Inhibitory synaptic interactions between cochlear nuclei

Babalian, A.; Ryugo, David K.; Vischer, Mattheus; Rouiller, Eric M.

doi:10.1097/00001756-199906230-00022

Cited by 24 publications

(23 citation statements)

References 9 publications

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“…Moreover, the inhibitory inputs are both glycinergic and GABAergic (Wenthold 1987;Ostapoff et al 1997;Alibardi 2000). Second, electrical stimulation of the contralateral auditory nerve in an in vitro whole brain preparation produces inhibitory postsynaptic potentials in 80% of DCN principal cells (Babalian et al 1999). The latencies of these inhibitory responses are suggestive of mono-and disynaptic connections from the contralateral cochlear nucleus.…”

Section: Introductionmentioning

confidence: 94%

Contralateral Effects and Binaural Interactions in Dorsal Cochlear Nucleus

Davis

2005

JARO

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The dorsal cochlear nucleus (DCN) receives afferent input from the auditory nerve and is thus usually thought of as a monaural nucleus, but it also receives inputs from the contralateral cochlear nucleus as well as descending projections from binaural nuclei. Evidence suggests that some of these commissural and efferent projections are excitatory, whereas others are inhibitory. The goals of this study were to investigate the nature and effects of these inputs in the DCN by measuring DCN principal cell (type IV unit) responses to a variety of contralateral monaural and binaural stimuli. As expected, the results of contralateral stimulation demonstrate a mixture of excitatory and inhibitory influences, although inhibitory effects predominate. Most type IV units are weakly, if at all, inhibited by tones but are strongly inhibited by broadband noise (BBN). The inhibition evoked by BBN is also low threshold and short latency. This inhibition is abolished and excitation is revealed when strychnine, a glycine-receptor antagonist, is applied to the DCN; application of bicuculline, a GABA Areceptor antagonist, has similar effects but does not block the onset of inhibition. Manipulations of discrete fiber bundles suggest that the inhibitory, but not excitatory, inputs to DCN principal cells enter the DCN via its output pathway, and that the short latency inhibition is carried by commissural axons. Consistent with their respective monaural effects, responses to binaural tones as a function of interaural level difference are essentially the same as responses to ipsilateral tones, whereas binaural BBN responses decrease with increasing contralateral level. In comparison to monaural responses, binaural responses to virtual space stimuli show enhanced sensitivity to the elevation of a sound source in ipsilateral space but reduced sensitivity in contralateral space. These results show that the contralateral inputs to the DCN are functionally relevant in natural listening conditions, and that one role of these inputs is to enhance DCN processing of spectral sound localization cues produced by the pinna.

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Section: Introductionmentioning

confidence: 94%

Contralateral Effects and Binaural Interactions in Dorsal Cochlear Nucleus

Davis

2005

JARO

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“…The primary projection of the O C axon contralaterally is to the CN, where, like the ipsilateral projection, it appears to be providing a wide-band inhibition over the entire CN to several of the major cell groups (Cant and Gaston, 1982;Schofield and Cant, 1996;Babalian et al, 1999Babalian et al, , 2002Alibardi, 2000;Shore et al, 2003). These may include both type 1 and 2 multipolar, globular and spherical bushy, octopus, and fusiform cells.…”

Section: Onset Choppersmentioning

confidence: 99%

Acoustic stria: Anatomy of physiologically characterized cells and their axonal projection patterns

Smith

Massie

Joris

2005

J of Comparative Neurology

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The mammalian cochlear nucleus (CN) has been a model structure to study the relationship between physiological and morphological cell classes. Several issues remain, in particular with regard to the projection patterns and physiology of neurons that exit the CN dorsally via the dorsal (DAS), intermediate (IAS), and commissural stria. We studied these neurons physiologically and anatomically using the intra-axonal labeling method. Multipolar cells with onset chopper (O(C)) responses innervated the ipsilateral ventral and dorsal CN before exiting the CN via the commissural stria. Upon reaching the midline they turned caudally to innervate the opposite CN. No collaterals were seen innervating any olivary complex nuclei. Octopus cells typically showed onset responses with little or no sustained activity. The main axon used the IAS and followed one of two routes occasionally giving off olivary complex collaterals on their way to the contralateral ventral nucleus of the lateral lemniscus (VNLL). Here they can have elaborate terminal arbors that surround VNLL cells. Fusiform and giant cells have overlapping but not identical physiology. Fusiform but not giant cells typically show pauser or buildup responses. Axons of both cells exit via the DAS and take the same course to reach the contralateral IC without giving off any collaterals en route.

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“…There is also a corticofugal pathway, which can influence olivocochlear efferent activity and cochlear output (Zhongju and Suga, 2001). Crossed inhibitory connections function to transmit activity between the direct and indirect pathways and could include commissural projections between the cochlear nuclei (Buchwald and Humphrey, 1972a;Young and Brownell, 1976;Cant and Gaston, 1982;Wenthold, 1987;Shore et al, 1992;Schofield and Cant, 1996a,b;Joris and Smith, 1998;Babalian et al, 1999Babalian et al, , 2002Needham and Paolini, 2003;Helfferich et al, 2003) and inferior colliculi (Smith, 1992;Moore et al, 1998;Malmierca et al, 2003), and the crossed olivocochlear pathway (Liberman, 1989), among others. Figure 14B shows the relative levels of SA in the auditory pathway.…”

Section: Effect Of Noise Exposure On 2dg-samentioning

confidence: 99%

Effect of unilateral noise exposure on the tonotopic distribution of spontaneous activity in the cochlear nucleus and inferior colliculus in the cortically intact and decorticate rat

Imig

Durham

2005

J of Comparative Neurology

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Effects of unilateral noise exposure on spontaneous activity (SA) in the anteroventral and dorsal cochlear nuclei (AVCN and DCN) and the central nucleus of the inferior colliculus (ICc) were studied in cortically intact and decorticate rats. SA was measured 1 week following exposure using uptake of 14C-labeled 2-deoxyglucose (2DG) in quiet. Optical density (OD) measurements were obtained in low- and high-frequency (LF and HF) areas of each nucleus. We refer to the ipsilateral AVCN and DCN (side of the noise-exposed ear) and the contralateral ICc as direct nuclei and to their opposite side counterparts as indirect nuclei. Noise exposure altered the tonotopic profile of SA in the direct pathway by causing a decrease in the ratio of HF OD to LF OD (HF/LF ratio). In intact animals, the decreased HF/LF ratio was due to decreased HF OD. In decorticate animals, it was due to decreased HF OD and increased LF OD, the latter occurring mainly in the DCN and ICc. Decorticate-intact differences may reflect corticofugal feedback inhibition. Lesion of the dorsal acoustic stria caused a substantial decrement of SA in the contralateral ICc. Furthermore, strong positive correlations between HF/LF ratios in the DCN, AVCN, and contralateral ICc suggest that the cochlear nucleus is a major contributor to SA in the ICc. Noise exposure had opposite and weaker effects on 2DG uptake in the indirect pathway that were attributed to crossed inhibition. Noise-induced changes in the tonotopic profile of SA may represent a neural correlate of tinnitus.

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Inhibitory synaptic interactions between cochlear nuclei

Cited by 24 publications

References 9 publications

Contralateral Effects and Binaural Interactions in Dorsal Cochlear Nucleus

Contralateral Effects and Binaural Interactions in Dorsal Cochlear Nucleus

Acoustic stria: Anatomy of physiologically characterized cells and their axonal projection patterns

Effect of unilateral noise exposure on the tonotopic distribution of spontaneous activity in the cochlear nucleus and inferior colliculus in the cortically intact and decorticate rat

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