Abstract
The motor cortex orchestrates simple to complex motor behaviors through its output projections to target areas. The primary (MOp) and secondary (MOs) motor cortices are known to produce specific output projections that are targeted to both similar and different target areas. These projections are further divided into layer 5 and 6 neuronal outputs, thereby producing four cortical outputs that may target other areas in a combinatorial manner. However, the precise network structure that integrates these four projections remains poorly understood. Here, we constructed a whole-brain, three-dimensional (3D) map showing the tract pathways and targeting locations of these four motor cortical outputs in mice. Remarkably, these motor cortical projections showed unique and separate tract pathways despite targeting similar areas. Within target areas, various combinations of these four projections were defined based on specific 3D spatial patterns, reflecting anterior-posterior, dorsal-ventral, and core-capsular relationships. This 3D topographic map ultimately provides evidence for the relevance of comparative connectomics: motor cortical projections known to be convergent are actually segregated in many target areas with unique targeting patterns, a finding that has anatomical value for revealing functional subdomains that have not been classified by conventional methods.
Highlights
MethodsAll injections were performed with a 10-μ l syringe (Hamilton Company), guide cannulas (33-gauge NanoFil Needle Assortment, blunt; World Precision Instruments), and a syringe pump (KD Scientific)
Two-photon (STP) tomography[43] and cortical layer-specific Cre-transgenic mice[32]
Mapping of layer-specific cortical projections derived from MOp and MOs motor cortical subdomains
Summary
All injections were performed with a 10-μ l syringe (Hamilton Company), guide cannulas (33-gauge NanoFil Needle Assortment, blunt; World Precision Instruments), and a syringe pump (KD Scientific). The MOp injection coordinate was 1.55 mm anterior, − 1.95 mm lateral, 0.8 mm (L5) or 0.9 mm (L6) ventral to bregma. The MOs injection coordinate was 1.55 mm anterior, − 1.0 mm lateral, 0.8 mm (L5) or 0.9 mm (L6) ventral to bregma. 0.6 μ l of recombinant AAV2/1.CAGGS.FLEX.ChR2.tdTomato.SV40 (5.0 × 1012 particles/ml; University of Pennsylvania) or AAV2/2.CAGGS.Flex.Arch.GFP (5.0 × 1012 particles/ml; University of North Carolina Vector Core) were injected into the MOp and MOs, respectively, at a rate of 0.065 μ l/min. For sagittal view images (Figs 4B and 5B), 0.6 μ l of recombinant AAV2/9.EF1α .dflox.hChR2(H134R).mCherry.WPRE.hGH (2.0 × 1012 particles/ ml; University of Pennsylvania) and AAV2/2.EF1α .DIO.eArch3.0.eYFP (2.0 × 1012 particles/ml; University of Pennsylvania) were injected into the MOp and MOs, respectively. The guide cannula was removed 5 minutes after completion of the injection
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
