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Auditory System (auditory + system)
Selected AbstractsSeasonal changes in frequency tuning and temporal processing in single neurons in the frog auditory midbrainDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2005Jozien BM Goense Abstract Frogs rely on acoustic signaling to detect, discriminate, and localize mates. In the temperate zone, reproduction occurs in the spring, when frogs emerge from hibernation and engage in acoustically guided behaviors. In response to the species mating call, males typically show evoked vocal responses or other territorial behaviors, and females show phonotactic responses. Because of their strong seasonal behavior, it is possible that the frog auditory system also displays seasonal variation, as evidenced in their vocal control system. This hypothesis was tested in male Northern leopard frogs by evaluating the response characteristics of single neurons in the torus semicircularis (TS; a homolog of the inferior colliculus) to a synthetic mating call at different times of the year. We found that TS neurons displayed a seasonal change in frequency tuning and temporal properties. Frequency tuning shifted from a predominance of TS units sensitive to intermediate frequencies (700,1200 Hz) in the winter, to low frequencies (100,600 Hz) in the summer. In winter and early spring, most TS neurons showed poor, or weak, time locking to the envelope of the amplitude-modulated synthetic call, whereas in late spring and early summer the majority of TS neurons showed robust time-locked responses. These seasonal differences indicate that neural coding by auditory midbrain neurons in the Northern leopard frog is subject to seasonal fluctuation. © 2005 Wiley Periodicals, Inc. J. Neurobiol, 2005 [source] Neural responses to uninterrupted natural speech can be extracted with precise temporal resolutionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2010Edmund C. Lalor Abstract The human auditory system has evolved to efficiently process individual streams of speech. However, obtaining temporally detailed responses to distinct continuous natural speech streams has hitherto been impracticable using standard neurophysiological techniques. Here a method is described which provides for the estimation of a temporally precise electrophysiological response to uninterrupted natural speech. We have termed this response AESPA (Auditory Evoked Spread Spectrum Analysis) and it represents an estimate of the impulse response of the auditory system. It is obtained by assuming that the recorded electrophysiological function represents a convolution of the amplitude envelope of a continuous speech stream with the to-be-estimated impulse response. We present examples of these responses using both scalp and intracranially recorded human EEG, which were obtained while subjects listened to a binaurally presented recording of a male speaker reading naturally from a classic work of fiction. This method expands the arsenal of stimulation types that can now be effectively used to derive auditory evoked responses and allows for the use of considerably more ecologically valid stimulation parameters. Some implications for future research efforts are presented. [source] Estrogen-dependent selectivity of genomic responses to birdsongEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2006Donna L. Maney Abstract Behavioral responses to sociosexual signals often depend on gonadal steroid hormones, which are thought to modulate behavior by acting on motivational systems in the brain. There is mounting evidence that sex steroids may also modulate perception of sociosexual signals by affecting sensory processing. In seasonally breeding songbirds such as the white-throated sparrow (Zonotrichia albicollis), the female's behavioral response to hearing male song depends on her plasma levels of estradiol (E2). Here, we examined whether plasma E2 also affects the selectivity of the song-induced zenk (egr-1) response in the auditory forebrain, which is known to vary according to the behavioral relevance of song stimuli. Non-breeding females were held on a winter-like photoperiod and implanted with silastic capsules containing either no hormone or E2. E2-treated birds hearing 42 min of conspecific song had more cells immunoreactive for the protein product of zenk in the auditory forebrain than did those hearing frequency-matched synthetic tones. In birds not treated with E2, however, the zenk response to song did not differ from that to tones. We found similar effects in the avian homolog of the inferior colliculus, indicating that E2 may affect the processing of auditory information upstream of the forebrain. Our data suggest that in females, zenk induction in the auditory system is selective for song only when plasma E2 exceeds non-breeding levels. E2-dependent plasticity of auditory pathways and processing centres may promote recognition of and attention to conspecific song during the breeding season. [source] Clinical application of neurotrophic factors: the potential for primary auditory neuron protectionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2005Lisa N. Gillespie Abstract Sensorineural hearing loss, as a result of damage to or destruction of the sensory epithelia within the cochlea, is a common cause of deafness. The subsequent degeneration of the neural elements within the inner ear may impinge upon the efficacy of the cochlear implant. Experimental studies have demonstrated that neurotrophic factors can prevent this degeneration in animal models of deafness, and can even provide functional benefits. Neurotrophic factor therapy may therefore provide similar protective effects in humans, resulting in improved speech perception outcomes among cochlear implant patients. There are, however, numerous issues pertaining to delivery techniques and treatment regimes that need to be addressed prior to any clinical application. This review considers these issues in view of the potential therapeutic application of neurotrophic factors within the auditory system. [source] Is there a role of visual cortex in spatial hearing?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2004Ulrike Zimmer Abstract The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory,visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1/V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction. [source] Aberrant responses to acoustic stimuli in mice deficient for neural recognition molecule NB-2EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2003Hong Li Abstract NB-2, a member of the contactin subgroup in the immunoglobulin superfamily, is expressed specifically in the postnatal nervous system, reaching a maximum level at 3 weeks postnatal. NB-2 displays neurite outgrowth-promoting activity in vitro. To assess its function in the nervous system, we generated mutant mice in which a part of the NB-2 gene was ablated and replaced with the tau-LacZ gene. The general appearance of NB-2-deficient mice and their gross anatomical features were normal. The LacZ expression patterns in heterozygous mice revealed that NB-2 is preferentially expressed in the central auditory pathways. In the audiogenic seizure test, NB-2-deficient mice exhibited a lower incidence of wild running, but a higher mortality rate than the wild-type littermates. c-Fos immunohistochemistry demonstrated that neural excitability induced by the audiogenic seizure test in the NB-2-deficient mice was prominently attenuated in both the dorsal and external cortices of the inferior colliculus, where enhanced neural excitability was observed in the wild-type mice. In response to pure-tone stimulation after priming, NB-2-deficient mice exhibited a diffuse and low level of c-Fos expression in the central nucleus of the inferior colliculus, which was distinctly different from the band-like c-Fos expression corresponding to the tonotopic map in the wild-type littermates. Taken together, these results suggest that a lack of NB-2 causes impairment of the neuronal activity in the auditory system. [source] Auditory activation of ,visual' cortical areas in the blind mole rat (Spalax ehrenbergi)EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Gilles Bronchti Abstract The mole rat (Spalax ehrenbergi) is a subterranean rodent whose adaptations to its fossorial life include an extremely reduced peripheral visual system and an auditory system suited for the perception of vibratory stimuli. We have previously shown that in this blind rodent the dorsal lateral geniculate nucleus, the primary visual thalamic nucleus of sighted mammals, is activated by auditory stimuli. In this report we focus on the manifestation of this cross-modal compensation at the cortical level. Cyto- and myeloarchitectural analyses of the occipital area showed that despite the almost total blindness of the mole rat this area has retained the organization of a typical mammalian primary visual cortex. Application of the metabolic marker 2-deoxyglucose and electrophysiological recording of evoked field potentials and single-unit activity disclosed that a considerable part of this area is activated by auditory stimuli. Previous neuronal tracing studies had revealed the origin of the bulk of this auditory input to be the dorsal lateral geniculate nucleus which itself receives auditory input from the inferior colliculus. [source] A method for the direct electrical stimulation of the auditory system in deaf subjects: A functional magnetic resonance imaging studyJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2002Adnan Z. Alwatban BSc Abstract Purpose To develop a safe functional magnetic resonance imaging (fMRI) procedure for auditory assessment of deaf subjects. Materials and Methods A gold-plated tungsten electrode has been developed which has zero magnetic susceptibility. Used with carbon leads and a carbon reference pad, it enables safe, distortion-free fMRI studies of deaf subjects following direct electrical stimulation of the acoustic nerve. Minor pickup of the radio frequency (RF) pulses by the electrode assembly is difficult to eliminate, and a SPARSE acquisition sequence is used to avoid any effects of unintentional auditory nerve stimulation. Results The procedure is demonstrated in a deaf volunteer. Activation is observed in the contralateral but not the ipsilateral primary auditory cortex. This is in sharp contrast to studies of auditory processing in hearing subjects, but consistent with the small number of previous positron emission tomography (PET) and MR studies on adult deaf subjects. Conclusion The fMRI procedure is able to demonstrate whether the auditory pathway is fully intact, and may provide a useful method for preoperative assessment of candidates for cochlear implantation. J. Magn. Reson. Imaging 2002;16:6,12. © 2002 Wiley-Liss, Inc. [source] Interactive roles of fibroblast growth factor 2 and neurotrophin 3 in the sequence of migration, process outgrowth, and axonal differentiation of mouse cochlear ganglion cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2008Waheeda A. Hossain Abstract A growth factor may have different actions depending on developmental stage. We investigated this phenomenon in the interactions of fibroblast growth factor 2 (FGF2) and neurotrophins on cochlear ganglion (CG) development. The portions of the otocyst fated to form the CG and cochlear epithelium were cocultured at embryonic day 11 (E11). Cultures were divided into groups fed with defined medium, with or without FGF2 and neurotrophin supplements, alone or in combination, for 7 days. We measured the number of migrating neuroblasts and distances migrated, neurite outgrowth, and axonlike processes. We used immunohistochemistry to locate neurotrophin 3 (NT3) and its high-affinity receptor (TrkC) in the auditory system, along with FGF2 and its R1 receptor, at comparable developmental stages in vitro and in situ from E11 until birth (P1) in the precursors of hair cells, support cells, and CG cells. Potential sites for interaction were localized to the nucleus, perikaryal cytoplasm, and cell surfaces, including processes and growth cones. Time-lapse imaging and quantitative measures support the hypothesis that FGF2 alone or combined with neurotrophins promotes migration and neurite outgrowth. Synergism or antagonism between NT3 and other factors suggest interactions at the receptor level. Formation of axons, endings, and synaptic vesicle protein 2 were increased by interactions of NT3 and FGF2. Similar experiments with a mutant overexpressor for FGF2 suggest that endogenous FGF2 supports migration and neurite outgrowth of CG neuroblasts as well as proliferation, leading to accelerated development. The findings suggest interactive and sequential roles for FGF2 and NT3. © 2008 Wiley-Liss, Inc. [source] Mild carbon monoxide exposure impairs the developing auditory system of the ratJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Douglas S. Webber Abstract The object of this study was to determine if chronic exposure to mild concentrations of CO in air caused changes in the integrity of the inferior colliculus during the most active period of synaptogenesis/auditory development. We examined all subregions of the inferior colliculus (IC) of rats by immunocytochemical approaches after pups were exposed chronically to CO concentrations of, 0, 12.5, 25, and 50 ppm in air starting at Day 8 through 20,22 days of age. Mother-reared pups were compared to the gastrostomy-reared pups with or without CO exposure for basal neural activity, using c-Fos immunoreactivity as a marker. Half the rats were examined at 27 days of age, 5 days after the end of CO exposure, and the other half were examined 50 days later at 75,77 days of age. In the central nucleus of the IC, the number of cells expressing a basal level of c-Fos was decreased significantly in the CO-exposed animals when compared to controls; however, there was little or no difference in the number of cells expressing c-Fos in the other subregions of the IC. We conclude that the central nucleus of the inferior colliculus is affected selectively by mild CO exposure (0.0012% in air) and that this reduction in neuronal activity persists into adulthood. © 2003 Wiley-Liss, Inc. [source] Neural recognition molecule NB-2 of the contactin/F3 subgroup in rat: Specificity in neurite outgrowth-promoting activity and restricted expression in the brain regionsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2001Junko Ogawa Abstract NB-2, a neural cell recognition molecule of the contactin/F3 subgroup, promoted neurite outgrowth of the cerebral cortical neurons but not the hippocampal neurons. NB-2 in rat became apparent after birth at protein level, reaching a maximum at postnatal day 14 in the cerebrum and postnatal day 3 in the cerebellum. NB-2 in the cerebellum declined abruptly thereafter. In situ hybridization demonstrated that NB-2 mRNA was highly expressed in regions implicated in the central auditory pathway, including the cochlear nuclei, superior olive, inferior colliculi, medial geniculate nuclei, and auditory cortex. In addition, a high level of NB-2 expression was observed in the accessory olfactory bulb, thalamic nuclei, facial nucleus, and inferior olive. By immunohistochemistry, intense immunoreactivity against NB-2 was also detected in the auditory pathway. Thus, NB-2 is expressed in highly restricted brain regions, including the auditory system, suggesting that it plays specific roles in the development and/or maturation of the regions. J. Neurosci. Res. 65:100,110, 2001. © 2001 Wiley-Liss, Inc. [source] Effect of hypoxia on the auditory system of goat fetuses during extrauterine incubationJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 2 2003Nobuko Nishioka Abstract Aim:, To investigate the effect of hypoxia on the auditory system in fetuses, we attempted to analyze the auditory brainstem response, the middle latency response, and changes of several physiological parameters of goat fetuses during extrauterine incubation. Methods:, We conducted extrauterine incubation of five goat fetuses at around 127 days of gestation (term = 148 days). Their physiological parameters, such as fetal heart rate, mean blood pressure, flow rate of carotid artery, as well as the auditory brainstem response and middle latency response, were recorded prior to and during hypoxia, and the two sets of data were compared with each other. Results:, In all five cases, the fetal heart rate decreased from 178 ± 12.2 b.p.m. to 144 ± 15.2 b.p.m. during hypoxia, while mean blood pressure and flow rate of carotid artery increased from 37.3 ± 3.7 mmHg to 43.2 ± 5.1 mmHg, and from 38.5 ± 5.5 mL/min to 47.0 ± 5.1 mL/min, respectively. The latency of the auditory brainstem response's wave V and of the middle latency response's Pa wave elongated from 5.24 ± 0.24 ms to 5.69 ± 0.20 ms, and from 19.2 ± 1.6 ms to 20.9 ± 1.4 ms, respectively. Conclusions:, Although fetal compensatory reactions, such as increases in mean blood pressure and flow rate of carotid artery during hypoxia were recognized, elongation of latency, and decrement of amplitude were observed in the auditory brainstem response and middle latency response. These results suggest that hypoxia itself influences the auditory system of the fetus. [source] Manganese-enhanced MRI of the mouse auditory pathwayMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Takashi Watanabe Abstract Functional mapping of the lateral lemniscus and the superior olivary complex as part of the auditory pathway was accomplished for the first time in mice in vivo using manganese-enhanced MRI (2.35T, 3D FLASH, 117 ,m isotropic resolution). These and other auditory centers in the brainstem presented with pronounced signal enhancements after systemic administration of manganese chloride when animals were exposed to acoustic stimuli for 48 hr, but not when kept in a quiet environment. The results indicate an activation-dependent accumulation of manganese in the neural circuit composed of the cochlear nucleus, the superior olivary complex, the lateral lemniscus, and the inferior colliculus. The marked enhancement of the lateral lemniscus suggests that the stimulus-related accumulation of manganese reflects not only a regional uptake from extracellular fluid but also a concurrent delivery by axonal transport within the auditory system. Magn Reson Med 60:210,212, 2008. © 2008 Wiley-Liss, Inc. [source] Involvement of the auditory brainstem system in spinocerebellar ataxia type 2 (SCA2), type 3 (SCA3) and type 7 (SCA7)NEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 5 2008F. Hoche Aims: The spinocerebellar ataxia type 2 (SCA2), type 3 (SCA3) and type 7 (SCA7) are clinically characterized by progressive and severe ataxic symptoms, dysarthria, dysphagia, oculomotor impairments, pyramidal and extrapyramidal manifestations and sensory deficits. Although recent clinical studies reported additional disease signs suggesting involvement of the brainstem auditory system, this has never been studied in detail in SCA2, SCA3 or SCA7. Methods: We performed a detailed pathoanatomical investigation of unconventionally thick tissue sections through the auditory brainstem nuclei (that is, nucleus of the inferior colliculus, nuclei of the lateral lemniscus, superior olive, cochlear nuclei) and auditory brainstem fibre tracts (that is, lateral lemniscus, trapezoid body, dorsal acoustic stria, cochlear portion of the vestibulocochlear nerve) of clinically diagnosed and genetically confirmed SCA2, SCA3 and SCA7 patients. Results: Examination of unconventionally thick serial brainstem sections stained for lipofuscin pigment and Nissl material revealed a consistent and widespread involvement of the auditory brainstem nuclei in the SCA2, SCA3 and SCA7 patients studied. Serial brainstem tissue sections stained for myelin showed loss of myelinated fibres in two of the auditory brainstem fibre tracts (that is, lateral lemniscus, trapezoid body) in a subset of patients. Conclusions: The involvement of the auditory brainstem system offers plausible explanations for the auditory impairments detected in some of our and other SCA2, SCA3 and SCA7 patients upon bedside examination or neurophysiological investigation. However, further clinical studies are required to resolve the striking discrepancy between the consistent involvement of the brainstem auditory system observed in this study and the comparatively low frequency of reported auditory impairments in SCA2, SCA3 and SCA7 patients. [source] The auditory system of last instars in Gryllus bimaculatus DeGeerPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2009ERICH M. STAUDACHER Abstract Aspects of the auditory development of Gryllus bimaculatus are compared with those of other Orthopterans and Mantodea. Auditory receptor cell branching patterns and first-order auditory interneurones of last-instar crickets are morphologically very similar to adult cells; auditory thresholds are 30,45 dB higher in last instars than in adults; the ears of most ultimate nymphs lack directionality; and the tympana of last instars are not set apart clearly from the surrounding cuticle, are still thick, backed by a thick layer of epithelium, and lack microtrichia. Thus, the development of the auditory system from last-instar to adult shows close similarities between G. bimaculatus and Teleogryllus commodus but not to other Orthopteran or Mantid species. This supports the hypothesis that the pattern of post-embryonic development of the auditory system in crickets differs significantly from that in other Orthopterans and in Mantodea. [source] Directional characteristics of the auditory system of cicadas: is the sound producing tymbal an integral part of directional hearing?PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2004P. J. Fonseca Abstract. Directional hearing is investigated in males of two species of cicadas, Tympanistalna gastrica (Stål) and Tettigetta josei Boulard, that are similar in size but show different calling song spectra. The vibrational response of the ears is measured with laser vibrometry and compared with thresholds determined from auditory nerve recordings. The data are used to investigate to what extent the directional characteristic of the tympanal vibrations is encoded by the activity of auditory receptors. Laser measurements show complex vibrations of the tympanum, and reveal that directional differences are rather high (>15 dB) in characteristic but limited frequency ranges. At low frequencies, both species show a large directional difference at the same frequency (3,5 kHz) whereas, above 10 kHz, the directional differences correspond to the different resonant frequencies of the respective tymbals. Consequently, due to the mechanical resonance of the tymbal, the frequency range at which directional differences are high differs between the two species that otherwise show similar dimensions of the acoustic system. The directional differences observed in the tympanal vibrations are also observed in the auditory nerve activity. These recordings confirm that the biophysically determined directional differences are available within the nervous system for further processing. Despite considerable intra as well as interindividual variability, the ears of the cicadas investigated here exhibit profound directional characteristics, because the thresholds determined from recordings of the auditory nerve at 30° to the right and left of the longitudinal axis differ by more than 5 dB. [source] Comparative gene expression analysis reveals a characteristic molecular profile of the superior olivary complexTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2006Hans Gerd Nothwang Abstract The superior olivary complex (SOC) is a very conspicuous structure in the mammalian auditory brainstem. It represents the first binaural processing center and is important for sound localization in the azimuth and in feedback regulation of cochlear function. In order to define molecular determinants of the SOC, which are of potential functional relevance, we have performed a comprehensive analysis of its transcriptome by serial analysis of gene expression in adult rats. Here, we performed a detailed analysis of the SOC's gene expression profile compared to that of two other neural tissues, the striatum and the hippocampus, and with extraocular muscle tissue. This tested the hypothesis that SOC-specific or significantly upregulated transcripts provide candidates for the specific function of auditory neurons. Thirty-three genes were significantly upregulated in the SOC when compared to the two other neural tissues. Thirteen encoded proteins involved in neurotransmission, including action potential propagation, exocytosis, and myelination; five genes are important for the energy metabolism, and five transcripts are unknown or poorly characterized and have yet to be described in the nervous system. The comparison of functional gene classes indicates that the SOC has the highest energy demand of the three neural tissues, yet protein turnover is apparently not increased. This suggests a high energy demand for fueling auditory neurotransmission. Such a demand may have implications on auditory-specific tasks and relate to central auditory processing disorders. Ultimately, these data provide new avenues to foster investigations of auditory function and to advance molecular physiology in the central auditory system. Anat Rec Part A, 2006. © 2006 Wiley-Liss, Inc. [source] Nicotinic acetylcholine receptor structure and function in the efferent auditory systemTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2006Lawrence R. Lustig Abstract This article reviews and presents new data regarding the nicotinic acetylcholine receptor subunits ,9 and ,10. Although phylogentically ancient, these subunits have only recently been identified as critical components of the efferent auditory system and medial olivocochlear pathway. This pathway is important in auditory processing by modulating outer hair cell function to broadly tune the cochlea and improve signal detection in noise. Pharmacologic properties of the functionally expressed ,9,10 receptor closely resemble the cholinergic response of outer hair cells. Molecular, immunohistochemical, and knockout mice studies have added further weight to the role this receptor plays in mediating the efferent auditory response. Alternate and complementary mechanisms of outer hair cell efferent activity might also be mediated through the nAChR ,9,10, either through secondary calcium stores, second messengers, or direct protein-protein interactions. We investigated protein-protein interactions using a yeast-two-hybrid screen of the nAChR ,10 intracellular loop against a rat cochlear cDNA library. Among the identified proteins was prosaposin, a precursor of saposins, which have been shown to act as neurotrophic factors in culture, can bind to a putative G0-coupled cell surface receptor, and may be involved in the prevention of cell death. This study and review suggest that nAChR ,9,10 may represent a potential therapeutic target for a variety of ear disorders, including preventing or treating noise-induced hearing loss, or such debilitating disorders as vertigo or tinnitus. Anat Rec Part A, 2006. © 2006 Wiley-Liss, Inc. [source] Calcium-binding protein immunoreactivity characterizes the auditory system of Gekko geckoTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 17 2010Kai Yan Abstract A transverse section through the nucleus laminaris and nucleus magnocellularis in Gekko gecko, labeled with an antibody against calretinin (red), with anti-parvalbumin double label (green). Both parvalbumin and calretinin immunoreactivity characterized the auditory nerve fibers above the nucleus laminaris in the nucleus magnocellularis. The red calretinin positive axons of the bitufted nucleus laminaris neurons run ventrally towards the olivary nuclei. Medial is to the right. The Journal of Comparative Neurology, Volume 518, Number 17, pages 3409,3426. [source] Calcium-binding protein immunoreactivity characterizes the auditory system of Gekko geckoTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 17 2010Kai Yan Abstract Geckos use vocalizations for intraspecific communication, but little is known about the organization of their central auditory system. We therefore used antibodies against the calcium-binding proteins calretinin (CR), parvalbumin (PV), and calbindin-D28k (CB) to characterize the gecko auditory system. We also examined expression of both glutamic acid decarboxlase (GAD) and synaptic vesicle protein (SV2). Western blots showed that these antibodies are specific to gecko brain. All three calcium-binding proteins were expressed in the auditory nerve, and CR immunoreactivity labeled the first-order nuclei and delineated the terminal fields associated with the ascending projections from the first-order auditory nuclei. PV expression characterized the superior olivary nuclei, whereas GAD immunoreactivity characterized many neurons in the nucleus of the lateral lemniscus and some neurons in the torus semicircularis. In the auditory midbrain, the distribution of CR, PV, and CB characterized divisions within the central nucleus of the torus semicircularis. All three calcium-binding proteins were expressed in nucleus medialis of the thalamus. These expression patterns are similar to those described for other vertebrates. J. Comp. Neurol. 518:3409,3426, 2010. © 2010 Wiley-Liss, Inc. [source] Frequency processing at consecutive levels in the auditory system of bush crickets (tettigoniidae)THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 15 2010Tim Daniel Ostrowski Abstract We asked how processing of male signals in the auditory pathway of the bush cricket Ancistrura nigrovittata (Phaneropterinae, Tettigoniidae) changes from the ear to the brain. From 37 sensory neurons in the crista acustica single elements (cells 8 or 9) have frequency tuning corresponding closely to the behavioral tuning of the females. Nevertheless, one-quarter of sensory neurons (approximately cells 9 to 18) excite the ascending neuron 1 (AN1), which is best tuned to the male's song carrier frequency. AN1 receives frequency-dependent inhibition, reducing sensitivity especially in the ultrasound. When recorded in the brain, AN1 shows slightly lower overall activity than when recorded in the prothoracic ganglion close to the spike-generating zone. This difference is significant in the ultrasonic range. The first identified local brain neuron in a bush cricket (LBN1) is described. Its dendrites overlap with some of AN1-terminations in the brain. Its frequency tuning and intensity dependence strongly suggest a direct postsynaptic connection to AN1. Spiking in LBN1 is only elicited after summation of excitatory postsynaptic potentials evoked by individual AN1-action potentials. This serves a filtering mechanism that reduces the sensitivity of LBN1 and also its responsiveness to ultrasound as compared to AN1. Consequently, spike latencies of LBN1 are long (>30 ms) despite its being a second-order interneuron. Additionally, LBN1 receives frequency-specific inhibition, most likely further reducing its responses to ultrasound. This demonstrates that frequency-specific inhibition is redundant in two directly connected interneurons on subsequent levels in the auditory system. J. Comp. Neurol. 518:3101,3116, 2010. © 2010 Wiley-Liss, Inc. [source] Somatostatin and gentamicin-induced auditory hair cell lossTHE LARYNGOSCOPE, Issue 5 2009Antje Caelers PhD Abstract Objective/Hypothesis: Hair cells of the mammalian auditory system do not regenerate, and therefore their loss leads to irreversible hearing loss. Aminoglycosides, among other substances, can irreversibly damage hair cells. Somatostatin, a peptide with hormone/neurotransmitter properties, has neuroprotective effects by binding to its receptor. In this study, we tested whether somatostatin can protect hair cells from gentamicin-induced damage in vitro. Study Design: This study confirmed the expression of somatostatin receptor mRNA within the cochlea and analyzed the effect of somatostatin on gentamicin-induced hair cell damage and death in vitro. Methods: Expression of somatostatin receptor mRNA in the rat cochlea was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). Protection of auditory hair cells from gentamicin was tested using two different concentrations (1 ,M and 5 ,M, respectively) of somatostatin. Results: We detected somatostatin receptor-1 and -2 mRNA and in the organ of Corti (OC), spiral ganglion, and stria vascularis by RT-PCR. Moreover, we could see significantly less hair cell loss in the OCs that were pretreated with either 1 ,M or 5 ,M of somatostatin as compared with samples treated with gentamicin alone. Conclusions: Decreased hair cell loss in somatostatin-treated samples that had been exposed to gentamicin provides evidence for a protective effect of somatostatin in aminoglycoside-induced hair cell death in vitro. [source] Electrophysiologic Effects of Placing Cochlear Implant Electrodes in a Perimodiolar Position in Young Children,THE LARYNGOSCOPE, Issue 1 2004Phillip A. Wackym MD Abstract Objective The purpose of this study was to intraoperatively record the electrically evoked auditory brainstem response (EABR) before and after placement of the electrode positioning system (EPS) (CII Bionic Ear with HiFocus I cochlear implant electrode array) as well as before and after stylet removal (Nucleus Contour cochlear implant electrode array). It was hypothesized that physiologic changes would occur after perimodiolar positioning of the electrode array and these changes would be evident from the EABR recordings. Study Design Consecutive young (11,36 month old) pediatric cochlear implant recipients (n = 17) had intraoperative EABRs recorded from three intracochlear electrodes that represented apical, medial, and basal locations. Wave V amplitudes and thresholds were studied relative to electrode location and pre- versus postperimodiolar positioning. These evoked potential measures were analyzed for statistical significance. Setting Tertiary referral children's hospital/medical college. Results Wave V thresholds of the EABR were lower, and amplitudes were larger after perimodiolar positioning, although the changes were dependent on electrode location and implant design. Statistically significant decreases in EABR wave V threshold and increases in suprathreshold wave V amplitude were found for the basal electrode for the CII Bionic Ear HiFocus I and for the apical electrode for the Nucleus Contour. Conclusions Placement of either the CII Bionic Ear HiFocus I or Nucleus Contour cochlear implant electrode array in the perimodiolar position in young children resulted in less electrical current necessary to stimulate the auditory system. Changes in electrophysiologic thresholds and amplitudes, measured with EABR, indicate that the electrode array is placed closer to the modiolus with both electrode designs. [source] Electric acoustic stimulation of the auditory system: experience and results of ten patients using MED-EL's M and FlexEAS electrodesCLINICAL OTOLARYNGOLOGY, Issue 3 2010A. Lee Clin. Otolaryngol. 2010, 35, 190,197 Objective:, To evaluate the hearing preservation rate and speech perception scores in patients with profound high frequency hearing loss and acoustically aidable low frequency hearing, managed with the MED-EL electric acoustic stimulation system referenced to the insertion depth of the electrode array. Study design:, Retrospective data analysis. Participants and setting:, Ten patients implanted at the Auditory Implant Centre, Guy's and St Thomas's Hospital, London, UK. Main outcome measures:, Pure tone audiometry, speech perception tests and electrode insertion depth angle. Results:, Postoperatively, functional hearing preservation allowing electric acoustic stimulation was achieved in eight patients and total preservation of residual hearing in five patients with follow-up periods of more than 12 months. Three of four (75%) patients with an insertion depth of >360° had a threshold shift of >25 dB, and all four patients had a threshold shift of >10 dB. All patients with total hearing preservation had the electrode inserted up to 360° at maximum. Overall, speech perception outcomes increased significantly and hearing impairment was significantly reduced after electric acoustic stimulation or electric stimulation alone as compared with the preoperative scores. Conclusion:, Electric acoustic stimulation provides significant benefit to individuals with profound high frequency hearing loss. Studies with larger number of patients are needed to establish the optimal electrode insertion angle as well as to further analyse the benefit of electric acoustic stimulation. [source] Independent mechanisms for ventriloquism and multisensory integration as revealed by theta-burst stimulationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2010Caterina Bertini Abstract The visual and auditory systems often concur to create a unified perceptual experience and to determine the localization of objects in the external world. Co-occurring auditory and visual stimuli in spatial coincidence are known to enhance performance of auditory localization due to the integration of stimuli from different sensory channels (i.e. multisensory integration). However, auditory localization of audiovisual stimuli presented at spatial disparity might also induce a mislocalization of the sound towards the visual stimulus (i.e. ventriloquism effect). Using repetitive transcranial magnetic stimulation we tested the role of right temporoparietal (rTPC), right occipital (rOC) and right posterior parietal (rPPC) cortex in an auditory localization task in which indices of ventriloquism and multisensory integration were computed. We found that suppression of rTPC excitability by means of continuous theta-burst stimulation (cTBS) reduced multisensory integration. No similar effect was found for cTBS over rOC. Moreover, inhibition of rOC, but not of rTPC, suppressed the visual bias in the contralateral hemifield. In contrast, cTBS over rPPC did not produce any modulation of ventriloquism or integrative effects. The double dissociation found in the present study suggests that ventriloquism and audiovisual multisensory integration are functionally independent phenomena and may be underpinned by partially different neural circuits. [source] The structure and function of auditory chordotonal organs in insectsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2004Jayne E. Yack Abstract Insects are capable of detecting a broad range of acoustic signals transmitted through air, water, or solids. Auditory sensory organs are morphologically diverse with respect to their body location, accessory structures, and number of sensilla, but remarkably uniform in that most are innervated by chordotonal organs. Chordotonal organs are structurally complex Type I mechanoreceptors that are distributed throughout the insect body and function to detect a wide range of mechanical stimuli, from gross motor movements to air-borne sounds. At present, little is known about how chordotonal organs in general function to convert mechanical stimuli to nerve impulses, and our limited understanding of this process represents one of the major challenges to the study of insect auditory systems today. This report reviews the literature on chordotonal organs innervating insect ears, with the broad intention of uncovering some common structural specializations of peripheral auditory systems, and identifying new avenues for research. A general overview of chordotonal organ ultrastructure is presented, followed by a summary of the current theories on mechanical coupling and transduction in monodynal, mononematic, Type 1 scolopidia, which characteristically innervate insect ears. Auditory organs of different insect taxa are reviewed, focusing primarily on tympanal organs, and with some consideration to Johnston's and subgenual organs. It is widely accepted that insect hearing organs evolved from pre-existing proprioceptive chordotonal organs. In addition to certain non-neural adaptations for hearing, such as tracheal expansion and cuticular thinning, the chordotonal organs themselves may have intrinsic specializations for sound reception and transduction, and these are discussed. In the future, an integrated approach, using traditional anatomical and physiological techniques in combination with new methodologies in immunohistochemistry, genetics, and biophysics, will assist in refining hypotheses on how chordotonal organs function, and, ultimately, lead to new insights into the peripheral mechanisms underlying hearing in insects. Microsc. Res. Tech. 63:315,337, 2004. © 2004 Wiley-Liss, Inc. [source] | |||||||||||||