Investigation of the visuo-motor timing mechanism employed in interceptive prehension movements
Year: 1994
Type: dissertation
Abstract: The question of how the human visual system processes information from moving objects, making possible precise eye-to-limb coordination, has long been one which has perplexed scientists (e.g., Gibson, 1950;Regan, Beverley, & Cynader, 1979).Numerous studies (e.g., Lee & Reddish, 1981;Wagner, 1982) have indicated that across changes in the approach velocity of objects or surfaces, the initiation of interceptive movements or coincidence timing skills seems to be most consistently geared to the remaining time-to-contact (h).It is how one perceives this information however is where question arises.One body of theorists believing that estimation is obtained from cognitive computation, the other suggests that its estimation is a direct process arising from interpretation of an optical image displayed on the retina.This has led to the emergence of two differing perspectives about the specific visual information used in the perception of, and in the regulation of action towards moving objects.The primary objective of this study was to determine exactly what perceptual information sources may be used to initiate and regulate coincidence timing tasks.Specifically, whether estimation is obtained through direct processes via the optic variable tau or from independently obtained distance and velocity information.Additionally, the effect of task constraints upon the control strategy adopted were investigated.Two experiments were conducted.The first experiment was to determine both the effect of varying the object approach velocity and the influence of constraining the task by predefining the point at which the object must be intercepted.The second to examine the effects of constraining viewing time, thus limiting the amount of optical expansion.Experiment 1 yielded little evidence to support the use of a constant tau strategy, although selected movement kinematics did provide some indication that optical expansion information was the perceptual source of information best utilized by subjects.Experiment 2 produced support for the use of a constant tau strategy, but only in conditions of severe task constraint such as that provided by a diminished viewing period and relatively fast object approach velocity.Movement kinematics provided inconclusive evidence as to the type of perceptual information utilized by subjects."Perception and action are interwoven and we are likely to loose perspective if we attend to one and neglect the other; for it is in the manner of this union that properties of each are rationalized.After all, there would be no point in perceiving if one could not act, and one could hardly act if one could not perceive".Turvey, (1977), p. 21 1 To my parents Angela and David, Thanks for everything.within the confines of the Simon Fraser University graduate vortex.First and foremost to my supervisor Dave Goodman, not only for his expertise and guidance in the academic field, but also for his continued support throughout my somewhat turbulent graduate career.Thanks must also be extended to my supervisory committee; most notably Digby Elliott, for despite the thousands of miles between us, he always managed to provide a helpful note whenever it was needed or asked for.To the collective members of HMS North and South, who despite numerous difficulties have remained colleagues, I must also express my gratitude, not only for their academic guidance, but also in their providing of various partners in crime.
Source: Summit (Simon Fraser University)
Author: Philip D Knight
Language: English
Topic: Motor Control and Adaptation
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2275997996