Journal of Neuroscience, Vol 10, 2420-2427, Copyright © 1990 by Society for Neuroscience
Parcellation of sensorimotor transformations for arm movements
M Flanders and JF Soechting
Department of Physiology, University of Minnesota, Minneapolis 55455.
Pointing to a visual target in 3-dimensional space requires a neural
transformation from a visually derived representation of target location to
an appropriate pattern of activity in arm muscles. Previous results
suggested that 1 step in this process involves a transformation from a
representation of target location to a representation of intended arm
orientation, and that the neural implementation of this transformation
involves a linear approximation to the mathematically exact, nonlinear
solution. These results led to the hypothesis that the transformation is
parceled into 2 separate channels. In 1 channel a representation of target
azimuth is transformed into a representation of arm yaw angles, while in
the other channel representations of target distance and target elevation
are transformed into a representation of arm elevation angles. The present
experiments tested this hypothesis by measuring the errors made by human
subjects as they pointed to various parameters of the remembered location
of a target in space. The results show that subjects can use the 2
hypothesized channels separately. For example, subjects can accurately
point to the target's azimuth while ignoring the target's elevation and
distance. The results also show that subjects are unable to point to the
target's elevation while ignoring the target's distance, consistent with
the hypothesis that information about target elevation and target distance
is tied together in the same channel. The parcellation demonstrated in this
study is compared to reports of parceled sensorimotor transformation in
other vertebrate species.
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