Thalamic Connections of Auditory Cortex in Marmoset Monkeys: Lateral Belt and Parabelt Regions

Authors

  • Lisa A. de la Mothe,

    Corresponding author
    1. Department of Psychology, Tennessee State University, Nashville, Tennessee
    2. Department of Hearing and Speech Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
    • Tennessee State University, 305 Clay Hall, 3500 John A. Merritt Boulevard, Nashville, TN 37209
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    • Fax: (615)-963-5140

  • Suzanne Blumell,

    1. Department of Hearing and Speech Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
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  • Yoshinao Kajikawa,

    1. Nathan Kline Institute, Orangeburg, New York
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  • Troy A. Hackett

    1. Department of Hearing and Speech Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
    2. Department of Psychology, Vanderbilt University, Nashville, Tennessee
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  • Abbreviations used: A1 = auditory area 1 (core); AChE = acetylcholinesterase; AD = medial geniculate complex, anterodorsal division; AL = anterolateral area (belt); BIC = brachium of the inferior colliculus; BrSC = brachium of the superior colliculus; CG = central grey; CIC = commissure of the inferior colliculus; CL = caudolateral area (belt); CM = caudomedial area (belt); CO = cytochrome oxidase; CPB = caudal parabelt area (parabelt); CTB = cholera toxin, subunit B (tracer); FR = fluororuby (tracer); Hb = habenular nucleus; Ins = insula; LGN = lateral geniculate nucleus; Lim = limitans nucleus; LS = lateral sulcus; M = medial geniculate complex, magnocellular division; MD = medial dorsal nucleus; MGad = medial geniculate complex, anterodorsal division; MGC = medial geniculate complex; MGd = medial geniculate complex, dorsal division; MGm = medial geniculate complex, magnocellular division; MGpd = medial geniculate complex, posterodorsal division; MGv = medial geniculate complex, ventral division; ML = middle lateral area (belt); MM = middle medial area (belt); PA = anterior (oral) pulvinar; PD = medial geniculate complex, posterodorsal division; PI = inferior pulvinar; Pic = inferior pulvinar, central division; Pim = inferior pulvinar, medial division; Pip = inferior pulvinar, posterior division; PL = lateral pulvinar; PM = medial pulvinar; Po = posterior nucleus; PPN = peripeduncular nucleus; PV = parietoventral area; R = rostral area (core); Ri = retroinsular area; RM = rostromedial area (belt); RPB = rostral parabelt area (parabelt); RT = rostrotemporal area (core); RTL = rostrotemporal lateral area (belt); RTM = rostrotemporal medial area (belt); S2 = somatosensory area 2; SC = superior colliculus; Sg = suprageniculate nucleus; SN = substantia nigra; STG = superior temporal gyrus; STS = superior temporal sulcus

Abstract

The primate auditory cortex is comprised of a core region of three primary areas, surrounded by a belt region of secondary areas and a parabelt region lateral to the belt. The main sources of thalamocortical inputs to the auditory cortex are the medial geniculate complex (MGC), medial pulvinar (PM), and several adjoining nuclei in the posterior thalamus. The distribution of inputs varies topographically by cortical area and thalamic nucleus, but in a manner that has not been fully characterized in primates. In this study, the thalamocortical connections of the lateral belt and parabelt were determined by placing retrograde tracer injections into various areas of these regions in the marmoset monkey. Both regions received projections from the medial (MGm) and posterodorsal (MGpd) divisions of the medial geniculate complex (MGC); however, labeled cells in the anterodorsal (MGad) division were present only from injections into the caudal belt. Thalamic inputs to the lateral belt appeared to come mainly from the MGC, whereas the parabelt also received a strong projection from the PM, consistent with its position as a later stage of auditory cortical processing. The results of this study also indicate that the organization of the marmoset auditory cortex is similar to other primates. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.

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