Natural vision is characterized by frequent saccadic eye movements to bring the line of sight to important objects quickly and accurately. Effective use of saccades is crucial for successful performance of everyday life visual tasks, including reading, search, navigation, or any task in which movements of the eye guide movements of the arm. The spatial pattern of saccades is widely believed to be derived from the distribution of attention;however, the relationship between attention and saccades is not understood. This proposal uses dual-task psychophysical methods (concurrent measurement of saccades and visual attention) to investigate the distribution of attention during the execution of sequences of saccades and the consequences of this attentional distribution for vision during intersaccadic pauses. The experiments will determine whether attention must be focused at the target of the next saccade or whether broader distributions are possible with no cost to saccadic performance. Preliminary results indicate that visual attention is distributed to targets of at least the next two upcoming saccades, with an overall suppression of vision during intersaccadic pauses relative to vision during steady fixation. Analytic methods developed in studies of attention shifts during steady fixation will be applied to the pre-saccadic attention shifts to better characterize the nature of the effects of pre-saccadic attention shifts on vision. The long-range significance of this work is that it should lead to a better understanding of the coordination between vision, attention and oculomotor programming in normal performance of complex tasks. This work should also lead to a better understanding of the consequences of attentional disorders for both vision and oculomotor control, better methods of distinguishing attentional and oculomotor dysfunction, and possible development of ways of reducing the functional consequences of these deficits through alternative strategies of task performance.
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