Cells in Auditory Cortex that Project to the Cochlear Nucleus in Guinea Pigs

Schofield, Brett R.; Coomes, Diana L.; Schofield, Ryan M.

doi:10.1007/s10162-005-0025-4

Cited by 23 publications

(14 citation statements)

References 62 publications

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“…It is unlikely that axons of layer VI cells travel through the IC to terminate at more caudal levels. The auditory cortex projects to a number of subcollicular targets in guinea pigs (Jacomme et al, 2003; Coomes and Schofield, 2004; Schofield et al, 2006; Peterson and Schofield, 2007). All these studies, which include experiments with the tracers used here, have identified layer V cells as the source of the projections to targets caudal to the IC.…”

Section: Discussionmentioning

confidence: 99%

“…The borders of cortical laminae were added by comparison with adjacent thionin-stained sections or by removing the coverslips from the plotted sections, re-hydrating them, staining them with thionin, and re-applying coverslips. The layers were identified according to criteria described previously (Schofield et al, 2006). In cases with CTB injections, well-labeled cells were drawn with a camera lucida attached to a Zeiss Axioskop.…”

Section: Methodsmentioning

confidence: 99%

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Projections to the inferior colliculus from layer VI cells of auditory cortex

Schofield

2009

Neuroscience

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A large injection of a retrograde tracer into the inferior colliculus of guinea pigs labeled two bands of cells in the ipsilateral auditory cortex: a dense band of cells in layer V and a second band of cells in layer VI. On the contralateral side, labeled cells were restricted to layer V. The ipsilateral layer VI cells were distributed throughout temporal cortex, suggesting projections from multiple auditory areas. The layer VI cells included pyramidal cells as well as several varieties of non-pyramidal cells. Small tracer injections restricted to the dorsal cortex or external cortex of the inferior colliculus consistently labeled cells in layer VI. Injections restricted to the central nucleus of the inferior colliculus labeled layer VI cells only rarely. Overall, 10% of the cells in temporal cortex that project to the ipsilateral inferior colliculus were located in layer VI, suggesting that layer VI cells make a significant contribution to the corticocollicular pathway.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Projections to the inferior colliculus from layer VI cells of auditory cortex

Schofield

2009

Neuroscience

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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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“…Interestingly, pyramidal cell axons from the A1auditory cortex distribute specifically to the granule cell domain of the cochlear nuclear complex in mouse, rat gerbil and guinea pig (Feliciano et al, 1995; Weedman and Ryugo, 1996a,b; Budinger et al, 2000; Jacomme, 2003; Schofield and Coomes, 2005a,b; Schofield et al, 2006a,b; Meltzer and Ryugo, 2006). In the hedgehog tenrec a similar projection seems to arise from the somatosensory cortex (Wolff and Künzle, 1997).…”

Section: The Fibers Targeting Ubcs In Cerebellum and Cochlear Nucleusmentioning

confidence: 99%

The unipolar brush cell: A remarkable neuron finally receiving deserved attention

Mugnaini

Sekerková

Martina

2011

Brain Research Reviews

161

152

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Unipolar brush cells (UBC) are small, glutamatergic neurons residing in the granular layer of the cerebellar cortex and the granule cell domain of the cochlear nuclear complex. Recent studies indicate that this neuronal class consists of three or more subsets characterized by distinct chemical phenotypes, as well as by intrinsic properties that may shape their synaptic responses and firing patterns. Yet, all UBCs have a unique morphology, as both the dendritic brush and the large endings of the axonal branches participate in the formation of glomeruli. Although UBCs and granule cells may share the same excitatory and inhibitory inputs, the two cell types are distinctively differentiated. Typically, whereas the granule cell has 4-5 dendrites that are innervated by different mossy fibers, and an axon that divides only once to form parallel fibers after ascending to the molecular layer, the UBC has but one short dendrite whose brush engages in synaptic contact with a single mossy fiber terminal, and an axon that branches locally in the granular layer; branches of UBC axons form a non-canonical, cortex-intrinsic category of mossy fibers synapsing with granule cells and other UBCs. This is thought to generate a feed-forward amplification of single mossy fiber afferent signals that would reach the overlying Purkinje cells via ascending granule cell axons and their parallel fibers.In sharp contrast to other classes of cerebellar neurons, UBCs are not distributed homogeneously across cerebellar lobules, and subsets of UBCs also show different, albeit overlapping, distributions. UBCs are conspicuously rare in the expansive lateral cerebellar areas targeted by the cortico-ponto-cerebellar pathway, while they are a constant component of the vermis and the flocculonodular lobe. The presence of UBCs in cerebellar regions involved in the sensorimotor processes that regulate body, head and eye position, as well as in regions of the cochlear nucleus that process sensorimotor information suggests a key role in these critical functions; it also invites further efforts to clarify the cellular biology of the UBCs and their specific functions in the neuronal microcircuits in which they are embedded. High density of UBCs in specific regions of the cerebellar cortex is a feature largely conserved across mammals and suggests an involvement of these neurons in fundamental aspects of the input/output organization as well as in clinical manifestation of focal cerebellar disease.

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Cells in Auditory Cortex that Project to the Cochlear Nucleus in Guinea Pigs

Cited by 23 publications

References 62 publications

Projections to the inferior colliculus from layer VI cells of auditory cortex

Projections to the inferior colliculus from layer VI cells of auditory cortex

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

The unipolar brush cell: A remarkable neuron finally receiving deserved attention

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