The mapping of visual space is a function of the structure of the visual field

Article Abstract:

Martha Flanders et al's model of the shoulder-centered reference system was compared with other studies of goal-directed arm movements. It was shown that an egocentric reference system used to process spatial information is common to all theories. An examination of the effects of a visual target in a structured visual field on a deafferented patient showed that spatial accuracy decreased when the target was presented in the unstructured visual field. The patient's divergent behavior was attributed to the absence of heterosensory processing of the hand-target relative position.

Visual perception

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Two paradoxes of pointing

Article Abstract:

Two paradoxes of pointing were presented, one of which suggested that subjects make consistent azimuth erros during pointing without vision or when they present data about the frame-of-reference shift toward the shoulder that occurs when subjects point without vision. This was interpreted as a change in the occurrence of the coordinate system axes that define azimuth and elevation. The second paradox delves on mirror reflected letters drawn by childre. This further suggest that there is a change in axes and the frame-of-reference.

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Error analysis, regression and coordinate systems

Article Abstract:

It was shown that the statistical analysis in Martha Flanders et al's article on targeted arm movement is not capable of supporting inferences about coordinate systems. The regressions mentioned in the article inform only that the coding of position changes the shape of space but no matter what the form of the predicted values it was shown that one cannot draw inferences about the validity of either spherical representation nor can one locate the appropriate centers with convincing accuracy.

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