Projections from the auditory cortex to the superior olivary complex in guinea pigs

Coomes, Diana L.; Schofield, Brett R.

doi:10.1111/j.0953-816x.2004.03317.x

Cited by 71 publications

(56 citation statements)

References 39 publications

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“…Cortico-olivary axons were distributed in a pattern described previously (Coomes and Schofield, 2004a). Axons and boutons were more numerous on the ipsilateral side than on the contralateral side.…”

Section: Experiments To Identify Cortical Contacts On Olivocollicularmentioning

confidence: 64%

“…The images were then related to physiological maps of auditory cortex in the guinea pig (Wallace et al, 2000(Wallace et al, , 2002 using reconstruction techniques described previously (Coomes and Schofield, 2004a). Transverse sections through cortex were also evaluated to assess injections relative to cortical layers.…”

Section: Discussionmentioning

confidence: 99%

“…The subdivisions of the IC -central nucleus, dorsal cortex (ICd), and external cortex (ICx) -were identified using criteria described in guinea pigs and rats (FayeLund and Osen, 1985;Malmierca et al, 1995). Nuclei within the SOC were distinguished according to criteria described previously Cant, 1991, Coomes andSchofield, 2004a).…”

Section: Discussionmentioning

confidence: 99%

“…Cortical projections to the superior olivary complex (SOC) may also participate in loops. The cortical projections terminate in the periolivary nuclei as well as the lateral superior olivary nucleus (Coomes and Schofield, 2004a), both of which are major sources of projections to the IC (Schofield and Cant, 1992). However, whether cortical axons contact olivary cells that project to the IC is unknown.…”

Section: Introductionmentioning

confidence: 99%

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Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Peterson

Schofield

2007

Hearing Research

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The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projections as well as sources of major ascending auditory pathways. This study examines whether the cortical projections contact cells in the SOC or IC that project to higher levels. First, we placed an anterograde tracer into the auditory cortex to label cortico-olivary axons and a retrograde tracer into the IC to label olivocollicular cells in guinea pigs. Cortical axons contacted many labeled cells in the ipsilateral SOC and fewer labeled cells in the contralateral SOC. Contacted cells projected to the ipsilateral or contralateral IC.In a second experiment, we labeled corticocollicular axons with an anterograde tracer and injected retrograde tracers into the medial geniculate (MG) to label colliculogeniculate cells. In the IC ipsilateral to the cortical injection, many cortical axons contacted colliculogeniculate cells in the dorsal cortex and external cortex of the IC. The contacted cells projected to the ipsilateral MG or, less often, to the contralateral MG.The results indicate that cortical projections are likely to contact cells in the SOC and IC that project to higher centers. This suggests that auditory cortex can modulate the ascending auditory pathways at multiple levels of the brainstem.

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Section: Experiments To Identify Cortical Contacts On Olivocollicularmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Peterson

Schofield

2007

Hearing Research

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“…A change in the balance between LTP and LTD may explain the decreased responsiveness of ACx in sound-deprived mice (21) and the decline of electrically evoked responses observed in congenitally deaf cats (45). L5 synaptic plasticity may have a significant impact on subthalamic processing because of the massive descending projection from ACx (28,(46)(47)(48)(49)(50). Furthermore, the specific complement of cortical plasticity mechanisms may support the functional takeover of ACx by other sensory modalities.…”

Section: Discussionmentioning

confidence: 99%

Developmental hearing loss eliminates long-term potentiation in the auditory cortex

Kotak

Breithaupt

Sanes³

2007

Proc. Natl. Acad. Sci. U.S.A.

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Severe hearing loss during early development is associated with deficits in speech and language acquisition. Although functional studies have shown a deafness-induced alteration of synaptic strength, it is not known whether long-term synaptic plasticity depends on auditory experience. In this study, sensorineural hearing loss (SNHL) was induced surgically in developing gerbils at postnatal day 10, and excitatory synaptic plasticity was examined subsequently in a brain slice preparation that preserves the thalamorecipient auditory cortex. Extracellular stimuli were applied at layer 6 (L6), whereas evoked excitatory synaptic potentials (EPSPs) were recorded from L5 neurons by using a whole-cell current clamp configuration. In control neurons, the conditioning stimulation of L6 significantly altered EPSP amplitude for at least 1 h. Approximately half of neurons displayed long-term potentiation (LTP), whereas the other half displayed long-term depression (LTD). In contrast, SNHL neurons displayed only LTD after the conditioning stimulation of L6. Finally, the vast majority of neurons recorded from control prehearing animals (postnatal days 9 -11) displayed LTD after L6 stimulation. Thus, normal auditory experience may be essential for the maturation of synaptic plasticity mechanisms.deafness ͉ long-term depression S evere hearing loss is known to affect auditory processing in humans. This loss includes impairments of signal detection in noise or in a multiple source environment, and disruption of intensity discrimination, frequency discrimination, and temporal resolution (1-4). Even transient bouts of conductive hearing loss can disrupt auditory processing, and months or years may be required for normal perception to resolve (5, 6). Because severe hearing loss during development is implicated in the deficient acquisition of auditory perceptual skills and language, which presumably require learning, we have examined whether synaptic plasticity is also affected.At a structural level, hearing impairments can lead to neuron death or atrophy and alter process outgrowth (7). Furthermore, direct examination of neuron function in brain slice preparations from deaf animals has revealed significant physiological changes to intrinsic and synaptic properties. In both the inferior colliculus and auditory cortex (ACx), early sensorineural hearing loss (SNHL) alters the balance of excitatory and inhibitory synaptic strength (8-10). A similar disruption in synaptic physiology and certain intrinsic properties also occurs in the auditory brainstem of the congenitally deaf mutant mouse (11,12).Both long-term potentiation (LTP) and depression (LTD) have been characterized in a series of studies on the rat ACx (13-18). For example, an NMDA receptor-mediated LTP in the ACx can be induced by stimulation of afferents innervating the ACx via the white matter (13), whereas thalamo-and corticocortical synapse activation can induce LTD (16). These cellular mechanisms may serve as a substrate for use-dependent alteration of coding properties in...

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Descending projections from the auditory cortex to the inferior colliculus in the gerbil, Meriones unguiculatus

Bajo¹,

Moore²

2005

J of Comparative Neurology

130

115

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Corticofugal projections to the auditory midbrain, the inferior colliculus (IC), influence the way in which specific sets of IC neurons process acoustic signals. We used retrograde tracer (Fluorogold, Fluororuby, microbeads) injections in the IC to study the morphology and location of cortico-collicular projecting neurons and anterograde tracer (dextran biotin) injections in auditory cortical fields to describe the distribution of terminals in the IC. Nissl staining, cytochrome oxidase activity, and neurofilament SMI32 immunostaining were used to delimit the different auditory areas. We defined a primary or "core" auditory cortex and a secondary "caudal" auditory area containing layer V pyramidal neurons that project to the IC. These projections target the central nucleus of the IC (CNIC) ipsilaterally and the IC cortices bilaterally, with the ipsilateral component predominant. Other secondary auditory areas, dorsal and ventral to the core, do not directly participate in this projection. The ventral secondary cortex targets midbrain periaqueductal gray. The projection from the core cortex originates from two classes of layer V pyramidal cells. Cells presenting a tufted apical dendrite in layer I have dense terminal fields in the IC cortices. Pyramids lacking layer I dendritic tufts target the CNIC in a less dense but tonotopic manner. The caudal cortex projection originates from smaller layer V pyramids and targets the IC cortices with dense terminal fields. Descending auditory inputs from the core and caudal areas converge in the dorsal and external cortices of the IC. Descending connections to the gerbil IC form a segregated system in which multiple descending channels originating from different neuronal subpopulations may modulate specific aspects of ascending auditory information.

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Projections from the auditory cortex to the superior olivary complex in guinea pigs

Cited by 71 publications

References 39 publications

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Developmental hearing loss eliminates long-term potentiation in the auditory cortex

Descending projections from the auditory cortex to the inferior colliculus in the gerbil, Meriones unguiculatus

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