title: Motor cortex is functionally organized as a set of spatially distinct representations for complex movements.
abstract: There is a long-standing debate regarding the functional organization of motor cortex. Intracortical microstimulation (ICMS) studies have provided two contrasting views depending on the duration of stimulation. In the rat, short-duration ICMS reveals two spatially distributed forelimb movement representations, the rostral forelimb area (RFA) and caudal forelimb area (CFA), eliciting identical movements. In contrast, long-duration ICMS reveals spatially distributed, complex, multijoint movement areas, with grasping found exclusively in the rostral area and reach-shaping movements of the arm located in the caudal area. To provide corroboration for which interpretation is correct, we selectively inactivated the RFA/grasp area during the performance of skilled forelimb behaviors using a reversible cortical cooling deactivation technique. A significant impairment of grasping in the single-pellet retrieval task and manipulations of pasta was observed during cooling deactivation of the RFA/grasp area, but not the CFA/arm area. Our results indicate a movement-based, rather than a muscle-based, functional organization of motor cortex, and provide evidence for a conserved homology of independent grasp and reach circuitry shared between primates and rats.
authors.affiliation: Hotchkiss Brain Institute, Departments of Neuroscience.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Brown
authors.affiliation: Hotchkiss Brain Institute, Departments of Neuroscience, Cell Biology and Anatomy, Psychology, and Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada gteskey@ucalgary.ca.
authors.forename: G Campbell
authors.initials: GC
authors.lastname: Teskey
mesh_terms: D000818:Animals; D001931:Brain Mapping; D003080:Cold Temperature; D003216:Conditioning, Operant / Q000502:physiology; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D005552:Forelimb / Q000294:innervation; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans
keywords: behavior; intracortical microstimulation; rat; reversible lesion