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

Peterson, Diana C.; Schofield, Brett R.

doi:10.1016/j.heares.2007.06.009

Cited by 34 publications

(18 citation statements)

References 60 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 situation is further complicated by the discovery that auditory cortex also projects directly to brainstem auditory nuclei below the IC (Feliciano et al, 1995). Recent studies suggest that these cortical projections could directly affect the ascending inputs to the IC (Schofield and Coomes, 2005; Peterson and Schofield, 2007). It seems likely that numerous corticofugal pathways could play an important role in IC function; understanding these roles will require more detailed understanding of the circuitry, including the origins and termination patterns of the direct pathway from cortex to the IC.…”

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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%

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confidence: 99%

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

Schofield

2009

Neuroscience

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“…FR or FD was injected into the AC because these tracers are highly effective in labeling the corticocollicular pathway (Coomes Peterson and Schofield, 2007). Two methods were used to deposit tracer across a wide expanse of the AC.…”

Section: Methodsmentioning

confidence: 99%

“…The circuitry underlying these effects is not clear. The AC projects directly to the contralateral IC, but this projection is much smaller than the ipsilateral one, and terminates exclusively in the cortical areas of the contralateral IC (Bajo and Moore, 2005; Bajo et al, 2007; Coomes Peterson and Schofield, 2007). There is no evidence of a cortical projection to the contralateral ICc, so both the excitatory and inhibitory effects of the AC on the contralateral ICc must depend on a disynaptic or multisynaptic pathway.…”

Section: Introductionmentioning

confidence: 99%

Auditory cortical axons contact commissural cells throughout the guinea pig inferior colliculus

2013

Self Cite

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Projections from auditory cortex (AC) affect how cells in both inferior colliculi (IC) respond to acoustic stimuli. The large projection from the AC to the ipsilateral IC is usually credited with the effects in the ipsilateral IC. The circuitry underlying effects in the contralateral IC is less clear. The direct projection from the AC to the contralateral IC is relatively small. An unexplored possibility is that the large ipsilateral cortical projection contacts the substantial number of cells in the ipsilateral IC that project through the commissure to the contralateral IC. Apparent contacts between cortical boutons and commissural cells were identified in the left IC after injection of different fluorescent tracers into the left AC and the right IC. Commissural cells were labeled throughout the left IC, and many (23–34%) appeared to be contacted by cortical axons. In the central nucleus, both disc-shaped and stellate cells were contacted. Antibodies to glutamic acid decarboxylase (GAD) were used to identify GABAergic commissural cells. The majority (>86%) of labeled commissural cells were GAD-immunonegative. Despite low numbers of GAD-immunopositive commissural cells, some of these cells were contacted by cortical boutons. Nonetheless, most cortically-contacted commissural cells were GAD-immunonegative (i.e., presumably glutamatergic). We conclude that auditory cortical axons contact primarily excitatory commissural cells in the ipsilateral IC that project to the contralateral IC. These corticocollicular contacts occur in each subdivision of the ipsilateral IC, suggesting involvement of commissural cells throughout the IC. This pathway – from AC to commissural cells in the ipsilateral IC - is a prime candidate for the excitatory effects of activation of the auditory cortex on responses in the contralateral IC. Overall this suggests that the auditory corticofugal pathway is integrated with midbrain commissural connections.

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“…There are multiple IC cell types that have been defined on morphological, connectional and physiological grounds (Peruzzi, Sivaramakrishnan and Oliver 2000; Ahuja and Wu 2007; Malmierca, Blackstad and Osen 2011). There are data suggesting that both commissural and tectothalamic cells receive axosomatic input from the AC (Coomes Peterson and Schofield 2007; Nakamoto, Sowick and Schofield 2013). However, most of the inputs from the CC system terminate in the neuropil, primarily on distal dendrites and spines (Nakamoto et al 2013), suggesting that the majority of the cell types receiving CC input and their projection targets have not yet been characterized.…”

Section: Molecular and Circuit-level Considerationsmentioning

confidence: 99%

The auditory corticocollicular system: Molecular and circuit-level considerations

Stebbings¹,

Lesicko²,

Llano

2014

Hearing Research

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We live in a world imbued with a rich mixture of complex sounds. Successful acoustic communication requires the ability to extract meaning from those sounds, even when degraded. One strategy used by the auditory system is to harness high-level contextual cues to modulate the perception of incoming sounds. An ideal substrate for this process is the massive set of top-down projections emanating from virtually every level of the auditory system. In this review, we provide a molecular and circuit-level description of one of the largest of these pathways: the auditory corticocollicular pathway. While its functional role remains to be fully elucidated, activation of this projection system can rapidly and profoundly change the tuning of neurons in the inferior colliculus. Several specific issues are reviewed. First, we describe the complex heterogeneous anatomical organization of the corticocollicular pathway, with particular emphasis on the topography of the pathway. We also review the laminar origin of the corticocollicular projection and discuss known physiological and morphological differences between subsets of corticocollicular cells. Finally, we discuss recent findings about the molecular micro-organization of the inferior colliculus and how it interfaces with corticocollicular termination patterns. Given the assortment of molecular tools now available to the investigator, it is hoped that his review will help guide future research on the role of this pathway in normal hearing.

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

Cited by 34 publications

References 60 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

Auditory cortical axons contact commissural cells throughout the guinea pig inferior colliculus

The auditory corticocollicular system: Molecular and circuit-level considerations

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