The auditory system consists of ascending pathways that transmit information from the ear to the cortex, where sound is perceived, and descending pathways from the cortex that modulate the processing and flow of ascending information. The descending pathways play a role in a wide variety of functions, including selective attention, learning, frequency selectivity, sound localization, and discrimination of speech sounds. Recent work has shown close ties between the descending pathways and the brainstem cholinergic system. Acetylcholine has been implicated in many of the same auditory functions just listed as well as arousal and detection of novel stimuli. Understanding the various functions of the descending and cholinergic systems has been impeded by lack of information on the underlying neuronal circuitry. The present proposal will combine multi-labeling anatomical tracing techniques with multi-labeling immunohistochemistry to identify the components and synaptic organization of these circuits. The experiments will focus on the inferior colliculus, a part of the midbrain that is involved in pathways for auditory perception as well as numerous aspects of auditory-driven behavior. The results will provide a framework for interpreting physiological and behavioral experiments, and will provide essential data for designing more advanced experiments to examine both the functions of these pathways and to determine the underlying cellular mechanisms.

Public Health Relevance

Descending auditory pathways and the pathways that use acetylcholine as a neurotransmitter play critical roles in functions such as selective attention and discrimination of sounds in a noisy environment. Understanding and improving these functions is an important goal in persons with hearing loss, cochlear implants or various disorders such as autism or schizophrenia. The present proposal will answer important questions about the circuitry that underlies these functions.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Study Section
Auditory System Study Section (AUD)
Program Officer
Platt, Christopher
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Northeast Ohio Medical University
Anatomy/Cell Biology
Schools of Medicine
United States
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Schofield, Brett R; Beebe, Nichole L (2018) Subtypes of GABAergic cells in the inferior colliculus. Hear Res :
Mellott, Jeffrey G; Beebe, Nichole L; Schofield, Brett R (2018) Bilateral projections to the thalamus from individual neurons in the inferior colliculus. J Comp Neurol :
Beebe, Nichole L; Schofield, Brett R (2018) Perineuronal nets in subcortical auditory nuclei of four rodent species with differing hearing ranges. J Comp Neurol 526:972-989
Mellott, Jeffrey G; Beebe, Nichole L; Schofield, Brett R (2018) GABAergic and non-GABAergic projections to the superior colliculus from the auditory brainstem. Brain Struct Funct 223:1923-1936
Crish, Samuel D; Schofield, Brett R (2018) Anterograde Tract Tracing for Assaying Axonopathy and Transport Deficits in Glaucoma. Methods Mol Biol 1695:171-185
Beebe, Nichole L; Young, Jesse W; Mellott, Jeffrey G et al. (2016) Extracellular Molecular Markers and Soma Size of Inhibitory Neurons: Evidence for Four Subtypes of GABAergic Cells in the Inferior Colliculus. J Neurosci 36:3988-99
Smith, Matthew A; Xia, Christina Z; Dengler-Crish, Christine M et al. (2016) Persistence of intact retinal ganglion cell terminals after axonal transport loss in the DBA/2J mouse model of glaucoma. J Comp Neurol 524:3503-3517
Foster, Nichole L; Mellott, Jeffrey G; Schofield, Brett R (2014) Perineuronal nets and GABAergic cells in the inferior colliculus of guinea pigs. Front Neuroanat 7:53
Mellott, Jeffrey G; Foster, Nichole L; Ohl, Andrew P et al. (2014) Excitatory and inhibitory projections in parallel pathways from the inferior colliculus to the auditory thalamus. Front Neuroanat 8:124
Mellott, Jeffrey G; Bickford, Martha E; Schofield, Brett R (2014) Descending projections from auditory cortex to excitatory and inhibitory cells in the nucleus of the brachium of the inferior colliculus. Front Syst Neurosci 8:188

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