title: Functional organization of human motor cortex: directional selectivity for movement.
abstract: In monkeys, neurons in the hand representation of the primary motor cortex (M1) are often tuned to the direction of hand movement, and there is evidence that these neurons are clustered according to their "preferred" direction of movement. However, this organizational principle has yet to be demonstrated in M1 of humans. We conducted a functional magnetic resonance imaging (fMRI) study in which participants used a joystick to move a cursor from a central origin to one of five equidistant targets. The fMRI signal of individual voxels was sensitive to the directional aspects of the reaching task and manifested direction-specific adaptation. Furthermore, the correlation between multivoxel patterns of responses for different movement directions depended on the angular distance between them. We conclude that M1 neurons are likely to be organized in clusters according to their preferred direction, since only such a coarse-grained representation can lead to directional selectivity of voxels, encompassing millions of neurons. A simple model that estimates cluster size suggests that the diameter of these clusters is on the order of a few hundred micrometers.
authors.affiliation: Department of Neurobiology, Life Sciences Institute and Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem 91904, Israel. eisenberg@mail.huji.ac.il
authors.forename: Michal
authors.initials: M
authors.lastname: Eisenberg
authors.forename: Lior
authors.initials: L
authors.lastname: Shmuelof
authors.forename: Eilon
authors.initials: E
authors.lastname: Vaadia
authors.forename: Ehud
authors.initials: E
authors.lastname: Zohary
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D010100:Oxygen / Q000097:blood; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
chemical_list: D010100:Oxygen