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Lee P. Lovejoy, Garth A. Fowler, Richard J. Krauzlis; Allocation of spatial attention during fixation and smooth pursuit. Journal of Vision 2004;4(8):747. doi: 10.1167/4.8.747.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Smooth pursuit eye movements require attention to the target, but the spatial allocation of attention during pursuit is poorly understood. To clarify the relationship between attention and smooth pursuit, we used a letter discrimination task to compare the spatial distribution of attention during smooth pursuit with that during fixation. METHODS: Human subjects (n=2) viewed a horizontal array of characters. The array consisted of 15 characters, each with dimensions 0.28 wide by 0.50 tall and an inter-character spacing of 0.55 . At the onset of each trial, all characters were block-letter 8′s, and subjects were given a cue identifying the central character. On fixation trials, the array was stationary and subjects fixated the central character, whereas on pursuit trials, the array moved at 13 /s and subjects smoothly pursued the central character. After a variable delay (500–2000 ms), a 180-ms probe interval occurred. During this probe interval, every character switched to either a block-letter 2 or 5 except for a single probe character, which switched to either an E (50%) or a 3 (50%). The probe character could appear at any of the 13 middle positions in the array. At the end of each trial, subjects reported whether the probe interval included an E or a 3 in a 2AFC design. Percent correct was calculated separately for fixation and pursuit trials, at each of the 13 possible probe positions within the character array. RESULTS and CONCLUSIONS: Performance was best at the central character and decreased as the probe character moved eccentrically from the central character, approaching chance by 1–2, showing that attention was spatially restricted. The pattern of results was similar in form and magnitude on both fixation and smooth pursuit trials, suggesting that the distribution of attention was the same during fixation and smooth pursuit.
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