No abstract available.
Cochlear Nucleus ; Patch-Clamp Techniques

OBJECTIVETo investigate the mechanisms of different response patterns of the cochlear nucleus neurons based on a digital model.

METHODSBased on the platform of Matlab7.0 and the integrate-and-fire model, we constructed the temporal coding model.

RESULTSThe model well simulated the response types of the primary-like, chopper, onset and buildup neurons by changing the settings of some parameters related to the properties of the neurons.

CONCLUSIONSThe properties of the neurons dictate the response patterns of the cochlear nucleus neurons. The simulation results are consistent with the literature. Understanding of the response properties of the cochlear nucleus neurons can provide assistance in the study of the auditory system.

Cochlear Nucleus ; physiology ; Computer Simulation ; Humans ; Models, Neurological ; Neurons ; physiology

No abstract available.
Animals ; Calcitonin Gene-Related Peptide* ; Calcitonin* ; Cochlear Nucleus* ; Rats*

The central projections of the peripheral cochlear nerve fiber from each turn to the cochlear nuclei (CN) in the mongolian gerbil were investigated using retrograde transportation of horseradish peroxidase (HRP). The organ of Corti and the osseous spiral lamina were scratched with an electrolytically-sharpened fine needle via a small hole at each turn of the cochlea. The cochlea was filled with a 30% horseradish peroxidase (HRP) solution. After 48 hours, 50 microns transverse serial sections of the brainstem were made with a vibratome. The tissue was processed with the diaminobenzidine procedure of the cobalt-glucose method. Our experiment revealed that the fibers from the basal turn terminated at the dorsomedial portion of anteroventral cochlear nuclei (AVCN), but those from the apical turn were distributed among the ventrolateral portion of the AVCN. In the posteroventral cochlear nuclei (PVCN) and dorsal cochlear nuclei (DCN), the fibers from basal to apical turns extend from the dorsal to the ventral portion of each nuclei. A distinct tonotopic arrangement could be found between the origin of cochlear fibers of each turn and their termination in the regions of the cochlear nuclei (CN). Also, the results suggested that the scratch method combined with retrograde transportation of horseradish peroxidase was useful in investigating the tonotopic arrangement of the peripheral auditory nerve in the CN.
Animal ; Cochlear Nerve/*anatomy & histology ; Cochlear Nucleus/*anatomy & histology ; Gerbillinae ; Horseradish Peroxidase ; Nerve Fibers

OBJECTIVE: To learn the neural response of spiral ganglion cell to electrical stimulus by comparing the neural response telemetry(NRT) value between straight electrode and contour electrode in Nucleus 24 cochlear implant system. METHOD: Fourty-six patients with Nucleus 24 cochlear implants were paired into two groups: 23 with contour electrode and 23 with straight electrode respectively. NRT value of each group were tested and compared. RESULT: The NRT value of straight electrode fell in the range of 160 microV to 170 microV and contour electrode 150 microV to 160 microV. The NRT were going up higher a little bit from electrode twenty to electrode one. CONCLUSION The contour electrode requires less power consumption than straight electrode in Nucleus 24 cochlear implant system.
Action Potentials ; Child ; Child, Preschool ; Cochlear Implantation ; Cochlear Implants ; Cochlear Nucleus ; Electrodes ; Female ; Humans ; Infant ; Male ; Telemetry

OBJECTIVE: The purpose of the study is to draw the three-dimensional reconstructions of nuclei and tracts of the auditory pathway structures of drainstem. METHOD: The drawings of 1 mm sections of the brainstem were scanned with a computer scanner into AUTOCAD program. All lines of structures except for the auditory pathway structures and outlines were removed. Each layer was plotted to a x, y, and z coordinated plotting reference to the corresponding points on the mid-sagittal plane and reconstructed to a three-dimensional drawing. Center point of the auditory pathway structures of all cross section layers were connected with a line in succession and that was thought to be a imaginary pathway of auditory pathway through the brainstem. RESULTS: This auditory pathway has several turning points, at the cochlear nucleus, superior olivary nucleus, and inferior colliculus which correspond with known generation sources of the peak of brainstem evoked potentials. CONCLUSION: This study presents a method for the conversion of the two-dimensional transverse sections into a three-dimensional format, to allow the visualization of the auditory pathway structures from multiple directions.
Auditory Pathways* ; Brain Stem* ; Cochlear Nucleus ; Evoked Potentials ; Inferior Colliculi ; Olivary Nucleus

Tinnitus-the perception of sound in the absence of an actual external sound-represents a symptom of an underlying condition rather than a single disease. Several theories have been proposed to explain the mechanisms underlying tinnitus. Tinnitus generators are theoretically located in the auditory pathway, and such generators and various mechanisms occurring in the peripheral auditory system have been explained in terms of spontaneous otoacoustic emissions, edge theory, and discordant theory. Those present in the central auditory system have been explained in terms of the dorsal cochlear nucleus, the auditory plasticity theory, the crosstalk theory, the somatosensory system, and the limbic and autonomic nervous systems. Treatments for tinnitus include pharmacotherapy, cognitive and behavioral therapy, sound therapy, music therapy, tinnitus retraining therapy, massage and stretching, and electrical suppression. This paper reviews the characteristics, causes, mechanisms, and treatments of tinnitus.
Auditory Pathways ; Autonomic Nervous System ; Cochlear Nucleus ; Massage ; Music Therapy ; Otoacoustic Emissions, Spontaneous ; Tinnitus

OBJECTIVEThe cochlear nucleus (CN) neurons show 3 principal response patterns to short tone bursts, namely the primary-like, chopper and onset response patterns. We previously established an excitatory model to simulate the response patterns of CN neurons to stimuli. In this study, we aimed to investigate the effects of excitatory intensity on the CN neuron response patterns and explore the role of inhibitory inputs under normal physiological conditions.

METHODSBased on the platform of Matlab and the excitatory model derived from the integrate-and-fire model, we altered the intensity of excitatory inputs in dB range and obtained the histograms to analyze the changes in the response patterns of the neurons using OriginPro 7.5 data analysis software.

RESULTSThe original primary-like response pattern of the neurons did not vary significantly while the chopper and onset response patterns changed into primary-like responses with the increase of the excitatory input intensity. But this response pattern alteration as a result of excitatory input intensity changes was rarely observed under normal physiological conditions.

CONCLUSIONSThe CN neurons receive balanced excitatory and inhibitory inputs, which stabilize the neuronal membrane potential within a limited range. The balanced inhibitory inputs decide the response pattern of a given neuron.

Acoustic Stimulation ; Cochlear Nucleus ; physiology ; Evoked Potentials, Auditory ; Models, Neurological ; Neurons ; physiology

OBJECTIVE: To investigate the distribution and morphology of olivocochlear neurons of superior olivary complex in cats. METHODS: Eight adult cats were divided into 2 groups randomly. Cholera toxin B subunit was injected to the left cochlea and fluoro-gold was injected to the right cochlea in the experimental group (n=5). Saline was injected to bilateral cochlea in the control group (n=3). Brainstem tissue was sectioned serially. All of the sections were immunohistochemically treated with ABC and stained with DAB, and then the labelled olivocochlear neurons were observed. RESULTS: The labelled olivocochlear neurons in the experimental group were 2 518 in total. Of them, the number of lateral olivocochlear (LOC) neurons was 1 738 (69.0%), mainly located in the middle of the pons, predominantly projected ipsilaterally. The total of medial olivocochlear (MOC) neurons was 780 (31%), mainly located in dorsomedial periolivary nucleus, medial nucleus of the trapezoid body and ventral nucleus of the trapezoid body, mainly distributed in the rostral extent of the pons, predominantly projected contralaterally. CONCLUSION In the distribution of olivocochlear neurons in cats, LOC neurons mainly project to the ipsilateral. While the projection of MOC neurons is predominantly contralateral, the distribution of MOC neurons is more adjacent to the rostral extent of the pons than LOC neurons.
Animals ; Auditory Pathways ; cytology ; Brain Stem ; cytology ; Cats ; Cholera Toxin ; administration & dosage ; Cochlea ; innervation ; Cochlear Nucleus ; cytology ; Female ; Injections ; Male ; Neurons ; cytology ; Neurons, Efferent ; cytology ; Olivary Nucleus ; cytology

OBJECTIVETo investigate the development of the electrophysiological property of bushy cells in the anterior ventral cochlear nucleus (AVCN) of neonatal Sprague Dawley (SD) rats.

METHODSThe development of action potential and spontaneous miniature excitatory postsynaptic currents (mEPSCs) in AVCN bushy cells were investigated by whole-cell patch-clamp technique in SD rats during the postnatal days 5-21 (P5-21). The half band width of the action potential (AP), 10%-90% risetime and decay tau of the mEPSCs were analyzed.

RESULTSThe AP of the bushy cells became faster with age from P5 to P21 and stopped changing around the period of hearing onset, as evidenced by the alteration of half band width of the AP. The time accuracy of mEPSCs of the bushy cells also increased with age and stabilized around hearing onset as shown by briefer 10%-90% rise time and decay tau of mEPSCs in P14/P21 than in P7.

CONCLUSIONThe functional refinement of the bushy cells in the AVCN precedes hearing onset in neonatal rats.

Action Potentials ; Animals ; Cochlear Nucleus ; cytology ; Excitatory Postsynaptic Potentials ; Hearing ; Neurons ; cytology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Synapses