedded pitch. Methods: Late-latency auditory evoked potentials were measured from 128 recording channels in 13 healthy subjects. Control stimuli consisted of 500 ms segments of broadband acoustic noise presented identically to both ears via earphones, evoking a perception of noise localized in the centre of the head. Dichotic pitch stimuli were created by introducing a dichotic delay to a narrow frequency region of the same noise segments, and resulted in a perception of both the centrally-located noise and a right-lateralized pitch.

Age-related hearing loss – presbycusis – is the most common communication problem and third most prevalent chronic medical disorder of the aged. The CBA and C57BL/6 mouse strains are useful for studying features of presbycusis. The CBA loses its hearing slowly, like most ...

The firing pattern of auditory neurons is determined in part by the type of voltage-sensitive potassium channels expressed. The expression patterns for two high-threshold potassium channels, Kv3.1 and Kv3.3, that differ in inactivation properties were examined in the rat auditory system. The positive activation voltage and rapid deactivation kinetics of these channels provide rapid repolarization of action potentials with little effect on action potential threshold. In situ hybridization experiments showed that Kv3.3 mRNA was highly expressed in most auditory neurons in the rat brainstem, whereas Kv3.

Musicians have a variety of perceptual and cortical specializations compared to non-musicians. Recent studies have shown that potentials evoked from primarily brainstem structures are enhanced in musicians, compared to non-musicians. Specifically, musicians have more robust representations of pitch periodicity and faster neural timing to sound onset when listening to sounds or both listening to and viewing a speaker. However, it is not known whether musician-related enhancements at the subcortical level are correlated with specializations in the cortex. Does musical training shape the auditory system in a coordinated manner or in disparate ways at cortical and subcortical levels? To answer this question, we recorded simultaneous brainstem and cortical evoked responses in musician and non-musician subjects. Brainstem response periodicity was related to early cortical response timing across all subjects, and this relationship was stronger in musicians. Peaks of the brainstem response evoked by sound onset and timbre cues were also related to cortical timing. Neurophysiological measures at both levels correlated with musical skill scores across all subjects. In addition, brainstem and cortical measures correlated with the age musicians began their training and the years of musical practice. Taken together, these data imply that neural representations of pitch, timing and timbre cues and cortical response timing are shaped in a coordinated manner, and indicate corticofugal modulation of subcortical afferent circuitry.

This experiment was designed to investigate the function of vocalisations of the parturient ewe Ž . to her lambs in two breeds of sheep, a highly selected lowland breed Suffolk , and a less selected Ž . hill breed Scottish Blackface . Sheep have a specific lambing vocalisation, the low-pitched bleat or "rumble", that is made almost exclusively to the lamb. The hypothesis was that this "care-giver" bleat will be important in the formation of the ewe-lamb bond. Ewes also make high-pitched bleats, considered to be "protest" or distress bleats, after the birth of the lamb. Vocalisation data were collected from inexperienced and experienced ewes of both breeds, and their lambs. Additionally, an embryo transfer study between the two breeds was carried out to investigate interactions between ewe and lamb bleating. Low-pitched bleating was higher in Ž primiparous ewes than multiparous ewes, and highest in primiparous Blackface ewes mean bleat rate: primiparous Blackfaces 7.04, multiparous Blackfaces 2.73, primiparous Suffolks 3.99, . multiparous Suffolks 2.18; P -0.005 . An increase in litter size, or raising lambs of a different breed, had no effect on the rate of low-pitched bleating. The number of Suffolk ewes making Ž high-pitched bleats was greater than Blackface ewes 61.4% vs. 35% for Suffolk and Blackface . ewes respectively, P -0.01 and the rate of bleating increased with twin litters. Suffolk lambs had Ž a higher bleat rate than Blackface lambs mean bleat rate: Blackfaces 0.252, Suffolks 0.622, . P -0.01 , and lambs born to a primiparous ewe had a higher bleat rate than lambs with a Ž . multiparous dam P -0.05 . Birth of the second twin lamb caused a doubling in individual lamb bleat rate in both breeds. Ewe low-pitched bleat rate is, therefore, affected by intrinsic factors, ewe breed and experience, but not by characteristics of the lamb in the immediate postnatal period. The function of the bleat may be to strengthen bonding with the lamb, and the higher rate in primiparous ewes may reflect both the immaturity of the system in inexperienced animals and a ) Corresponding author. 0168-1591r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.

Human capital (HC) represents the cumulative tacit knowledge that is embedded in the minds of people in organisations. HC is important to organisations because it serves as a source of innovation and strategic renewal. Individuals carry HC when they join an organisation and take their talent, skills and tacit knowledge with them when they leave the organisation. Thus HC is volatile in nature. Organisations are therefore keen to do what they can to foster and develop HC as a means of achieving sustainable competitive advantage. This paper argues that neuro-linguistic programming (NLP) has the potential of developing and enhancing the stock of HC in organisations. NLP emerged in the 1970s from the University of California, USA. NLP suggests that subjective experience is encoded in terms of three main representation systems: visual, auditory, and kinaesthetic (VAK). NLP practitioners claim that people tend to have one preferred representation system over another in a given context. Des...

A sign language is a language which, instead of acoustically conveyed sound patterns, uses visually transmitted sign patterns. Sign languages are commonly developed for deaf communities, which can include interpreters, friends and families of deaf people as well as people who are deaf or hard of hearing themselves. Developing a sign language recognition system will help the hearing impaired to communicate more fluently with the normal people. This paper presents a simple sign language recognition system that has been developed using skin color segmentation and Artificial Neural Network. The moment invariants features extracted from the right and left hand gesture images are used to develop a network model. The system has been implemented and tested for its validity. Experimental results show that the average recognition rate is 92.85%.

Some hearing aid models such as the in-the-ear or in-the-canal model are small, and due to size constraints, only a single microphone per hearing aid can be fitted. As a result, only the single-channel noise reduction schemes can be integrated in them. However, in the near future, binaural hearing aids will be available. These hearing aids will allow hearing devices on each side of the head to receive information from the microphones located on both devices via a wireless link. This additional information allows the use of joint statistics and/or spatial information, which allows the use of better denoising methods. The main contribution of this paper is to introduce a binaural target power spectral density (PSD) estimator for binaural hearing aids under the presence of a background interfering talker (or a lateral transient noise). This paper then presents an example of how the proposed target PSD estimator and another recently developed binaural diffuse noise PSD estimator can be integrated to produce a binaural noise reduction scheme that can operate in real-life complex acoustic environments that are composed of time-varying diffuse noise, multiple directional nonstationary talkers (or noises), and reverberant conditions. Such a binaural noise reduction system allows the substantial reduction of different combinations of diverse background noises and the increase in speech intelligibility while guaranteeing the preservation of the interaural cues of both the target speech and the directional background noises. A comparison with several advanced denoising algorithms is made in this paper by using several objective measures and real-life hearing aid signals, showing the good performance of the example binaural noise reduction scheme that uses the proposed PSD estimator.

A novel approach to hearing-aid signal processing is described, which attempts to re-establish a normal neural representation in the sensorineural impaired auditory system. Most hearing-aid ÿtting procedures are based on heuristics or some initial qualitative theory. These theories, such as loudness normalization, loudness equalization or maximal intelligibility can give vastly di erent results for a given individual, and each may provide variable results for di erent hearing impaired individuals with the same audiogram. Recent research in characterizing sensorineural hearing loss has delineated the importance of hair cell damage in understanding the bulk of sensorineural hearing impairments. A novel methodology based on restoring normal neural representation after the sensorineural impairment is presented here. This approach can be used for designing hearing-aid signal processing algorithms, as well as providing a general, automated means of predicting the relative intelligibility of a given speech sample in normal hearing and hearing impaired subjects. ? 2004 Elsevier B.V. All rights reserved.

The energy-yielding pathways that provide the large amounts of metabolic energy required by inner ear sensorineural cells are poorly understood. Neuroglobin (Ngb) is a neuron-specific hemoprotein of the globin family, which is suggested to be involved in oxidative energy metabolism. Here, we present quantitative real-time reverse transcription PCR, in situ hybridization, immunohistochemical, and Western blot evidence that neuroglobin is highly expressed in the mouse and rat cochlea. For primary cochlea neurons, Ngb expression is limited to the subpopulation of type I spiral ganglion cells, those which innervate inner hair cells, while the subpopulation of type II spiral ganglion cells which innervate the outer hair cells do not express Ngb.We further investigated Ngb distribution in rat, mouse, and human auditory brainstem centers, and found that the cochlear nuclei and superior
olivary complex (SOC) also express considerable amounts of Ngb. Notably, the majority of olivocochlear neurons, those which provide efferent innervation of outer hair cells as identified by neuronal tract tracing, were Ngb-immunoreactive.
We also observed that neuroglobin in the SOC frequently co-localized with neuronal nitric oxide synthase, the enzyme responsible for nitric oxide production. Our findings suggest that neuroglobin is well positioned to play an important physiologic role in the oxygen homeostasis of the peripheral and central auditory nervous system, and provides the first evidence that Ngb signal differentiates the central projections of the inner and outer hair cells.

Vocal vibrato and tremor are characterized by oscillations in voice fundamental frequency (F 0). These oscillations may be sustained by a control loop within the auditory system. One component of the control loop is the pitch-shift reflex ͑PSR͒. The PSR is a closed loop negative feedback reflex that is triggered in response to discrepancies between intended and perceived pitch with a latency of ϳ100 ms. Consecutive compensatory reflexive responses lead to oscillations in pitch every ϳ200 ms, resulting in ϳ5-Hz modulation of F 0. Pitch-shift reflexes were elicited experimentally in six subjects while they sustained /É/ vowels at a comfortable pitch and loudness. Auditory feedback was sinusoidally modulated at discrete integer frequencies ͑1 to 10 Hz͒ with Ϯ25 cents amplitude. Modulated auditory feedback induced oscillations in voice F 0 output of all subjects at rates consistent with vocal vibrato and tremor. Transfer functions revealed peak gains at 4 to 7 Hz in all subjects, with an average peak gain at 5 Hz. These gains occurred in the modulation frequency region where the voice output and auditory feedback signals were in phase. A control loop in the auditory system may sustain vocal vibrato and tremorlike oscillations in voice F 0 .

A dual-channel directional digital hearing aid front end using microelectromechanical-systems microphones, and an adaptive-power analog processing signal chain are presented. The analog front end consists of a double differential amplifier-based capacitance-to-voltage conversion circuit, 40-dB variable gain amplifier (VGA) and a power-scalable continuous time sigma delta analog-to-digital converter (ADC), with 68-dB signal-to-noise ratio dissipating 67 W from a 1.2-V supply. The MEMS microphones are fabricated using a standard surface micromachining technology. The VGA and power-scalable ADC are fabricated on a 0.25-m complementary metal-oxide semciconductor TSMC process.

We present a review on perception and cognition models designed for or applicable to music. An emphasis is put on computational implementations. We include findings from different disciplines: neuroscience, psychology, cognitive science, artificial intelligence, and musicology. The article summarizes the methodology that these disciplines use to approach the phenomena of music understanding, the localization of musical processes in the brain, and the flow of cognitive operations involved in turning physical signals into musical symbols, going from the transducers to the memory systems of the brain. We discuss formal models developed to emulate, explain and predict phenomena involved in early auditory processing, pitch processing, grouping, source separation, and music structure computation. We cover generic computational architectures of attention, memory, and expectation that can be instantiated and tuned to deal with specific musical phenomena. Criteria for the evaluation of such models are presented and discussed. Thereby, we lay out the general framework that provides the basis for the discussion of domain-specific music models in Part II.

Recent studies have demonstrated the use of manganese ion (Mn 2+ ) as an in vivo neuronal tract tracer. In contrast to histological approaches, manganese tracing can be performed repeatedly on the same living animal. In this study, we describe the neuroaxonal tracing of the auditory pathway in the living guinea pig, relying on the fact that Mn 2+ ion enters excitable cells through voltage-gated calcium channels and is an excellent MRI paramagnetic tract-tracing agent. Small focal injections of Mn 2+ ion into the cochlea produced significant contrast enhancement along the known neuronal circuitry. This in vivo approach, allowing repeated measures, is expected to open new vistas to study auditory physiology and to provide new insights on in vivo axonal transport and neuronal activity in the central auditory system. D

Dynamicity is one of the main challenges in providing sustainable solutions for the homecare domain. The dynamicity of homecare systems, caused by external entities like care-receivers and care-givers, can be addressed through combining distributed and heterogenous services both in design and runtime. In general, several research fields such as dynamic service composition, context-aware service composition and dynamic configuration contribute to provide solutions to handle the dynamicity. However, the dynamicity requirements and constrains in homecare domain demands its own solutions. In this paper, we explain our understanding of a homecare provisioning platform and its external entities which interact with the platform. Based on our application scenario and literature study, we identify different types of changes which are imposed by the external entities. Moreover, the characteristics of the external entities, which need to be taken into account to address the dynamicity, are discussed. Then, we study the existing dynamic service composition approaches to see their feasibility for the homecare domain. Finally, we explain our motivation for choosing a hybrid service composition approach as our basis for the homecare provisioning platform with respect to the identified changes and characteristics coming from the external entities.

Segregation of information flow along a dorsally directed pathway for processing object location and a ventrally directed pathway for processing object identity is well established in the visual and auditory systems, but is less clear in the somatosensory system. We hypothesized that segregation of location vs. identity information in touch would be evident if texture is the relevant property for stimulus identity, given the salience of texture for touch. Here, we used functional magnetic resonance imaging (fMRI) to investigate whether the pathways for haptic and visual processing of location and texture are segregated, and the extent of bisensory convergence. Haptic textureselectivity was found in the parietal operculum and posterior visual cortex bilaterally, and in parts of left inferior frontal cortex. There was bisensory texture-selectivity at some of these sites in posterior visual and left inferior frontal cortex. Connectivity analyses demonstrated, in each modality, flow of information from unisensory non-selective areas to modality-specific textureselective areas and further to bisensory texture-selective areas. Location-selectivity was mostly bisensory, occurring in dorsal areas, including the frontal eye fields and multiple regions around the intraparietal sulcus bilaterally. Many of these regions received input from unisensory areas in both modalities. Together with earlier studies, the activation and connectivity analyses of the present study establish that somatosensory processing flows into segregated pathways for location and object identity information. The location-selective somatosensory pathway converges with its visual counterpart in dorsal frontoparietal cortex, while the texture-selective somatosensory

Research on event-related potential (ERP) correlates of auditory deviance-detection in newborns provided inconsistent results; temporal and topographic ERP characteristics differed widely across studies and individual infants. Robust and reliable ERP responses were, however, obtained to sounds (termed 'novel' sounds), which cover a wide range of frequencies and widely differ from the context provided by a repeating sound ) NeuroReport, 13, 1843-1848. The question we investigated here is whether this effect can be attributed to novelty per se or to acoustic characteristics of the 'novel' sounds, such as their wide frequency spectrum and high signal energy compared with the repeated tones. We also asked how sensitivity to these stimulus aspects changes with development. Twelve newborns and 11 adults were tested in four different oddball conditions, each including a 'standard' sound presented with the probability of 0.8 and two types of infrequent 'deviant' sounds (0.1 probability, each). Deviants were (i) 'novel' sounds (diverse environmental noises); (ii) white-noise segments, or harmonic tones of (iii) a higher pitch, or (iv) higher intensity. In newborns, white-noise deviants elicited the largest response in all latency ranges, whereas in adults, this phenomenon was not found. Thus, newborns appear to be especially sensitive to sounds having a wide frequency spectrum. On the other hand, the pattern of results found for the late discriminative ERP response indicates that newborns may also be able to detect novelty in acoustic stimulation, although with a longer latency than adults, as shown by the ERP response. Results are discussed in terms of developmental refinement of the initially broadly tuned neonate auditory system.

Noise exposure is known to cause hearing loss and a variety of disturbances, such as annoyance, hypertension and loss of sleep. It is generally accepted that these situations are caused by the acoustical events processed by the auditory system. However, there are acoustical events that are not necessarily processed by the auditory system, but that nevertheless cause harm. Infrasound and low frequency noise (ILFN, <500Hz) are acoustical phenomena that can impact the human body causing irreversible organic damage to the organism, but that do not cause classical hearing impairment. Acoustical environments are normally composed of all types of acoustical events: those that are processed by the auditory system, and those that are not. It is generally assumed that acoustical phenomena not captured by the human auditory system are not harmful. This is reflected by current noise assessment procedures that merely require the quantification of the acoustical phenomena that are audible to human hearing (hence the dBA unit). Thus, studies investigating the effects of noise exposure on public health that do not take into account the entire spectrum of acoustical energy are misleading and may, in fact, be scientifically unsound. Two cases of in-home ILFN are described.

Digital hearing aids identify acoustic feedback signals and cancel them continuously in a closed loop with an adaptive filter. This scheme facilitates larger hearing aid gain and improves the output sound quality of hearing aids. However, the output sound quality deteriorates as the hearing aid gain is increased. This paper presents two methods to modify the forward path gain in digital hearing aids. The first approach employs a variable, frequency-dependent gain function that is lower at frequencies of the incoming signal where the information is perceptually insignificant. The second method of this paper automatically identifies and suppresses residual acoustical feedback components at frequencies that have the potential to drive the system to instability. The suppressed frequency components are monitored and the suppression is removed when such frequencies no longer pose a threat to drive the hearing aid system into instability. Together, the gain processing methods of this paper provide 8 to 12 dB more hearing aid gain than feedback cancelers with fixed gain functions. Furthermore, experimental results obtained with real world hearing aid gain profiles indicate that the gain processing methods of this paper, individually and combined, provide less distortion in the output sound quality than classical feedback cancelers enabling the use of more comfortable style hearing aids for patients with moderate to profound hearing loss.

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