title: Multiple layer 5 pyramidal cell subtypes relay cortical feedback from secondary to primary motor areas in rats.
abstract: Higher-order motor cortices, such as the secondary motor area (M2) in rodents, select future action patterns and transmit them to the primary motor cortex (M1). To better understand motor processing, we characterized "top-down" and "bottom-up" connectivities between M1 and M2 in the rat cortex. Somata of pyramidal cells (PCs) in M2 projecting to M1 were distributed in lower layer 2/3 (L2/3) and upper layer 5 (L5), whereas PCs projecting from M1 to M2 had somata distributed throughout L2/3 and L5. M2 afferents terminated preferentially in upper layer 1 of M1, which also receives indirect basal ganglia output through afferents from the ventral anterior and ventromedial thalamic nuclei. On the other hand, M1 afferents terminated preferentially in L2/3 of M2, a zone receiving indirect cerebellar output through thalamic afferents from the ventrolateral nucleus. While L5 corticopontine (CPn) cells with collaterals to the spinal cord did not participate in corticocortical projections, CPn cells with collaterals to the thalamus contributed preferentially to connections from M2 to M1. L5 callosal projection (commissural) cells participated in connectivity between M1 and M2 bidirectionally. We conclude that the connectivity between M1 and M2 is directionally specialized, involving specific PC subtypes that selectively target lamina receiving distinct thalamocortical inputs.
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan, Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan and.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Ueta
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan, Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan and Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8787, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Otsuka
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan, Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan and Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8787, Japan.
authors.forename: Mieko
authors.initials: M
authors.lastname: Morishima
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan, Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan and.
authors.forename: Mika
authors.initials: M
authors.lastname: Ushimaru
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan, Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan and Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8787, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawaguchi
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D025461:Feedback, Physiological / Q000502:physiology*; D007150:Immunohistochemistry; D008839:Microelectrodes; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology; D056347:Neuroanatomical Tract-Tracing Techniques; D017966:Pyramidal Cells / Q000033:anatomy & histology / Q000502:physiology*; D017208:Rats, Wistar; D013787:Thalamic Nuclei / Q000033:anatomy & histology / Q000502:physiology
keywords: Ctip2; corticocortical; corticopontine; corticospinal; corticothalamic