1 40 2 Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. URL Address <a href="http://doi.org/10.3389/fnana.2014.00124" target="_blank" rel="noreferrer noopener">http://doi.org/10.3389/fnana.2014.00124</a> Pages 124–124 Volume 8 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Excitatory and inhibitory projections in parallel pathways from the inferior colliculus to the auditory thalamus. Publisher An entity responsible for making the resource available Frontiers in neuroanatomy Date A point or period of time associated with an event in the lifecycle of the resource 2014 1905-07 Subject The topic of the resource GABA; auditory system; GAD; lemniscal; medial geniculate; non-lemniscal; tectothalamic Creator An entity primarily responsible for making the resource Mellott Jeffrey G; Foster Nichole L; Ohl Andrew P; Schofield Brett R Description An account of the resource Individual subdivisions of the medial geniculate body (MG) receive a majority of their ascending inputs from 1 or 2 subdivisions of the inferior colliculus (IC). This establishes parallel pathways that provide a model for understanding auditory projections from the IC through the MG and on to auditory cortex. A striking discovery about the tectothalamic circuit was identification of a substantial GABAergic component. Whether GABAergic projections match the parallel pathway organization has not been examined. We asked whether the parallel pathway concept is reflected in guinea pig tectothalamic pathways and to what degree GABAergic cells contribute to each pathway. We deposited retrograde tracers into individual MG subdivisions (ventral, MGv; medial, MGm; dorsal, MGd; suprageniculate, MGsg) to label tectothalamic cells and used immunochemistry to identify GABAergic cells. The MGv receives most of its IC input (\textasciitilde75%) from the IC central nucleus (ICc); MGd and MGsg receive most of their input (\textasciitilde70%) from IC dorsal cortex (ICd); and MGm receives substantial input from both ICc (\textasciitilde40%) and IC lateral cortex (\textasciitilde40%). Each MG subdivision receives additional input (up to 32%) from non-dominant IC subdivisions, suggesting cross-talk between the pathways. The proportion of GABAergic cells in each pathway depended on the MG subdivision. GABAergic cells formed \textasciitilde20% of IC inputs to MGv or MGm, \textasciitilde11% of inputs to MGd, and 4% of inputs to MGsg. Thus, non-GABAergic (i.e., glutamatergic) cells are most numerous in each pathway with GABAergic cells contributing to different extents. Despite smaller numbers of GABAergic cells, their distributions across IC subdivisions mimicked the parallel pathways. Projections outside the dominant pathways suggest opportunities for excitatory and inhibitory crosstalk. The results demonstrate parallel tectothalamic pathways in guinea pigs and suggest numerous opportunities for excitatory and inhibitory interactions within and between pathways. Identifier An unambiguous reference to the resource within a given context <a href="http://doi.org/10.3389/fnana.2014.00124" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00124</a> Rights Information about rights held in and over the resource Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s). 2014 Auditory system Department of Anatomy & Neurobiology Foster Nichole L Frontiers in neuroanatomy GABA GAD lemniscal medial geniculate Mellott Jeffrey G NEOMED College of Medicine non-lemniscal Ohl Andrew P Schofield Brett R tectothalamic Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. URL Address <a href="http://doi.org/10.3389/fnana.2014.00017" target="_blank" rel="noreferrer noopener">http://doi.org/10.3389/fnana.2014.00017</a> Pages 17–17 Volume 8 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Distribution of GABAergic cells in the inferior colliculus that project to the thalamus. Publisher An entity responsible for making the resource available Frontiers in neuroanatomy Date A point or period of time associated with an event in the lifecycle of the resource 2014 1905-07 Subject The topic of the resource inhibition; auditory system; GAD; medial geniculate; tectothalamic Creator An entity primarily responsible for making the resource Mellott Jeffrey G; Foster Nichole L; Nakamoto Kyle T; Motts Susan D; Schofield Brett R Description An account of the resource A GABAergic component has been identified in the projection from the inferior colliculus (IC) to the medial geniculate body (MG) in cats and rats. We sought to determine if this GABAergic pathway exists in guinea pig, a species widely used in auditory research. The guinea pig IC contains GABAergic cells, but their relative abundance in the IC and their relative contributions to tectothalamic projections are unknown. We identified GABAergic cells with immunochemistry for glutamic acid decarboxylase (GAD) and determined that \textasciitilde21% of IC neurons are GABAergic. We then combined retrograde tracing with GAD immunohistochemistry to identify the GABAergic tectothalamic projection. Large injections of Fast Blue, red fluorescent beads or FluoroGold were deposited to include all subdivisions of the MG. The results demonstrate a GABAergic pathway from each IC subdivision to the ipsilateral MG. GABAergic cells constitute \textasciitilde22% of this ipsilateral pathway. In addition, each subdivision of the IC had a GABAergic projection to the contralateral MG. Measured by number of tectothalamic cells, the contralateral projection is about 10% of the size of the ipsilateral projection. GABAergic cells constitute about 20% of the contralateral projection. In summary, the results demonstrate a tectothalamic projection in guinea pigs that originates in part from GABAergic cells that project ipsilaterally or contralaterally to the MG. The results show similarities to both rats and cats, and carry implications for the role of GABAergic tectothalamic projections vis-a-vis the presence (in cats) or near absence (in rats and guinea pigs) of GABAergic interneurons in the MG. Identifier An unambiguous reference to the resource within a given context <a href="http://doi.org/10.3389/fnana.2014.00017" target="_blank" rel="noreferrer noopener">10.3389/fnana.2014.00017</a> Rights Information about rights held in and over the resource Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s). 2014 Auditory system Department of Anatomy & Neurobiology Foster Nichole L Frontiers in neuroanatomy GAD inhibition medial geniculate Mellott Jeffrey G Motts Susan D Nakamoto Kyle T NEOMED College of Medicine Schofield Brett R tectothalamic