This thesis gives an overview of my work over the last four years on the development of analogue electronic building blocks for the auditory pathway, and their application to some models of processing in the auditory brainstem. The anatomy and physiology of the human ear is presented, and is decomposed into three key elements, i.e., the basilar membrane band-pass filters, the transduction into a neural signal performed by the inner hair cells, and the mechanical feedback introduced by the outer hair cells. An electronic model for the first two of these elements is presented and measurement results are shown to compare these circuits with their biological counterparts. The remaining part of the human auditory pathway consists of several groups of different types of spiking neurons. Since the main part of signal processing in the auditory pathway is performed by these different types of spiking neurons, a good spiking neuron model is essential. The electrophysiology and anatomy needed to understand the
Auditory brainstem neurons fire at very high rates with extraordinarily high temporal precision, allowing them to encode specific features of sound stimuli. Une...
Tonotopy, the orderly representation of sound frequency is a fundamental organizing principle of the auditory system. However, the mechanisms by which precise t...
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Ultrafast and temporally precise action potentials (APs) are biophysical specializations of auditory brainstem neurons; properties necessary for encoding sound localization and communication cues. Fundamental to these specializations are voltage dependent potassium (KV) and sodium (NaV) ion channels. Here we characterized the functional development of these ion channels and quantified how they shape AP properties in the avian cochlear nucleus magnocellularis (NM). We report that late developing NM neurons (embryonic [E] days 19-21) generate fast APs that reliably phase lock to sinusoidal inputs at 75 Hz. In contrast, early developing neurons (E19) contained NaV channels that inactivate at more negative voltages, suggesting alterations in NaV channel subtypes. Taken together, our results indicate that the refinement of passive and active ion channel properties operate differentially in order to develop fast and reliable APs in the avian NM.
Neurons in the dorsal nucleus of the lateral lemniscus (DNLL) receive excitatory and inhibitory inputs from the superior olivary complex (SOC) and convey GABAergic inhibition to the contralateral DNLL and the inferior colliculi. Unlike the fast glycinergic inhibition in the SOC, this GABAergic inhibition outlasts auditory stimulation by tens of milliseconds. Two mechanisms have been postulated to explain this persistent inhibition. One, an "integration-based" mechanism, suggests that postsynaptic excitatory integration in DNLL neurons generates prolonged activity, and the other favors the synaptic time course of the DNLL output itself. The feasibility of the integration-based mechanism was tested in vitro in DNLL neurons of Mongolian gerbils by quantifying the cellular excitability and synaptic input-output functions (IO-Fs). All neurons were sustained firing and generated a near monotonic IO-F on current injections. From synaptic stimulations, we estimate that activation of approximately five ...
Glutamate receptors mediate most excitatory synaptic transmission in the adult vertebrate brain, but their activation in developing neurons also influences developmental processes. However, little is known about the developmental regulation of the subunits composing these receptors. Here we have studied age-dependent changes in the expression of α-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) and N-methyl-d-aspartate (NMDA) receptor subunits in the cochlear nucleus complex (CN), the superior olivary complex (SOC), the nuclei of the lateral lemniscus, and the inferior colliculus of the developing rat. In the lateral superior olive, the medial nucleus of the trapezoid body, and the ventral nucleus of the lateral lemniscus, the distribution of AMPA receptor subunits changed drastically with age. While GluR1 and GluR2 subunits were highly expressed in the first 2 postnatal weeks, GluR4 staining was detectable only thereafter. GluR1 and GluR2 immunoreactivities rapidly decreased during the third ...
Auditory and Vestibular Systems The Central Auditory System John F. Brugge Structure and Organization The major ascending auditory pathways of the brain stem and thalamus are shown schematically in Figure 1. In addition to these pathways, over which impulses originating in the cochlea reach the cerebral cortex, there are corticofugal connections and interneuronal circuits that, together with ascending projections, provide numerous opportunities at all levels of the auditory system for convergence and divergence of afferent input, serial and parallel processing of information, and feedback modulation. There are also connections between the principal auditory centers and the cranial and spinal motor nuclei, which subserve acoustic reflexes, but little is known about them. Finally, there is topographically patterned input to the superior colliculus and to the cerebellum, the latter receiving some of its input from the pontine nuclei activated by acoustic stimulation. Cochlear Nuclei All auditory ...
Definition of olivary complex in the Legal Dictionary - by Free online English dictionary and encyclopedia. What is olivary complex? Meaning of olivary complex as a legal term. What does olivary complex mean in law?
The inferior colliculus, the primary nucleus in the mammalian auditory midbrain, occupies a central position in the ascending auditory pathway. Nearly all ascending neural pathways converge and synapse in the central nucleus of the inferior colliculus (ICC). Further, the anatomical arrangement of axons and neurons in the ICC suggests the existence of functional regions which may play a role in organizing different types of physiological information. To investigate this organization, we characterized the response properties of neighboring neurons in the ICC. To record reliably from neighboring neurons, we adopted a relatively new electrophysiological technique, tetrode recordings. Tetrodes have four closely spaced recording sites (,20[mu]m) which record multi-unit activity from a small number of neighboring neurons. The recorded signals contain action potentials originating from more than one neuron. Based on action potential wave shape differences across the four channels, we can reconstruct the ...
TY - JOUR. T1 - The development of synaptic function and integration in the central auditory system. AU - Sanes, Dan. PY - 1993. Y1 - 1993. N2 - The development of inhibitory synaptic transmission is difficult to assess because the afferents usually arise from intrinsic neurons that are difficult to stimulate independently. The postnatal maturation of excitatory and inhibitory synaptic function was compared in the gerbil lateral superior olive (LSO), where it is possible to stimulate physically discrete afferent projections. Intracellular recordings obtained in a brain slice preparation revealed that transmission was prominent at birth. The EPSPs and IPSPs were up to 2 orders of magnitude longer than in more mature animals. Brief trains of electrical stimulus pulses led to a temporal summation of postsynaptic potentials (PSPs) in 1-14 d animals resulting in prolonged depolarizations or hyperpolarizations. In neonates, the depolarization could exceed 1 sec following a 70 msec stimulus train. The ...
88 Cochlea and Auditory Pathways Anatomical Considerations External ear: The external auditory meatus (canal) is formed by auricular and annular cartilages, plus a short…
The auditory pathway conveys the special sense of hearing. Information travels from the receptors in the organ of Corti of the inner ear - the cochlear hair cells - to the central nervous system, carried by the vestibulocochlear nerve (CN VIII).
9780387989037 Integrative Functions in the Mammalian Auditory Pathway (Springer Handbook of Auditory Research),books, textbooks, text book
Both avian and crocodilian auditory circuits appear to conform to the requirements of the Jeffress model (Jeffress, 1948; Joris et al., 1998; Grothe et al., 2005). The auditory nerve and NM phase lock to sound in birds and crocodilians (Köppl, 1997b), while NMs target neurons in NL act as coincidence detectors for both tones and noise. Internal delays, equal and opposite to interaural delays, characterize barn owls (Carr and Konishi, 1990; Peña et al., 2001), chickens (Overholt et al., 1992; Funabiki et al., 1998; Köppl and Carr, 2008), and alligators (this study). Best delays in NL are such that neurons respond maximally to sound sources in the contralateral hemifield. Similarly, contralateral click delays are longer than ipsilateral (Wagner et al., 2005; Köppl and Carr, 2008). Thus, the axonal delays from NM appear sufficient to account for the range of observed ITDs. Cochlear disparities or stereausis are an alternative to axonal delays (Shamma et al., 1989; Peña et al., 2001), but when ...
The inferior colliculus (IC) is thought to have two main subdivisions, a central region that forms an important stop on the ascending auditory pathway and a surrounding shell region that may play a more modulatory role ...
An interesting response property of auditory neurons that can be observed at various levels of the auditory pathway, but is particularly versatile in the IC, is selectivity in discharge rate to temporal features of sound, such as, e.g., amplitude modulations and frequency modulations (Brand et al., 2000; McAlpine, 2004; Woolley and Casseday, 2005; Pérez-González et al., 2006; Krebs et al., 2008). These versatile tuning patterns result from the complex set of synaptic inputs IC cells receive and are therefore dependent on outputs of the various auditory nuclei converging at the IC. The dependence of AM selectivity of single IC neurons on network states is nicely illustrated by the finding that AM selectivity can be modulated by changing sound location (Koch and Grothe, 2000) or by blocking inhibition (Casseday et al., 1994; Fuzessery and Hall, 1996; Casseday et al., 2002). We observed a significant decrease in temporal selectivity of IC neurons in aged animals. As mentioned above, selectivity ...
The auditory system is responsible for detecting, encoding, and deciphering hearing. The inferior colliculus (IC) is a major relay hub situated in the midbrain, that is subdivided into a central nucleus, and surrounding dorsal and lateral cortices. The central nucleus of the inferior colliculus (CNIC) is organized tonotopically based on a frequency gradient and strictly processes auditory information. In contrast, recent studies show that the lateral cortex of the inferior colliculus (LCIC) is actually multimodal, receiving inputs from not just auditory sources, but also somatosensory and visual structures. The precise organization of patterned inputs to the LCIC and their development has yet to be fully established. Mounting evidence suggests a modular LCIC framework with surrounding extramodular zones that provide an anatomical substrate for input-output arrays. Previously, a series of histochemical and immunocytochemical stains including acetylcholinesterase (AChE), cytochrome oxidase (CO), glutamic
a neural structure that serves as the last of a series of processing centers along the auditory pathway from the cochlea to the temporal lobe of the cerebral cortex. ...
Definition of Acoustic lemniscus with photos and pictures, translations, sample usage, and additional links for more information.
OBJECTIVE: Binaural interaction can be investigated using auditory evoked potentials. A binaural interaction component can be derived from the auditory brainstem response (ABR-BIC) and is considered evidence for binaural interaction at the level of the brainstem. Although click ABR-BIC has been investigated thoroughly, data on 500 Hz tone-burst (TB) ABR-BICs are scarce. In this study, characteristics of click and 500 Hz TB ABR-BICs are described. Furthermore, reliability of both click and 500 Hz TB ABR-BIC are investigated. METHODS: Eighteen normal hearing young adults (eight women, ten men) were included. ABRs were recorded in response to clicks and 500 Hz TBs. ABR-BICs were derived by subtracting the binaural response from the sum of the monaural responses measured in opposite ears. RESULTS: Good inter-rater reliability is obtained for both click and 500 Hz TB ABR-BICs. The most reliable peak in click ABR-BIC occurs at a mean latency of 6.06 ms (SD 0.354 ms). Reliable 500 Hz TB ABR-BIC are obtained
Looking for online definition of Brachium of the inferior colliculus in the Medical Dictionary? Brachium of the inferior colliculus explanation free. What is Brachium of the inferior colliculus? Meaning of Brachium of the inferior colliculus medical term. What does Brachium of the inferior colliculus mean?
Bushy cells in the anteroventral cochlear nucleus (AVCN) receive their principal excitatory input from the auditory nerve and are the primary source of excitatory input to more centrally located brainstem auditory nuclei. Despite this pivotal position in the auditory pathway, details of the basic physiological information being carried by axons of these cells and their projections to more central auditory nuclei have not been fully explored. In an attempt to clarify these details, we have physiologically characterized and anatomically labeled individual axons of the spherical bushy cell (SBC) class of the cat AVCN. The characteristic frequencies (CFs) of our injected SBC population are low, all less than 12 kHz and primarily (83%) less than 3 kHz, while their spontaneous activity is comparatively high (mean of 59 spikes/sec). In response to short tone bursts at CF, low CF (, 1 kHz) SBC units can phase-lock better than auditory nerve fibers. SBCs with CFs above 1 kHz have primary-like responses ...
Vol 8: The relative contributions of MNTB and LNTB neurons to inhibition in the medial superior olive assessed through single and paired recordings.. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
About 95 percent of sound input to the brain comes from the ears inner hair cells.. "These inner hair cells are like spark plugs in an 8-cylinder engine," says Salvi. "A car wont run well if you remove half of those spark plugs, but people can still present with normal hearing thresholds if theyve lost half or even three-quarters of their inner hair cells.". Ear damage reduces the signal that goes the brain. That results in trouble hearing, but thats not whats happening here, because the brain "has a central gain control, like a radio, the listener can turn up the volume control to better hear a distant station." Salvi says.. Sound is converted to neural activity by the inner hair cells in the auditory part of the ear, called the cochlea.. Sound-evoked neural activity then travels from the cochlea to the auditory nerve and into the central auditory pathway of the brain. Halfway up the auditory pathway the information is relayed into a structure known as the inferior colliculus, before ...
The auditory circuit that we are studying helps to locate sound sources in space and illustrates beautifully how development is instrumental in shaping function. A major cue for an animal to locate sound sources compares the arrival time of the sound at the two ears. The time difference in sound reaching each ear, termed interaural time difference (ITD), varies from zero (sound directly ahead) to approximately 300 microseconds (depending on the size of head). The circuit operates as an AND logical gate where synaptic input from the ear closest to the sound sets up a map of space along an array of neurons which is compared to synaptic input from the ear furthest away from the sound. This identifies the location of sound in a subset of neurons along this array through dendritic integration to detect temporal coincidence of the two inputs. This calculation is performed at each characteristic frequency of sound using different arrays of neurons that are juxtaposed to form a sheet of cells in the ...
Fig. 1: The main ascending pathways in the mammalian auditory system. AN, auditory nerve; CN, cochlear nucleus; SO, superior olive; NLL, nuclei of the lateral lemniscus; IC, inferior colliculus; MGB, thalamus; and A1, cortex. One goal of the lab is to identify functional pathways (patterns of afferent convergence) that link the brainstem auditory nuclei.. Current research in the laboratory centers on the central nucleus of the inferior colliculus (ICC) because it occupies a pivotal position in the auditory system; it receives direct inputs from most, if not all, of the auditory nuclei in the brainstem and, in turn, provides nearly all of the input to the auditory forebrain. Anatomical evidence suggests that the projections to the ...
-BANDWIDTH PRODUCTS EXCEEDING 10,000, USING PASSIVE, UNGUIDED PROPAGATION. The report presents experimental results on a delay line having 1/2 millisecond delay and 5 MHz bandwidth. This is a helical SAW delay line on a Bi12GeO20 wrap-around crystal plate, operating at 50 MHz, which proves that practical two-port delay lines operating in the millisecond range are within the current technology. An analysis has been made of the problem of broadbanding the transducers for long delay lines of this kind, which involve different considerations than for standard short delay lines. A loss balancing criterion is developed, and computer results are presented which show the general design parameters for delay lines having time delays extending to one millisecond together with bandwidth extending to 60 MHz, using graded interdigital transducer arrays. (Modified author abstract)*Acoustic delay lines
Background and purpose: Auditory processing disorders (APD), tinnitus and hearing loss (HL) are typical issues reported by patients in audiologic clinics. These auditory impairments can be concomitant or mutually excluding. APD are not necessarily accompanied by significant HL, whereas many adults exhibit peripheral HL and typical cognitive deficits often associated with APD. Since HL, tinnitus and APD affects to several parts of the ascending auditory pathway from the periphery to the auditory cortex, there could be some interrelationship between them. For instance, tinnitus has been reported to degrade the auditory localization capacity. Tinnitus is believed to be triggered by deafferentation of normal peripheral input to the central auditory system. This peripheral deficit can be accompanied by HL or not, since a type of permanent cochlear damage (thus deafferentation) without an elevation of hearing thresholds might persist. Therefore, a combined study of APD, tinnitus and HL on the same cohort of
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The medial geniculate body (MGB) of the thalamus is a key component of the auditory system. It is involved in relaying and transforming auditory information to the cortex and in top-down modulation of processing in the midbrain, brainstem, and ear. Functional imaging investigations of this region in humans, however, have been limited by the difficulty of distinguishing MGB from other thalamic nuclei. Here, we introduce two methods for reliably delineating MGB anatomically in individuals based on conventional and diffusion MRI data. The first uses high-resolution proton density weighted scanning optimized for subcortical grey-white contrast. The second uses diffusion-weighted imaging and probabilistic tractography to automatically segment the medial and lateral geniculate nuclei from surrounding structures based on their distinctive patterns of connectivity to the rest of the brain. Both methods produce highly replicable results that are consistent with published atlases. Importantly, both methods rely
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Full text Supplement:. Tinnitus, the phantom perception of sound in the absence of a corresponding acoustic stimulus affects 10 to 15% of the adult population worldwide. Despite this prevalence, there are currently no effective drug therapies due to limited understanding of the mechanisms that underlie tinnitus onset following triggers such as exposure to loud sound. Many studies support the prevailing idea that tinnitus arises in response to enhanced multisensory synaptic transmission to the dorsal cochlear nucleus (DCN), the first relay in the auditory brainstem integrating acoustic and multisensory inputs. Such findings include a correlation between tinnitus and aberrant neural activity in the DCN (Kaltenbach 2007), altered excitability in the DCN initiating a complex sequence of events in the auditory pathway (Brozoski et al., 2002) and an increased synchrony in the network activity (Shore et al., 2016). We investigate the role of plasticity in the DCN at the early stages following acoustic ...
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This paper proposes modifications to the Multi-resolution RASTA (MRASTA) feature extraction technique for the automatic speech recognition (ASR). By emulating asymmetries of the temporal receptive field (TRF) profiles of higher level auditory neurons, we obtain more than 11.4% relative improvement in word error rate on OGI-Digits database. Experiments on TIMIT database confirm that proposed modifications are indeed useful. Sivaram, Garimella S. V. S.; Hermansky, Hynek
... The formation of the spinal nerve from the dorsal and ventral roots.
By Andrew Liszewski. As far as I know theres no real cure for Tinnitus, but a company called Neuromonics claims to have created an effective treatment that will reduce the symptoms almost immediately and provide some level of long-term relief. At the core of the treatment is the Oasis audio device which plays specifically designed music thats embedded with a "pleasant acoustic neural stimulus." These sounds, which are customized for every patient based on their audiological profile, stimulate the auditory pathway to promote neural plastic changes. And over time its these new connections that help the brain filter out the tinnitus disturbance. So as far as I can tell the process doesnt cure the problem, it just trains your brain to ignore it.. The treatments usually last for 6 months, and during the first 2 months youll need to listen to the device for about 2 hours or longer every day. During the last 4 months that duration will gradually decrease, and once the treatment is over you may ...
We report the design and testing of a novel linear scanning periodic optical delay line (ODL) by use of a helicoid reflective mirror based on a tilted parabolic generatrix that was driven by an electrical motor for a periodic change in the optical path length of the reflected light beam. The divergence and pulse front distortion of the optical beam reflected by the helicoid reflective mirror were simulated based on differential geometry. With a round-trip pass arrangement, a scanning range of delay time as large as ...
WASHINGTON, March 24, 2009 - The Federal Communications Commission on Tuesday outlined the procedures by which parties wishing to provide written or oral
Synaptic Mechanisms in the Auditory System. by. Springer Handbook of Auditory Research (Book 41) Share your thoughts Complete your review. Tell readers what you thought by rating and reviewing this book. Rate it * You Rated it *.
The inferior colliculus (IC) (Latin, lower hill) is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex. The inferior colliculus has three subdivisions: the central nucleus, a dorsal cortex by which it is surrounded, and an external cortex which is located laterally. Its bimodal neurons are implicated in auditory-somatosensory interaction, receiving projections from somatosensory nuclei. This multisensory integration may underlie a filtering of self-effected sounds from vocalization, chewing, or respiration activities. The inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina, and also part of the tectal region of the midbrain. The inferior colliculus lies caudal to its counterpart - the superior colliculus - above the trochlear nerve, and at the base of the projection of the medial geniculate nucleus and the lateral ...
Changes in neuronal excitability contribute to neurologic dysfunction in FXS (Contractor et al., 2015). In the auditory brainstem, where synaptic balance is a key factor in sound processing and sound localization (Tollin, 2003), increased excitability could lead to hyperacusis and difficulties in sound localization. Indeed, Fmr1 KO mice have shifted sensitivity for interaural level differences (Garcia-Pino et al., 2017). Enhanced gain leading to hyperacusis in FXS may originate, at least in part, in the auditory brainstem nuclei. The increase in VGAT in MNTB, a sign-inverting relay nucleus, could lead to enhanced excitation in targets of MNTB (Rotschafer et al., 2015); additionally, increased excitation in LSO has also been shown to arise from VCN (Garcia-Pino et al., 2017). Both of these observations suggest that the superior olivary complex may increase gain in the auditory pathway in Fmr1 KO mice.. In MNTB, increased VGAT expression in Fmr1 KO mice was seen at P6 and persisted into adulthood. ...
TY - JOUR. T1 - Heterogeneous kinetics and pharmacology of synaptic inhibition in the chick auditory brainstem. AU - Kuo, Sidney P.. AU - Bradley, Laura A.. AU - Trussell, Laurence. PY - 2009/7/29. Y1 - 2009/7/29. N2 - Identification of shared features between avian and mammalian auditory brainstem circuits has provided much insight into the mechanisms underlying early auditory processing. However, previous studies have highlighted an apparent difference in inhibitory systems; synaptic inhibition is thought to be slow and GABAergic in birds but to have fast kinetics and be predominantly glycinergic in mammals. Using patch-clamp recordings in chick brainstem slices, we found that this distinction is not exclusively true. Consistent with previous work, IPSCs in nucleus magnocellularis (NM) were slow and mediated by GABA A receptors. However, IPSCs in nucleus laminaris (NL) and a subset of neurons in nucleus angularis (NA) had rapid time courses twofold to threefold faster than those in NM. ...
Tinnitus can arise anywhere along the auditory pathway, from the outer ear through the middle and inner ear to the brains auditory cortex, where its thought to be encoded (in a sense, imprinted). One of the most common causes of tinnitus is damage to the hair cells in the cochlea (see "Auditory pathways and tinnitus"). These cells help transform sound waves into nerve signals. If the auditory pathways or circuits in the brain dont receive the signals theyre expecting from the cochlea, the brain in effect "turns up the gain" on those pathways in an effort to detect the signal - in much the same way that you turn up the volume on a car radio when youre trying to find a stations signal. The resulting electrical noise takes the form of tinnitus - a sound that is high-pitched if hearing loss is in the high-frequency range and low-pitched if its in the low-frequency range. This kind of tinnitus resembles phantom limb pain in an amputee - the brain is producing abnormal nerve signals to ...
TY - JOUR. T1 - Histological determination of the areas enriched in cholinergic terminals and m2 and m3 muscarinic receptors in the mouse central auditory system. AU - Hamada, Satoko. AU - Houtani, Takeshi. AU - Trifonov, Stefan. AU - Kase, Masahiko. AU - Maruyama, Masato. AU - Shimizu, Jun Ichi. AU - Yamashita, Toshio. AU - Tomoda, Koichi. AU - Sugimoto, Tetsuo. PY - 2010/8/1. Y1 - 2010/8/1. N2 - Cholinergic projections to auditory system are vital for coupling arousal with sound processing. Systematic search with in situ hybridization and immunohistochemistry indicated that the ventral nucleus of the medial geniculate body and the nucleus of the brachium of the inferior colliculus constituted cholinergic synaptic sites in the brainstem auditory system, containing a significant number of cholinergic axon terminals and m2 receptor-expressing cell bodies.. AB - Cholinergic projections to auditory system are vital for coupling arousal with sound processing. Systematic search with in situ ...
Synaptic Reorganization in the Adult Rats Ventral Cochlear Nucleus following Its Total Sensory Deafferentation. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
The age related decline in auditory performance, or presbycusis, was reviewed and discussed. Topics reviewed included: anatomy and physiology of the cochlea and central auditory pathway; laboratory animal models of presbycusis; age related structural losses in humans; age related changes in brainstem evoked response; interaction of aging and noise; hearing levels in subjects with military and indu
Developing chick NL neurons express both HVA and LVA-type Ca2+ channels in their dendrites. These currents were larger than those recorded from the avian cochlear nucleus magnocellularis (Koyano et al. 1996; Sivaramakrishnan and Laurent 1995), mammalian ventral cochlear nucleus (octopus cells: Bal and Oertel 2007), or neurons enzymatically isolated from the mammalian dorsal cochlear nucleus (Molitor and Manis 1999). Both current types could be activated rapidly by spikes. Given that these signals arose within milliseconds of the stimulus (and thus are not likely to arise from Ca2+ diffusion from distant sources) and were larger in more distal dendrites than proximal ones, it is likely that HVA and LVA channels are distributed even on the most distal processes of NL.. Because NL dendrites are relatively small, it is difficult to determine directly the amplitude of the voltage transient that activated Ca2+ channels. Recent studies indicate that spikes in NL of hatchling chicks are initiated in the ...
Hearing loss leads to a reorganization of the pathways in the central auditory system.12,20,22,23 These changes may occur rapidly24 and lead to abnormal interactions between auditory and other central pathways.20Analogous changes in the somatosensory system linked to phantom pain25 led us to suggest that there are similarities between neuropathic pain and tinnitus.12 In patients with gaze-evoked tinnitus, lateral eye movements failto produce the inhibition of the auditory cortex observed in controls.20 The absence of this phenomenon, called cross-modal inhibition, may contribute to the false perception of sounds.. Levine hypothesized that a reduction in auditory-nerve input leads to disinhibition of the dorsal cochlear nucleus and an increase in spontaneous activity in the central auditory system, which is experienced as tinnitus.26 This mechanism could explain the temporary ringing sensation that may follow exposure to noise,27 the effects of some drugs such as furosemide, and spontaneous ...