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Updated: Aug 18, 2026

Long-range Channelrhodopsin-assisted Circuit Mapping of Inferior Colliculus Neurons with Blue and Red-shifted Channelrhodopsins
Published on: February 7, 2020
Unilateral and bilateral projections from cortical cells to the inferior colliculus in guinea pigs
Diana L Coomes1, Ryan M Schofield, Brett R Schofield
1Department of Anatomical Sciences and Neurobiology, University of Louisville, 500 S. Preston Street, Louisville, KY 40202, USA.
Auditory cortex projects directly and bilaterally to the inferior colliculus (IC). We used multiple fluorescent retrograde tracers to determine whether individual cortical cells project to both the left and right IC. Injection of different tracers into each IC labeled many cells in a sheet that extended throughout much of temporal cortex in both hemispheres. Most cells contained a single tracer, with the majority of these labeled from the ipsilateral IC. Numerous double-labeled cells were observed throughout the same areas of temporal cortex. The double-labeled cells form a small percentage of the cortical cells that project to the ipsilateral IC (6.1% on average) and a much larger percentage of the cells that project to the contralateral IC (46.4% on average). Unilaterally projecting cells are well positioned to have effects limited to one IC, whereas bilaterally projecting cells are likely to have a broader influence and may coordinate activity on the two sides of the midbrain.
Auditory cortex projects directly and bilaterally to the inferior colliculus (IC). We used multiple fluorescent retrograde tracers to determine whether individual cortical cells project to both the left and right IC. Injection of different tracers into each IC labeled many cells in a sheet that extended throughout much of temporal cortex in both hemispheres. Most cells contained a single tracer, with the majority of these labeled from the ipsilateral IC. Numerous double-labeled cells were observed throughout the same areas of temporal cortex. The double-labeled cells form a small percentage of the cortical cells that project to the ipsilateral IC (6.1% on average) and a much larger percentage of the cells that project to the contralateral IC (46.4% on average). Unilaterally projecting cells are well positioned to have effects limited to one IC, whereas bilaterally projecting cells are likely to have a broader influence and may coordinate activity on the two sides of the midbrain.
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