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Most studies that have compared pointing to visible versus remembered targets have involved situations when both the limb and target are present (closed loop-target present), or when both the limb and target are occluded (open loop-target absent). This comparison confounds vision of the target with vision of the hand. In order to dissociate these two sources of visual information in pointing, it is necessary to examine conditions in which only one of these sources of information is occluded, that is, when only vision of the hand (open loop-target present) or vision of the target (closed loop-target absent) is occluded. Some studies have compared subsets of these four conditions to examine, for example, the role of vision of the hand in pointing where the target is present throughout the movement but vision of the hand is occluded (open loop) or not (closed loop). Very few studies to date have compared all of these conditions to examine the relative contribution of these two sources of information in pointing. The purpose of this study was to make these comparisons and to examine whether aging had an effect on how these sources of information were used in pointing. To address this, we asked young (N=10, mean age = 21.8 years, 6 females, 4 males) and older (N=9, mean age = 73.8 years, 4 females, 5 males) right-handed adults to point to each of three targets: one situated at the midline and one each at 45 degrees to the left (contralateral) and right (ipsilateral) of the midline, while manipulating whether participants had vision of their pointing limb, the target, or both. In target-absent trials, the time between target occlusion and movement initiation was also manipulated (movement initiation immediately after occlusion or following a delay of 2 seconds) to examine the time course of the representation of target information in memory. All conditions were randomized between each participant. Results showed vision of the limb significantly affects the movement in a positive manner, such that endpoint error and variability were less than conditions in which the limb was not available during movement. This was true for both target present and absent actions, suggesting limb vision provides crucial visual and proprioceptive information to result in a much more precise and consistent movement to targets. This information may also be more important to the participant than target presence, in terms of accuracy and variability, as there tended to be little differences between target present and target absence trials. Where target presence made a difference was during the decelerative phase of movement time (after peak velocity has been reached), where relatively more time was allotted in this period when the target was visible throughout the movement. Because this time is indicative of online feedback processing, this suggests that vision of the target was contributing some type of information to the movement. Interestingly, there was no significant main effect of age group in this study. However, age did play a role in the way participants moved to the targets. In the directional (x) axis, young adults were more likely to aim to targets that were biased further from their body, whereas elderly adult participants displayed the opposite bias: their accuracy data show they tend to aim closer to their body.

Most studies that have compared pointing to visible versus remembered targets have involved situations when both the limb and target are present (closed loop-target present), or when both the limb and target are occluded (open loop-target absent). This comparison confounds vision of the target with vision of the hand. In order to dissociate these two sources of visual information in pointing, it is necessary to examine conditions in which only one of these sources of information is occluded, that is, when only vision of the hand (open loop-target present) or vision of the target (closed loop-target absent) is occluded. Some studies have compared subsets of these four conditions to examine, for example, the role of vision of the hand in pointing where the target is present throughout the movement but vision of the hand is occluded (open loop) or not (closed loop). Very few studies to date have compared all of these conditions to examine the relative contribution of these two sources of information in pointing. The purpose of this study was to make these comparisons and to examine whether aging had an effect on how these sources of information were used in pointing. To address this, we asked young (N=10, mean age = 21.8 years, 6 females, 4 males) and older (N=9, mean age = 73.8 years, 4 females, 5 males) right-handed adults to point to each of three targets: one situated at the midline and one each at 45 degrees to the left (contralateral) and right (ipsilateral) of the midline, while manipulating whether participants had vision of their pointing limb, the target, or both. In target-absent trials, the time between target occlusion and movement initiation was also manipulated (movement initiation immediately after occlusion or following a delay of 2 seconds) to examine the time course of the representation of target information in memory. All conditions were randomized between each participant. Results showed vision of the limb significantly affects the movement in a positive manner, such that endpoint error and variability were less than conditions in which the limb was not available during movement. This was true for both target present and absent actions, suggesting limb vision provides crucial visual and proprioceptive information to result in a much more precise and consistent movement to targets. This information may also be more important to the participant than target presence, in terms of accuracy and variability, as there tended to be little differences between target present and target absence trials. Where target presence made a difference was during the decelerative phase of movement time (after peak velocity has been reached), where relatively more time was allotted in this period when the target was visible throughout the movement. Because this time is indicative of online feedback processing, this suggests that vision of the target was contributing some type of information to the movement. Interestingly, there was no significant main effect of age group in this study. However, age did play a role in the way participants moved to the targets. In the directional (x) axis, young adults were more likely to aim to targets that were biased further from their body, whereas elderly adult participants displayed the opposite bias: their accuracy data show they tend to aim closer to their body.

Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Brij N. Agrawal, Hong-Jen Chen. Includes bibliographical references (p. 63). Also available online.

This thesis investigated some of the eye movement factors related to the development and use of eye pointing devices with three dimensional displays (stereoscopic and linear perspective). In order for eye pointing to be used as a successful device for input-control of a 3D display it is necessary to characterise the accuracy and speed with which the binocular point of foveation can locate a particular point in 3D space. Linear perspective was found to be insufficient to elicit a change in the depth of the binocular point of fixation except under optimal conditions (monocular viewing, accommodative loop open and constant display paradigm). Comparison of the oculomotor responses made between a stereoscopic 'virtual' and a 'real' display showed there were no differences with regards to target fixational accuracy. With one exception, subjects showed the same degree of fixational accuracy with respect to target direction and depth. However, close target proximity (in terms of direction) affected the accuracy of fixation with respect to depth (but not direction). No differences were found between fixational accuracy of large and small targets under either display conditions. The visual conditions eliciting fast changes in the location of the binocular point of foveation, i.e. saccade disconjugacy, were investigated. Target-directed saccade disconjugacy was confirmed, in some cases, between targets presented at different depths on a stereoscopic display. However, in general the direction of saccade disconjugacy was best predicted by the horizontal direction of the target. Leftward saccade disconjugacy was more divergent than rightward. This asymmetry was overlaid on a disconjugacy response, which when considered in relative terms, was appropriated for the level of vergence demand. Linear perspective depth cues did not elicit target-directed disconjugate saccades.

Thesis (Ph. D.)--University of Wyoming, 2005. / Title from PDF title page (viewed on March 10, 2008). Includes bibliographical references (p. 84-88).

Dissertation (Ph.D.) - Simon Fraser University, 2005. / Dissertation (Dept. of Psychology) / Simon Fraser University.

Dissertation (Ph.D.) - Simon Fraser University, 2005. / Dissertation (Dept. of Psychology) / Simon Fraser University.

Thesis (M.A.)--York University, 2006. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 48-55). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19674

Thesis (Aeronautical and Astronautical Engineer Degree and M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2002. / Thesis advisor(s): Brij Agrawal, Hong-Jen Chen. Includes bibliographical references (p. 85-88). Also available online.