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Different learned coordinate frames for planning trajectories and final positions in reaching. J Neurophysiol 2007 Dec;98(6):3614-26

Date

09/07/2007

Pubmed ID

17804576

DOI

10.1152/jn.00652.2007

Scopus ID

2-s2.0-37549000174 (requires institutional sign-in at Scopus site)   63 Citations

Abstract

We previously reported that the kinematics of reaching movements reflect the superimposition of two separate control mechanisms specifying the hand's spatial trajectory and its final equilibrium position. We now asked whether the brain maintains separate representations of the spatial goals for planning hand trajectory and final position. One group of subjects learned a 30 degrees visuomotor rotation about the hand's starting point while performing a movement reversal task ("slicing") in which they reversed direction at one target and terminated movement at another. This task required accuracy in acquiring a target mid-movement. A second group adapted while moving to -- and stabilizing at -- a single target ("reaching"). This task required accuracy in specifying an intended final position. We examined how learning in the two tasks generalized both to movements made from untrained initial positions and to movements directed toward untrained targets. Shifting initial hand position had differential effects on the location of reversals and final positions: Trajectory directions remained unchanged and reversal locations were displaced in slicing whereas final positions of both reaches and slices were relatively unchanged. Generalization across directions in slicing was consistent with a hand-centered representation of desired reversal point as demonstrated previously for this task whereas the distributions of final positions were consistent with an eye-centered representation as found previously in studies of pointing in three-dimensional space. Our findings indicate that the intended trajectory and final position are represented in different coordinate frames, reconciling previous conflicting claims of hand-centered (vectorial) and eye-centered representations in reach planning.

Author List

Ghez C, Scheidt R, Heijink H

Author

Robert Scheidt BS,MS,PhD Associate Professor in the Biomedical Engineering department at Marquette University




MESH terms used to index this publication - Major topics in bold

Adult
Algorithms
Arm
Biomechanical Phenomena
Data Interpretation, Statistical
Female
Humans
Learning
Male
Middle Aged
Psychomotor Performance
Rotation