• Open Access

Divergent and point-to-point connections in the commissural pathway between the inferior colliculi

Authors

  • Manuel S. Malmierca,

    Corresponding author
    1. Auditory Neurophysiology Unit, Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
    2. Department Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, and Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
    • Auditory Neurophysiology Unit (Lab No. 1), Institute of Neuroscience of Castilla y León, University of Salamanca, C/ Pintor Fernando Gallego 1, 37007 Salamanca, Spain
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  • Olga Hernández,

    1. Auditory Neurophysiology Unit, Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
    2. Department Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, and Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
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  • Flora M. Antunes,

    1. Auditory Neurophysiology Unit, Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
    2. Department Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, and Institute for Neuroscience of Castilla y León, 37007 Salamanca, Spain
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  • Adrian Rees

    1. Auditory Group, Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH United Kingdom
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Abstract

The commissure of the inferior colliculus interconnects the left and right sides of the auditory midbrain and provides the final opportunity for interaction between the two sides of the auditory pathway at the subcortical level. Although the functional properties of the commissure are beginning to be revealed, the topographical organization of its connections is unknown. A combination of neuroanatomical tracing studies, 3D reconstruction, and neuronal density maps was used to study the commissural connections in rat. The results demonstrate that commissural neurons in the central nucleus of the inferior colliculus send a divergent projection to the equivalent frequency-band laminae in the central nucleus and dorsal and lateral cortices on the opposite side. The density of this projection, however, is weighted toward a point that matches the position of the tracer injection; consistent with a point-to-point emphasis in the wiring pattern. In the dorsal cortex of the inferior colliculus there may be two populations of neurons that project across the commissure, one projecting exclusively to the frequency-band laminae in the central nucleus and the other projecting diffusely to the dorsal cortex. Neurons in the lateral cortex of the inferior colliculus make only a very weak contribution to the commissural pathway. The point-to-point pattern of connections permits interactions between specific regions of corresponding frequency-band laminae, whereas the divergent projection pattern could subserve integration across the lamina. J. Comp. Neurol. 514:226–239, 2009. © 2009 Wiley-Liss, Inc.

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