Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The purpose of this thesis was to examine visually guided movements of the upper limbs which approximated normal reaching behaviour, and to describe the production of these movements on the basis of a number of interrelated measures. The series of studies required subjects to point quickly and accurately to small visual targets presented lateral to a visual fixation point, on an otherwise featureless screen. In Studies 1 and 2 the kinematic characteristics of the limb movements were examined by a frame-by-frame analysis of video records of the subjects' performance. The use of visual feedback information in the guidance of the limb was evident from the modifications in trajectory during periods of low velocity at the end of the movements, and also from the increased accuracy and longer movement duration when the subjects pointed to persistent rather than briefly visible targets. Studies 1 and 2 also revealed that reaches of either limb which crossed the body axis were less efficient, in terms of movement velocity, than those performed within the extrapersonal space ipsilateral to the limb being used. As long as the subjects fixated a point directly in front of their body axis before the target was presented, these ipsilateral reaches were also initiated more quickly and were more accurate. Unlike movement velocity, the latency and accuracy of the limb movement were altered when the subjects fixated an eccentric point so that the visual field did not correspond to extrapersonal space relative to the body axis. Studies 1 and 3 found a low but statistically correlation between the latency to initiate movement of the eyes and hand. The results of Study 3 suggested that this correlation may be reduced by previous trials in which only the eyes or the hand were directed to the target. In Study 1 the eye and limb movement latencies were lower for ipsilaterally presented targets and for blocks of trials in which the subjects reached with their right hand. The results suggest the existence of a hemispherically organized network of cortical areas which is involved in the integration of sensorimotor information for the control of visually directed eye and limb movements.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.