| We rely heavily on vision to understand what and who is around us, where those things and people are, and how we might interact with, or avoid, them. Consequently we move our eyes 3 or 4 times every second to gather as much visual information, with the greatest acuity as possible, to best direct our actions. However, these constant eye movements result in a continuously changing or shifting visual world. So, to compensate we must update our representation of our environment with every eye movement so that we can perceive the world to be stable, which is what allows us to function.;In Chapter 1, I provide the necessary background information to understand the rationale and basis of the experiments discussed in the following chapters. Chapter 2 establishes that visuospatial memory is updated in eye-centred coordinates regardless of how slowly the eyes move away from the target site, and also explores the contributions of retinal versus extraretinal information. I next investigate, in Chapter 3, the relative contributions of ego-and allo-centric information in coding multiple targets for generating a sequence of reaches to them. And finally, in Chapter 4, I investigate theories of reference frame transformation and demonstrate for the first time that remembered target locations are coded and updated in eye-centred coordinates well after a person has begun to reach to them.;This dissertation provides novel contributions as to the sources of information (and their relative contributions) used in updating visual space to direct reaching and pointing movements. In Chapter 5 I summarise my experimental findings and present a robust conceptual model which describes eye-centred spatial updating in the visuomotor and arm-motor systems.;Previous research suggests that remembered target locations are stored and updated in a reference frame that is dependent on the relative distance between gaze and a target location for both visual and non-visual targets (e.g., auditory, tactile, proprioceptive). This eye-centred updating of visuospatial memory is evidenced by reaching and pointing errors that vary as a function of the distance between gaze and a remembered target's location. This dissertation explores this idea, and extends these findings. |
