Shuichi Hayashi    Department   Kawasaki Medical School  Kawasaki Medical School, Department of Anatomy,    Position   Associate Professor
Article types	原著
Language	English
Peer review	Peer reviewed
Title	Subset of cortical layer 6b neurons selectively innervates higher order nuclei in the thalamus in mouse.
Journal	Formal name：Cerebral Cortex
Domestic / Foregin	Foregin
Volume, Issue, Page	28(5),pp.1882-1897
Author and coauthor	Hoerder-Suabedissen, A., Hayashi, S., Upton, L., Nolan, Z., Casas-Torremocha, D., Grant., E., Kanold, P., Clasca, F., Kim, Y., Molnar, Z.
Authorship	2nd author
Publication date	2018
Summary	The thalamus receives input from 3 distinct cortical layers, but input from only 2 of these has been well characterized. We therefore investigated whether the third input, derived from layer 6b, is more similar to the projections from layer 6a or layer 5. We studied the projections of a restricted population of deep layer 6 cells ("layer 6b cells") taking advantage of the transgenic mouse Tg(Drd1a-cre)FK164Gsat/Mmucd (Drd1a-Cre), that selectively expresses Cre-recombinase in a subpopulation of layer 6b neurons across the entire cortical mantle. At P8, 18% of layer 6b neurons are labeled with Drd1a-Cre::tdTomato in somatosensory cortex (SS), and some co-express known layer 6b markers. Using Cre-dependent viral tracing, we identified topographical projections to higher order thalamic nuclei. VGluT1+ synapses formed by labeled layer 6b projections were found in posterior thalamic nucleus (Po) but not in the (pre)thalamic reticular nucleus (TRN). The lack of TRN collaterals was confirmed with single-cell tracing from SS. Transmission electron microscopy comparison of terminal varicosities from layer 5 and layer 6b axons in Po showed that L6b varicosities are markedly smaller and simpler than the majority from L5. Our results suggest that L6b projections to the thalamus are distinct from both L5 and L6a projections.