An ERP investigation of the consequences of motor preparation on visual processing.

Action and perception have traditionally be studied in isolation, as separate and unitary cognitive processes. More recent evidence has demonstrated a lively interaction between the two. Preparing an action – either a saccade or a manual movement - causes enhanced processing of action-relevant stimuli in the environment, at the expense of the action-irrelevant. The aim of the research reported in this thesis are to provide further detail about this effect. The experiments are reported in this thesis are concerned with how the spatial, temporal and functional properties of action affect perception. Chapter three reports an experiment in which the spatial properties of a grasped object, which make different demands of accuracy, were manipulated. The experiment in chapter four compared goal and effector locations, and measured visual processing across the time course of motor preparation. Chapter five reports an experiment that measured visual processing not just at goal and effector locations, but also at more distant locations not involved in movement, in order to estimate the spatial profile of the effect. Results showed clear enhancement of goal and effector locations simultaneously during motor preparation, although the goal location was enhanced over a broader time period than the effector, suggesting the two components of movement are not equivalent in terms of the relative priorities assigned to them during motor preparation. The spatial profile of the effect fell-off with distance from the goal and effector, and is discussed in terms of theories concerning the spatial profile of visual attention. Taken together, the results of all three experiments suggest that the processes initiated by motor preparation cause shifts in the patterns of perceptual facilitation and inhibition that ultimately achieve selectivity. The inclusion of the effector location in this process suggests that it is not limited to one representation at a time, but operates instead as a flexible and dynamic rebalancing of perception that adapts to any given cognitive task