Resolution of lateral acoustic space assessed by electroencephalography and psychoacoustics

The encoding of auditory spatial acuity (measured as the precision to distinguish between two spatially distinct stimuli) by neural circuits in both auditory cortices is a matter of ongoing research. Here, the event-related potential (ERP) mismatch negativity (MMN), a sensitive indicator of preattentive auditory change detection, was used to tap into the underlying mechanism of cortical representation of auditory spatial information. We characterized the MMN response affected by the degree of spatial deviance in lateral acoustic space using a passive oddball paradigm. Two stimulation conditions (SCs)—specifically focusing on the investigation of the mid- and far-lateral acoustic space—were considered: (1) 65° left standard position with deviant positions at 70, 75, and 80°; and (2) 95° left standard position with deviant positions at 90, 85, and 80°. Additionally, behavioral data on the minimum audible angle (MAA) were acquired for the respective standard positions (65, 95° left) to quantify spatial discrimination in separating distinct sound sources. The two measurements disclosed the linkage between the (preattentive) MMN response and the (attentive) behavioral threshold. At 65° spatial deviations as small as 5° reliably elicited MMNs. Thereby, the MMN amplitudes monotonously increased as a function of spatial deviation. At 95°, spatial deviations of 15° were necessary to elicit a valid MMN. The behavioral data, however, yielded no difference in mean MAA thresholds for position 65 and 95°. The different effects of laterality on MMN responses and MAA thresholds suggest a role of spatial selective attention mechanisms particularly relevant in active discrimination of neighboring sound sources, especially in the lateral acoustic space

Age-related dissociation of sensory and decision-based auditory motion processing

Studies on the maturation of auditory motion processing in children have yielded inconsistent reports. The present study combines subjective and objective measurements to investigate how the auditory perceptual abilities of children change during development and whether these changes are paralleled by changes in the event-related brain potential (ERP). We employed the mismatch negativity (MMN) to determine maturational changes in the discrimination of interaural time differences (ITDs) that generate lateralized moving auditory percepts. MMNs were elicited in children, teenagers, and adults, using a small and a large ITD at stimulus offset with respect to each subject's discrimination threshold. In adults and teenagers large deviants elicited prominent MMNs, whereas small deviants at the behavioral threshold elicited only a marginal or no MMN. In contrast, pronounced MMNs for both deviant sizes were found in children. Behaviorally, however, most of the children showed higher discrimination thresholds than teens and adults. Although automatic ITD detection is functional, active discrimination is still limited in children. The lack of MMN deviance dependency in children suggests that unlike in teenagers and adults, neural signatures of automatic auditory motion processing do not mirror discrimination abilities. The study critically accounts for advanced understanding of children's central auditory development

Evaluation of Central Auditory Discrimination Abilities in Older Adults

The present study focuses on auditory discrimination abilities in older adults aged 65-89 years. We applied the ‘Leipzig Inventory for Patient Psychoacoustic’ (LIPP), a psychoacoustic test battery specifically designed to identify deficits in central auditory processing. These tests quantify the just noticeable differences (JND) for the three basic acoustic parameters (i.e. frequency, intensity, and signal duration). Three different test modes (monaural, dichotic signal/noise [s/n] and interaural) were used, stimulus level was 35dB sensation level. The tests are designed as three-alternative forced-choice procedure with a maximum-likelihood procedure estimating p=0,5 correct response value. These procedures have proven to be highly efficient and provide a reliable outcome. The measurements yielded significant age-dependent deteriorations in the ability to discriminate single acoustic features pointing to progressive impairments in central auditory processing. The degree of deterioration was correlated to the different acoustic features and to the test modes. Most prominent, interaural frequency and signal duration discrimination at low test frequencies was elevated which indicates a deterioration of time- and phase-dependent processing at brain stem and cortical levels. LIPP proves to be an effective tool to identify basic pathophysiological mechanisms and the source of a specific impairment in auditory processing of the elderly

The Cl--channel TMEM16A is involved in the generation of cochlear Ca2+ waves and promotes the refinement of auditory brainstem networks in mice

Before hearing onset (postnatal day 12 in mice), inner hair cells (IHCs) spontaneously fire action potentials, thereby driving pre-sensory activity in the ascending auditory pathway. The rate of IHC action potential bursts is modulated by inner supporting cells (ISCs) of Kölliker’s organ through the activity of the Ca2+-activated Cl--channel TMEM16A (ANO1). Here, we show that conditional deletion of Ano1 (Tmem16a) in mice disrupts Ca2+ waves within Kölliker’s organ, reduces the burst-firing activity and the frequency selectivity of auditory brainstem neurons in the medial nucleus of the trapezoid body (MNTB), and also impairs the functional refinement of MNTB projections to the lateral superior olive. These results reveal the importance of the activity of Kölliker’s organ for the refinement of central auditory connectivity. In addition, our study suggests the involvement of TMEM16A in the propagation of Ca2+ waves, which may also apply to other tissues expressing TMEM16A

Problematizando Experiências de Vítimas de Violências: Indagações e Análises

Título Problematizando experiências de vítimas de violência: indagações e análises. Autor Thiago Sandrini Mansur RESUMO Em geral, as reflexões sobre as pessoas que sofrem algum tipo de violência foram, por muito tempo, negligenciadas pelas sociedades em todo o mundo. Isso se torna ainda mais enfático no que diz respeito aos segmentos menos favorecidos da sociedade, sobretudo com relação àqueles que estão confinados em estabelecimentos de internação. No Brasil, este cenário foi se modificando lentamente ao longo do século XX, ganhando novos contornos por meio das experiências dos movimentos de defesa dos direitos humanos, sobretudo, a partir do período de contestação à ditadura militar. Num período mais recente de nossa história, o surgimento de centros de apoio às vítimas de violência pode ser considerado como uma maneira de colocar em análise as diversas formas de manifestação da violência, embora tais estabelecimentos não sejam os únicos, nem os primeiros a fazer isso. Os centros de apoio se tornaram locais não somente para que as vítimas de violência recebessem atendimento, mas, sobretudo, para que se incitasse a luta pela responsabilização de seus algozes e a criação de novos paradigmas para uma cultura de paz e não-violência. Tendo em vista este cenário, objetivou-se problematizar as experiências de pessoas que foram atingidas pela violência, residentes na Região Metropolitana da Grande Vitória e que buscaram apoio em um desses centros de atendimento. Problematizar uma experiência significa se perguntar como um conjunto de práticas discursivas e não discursivas que antes era aceito em uma sociedade sem questionamentos e tido como familiar e natural se torna um motivo de preocupação, incitando discussões, polemizando debates, suscitando mudanças de comportamento e instigando novos hábitos. Para alcançar tal propósito, foram realizadas atividades em grupo, nas quais se problematizou as experiências de mães que tiveram seus filhos violentados por agentes do Estado, quando em cumprimento de medida sócio-educativa de privação de liberdade. Também foram feitas entrevistas de restituição nas quais as mães puderam avaliar as experiências em grupo, bem como discutir os resultados e as conclusões da pesquisa. O objetivo dessas atividades foi compreender que práticas discursivas e não-discursivas sobre (e de) vítimas de violência se atualizam através de falas, ações, sentimentos e pensamentos. A que supostas verdades remetem? Que relações de saber-poder fazem funcionar? Como a experiência de estar em grupo coloca em questão certos modos de ser das vítimas? Em primeiro lugar, evidenciou-se que as pessoas participantes da pesquisa eram, em sua grande maioria, pobres, afro-descendentes, moradores de periferia e com baixa escolaridade, justamente o perfil típico das pessoas atingidas pela violência. Os resultados e as discussões levaram à conclusão de que muitas das pessoas atingidas pela violência, bem como seus familiares, embora sob esse forte impacto, apostaram e ainda apostam em afirmar a vida, ao invés de se colocarem no lugar de resignação, que muitas vezes é destinado às vítimas. Percebeu-se que conhecer e compartilhar as experiências dessas pessoas pode contribuir para a discussão acadêmica do problema e para a transformação de alguns dos efeitos deletérios da violência. Atualmente, quando falamos em vítimas de violência, imediatamente nos surgem imagens de indivíduos passivos e inertes que padecem na dor pelo resto de suas vidas. Tais imagens estão atreladas a uma visão intimista da realidade (SENNET, 1998), na qual se pensam as experiências como vivências individuais e particulares de cada um. Sendo assim, aquilo que uma pessoa vive diria respeito apenas a ela mesma e a mais ninguém. A existência dos centros de apoio às vítimas de violência delimita a constituição de espaços em que essas experiências podem ser problematizadas em suas verdades instituídas. Entendemos que problematizar uma experiência é evidenciar seu caráter de produção histórica e social. Isto significa dizer que aquilo que denominamos vítima de violência apresenta-se como uma forma circunstancial e provisória, ou seja, não-natural. Palavras-chave: Violência; Vítima; Experiência

Error Signals from the Brain: 7th Mismatch Negativity Conference

The 7th Mismatch Negativity Conference presents the state of the art in methods, theory, and application (basic and clinical research) of the MMN (and related error signals of the brain). Moreover, there will be two pre-conference workshops: one on the design of MMN studies and the analysis and interpretation of MMN data, and one on the visual MMN (with 20 presentations). There will be more than 40 presentations on hot topics of MMN grouped into thirteen symposia, and about 130 poster presentations. Keynote lectures by Kimmo Alho, Angela D. Friederici, and Israel Nelken will round off the program by covering topics related to and beyond MMN

Functional Development of Principal Neurons in the Anteroventral Cochlear Nucleus Extends Beyond Hearing Onset

Sound information is transduced into graded receptor potential by cochlear hair cells and encoded as discrete action potentials of auditory nerve fibers. In the cochlear nucleus, auditory nerve fibers convey this information through morphologically distinct synaptic terminals onto bushy cells (BCs) and stellate cells (SCs) for processing of different sound features. With expanding use of transgenic mouse models, it is increasingly important to understand the in vivo functional development of these neurons in mice. We characterized the maturation of spontaneous and acoustically evoked activity in BCs and SCs by acquiring single-unit juxtacellular recordings between hearing onset (P12) and young adulthood (P30) of anesthetized CBA/J mice. In both cell types, hearing sensitivity and characteristic frequency (CF) range are mostly adult-like by P14, consistent with rapid maturation of the auditory periphery. In BCs, however, some physiological features like maximal firing rate, dynamic range, temporal response properties, recovery from post-stimulus depression, first spike latency (FSL) and encoding of sinusoid amplitude modulation undergo further maturation up to P18. In SCs, the development of excitatory responses is even more prolonged, indicated by a gradual increase in spontaneous and maximum firing rates up to P30. In the same cell type, broadly tuned acoustically evoked inhibition is immediately effective at hearing onset, covering the low- and high-frequency flanks of the excitatory response area. Together, these data suggest that maturation of auditory processing in the parallel ascending BC and SC streams engages distinct mechanisms at the first central synapses that may differently depend on the early auditory experience

Orienting asymmetries and lateralized processing of sounds in humans

<p>Abstract</p> <p>Background</p> <p>Lateralized processing of speech is a well studied phenomenon in humans. Both anatomical and neurophysiological studies support the view that nonhuman primates and other animal species also reveal hemispheric differences in areas involved in sound processing. In recent years, an increasing number of studies on a range of taxa have employed an orienting paradigm to investigate lateralized acoustic processing. In this paradigm, sounds are played directly from behind and the direction of turn is recorded. This assay rests on the assumption that a hemispheric asymmetry in processing is coupled to an orienting bias towards the contralateral side. To examine this largely untested assumption, speech stimuli as well as artificial sounds were presented to 224 right-handed human subjects shopping in supermarkets in Germany and in the UK. To verify the lateralized processing of the speech stimuli, we additionally assessed the brain activation in response to presentation of the different stimuli using functional magnetic resonance imaging (fMRI).</p> <p>Results</p> <p>In the naturalistic behavioural experiments, there was no difference in orienting behaviour in relation to the stimulus material (speech, artificial sounds). Contrary to our predictions, subjects revealed a significant left bias, irrespective of the sound category. This left bias was slightly but not significantly stronger in German subjects. The fMRI experiments confirmed that the speech stimuli evoked a significant left lateralized activation in BA44 compared to the artificial sounds.</p> <p>Conclusion</p> <p>These findings suggest that in adult humans, orienting biases are not necessarily coupled with lateralized processing of acoustic stimuli. Our results – as well as the inconsistent orienting biases found in different animal species – suggest that the orienting assay should be used with caution. Apparently, attention biases, experience, and experimental conditions may all affect head turning responses. Because of the complexity of the interaction of factors, the use of the orienting assay to determine lateralized processing of sound stimuli is discouraged.</p

Reliability of Synaptic Transmission at the Synapses of Held In Vivo under Acoustic Stimulation

BACKGROUND:The giant synapses of Held play an important role in high-fidelity auditory processing and provide a model system for synaptic transmission at central synapses. Whether transmission of action potentials can fail at these synapses has been investigated in recent studies. At the endbulbs of Held in the anteroventral cochlear nucleus (AVCN) a consistent picture emerged, whereas at the calyx of Held in the medial nucleus of the trapezoid body (MNTB) results on the reliability of transmission remain inconsistent. In vivo this discrepancy could be due to the difficulty in identifying failures of transmission. METHODS/FINDINGS:We introduce a novel method for detecting unreliable transmission in vivo. Based on the temporal relationship between a cells' waveform and other potentials in the recordings, a statistical test is developed that provides a balanced decision between the presence and the absence of failures. Its performance is quantified using simulated voltage recordings and found to exhibit a high level of accuracy. The method was applied to extracellular recordings from the synapses of Held in vivo. At the calyces of Held failures of transmission were found only rarely. By contrast, at the endbulbs of Held in the AVCN failures were found under spontaneous, excited, and suppressed conditions. In accordance with previous studies, failures occurred most abundantly in the suppressed condition, suggesting a role for inhibition. CONCLUSIONS/SIGNIFICANCE:Under the investigated activity conditions/anesthesia, transmission seems to remain largely unimpeded in the MNTB, whereas in the AVCN the occurrence of failures is related to inhibition and could be the basis/result of computational mechanisms for temporal processing. More generally, our approach provides a formal tool for studying the reliability of transmission with high statistical accuracy under typical in vivo recording conditions