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  • 1
    Electronic Resource
    Electronic Resource
    Discharge patterns in the cochlear nucleus of the chinchilla following noise induced asymptotic threshold shift (1978)
    Springer
    Experimental brain research 32 (1978), S. 301-320 
    Details
    ISSN: 1432-1106
    Keywords: Cochlear nucleus ; Noise induced deafness ; Cochleagrams ; Tuning curves ; Spontaneous activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Chinchillas were exposed to an 86 dB SPL octave band of noise centered at 4.0 kHz for 3.5–5 days. The noise elevated the hearing thresholds between 4.0 and 16.0 kHz to between 60 and 75 dB SPL. Measurements from single neurons in the cochlear nucleus revealed abnormalities in the response properties of neurons with characteristic frequencies (CF) above 2.0 kHz. Units above 2.0 kHz had elevated thresholds (between 50 and 90 dB SPL) and broad tuning curves due to a greater loss in sensitivity near CF than at lower frequencies. The tuning curve Q10dB values for high frequency neurons were generally less than 3.0 and approached the Q10dB values for basilar membrane displacement. Spontaneous activity rates in units above 2.0 kHz were also low. In a few units, the threshold for single tone inhibition was significantly lower than that for excitation; the best inhibitory frequencies were always below 2.0 kHz. Two-tone inhibition was present in both low and high threshold neurons, but its strength was not assessed. Cochleagrams obtained 12 hours postexposure revealed discrete hair cell lesions in the basal third of the cochlea. The locations of the lesions were consistent with the frequencies of maximum hearing loss. The behavioral thresholds and the thresholds at CF of the most sensitive units were within 10–15 dB of each other. The results indicate that intense sounds reduce the sensitivity, frequency selectivity and spontaneous activity of units in the cochlear nucleus. The findings are similar to those obtained in auditory nerve fibers with ototoxic drugs and hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238704
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  • 2
    Electronic Resource
    Electronic Resource
    Changing electrophysiological properties in differentiating human cord blood-derived neural stem cells (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 85 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ion channels were assessed on both differentiated and nondifferentiated human cord blood-derived neural stem cells (HUCB-NSC). HUCB-NSC displayed two types of voltage-sensitive currents: (1) hyperpolarization-activated inward current [Ih] and (2) outward rectifying K+ current [IK+]. Ih was recorded from most of the neuron-shaped HUCB-NSC differentiated with dBcAMP/ascorbic acid for 12 days. Ih was blocked by external Cs+ (5 mm) and recovered after Cs+ removal. Ik+ was recorded from approximately 40% of cAMP/ascorbic acid-differentiated cells and was blocked by TEA (15 mm) or 4-AP (1 mm), but not by externally applied Cs+. While nondifferentiated HUCB-NSC also displayed Ih, none displayed IK+. Differentiated HUCB-NSC expressed ligand-gated channels indicated by (1) kainic acid (KA), a non-NMDA glutamate-receptor agonist- and (2) serotonin-evoked inward currents. KA-induced current was not observed in nondifferentiated HUCB-NSC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.85.s2.21_3.x
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  • 3
    Electronic Resource
    Electronic Resource
    Discharge patterns of cochlear ganglion neurons in the chicken (1992)
    Springer
    Journal of comparative physiology 170 (1992), S. 227-241 
    Details
    ISSN: 1432-1351
    Keywords: Cochlear ganglion neurons ; Characteristic frequency ; Threshold ; Tuning curve ; Spontaneous activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Physiological recordings were made of the compound action potential from the round window and single neurons in the cochlear ganglion of normal adult chickens (Gallus domesticus). The compound action potential threshold to tone bursts decreased from approximately 42 dB at 0.25 kHz to 30 dB between 1 and 2 kHz and then increased to 51 dB at 4 kHz. Most of the cochlear ganglion cells had characteristic frequencies below 2 kHz and the thresholds of most neurons were roughly 30–35 dB lower than the compound action potential thresholds. At any given characteristic frequency, thresholds varied by as much as 60 dB and units with the highest thresholds tended to have the lowest spontaneous rates. Spontaneous discharge rates ranged from 0 to 200 spikes/s with a mean rate of 86 spikes/s. Interspike interval histograms of spontaneous activity often contained regular peaks with the time interval between peaks approximately equal to 1/(characteristic frequency). Tuning curves were sharply tuned and V-shaped with approximately equal slopes to the curves above and below characteristic frequency. Q10dB and Q30dB values for the tuning curves increased with characteristic frequency. Post stimulus time histograms showed sustained firing during the stimulus and were characterized by a slight-to-moderate peak at stimulus onset. Most units showed vigorous phase-locking to tones at characteristic frequency although the degree of phase-locking declined sharply with increasing characteristic frequency. Discharge rate-level functions at characteristic frequency had a mean dynamic range of 42 dB and a mean saturation firing rate of 327 spikes/s. In general, the firing patterns of cochlear ganglion neurons are similar in most respects to those reported in other avians, but differ in several important respects from those seen in mammals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196905
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  • 4
    Electronic Resource
    Electronic Resource
    Discharge patterns of chicken cochlear ganglion neurons following kanamycin-induced hair cell loss and regeneration (1994)
    Springer
    Journal of comparative physiology 174 (1994), S. 351-369 
    Details
    ISSN: 1432-1351
    Keywords: Cochlear ganglion neurons ; Hair cell regeneration ; Tuning curves ; Spontaneous activity ; Threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Hair cells in the basal, high frequency region (〉1100 Hz) of the chicken cochlea were destroyed with kanamycin (400 mg/kg/d × 10 d) and allowed to regenerate. Afterwards, single unit recordings were made from cochlear ganglion neurons at various times post-treatment. During the first few weeks post-treatment, only neurons with low characteristic frequencies (〈1100 Hz) responded to sound. Despite the fact that the low frequency region of the cochlea was not destroyed, neurons with low characteristic frequencies had elevated thresholds, abnormally broad U-shaped or W-shaped tuning curves and low spontaneous discharge rates. At 2 days post-treatment, the spontaneous discharge rates of some acoustically unresponsive units fluctuated in a rhythmical manner. As recovery time increased, thresholds decreased, tuning curves narrowed and developed a symmetrical V-shape, spontaneous rate increased and neurons with higher characteristic frequencies began to respond to sound. In addition, the proportion of interspike interval histograms with regularly spaced peaks increased. These improvements progressed along a low-to-high characteristic frequency gradient. By 10–20 weeks post-treatment, the thresholds and tuning curves of neurons with characteristic frequencies below 2000 Hz were within normal limits; however, the spontaneous discharge rates of the neurons were still significantly lower than those from normal animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240217
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Auditory nerve activity and cochlear morphology after noise exposure (1979)
    Springer
    European archives of oto-rhino-laryngology and head & neck 224 (1979), S. 111-116 
    Details
    ISSN: 1434-4726
    Keywords: Auditory nerve fiber ; Acoustic trauma ; Hair cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four chinchillas were exposed for 5 days to an octave band of noise centered at 4 kHz and having an SPL of 86 dB. After a recovery period of approximately 6 months, behavioral audiograms were obtained and auditory nerve fiber activity was recorded. The animals were killed and the cochleas embedded in plastic to obtain a surface preparation and 1 μ radial sections of the organ of Corti. Behavioral threshold shifts ranged from 5 to 20 dB at frequencies between 4 and 11 kHz. Auditory nerve fiber thresholds were elevated up to 70 dB for units with characteristic frequencies between 4 and 14 kHz. Units with higher and lower characteristic frequencies had normal thresholds. Cochleagrams showed narrow lesions of inner and/or outer hair cells over approximately a 1 mm distance. A comparison of the three realms of data revealed the following: (1) The greatest threshold shifts from the noise exposure were seen in the single nerve fiber thresholds while the smallest shifts were seen in the behavioral thresholds, (2) the greatest behavioral and neural threshold shifts and greatest cochlear damage occurred 1 octave above the center frequency of the noise exposure, and (3) based on the frequency-place map of the chinchilla cochlea, the range of fibers with elevated thresholds exceeded the extent of the OHC lesion. A number of anatomical changes were seen that effectively increased the extent of the damage found in the chochleagram. These changes included: distortions in the surface topography of the organ of Corti affecting the orientation of IHC; missing pillar cells in the presence of normal OHC and/or IHC and protrusion of the IHC cuticular plate into the subtectorial space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455233
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    Paper (German National Licenses)
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