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Anne Giersch; Interactions between spatial attention and the processing of discontinuities. Journal of Vision 2002;2(7):8. doi: 10.1167/2.7.8.
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A modified short-term priming task was combined with a cueing procedure to explore attentional effects on the modulation of the processing of discontinuities. Stimuli were displayed successively with a SOA of 250 msec: they were composed of two horizontal line-segments, either collinear or parallel, subtending 1° of visual angle. Parallel elements were connected on one side, forming a U-shape, whereas collinear elements differed on their length. The subjects's task was to decide whether the gap separating the elements of the second stimulus was located to the right or to the left. Previous results showed that RTs increase when a stimulus composed of collinear elements is followed by a stimulus composed of parallel elements with a gap on the same side, or the reverse. A series of experiments showed that these effects were orientation and location dependent and suggested that they rely on the modulation of the processing of line-ends and virtual lines (Giersch & Fahle, in press, Perception & Psychophysics). In the present experiments, the first sequence included two identical stimuli instead of one, in two square frames 4° wide. The second stimulus was unique as previously. Either one or the two frames were cued at the end of the first stimulus presentation. Results showed (1) a global disadvantage for stimuli composed of collinear elements, especially in non-valid conditions. (2) The cueing effects varied with the characteristics of the first stimulus, and (3) were reversed by lorazepam (benzodiazepine affecting GABA transmission and believed to affect the processing of discontinuities, Giersch, Vis. Cogn., 8, 549–564, 2001). (4) Location-specific modulations of the processing of discontinuities were absent in valid and non-valid conditions. The results suggest that attentional effects are dependent of the characteristics of the stimuli displayed in the cued location. Interactions between attention and the processing of discontinuities may arise, in a diffuse way.
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