title: Modality-based organization of ascending somatosensory axons in the direct dorsal column pathway.
abstract: The long-standing doctrine regarding the functional organization of the direct dorsal column (DDC) pathway is the "somatotopic map" model, which suggests that somatosensory afferents are primarily organized by receptive field instead of modality. Using modality-specific genetic tracing, here we show that ascending mechanosensory and proprioceptive axons, two main types of the DDC afferents, are largely segregated into a medial-lateral pattern in the mouse dorsal column and medulla. In addition, we found that this modality-based organization is likely to be conserved in other mammalian species, including human. Furthermore, we identified key morphological differences between these two types of afferents, which explains how modality segregation is formed and why a rough "somatotopic map" was previously detected. Collectively, our results establish a new functional organization model for the mammalian direct dorsal column pathway and provide insight into how somatotopic and modality-based organization coexist in the central somatosensory pathway.
authors.affiliation: Department of Neuroscience and Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, Shriners Hospital Pediatric Research Center and Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, Department of Neurology, the First People's Hospital of Chenzhou, Chenzhou, Hunan, China, Retinal Circuit Development & Genetics Unit, National Eye Institute, Bethesda, Maryland 20892, and Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Niu
authors.forename: Long
authors.initials: L
authors.lastname: Ding
authors.forename: Jian J
authors.initials: JJ
authors.lastname: Li
authors.forename: Hyukmin
authors.initials: H
authors.lastname: Kim
authors.forename: Jiakun
authors.initials: J
authors.lastname: Liu
authors.forename: Haipeng
authors.initials: H
authors.lastname: Li
authors.forename: Andrew
authors.initials: A
authors.lastname: Moberly
authors.forename: Tudor C
authors.initials: TC
authors.lastname: Badea
authors.forename: Ian D
authors.initials: ID
authors.lastname: Duncan
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Son
authors.forename: Steven S
authors.initials: SS
authors.lastname: Scherer
authors.forename: Wenqin
authors.initials: W
authors.lastname: Luo
mesh_terms: D000344:Afferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology*; D002415:Cats; D004285:Dogs; D006801:Humans; D008253:Macaca mulatta; D008465:Mechanoreceptors / Q000502:physiology; D051379:Mice; D011434:Proprioception / Q000502:physiology; D051381:Rats; D011984:Sensory Receptor Cells / Q000502:physiology*; D013116:Spinal Cord / Q000033:anatomy & histology* / Q000502:physiology; D014110:Touch / Q000502:physiology