Systematic errors of planar arm movements provide evidence for space categorization effects and interaction of multiple frames of reference |
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Authors: | Gourtzelidis P Smyrnis N Evdokimidis I Balogh A |
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Institution: | (1) Cognition and Action Group, Neurology Department, National University of Athens, Aeginition Hospital, Greece,;(2) 401 Army General Hospital, Neurophysiology Department, 138 Mesogeion and Katehaki, Athens, 11525, Greece,;(3) University Mental Health Research Institute, National University of Athens, Athens, Greece, |
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Abstract: | Healthy humans performed arm movements in a horizontal plane, from an initial position toward remembered targets, while the
movement and the targets were projected on a vertical computer monitor. We analyzed the mean error of movement endpoints and
we observed two distinct systematic error patterns. The first pattern resulted in the clustering of movement endpoints toward
the diagonals of the four quadrants of an imaginary circular area encompassing all target locations (oblique effect). The
second pattern resulted in a tendency of movement endpoints to be closer to the body or equivalently lower than the actual
target positions on the computer monitor (y-effect). Both these patterns of systematic error increased in magnitude when a time delay was imposed between target presentation
and initiation of movement. In addition, the presence of a stable visual cue in the vicinity of some targets imposed a novel
pattern of systematic errors, including minimal errors near the cue and a tendency for other movement endpoints within the
cue quadrant to err away from the cue location. A pattern of systematic errors similar to the oblique effect has already been
reported in the literature and is attributed to the subject's conceptual categorization of space. Given the properties of
the errors in the present work, we discuss the possibility that such conceptual effects could be reflected in a broad variety
of visuomotor tasks. Our results also provide insight into the problem of reference frames used in the execution of these
aiming movements. Thus, the oblique effect could reflect a hand-centered reference frame while the y-effect could reflect a body or eye-centered reference frame. The presence of the stable visual cue may impose an additional
cue-centered (allocentric) reference frame.
Electronic Publication |
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Keywords: | Motor control Visuomotor transformation Frame of reference Space perception Category Human |
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