Laminar distribution of cortical projection neurons to the pulvinar: A comparative study in cats and mice
The cortical processing of visual information is thought to follow a hierarchical framework. This framework of connections between visual areas is based on the laminar patterns of direct feedforward and feedback cortico‐cortical projections. However, this view ignores the cortico‐thalamo‐cortical pr...
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| Published in: | Journal of comparative neurology (1911) Vol. 529; no. 8; pp. 2055 - 2069 |
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| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Hoboken, USA
John Wiley & Sons, Inc
01-06-2021
Wiley Subscription Services, Inc |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | The cortical processing of visual information is thought to follow a hierarchical framework. This framework of connections between visual areas is based on the laminar patterns of direct feedforward and feedback cortico‐cortical projections. However, this view ignores the cortico‐thalamo‐cortical projections to the pulvinar nucleus in the thalamus, which provides an alternative transthalamic information transfer between cortical areas. It was proposed that corticothalamic (CT) pathways follow a similar hierarchical pattern as cortico‐cortical connections. Two main types of CT projections have been recognized: drivers and modulators. Drivers originate mainly in Layer 5 whereas modulators are from Layer 6. Little is known about the laminar distribution of these projections to the pulvinar across visual cortical areas. Here, we analyzed the distribution of CT neurons projecting to the lateral posterior (LP) thalamus in two species: cats and mice. Injections of the retrograde tracer fragment B of cholera toxin (CTb) were performed in the LP. The morphology and cortical laminar distribution of CTb‐labeled neurons was assessed. In cats, neurons were mostly found in Layer 6 except in Area 17, where they were mostly in Layer 5. In contrast, CT neurons in mice were mostly located in Layer 6 across all areas. Thus, our results demonstrate that CT projections in mice do not follow the same organization as cats suggesting that the transthalamic pathways play distinct roles in these species.
The laminar distribution of corticothalamic (CT) neurons projecting to the pulvinar thalamic nucleus was assessed in two species: cats and mice. Following injections of the retrograde tracer fragment B of cholera toxin (CTb) in the pulvinar, the morphology, and distribution of labeled neurons in the infragranular layers of the visual cortex was compared between the two species. In cats, CT neurons were mostly distributed in Layer 6 in all extrastriate areas. The exception was Area 17 that labeled neurons where almost exclusively located in Layer 5. In mice, CT neurons were mostly located in Layer 6 across all areas, including V1. Our findings show a distinct pattern of CT projections in mice in comparison to the one in cats suggesting that the pulvinar nucleus plays distinct roles in the transthalamic transmission of visual information in these species. |
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| Bibliography: | Funding information Institute of Neurosciences, Mental Health and Addiction, Grant/Award Number: PJT‐148959; Natural Sciences and Engineering Research Council of Canada, Grant/Award Number: RGPIN‐203702; Réseau de la Recherche en Santé de la Vision ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0021-9967 1096-9861 |
| DOI: | 10.1002/cne.25072 |