title: Dynamical organization of directional tuning in the primate premotor and primary motor cortex.
abstract: Although previous studies have shown that activity of neurons in the motor cortex is related to various movement parameters, including the direction of movement, the spatial pattern by which these parameters are represented is still unresolved. The current work was designed to study the pattern of representation of the preferred direction (PD) of hand movement over the cortical surface. By studying pairwise PD differences, and by applying a novel implementation of the circular variance during preparation and movement periods in the context of a center-out task, we demonstrate a nonrandom distribution of PDs over the premotor and motor cortical surface of two monkeys. Our analysis shows that, whereas PDs of units recorded by nonadjacent electrodes are not more similar than expected by chance, PDs of units recorded by adjacent electrodes are. PDs of units recorded by a single electrode display the greatest similarity. Comparison of PD distributions during preparation and movement reveals that PDs of nearby units tend to be more similar during the preparation period. However, even for pairs of units recorded by a single electrode, the mean PD difference is typically large (45 degrees and 75 degrees during preparation and movement, respectively), so that a strictly modular representation of hand movement direction over the cortical surface is not supported by our data.
authors.affiliation: Department of Physiology, Hadassah Medical School and the Interdisciplinary Center for Neural Computation, The Hebrew University, Jerusalem, Israel 91120. ybss@md2.huji.ac.il
authors.forename: Yoram
authors.initials: Y
authors.lastname: Ben-Shaul
authors.forename: Eran
authors.initials: E
authors.lastname: Stark
authors.forename: Itay
authors.initials: I
authors.lastname: Asher
authors.forename: Rotem
authors.initials: R
authors.lastname: Drori
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Nadasdy
authors.forename: Moshe
authors.initials: M
authors.lastname: Abeles
mesh_terms: D000818:Animals; D001931:Brain Mapping; D004566:Electrodes; D004594:Electrophysiology; D008252:Macaca fascicularis; D009044:Motor Cortex / Q000502:physiology*