Undergraduate Honours Theses
The purpose of this study was to determine whether indirectly viewing an object through a mirror causes reach-to-grasp kinematics to differ from those performed under normal conditions, when participants directly observe the object to be grasped. Participants, in a supine position, reached for objects placed on a presentation platform (workspace) resting above their thighs. In the indirect viewing condition, a two-mirror viewing system was placed above the head that allowed participants to view the workspace. In the direct viewing condition, participants' heads were elevated and tilted forward such that they could directly view the workspace. Three infrared markers were attached to participants' right index fingertip, the tip of the right thumb and the knuckle of the right index-finger. Hand movements were captured using an OPTOTRAK 3020 camera system and kinematics were calculated offline following the experiment. It was found that reaches made under the indirect viewing condition were performed at a slower speed, and overall took longer than reaches made under the direct viewing condition. Hand shaping was effected by viewing condition and object size interaction. The results from this study reveal that reach-to-grasp movements performed under different viewing conditions are quantifiably different and may suggest that different neural substrates and/or different computational loads are present during these two viewing conditions. These results suggest that there may be experimental confounds in several of the previously published reach-to-grasp neuroimaging studies, specifically those that have used optical manipulations to view the hand and workspace within the fMRI scanning environment.