Olivocochlear neurons in the chinchilla: a retrograde fluorescent labelling study

Azeredo, William J.; Kliment, Molly L; Morley, Barbara J.; Relkin, Evan M.; Slepecky, Norma; Sterns, Anita; Warr, W. Bruce; Weekly, J.Mathew; Woods, Charles I.

doi:10.1016/s0378-5955(99)00069-6

Cited by 26 publications

(20 citation statements)

References 56 publications

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“…Most afferent axons innervate IHCs, which constitute the main cochlear sensory receptors. In contrast, OHCs receive predominantly efferent fibers originating near the medial superior olivary nuclei (Guinan, 1996;Azeredo et al, 1999), and in addition to their function as receptors they also act as mechanical effectors boosting cochlear vibrations for low-level stimuli (Dallos, 1992). Neuroanatomical evidences show that descending pathways originate in the auditory cortex and reach the cochlea via olivocochlear efferents (Warr, 1975;Feliciano et al, 1995;Mulders and Robertson, 2000).…”

Section: Reduction Of Cochlear Sensitivity During Visual Selective Atmentioning

confidence: 99%

Selective Attention to Visual Stimuli Reduces Cochlear Sensitivity in Chinchillas

Délano¹,

Elgueda²,

Hamamé³

et al. 2007

J. Neurosci.

142

141

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It is generally accepted that during periods of attention to specific stimuli there are changes in the neural activity of central auditory structures; however, it is controversial whether attention can modulate auditory responses at the cochlear level. Several studies performed in animals as well as in humans have attempted to find a modulation of cochlear responses during visual attention with contradictory results. Here, we have appraised cochlear sensitivity in behaving chinchillas by measuring, with a chronically implanted roundwindow electrode, sound-evoked auditory-nerve compound action potentials and cochlear microphonics, a measure of outer hair cell function, during selective attention to visual stimuli. Chinchillas were trained in a visual discrimination or in an auditory frequency discrimination two-choice task. We found a significant decrease of cochlear sensitivity during the period of attention to visual stimuli in the animals performing the visual discrimination task, but not in those performing the auditory task, demonstrating that this physiological effect is related to selective attention to visual stimuli rather than to an increment in arousal level. Furthermore, the magnitude of the cochlear-sensitivity reductions increased in sessions performed with shorter target-light durations (4 -0.5 s), suggesting that this effect is stronger for higher attentional demands of the task. These results demonstrate that afferent auditory activity is modulated by selective attention as early as at sensory transduction, possibly through activation of olivocochlear efferent fibers.

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Section: Reduction Of Cochlear Sensitivity During Visual Selective Atmentioning

confidence: 99%

Selective Attention to Visual Stimuli Reduces Cochlear Sensitivity in Chinchillas

Délano¹,

Elgueda²,

Hamamé³

et al. 2007

J. Neurosci.

142

141

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“…MOC-activation effects on cochlear responses have been mainly studied in cat and guinea pig (Galambos 1956;Desmedt 1962;Gifford and Guinan 1987;Murugasu and Russell 1996); however, evidence showing significant differences in the anatomy and distribution of OC neurons between the chinchilla and other mammals (Iurato et al 1978;Azeredo et al 1999) makes it important to measure these efferent effects in this widely used hearing model. The aim of this work is to report the effects of electrical stimulation of MOC fibers on cochlear potentials (i.e., CAP and CM) in the anesthetized chinchilla, comparing them with those observed in other commonly used laboratory animals (e.g., cats, guinea pigs).…”

Section: Introductionmentioning

confidence: 99%

Effects of Electrical Stimulation of Olivocochlear Fibers in Cochlear Potentials in the Chinchilla

Elgueda

Délano

Robles

2011

JARO

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The mammalian cochlea has two types of sensory cells; inner hair cells, which receive auditory-nerve afferent innervation, and outer hair cells, innervated by efferent axons of the medial olivocochlear (MOC) system. The role of the MOC system in hearing is still controversial. Recently, by recording cochlear potentials in behaving chinchillas, we suggested that one of the possible functions of the efferent system is to reduce cochlear sensitivity during attention to other sensory modalities (Delano et al. in J Neurosci 27:4146-4153, 2007). However, in spite of these compelling results, the physiological effects of electrical MOC activation on cochlear potentials have not been described in detail in chinchillas. The main objective of the present work was to describe these efferent effects in the chinchilla, comparing them with those in other species and in behavioral experiments. We activated the MOC efferent axons in chinchillas with sectioned middle-ear muscles by applying current pulses at the fourth-ventricle floor. Auditory-nerve compound action potentials (CAP) and cochlear microphonics (CM) were acquired in response to clicks and tones of several frequencies, using a round-window electrode. Electrical efferent stimulation produced CAP amplitude suppressions reaching up to 11 dB. They were higher for low to moderate sound levels. Additionally, CM amplitude increments were found, the largest (≤ 2.5 dB) for low intensity tones. CAP suppression was present at all stimulus frequencies, but was greatest for 2 kHz. CM increments were highest for low-frequency tones, and almost absent at high frequencies. We conclude that the effect obtained in chinchilla is similar to but smaller than that observed in cats, and that the effects seen in awake chinchillas, albeit different in magnitude, are consistent with the activation of efferent fibers.

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“…Although some tendency toward undulation can also be found in the caudorostral plots of VNTB neurons, it was not as clear as that observed in the plots of DMPO/MNTB neurons. Interestingly, undulation can be seen in caudorostral plots of MOC neurons in other species, including the chinchilla (Azeredo et al 1999), guinea pig, and rat (Aschoff and Ostwald 1987), but the phenomenon had not been speci®cally noted or discussed in these earlier studies.…”

Section: Concentration Of Moc Neurons In the Rostral Socmentioning

confidence: 95%

“…Thus, large and small LOC neurons have been described in the guinea pig (Robertson et al 1987), squirrel monkey (Thompson and Thompson 1986), chinchilla (Azeredo et al 1999), and, on the basis of ChAT immunocytochemistry, in humans (Moore et al 1999). In the gerbil, small LOC neurons within the LSO and large neurons outside the LSO differ in their selective retrograde transport, respectively, of D-aspartic acid (Ryan et al 1987) and nipecotic acid (Ryan et al 1992).…”

Section: Comparative Studies Of Loc Neuronsmentioning

confidence: 99%

“…In the gerbil, small LOC neurons within the LSO and large neurons outside the LSO differ in their selective retrograde transport, respectively, of D-aspartic acid (Ryan et al 1987) and nipecotic acid (Ryan et al 1992). than cat, including the chinchilla (Azeredo et al 1999), hamster (Simmons et al 1999 (Aschoff et al 1988), and three species of bats: Pteronotis (Bishop and Henson 1987), Rhinopoma, and Tadarida (Aschoff and Ostwald 1987). Ignoring for the moment the fact that, across species, MOC neurons exhibit a range of different dorsoventral periolivary locations, many animals nevertheless exhibit a well-de®ned peak in MOC neuron density at the rostral end of the SOC.…”

Section: Comparative Studies Of Loc Neuronsmentioning

confidence: 99%

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Organization of Olivocochlear Neurons in the Cat Studied with the Retrograde Tracer Cholera Toxin-B

Warr

Boche

et al. 2002

JARO - Journal of the Association for Research in Otolaryngolog

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We employed cholera toxin-B (CTB), an ef®cient retrograde tracer, to examine olivocochlear (OC) neurons in the cat. Our primary goals were (1) to determine whether the cat has two types of lateral OC (LOC) neurons as is found in certain rodents and (2) to document the morphology, number, and caudorostral distribution of OC neurons, bilaterally. Adult cats received injections of CTB through the round window of the left cochlea, and, after 3±6 days, the brains were sectioned transversely and CTB was revealed immunocytochemically in every section. In three cats, OC neurons were mapped, counted differentially according to cell group, and the numbers of each plotted bilaterally from caudal to rostral. In one cat, measurements were made on labeled LOC and medial OC (MOC) neurons. The results indicate that LOC neurons can be divided into two groups based on their proximity to the lateral superior olive (LSO): a more populous group of small neurons that have intimate contact with the LSO, designated marginal-LOC neurons, and a less populous, morphologically heterogeneous group, lying more distantly from the LSO, designated para-LOC neurons. Para-LOC neurons lying dorsal and rostral to LSO were signi®-cantly larger than marginal-LOC. We hypothesize that the cat marginal-LOC neurons and most probably the larger para-LOC neurons correspond to rodent intrinsic and shell LOC neurons, respectively, which have focal versus diffuse projections beneath the inner hair cells. Concerning MOC neurons, we con®rm and extend previous observations on the clustering of these neurons near the rostral tip of the medial superior olivary nucleus and also show that MOC neurons differ in size according to cell group. Finally, we compare the present counts of OC neurons (mean total 1607, consisting of 1058 LOC neurons and 549 MOC neurons innervating one cochlea) and their proportional distribution ipsilaterally and contralaterally with those reported previously. Our estimate of the number of LOC neurons is somewhat higher than those previously obtained either by retrograde labeling with horseradish peroxidase or by counting unmyelinated axons in the olivocochlear bundle. In contrast, our estimate of the number of MOC neurons is very similar to those previously reported.

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Olivocochlear neurons in the chinchilla: a retrograde fluorescent labelling study

Cited by 26 publications

References 56 publications

Selective Attention to Visual Stimuli Reduces Cochlear Sensitivity in Chinchillas

Selective Attention to Visual Stimuli Reduces Cochlear Sensitivity in Chinchillas

Effects of Electrical Stimulation of Olivocochlear Fibers in Cochlear Potentials in the Chinchilla

Organization of Olivocochlear Neurons in the Cat Studied with the Retrograde Tracer Cholera Toxin-B

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