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Frontiers in Neural Circuits 2014
Topics: Animals; Humans; Inferior Colliculi; Nerve Net; Neurons
PubMed: 25346661
DOI: 10.3389/fncir.2014.00113 -
Frontiers in Neural Circuits 2022
Topics: Auditory Perception; Inferior Colliculi
PubMed: 35664460
DOI: 10.3389/fncir.2022.898646 -
Hearing Research Nov 2022Sensory processing is frequently conceptualized as a linear flow of information from peripheral receptors through hierarchically organized brain regions, ultimately... (Review)
Review
Sensory processing is frequently conceptualized as a linear flow of information from peripheral receptors through hierarchically organized brain regions, ultimately reaching the cortex. In reality, this ascending stream is accompanied by massive descending connections that cascade from the cortex toward more peripheral subcortical structures. In the central auditory system, these feedback connections influence information processing at virtually every level of the pathway, including the thalamus, midbrain, and brainstem, and exert influence even at the level of the cochlea. The auditory cortico-collicular system, which connects the auditory cortex to the auditory midbrain, mediates manifold functions ranging from tuning shifts to defense behavior. In this review, we first summarize recent findings regarding the anatomical organization and physiological properties of the auditory cortico-collicular pathway. We then highlight several new studies that show that this projection system mediates high-level cognitive processes, acoustico-motor behaviors, and auditory plasticity, and discuss the circuit mechanisms through which they are mediated. Finally, we discuss remaining unanswered questions regarding cortico-collicular circuitry and function and potential avenues for future exploration.
Topics: Acoustic Stimulation; Auditory Cortex; Auditory Pathways; Inferior Colliculi
PubMed: 35351323
DOI: 10.1016/j.heares.2022.108488 -
Hearing Research May 2019The inferior colliculus occupies a central position in ascending and descending auditory pathways. A substantial proportion of its neurons are GABAergic, and these... (Review)
Review
The inferior colliculus occupies a central position in ascending and descending auditory pathways. A substantial proportion of its neurons are GABAergic, and these neurons contribute to intracollicular circuits as well as to extrinsic projections to numerous targets. A variety of types of evidence - morphology, physiology, molecular markers - indicate that the GABAergic cells can be divided into at least four subtypes that serve different functions. However, there has yet to emerge a unified scheme for distinguishing these subtypes. The present review discusses these criteria and, where possible, relates the different properties. In contrast to GABAergic cells in cerebral cortex, where subtypes are much more thoroughly characterized, those in the inferior colliculus contribute substantially to numerous long range extrinsic projections. At present, the best characterized subtype is a GABAergic cell with a large soma, dense perisomatic synaptic inputs and a large axon that provides rapid auditory input to the thalamus. This large GABAergic subtype projects to additional targets, and other subtypes also project to the thalamus. The eventual characterization of these subtypes can be expected to reveal multiple functions of these inhibitory cells and the many circuits to which they contribute.
Topics: Animals; Auditory Pathways; Calcium-Binding Proteins; Cell Surface Extensions; GABAergic Neurons; Inferior Colliculi; Models, Neurological; Receptors, Neurotransmitter; Vesicular Glutamate Transport Protein 2
PubMed: 30314930
DOI: 10.1016/j.heares.2018.10.001 -
Neuron Jan 2022Selective attention modulates neuronal activity in multiple brain regions, but the origins of attention signals remain unclear. We show that, during a visual task...
Selective attention modulates neuronal activity in multiple brain regions, but the origins of attention signals remain unclear. We show that, during a visual task requiring spatial attention directed by an auditory cue, an inferior-superior colliculus circuit provides the key attention signal. In mice performing a task based on a visual stimulus in the cued hemifield while ignoring a conflicting stimulus on the uncued side, the visual cortex (V1) and superior colliculus (SC) showed strong attentional modulation, with a shorter latency in the SC. The nucleus of the brachium of the inferior colliculus (nBIC), which provides auditory inputs to the SC, was activated not only at auditory cue onset but also during the delay period before the visual stimulus. The delay activity, but not cue onset activity, was crucial for task performance and attentional modulation in the SC and V1. These results establish a new behavioral paradigm for studying visual attention in mice and identify a midbrain signal controlling auditory cue-directed spatial attention.
Topics: Animals; Cues; Inferior Colliculi; Mice; Neurons; Superior Colliculi; Visual Cortex
PubMed: 34699777
DOI: 10.1016/j.neuron.2021.10.004 -
The Journal of Comparative Neurology Jun 2021Adrenergic receptors are mediators of adrenergic and noradrenergic modulation throughout the brain. Previous studies have provided evidence for the expression of...
Adrenergic receptors are mediators of adrenergic and noradrenergic modulation throughout the brain. Previous studies have provided evidence for the expression of adrenergic receptors in the midbrain auditory nucleus, the inferior colliculus (IC), but have not examined the cellular patterns of expression in detail. Here, we utilize multichannel fluorescent in situ hybridization to detect the expression of adrenergic receptor-encoding mRNA in the inferior colliculus of male and female mice. We found expression of α , α , and β receptor-encoding mRNA throughout all areas of the IC. While we observed similar levels of expression of α receptor-encoding mRNA across the subregions of the IC, α and β receptor-encoding mRNA was expressed differentially. To account for developmental changes in noradrenergic receptor expression, we measured expression levels in mice aged P15, P20, and P60. We observed little change in levels of expression across these ages. To ascertain the modulatory potential of multiple adrenergic receptor subtypes in a single IC cell, we measured co-expression of α , α , and β receptor-encoding mRNA. We found greater proportions of cells in the IC that expressed no adrenergic receptor-encoding mRNA, α1 and α2A adrenergic receptor-encoding mRNA, and α1, α2A, and β2 receptor-encoding mRNA than would be predicted by independent expression of each receptor subtype. These data suggest a coordinated pattern of adrenergic receptor expression in the IC and provide the first evidence for adrenergic receptor expression and co-expression in the subregions of the mouse auditory midbrain.
Topics: Animals; Female; Inferior Colliculi; Male; Mice; RNA, Messenger; Receptors, Adrenergic
PubMed: 33067825
DOI: 10.1002/cne.25053 -
Journal of Chemical Neuroanatomy Dec 2022Neurons in the inferior colliculus (IC), the midbrain hub of the central auditory pathway, send ascending and descending projections to other auditory brain regions, as...
Neurons in the inferior colliculus (IC), the midbrain hub of the central auditory pathway, send ascending and descending projections to other auditory brain regions, as well as projections to other sensory and non-sensory brain regions. However, the axonal projection patterns of individual classes of IC neurons remain largely unknown. Vasoactive intestinal polypeptide (VIP) is a neuropeptide expressed by subsets of neurons in many brain regions. We recently identified a class of IC stellate neurons that we called VIP neurons because they are labeled by tdTomato (tdT) expression in VIP-IRES-Cre x Ai14 mice. Here, using fluorescence in situ hybridization, we found that tdT+ neurons in VIP-IRES-Cre x Ai14 mice express Vglut2, a marker of glutamatergic neurons, and VIP, suggesting that VIP neurons use both glutamatergic and VIPergic signaling to influence their postsynaptic targets. Next, using viral transfections with a Cre-dependent eGFP construct, we labeled the axonal projections of VIP neurons. As a group, VIP neurons project intrinsically, within the ipsilateral and contralateral IC, and extrinsically to all the major targets of the IC. Within the auditory system, VIP neurons sent axons and formed axonal boutons in higher centers, including the medial geniculate nucleus and the nucleus of the brachium of the IC. Less dense projections terminated in lower centers, including the nuclei of the lateral lemniscus, superior olivary complex, and dorsal cochlear nucleus. VIP neurons also project to several non-auditory brain regions, including the superior colliculus, periaqueductal gray, and cuneiform nucleus. The diversity of VIP projections compared to the homogeneity of VIP neuron intrinsic properties suggests that VIP neurons play a conserved role at the microcircuit level, likely involving neuromodulation through glutamatergic and VIPergic signaling, but support diverse functions at the systems level through their participation in different projection pathways.
Topics: Mice; Animals; Inferior Colliculi; Vasoactive Intestinal Peptide; In Situ Hybridization, Fluorescence; Auditory Pathways; Neurons; Axons; Neurotransmitter Agents; Phenotype
PubMed: 36375740
DOI: 10.1016/j.jchemneu.2022.102189 -
The Journal of Physiological Sciences :... Nov 2015The inferior colliculus (IC) is a critical nexus between the auditory brainstem and the forebrain. Parallel auditory pathways that emerge from the brainstem are... (Review)
Review
The inferior colliculus (IC) is a critical nexus between the auditory brainstem and the forebrain. Parallel auditory pathways that emerge from the brainstem are integrated in the IC. In this integration, de-novo auditory information processed as local and ascending inputs converge via the complex neural circuit of the IC. However, it is still unclear how information is processed within the neural circuit. The purpose of this review is to give an anatomical and physiological overview of the IC neural circuit. We address the functional organization of the IC where the excitatory and inhibitory synaptic inputs interact to shape the responses of IC neurons to sound.
Topics: Animals; Inferior Colliculi; Mammals; Neurons
PubMed: 26362672
DOI: 10.1007/s12576-015-0394-3 -
Journal of Comparative Physiology. A,... Jan 2023The mammalian inferior colliculus (IC) is massively innervated by multiple descending projection systems. In addition to a large projection from the auditory cortex (AC)... (Review)
Review
The mammalian inferior colliculus (IC) is massively innervated by multiple descending projection systems. In addition to a large projection from the auditory cortex (AC) primarily targeting the non-lemniscal portions of the IC, there are less well-characterized projections from non-auditory regions of the cortex, amygdala, posterior thalamus and the brachium of the IC. By comparison, the frog auditory midbrain, known as the torus semicircularis, is a large auditory integration center that also receives descending input, but primarily from the posterior thalamus and without a projection from a putative cortical homolog: the dorsal pallium. Although descending projections have been implicated in many types of behaviors, a unified understanding of their function has not yet emerged. Here, we take a comparative approach to understanding the various top-down modulators of the IC to gain insights into their functions. One key question that we identify is whether thalamotectal projections in mammals and amphibians are homologous and whether they interact with evolutionarily more newly derived projections from the cerebral cortex. We also consider the behavioral significance of these descending pathways, given anurans' ability to navigate complex acoustic landscapes without the benefit of a corticocollicular projection. Finally, we suggest experimental approaches to answer these questions.
Topics: Animals; Auditory Pathways; Inferior Colliculi; Auditory Cortex; Mesencephalon; Amygdala; Mammals
PubMed: 36323876
DOI: 10.1007/s00359-022-01588-5 -
The Journal of Neuroscience : the... Apr 2022The dorsal cochlear nucleus (DCN) integrates auditory nerve input with nonauditory sensory signals and is proposed to function in sound source localization and...
The dorsal cochlear nucleus (DCN) integrates auditory nerve input with nonauditory sensory signals and is proposed to function in sound source localization and suppression of self-generated sounds. The DCN also integrates activity from descending auditory pathways, including a particularly large feedback projection from the inferior colliculus (IC), the main ascending target of the DCN. Understanding how these descending feedback signals are integrated into the DCN circuit and what role they play in hearing requires knowing the targeted DCN cell types and their postsynaptic responses. In order to explore these questions, neurons in the DCN that received descending synaptic input from the IC were labeled with a trans-synaptic viral approach in male and female mice, which allowed them to be targeted for whole-cell recording in acute brain slices. We tested their synaptic responses to optogenetic activation of the descending IC projection. Every cell type in the granule cell domain received monosynaptic, glutamatergic input from the IC, indicating that this region, considered an integrator of nonauditory sensory inputs, processes auditory input as well and may have complex and underappreciated roles in hearing. Additionally, we found that DCN cell types outside the granule cell regions also receive descending IC signals, including the principal projection neurons, as well as the neurons that inhibit them, leading to a circuit that may sharpen tuning through feedback excitation and lateral inhibition. Auditory processing starts in the cochlea and ascends through the dorsal cochlear nucleus (DCN) to the inferior colliculus (IC) and beyond. Here, we investigated the feedback projection from IC to DCN, whose synaptic targets and roles in auditory processing are unclear. We found that all cell types in the granule cell regions, which process multisensory feedback, also process this descending auditory feedback. Surprisingly, all except one cell type in the entire DCN receive IC input. The IC-DCN projection may therefore modulate the multisensory pathway as well as sharpen tuning and gate auditory signals that are sent to downstream areas. This excitatory feedback loop from DCN to IC and back to DCN could underlie hyperexcitability in DCN, widely considered an etiology of tinnitus.
Topics: Animals; Auditory Pathways; Axons; Cochlear Nucleus; Female; Inferior Colliculi; Male; Mice; Neurons
PubMed: 35273085
DOI: 10.1523/JNEUROSCI.1190-21.2022