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M. Hayhoe, P. Aivar, R. Mruczek, C. Chizk; Memory for spatial structure in saccadic targeting. Journal of Vision 2001;1(3):261. doi: 10.1167/1.3.261.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work on the ability to integrate information across saccadic eye movements suggests that only a small part of the information in the visual scene is retained following the change in eye position. However visual representations must be sufficiently extensive to mediate coordinated movements. This requires some continuity across different fixation positions, to represent the current space and the layout of prominent objects. We examined eye and hand movements in two natural tasks that suggest that some representation of the spatial information in a scene is built up over fixations. When making sandwiches, subjects scan the scene upon the initial exposure, and make a series of fixations on the objects in a scene before the first reaching movement is initiated, as expected if subjects are building a representation of scene layout for later use. We also found that about 30% of the reaches made to pick up objects were preceded by a fixation on that object in the recent past (less than 10 sec). These fixations may indicate that the subject is planning a reach in a coordinate frame independent of eye position. In another experiment, subjects copied a toy model in a virtual environment. We examined saccadic targeting performance to see if subjects took advantage of regularities in the spatial arrangement of the component pieces as suggested by Chun & Nakayama, Visual Cognition (2000). In one condition this arrangement was changed randomly every time the subject looked away from the area. The results showed that about 20% of saccades went either directly to the location of next component to be copied, or to its old location before the change. This supports the idea that the detailed spatial structure of the environment is typically retained across fixations and used to guide eye movements. This ability may be important for movement planning.
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