A journey through time and space: the spatiotemporal profile of attention relative to saccade and reach

Abstract

In an interactive environment, we use a multitude of eye and hand movements to gather information about our surroundings, and to act upon what we see. While these are the eventual, overt behaviours that we observe, there are countless hidden neural processes guiding where we move our eyes and hands. This thesis will examine one such of these processes: visual attention. Visual attention has been shown to produce perceptual benefits, such as an increase in contrast sensitivity, at the attended location, and there is evidence that before an eye or hand movement is made, attention shifts to the location of that upcoming movement target. This thesis aimed to comprehensively map the spatiotemporal profile of attention when reaches and saccades were being planned and executed, in order to compare how attention shifts when different types of movements are being made. The first experiment mapped the spatiotemporal profile of attention relative to a reach alone. Results of this study showed that when a reach alone is being planned, there is a broad spatial allocation of attention across the visual field, while the temporal profile shows a slight increase before the onset of a reach, with a dramatic drop in performance once the hand is in flight. The second experiment compared the spatiotemporal profile of attention for saccades alone, and saccades with a concurrent reach. These results, in contrast showed a large increase in performance before the start of a movement, and a plateau of performance during the movement itself. The third experiment aimed to explore how attention may differ depending on where a probed location is situated relative to the direction of a movement, and to compare how this may change across different movement effectors. Results showed that the profile of attention differed depending on both movement effector and whether the probe appeared in line with or orthogonal to the direction of a movement. These results also suggest that attention spreads differently when a saccade is being made, irrespective of whether a reach is being conducted or not. Overall, the results of this thesis showed three main effects: the spatiotemporal profile of attention is different when a saccade is being made compared to a reach alone; attentional facilitation at the location of a probe is different depending on where the probe is located, relative to the direction of movement; and this profile of attention varies depending on the type of movement being enacted. Additional results also suggest that attention may act in a dual facilitatory/inhibitory manner, depending on the movement effector. Taken together, these results provide evidence that different types of movement planning may require different levels of attentional guidance, and also provide evidence that pre-movement attention may be a flexibly allocated resource, depending on the demands of the task, and the movements being enacted.