Mouse corticospinal system comprises different functional neuronal ensembles depending on their hodology

• Published in: BMC neuroscience Vol. 20; no. 1; p. 50
• Main Authors: Olivares-Moreno, Rafael, López-Hidalgo, Mónica, Altamirano-Espinoza, Alain, González-Gallardo, Adriana, Antaramian, Anaid, Lopez-Virgen, Verónica, Rojas-Piloni, Gerardo
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 23.09.2019; BioMed Central; BMC
• Subjects: Animals; Brain; Brain slice preparation; Calcium - metabolism; Calcium imaging; Connectome; Dorsal horn; Fluorescent Antibody Technique - methods; Functional morphology; GCaMP; Gene expression; Genetic engineering; Laboratory rats; Lasers; Layer 5; Mice; Mice, Transgenic; Motor Cortex - metabolism; Motor Cortex - physiology; Nervous system; Neural circuitry; Neural circuits; Neural Pathways - metabolism; Neural Pathways - physiology; Neuroanatomical Tract-Tracing Techniques - methods; Neuroimaging; Neurons; Neurons - physiology; Physiological aspects; Pyramidal cells; Pyramidal tract neurons; Pyramidal tracts; Pyramidal Tracts - metabolism; Pyramidal Tracts - physiology; Sensorimotor cortex; Somatosensory cortex; Spinal cord; Spinal Cord - metabolism; Spinal Cord - physiology; Tracers; Transgenic mice; GCaMP; Calcium imaging; Sensorimotor cortex; Pyramidal tract neurons; Neural circuits; Layer 5
• ISSN: 1471-2202; 1471-2202
• DOI: 10.1186/s12868-019-0533-5

Movement performance depends on the synaptic interactions generated by coherent parallel sensorimotor cortical outputs to different downstream targets. The major outputs of the neocortex to subcortical structures are driven by pyramidal tract neurons (PTNs) located in layer 5B. One of the main targets of PTNs is the spinal cord through the corticospinal (CS) system, which is formed by a complex collection of distinct CS circuits. However, little is known about intracortical synaptic interactions that originate CS commands and how different populations of CS neurons are functionally organized. To further understand the functional organization of the CS system, we analyzed the activity of unambiguously identified CS neurons projecting to different zones of the same spinal cord segment using two-photon calcium imaging and retrograde neuronal tracers. Sensorimotor cortex slices obtained from transgenic mice expressing GCaMP6 funder the Thy1 promoter were used to analyze the spontaneous calcium transients in layer 5 pyramidal neurons. Distinct subgroups of CS neurons projecting to dorsal horn and ventral areas of the same segment show more synchronous activity between them than with other subgroups. The results indicate that CS neurons projecting to different spinal cord zones segregated into functional ensembles depending on their hodology, suggesting that a modular organization of CS outputs controls sensorimotor behaviors in a coordinated manner.