Intracortical mechanisms for the recruitment of motor cortex neurons. 1993

P Zarzecki, and P Kirchberger, and P Istvan
Department of Physiology, Queen's University, Kingston, Ontario, Canada.

Neurons project out of motor cortex to the spinal cord and to other targets. Not all projection neurons recruit in the same way during behavior, but instead recruitment patterns depend on the projection target of the neurons. The problem is to understand how neurons projecting to different targets are recruited selectively. We have investigated possible mechanisms for the recruitment of motor cortex neurons with electrophysiological approaches in anesthetized cats. To determine if neurons projecting out of motor cortex to different targets have selective input connectivity from extrinsic sources we electrically stimulated corticocortical, callosal and thalamocortical pathways. Subthreshold effects of input pathways were detected by monitoring latency variations of antidromic responses. Intracortical connections to identified output neurons were evaluated by cross-correlation and a new variation of the antidromic latency method. Output neurons in different layers along single electrode tracks usually had different inputs from extrinsic sources. Neurons in close proximity were most likely to share the same inputs, especially when they projected axons to the same target. These results support the conclusion that combinations of inputs from extrinsic sources could selectively recruit efferent neurons from separate cortical layers or from within groups of nearby neurons, according to the target of their axonal projections. In contrast, the data on intracortical connectivity suggest that common drive causes a more synchronous activation of nearby cortical neurons. Combining the conclusions on effects of inputs from extrinsic and intracortical sources leads to the speculation that motor cortex neurons that might at one time be recruited selectively by action of extrinsic afferent pathways to cortex could at another time be bound into synchrony by a common drive shared with their neighbours.

UI MeSH Term Description Entries
D009044 Motor Cortex Area of the FRONTAL LOBE concerned with primary motor control located in the dorsal PRECENTRAL GYRUS immediately anterior to the central sulcus. It is comprised of three areas: the primary motor cortex located on the anterior paracentral lobule on the medial surface of the brain; the premotor cortex located anterior to the primary motor cortex; and the supplementary motor area located on the midline surface of the hemisphere anterior to the primary motor cortex. Brodmann Area 4,Brodmann Area 6,Brodmann's Area 4,Brodmann's Area 6,Premotor Cortex and Supplementary Motor Cortex,Premotor and Supplementary Motor Cortices,Anterior Central Gyrus,Gyrus Precentralis,Motor Area,Motor Strip,Precentral Gyrus,Precentral Motor Area,Precentral Motor Cortex,Premotor Area,Premotor Cortex,Primary Motor Area,Primary Motor Cortex,Secondary Motor Areas,Secondary Motor Cortex,Somatic Motor Areas,Somatomotor Areas,Supplementary Motor Area,Area 4, Brodmann,Area 4, Brodmann's,Area 6, Brodmann,Area 6, Brodmann's,Area, Motor,Area, Precentral Motor,Area, Premotor,Area, Primary Motor,Area, Secondary Motor,Area, Somatic Motor,Area, Somatomotor,Area, Supplementary Motor,Brodmann's Area 6s,Brodmanns Area 4,Brodmanns Area 6,Central Gyrus, Anterior,Cortex, Motor,Cortex, Precentral Motor,Cortex, Premotor,Cortex, Primary Motor,Cortex, Secondary Motor,Cortices, Secondary Motor,Gyrus, Anterior Central,Gyrus, Precentral,Motor Area, Precentral,Motor Area, Primary,Motor Area, Secondary,Motor Area, Somatic,Motor Areas,Motor Cortex, Precentral,Motor Cortex, Primary,Motor Cortex, Secondary,Motor Strips,Precentral Motor Areas,Precentral Motor Cortices,Premotor Areas,Primary Motor Areas,Primary Motor Cortices,Secondary Motor Area,Secondary Motor Cortices,Somatic Motor Area,Somatomotor Area,Supplementary Motor Areas
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011999 Recruitment, Neurophysiological The spread of response if stimulation is prolonged. (Campbell's Psychiatric Dictionary, 8th ed.) Recruitment, Motor Unit,Motor Unit Recruitment,Neurophysiological Recruitment
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D002540 Cerebral Cortex The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulci. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions. Allocortex,Archipallium,Cortex Cerebri,Cortical Plate,Paleocortex,Periallocortex,Allocortices,Archipalliums,Cerebral Cortices,Cortex Cerebrus,Cortex, Cerebral,Cortical Plates,Paleocortices,Periallocortices,Plate, Cortical
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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