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Rhys Davies, Casimir Ludwig; Saccadic decisions in response to new objects in spatiotopic and retinotopic reference frames. Journal of Vision 2011;11(11):520. doi: 10.1167/11.11.520.
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© ARVO (1962-2015); The Authors (2016-present)
When making saccadic eye movements, the retinal coordinates of objects are altered, but their spatiotopic (i.e. world) coordinates remain stable. In short sequences of saccades we examined how previous visual stimulation influenced decisions about where to look next. During an initial saccade to the centre of the screen, a test display appeared with two noisy luminance patterns of different contrasts. Participants had to direct their second saccade to the higher contrast pattern. The number of patterns in a preview display shown before the first saccade varied between 0, 2 and 4. When present, the patterns in the preview were of equal contrast. The spatial configuration of the preview and test displays was such that an object could be a retinotopic and spatiotopic onset (experiment 1); a spatiotopic onset, but retinotopic match (experiment 2); a retinotopic onset, but spatiotopic match (experiments 2 and 3); and a retinotopic and spatiotopic match (experiment 3). We assessed choice accuracy as a function of the retinotopic/spatiotopic nature of the patterns. When both retinotopic and spatiotopic onsets were present, participants were split in their preferences: half preferentially responded to new objects in world co-ordinates; half preferentially responded to new objects in retinal co-ordinates. When all objects were spatiotopically stable, all participants preferentially responded to retinotopic onsets. This preference may reflect a saccadic response bias towards locations coded by mechanisms that receive novel stimulation. Such a bias would contribute to directing the eyes towards discontinuities in the retinal image, which could facilitate image segmentation.
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