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Yamaya Sosa, Mark E. McCourt; Phasic modulation of tonic attentional biases in horizontal and vertical dimensions: A cued visual line bisection study. Journal of Vision 2012;12(9):925. doi: 10.1167/12.9.925.
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© ARVO (1962-2015); The Authors (2016-present)
Background. Biases of spatial attention occur in both horizontal and vertical dimensions. Normal observers exhibit a tonic leftward error in the perceived midpoint of horizontal lines thought to result from a surplus of spatial attention directed into the left (contralateral) hemifield (or toward the left half of objects) by the dominant right hemisphere which induces a left-side size overestimation. Less well-studied is the tonic upward error in the perceived midpoint of vertical lines which, interestingly, is common to both normal observers and neglect patients. Transient visual cues phasically modulate the tonic leftward error for horizontal lines; the effect of cues on vertical bisection error is unknown. Method. In two experiments (E1, E2) observers (N = 34 and 32) bisected horizontal (E1) and vertical (E2) lines (50% contrast; 26.7° by 3°; viewing distance = 57 cm), in both cued (3° diameter circular cosines, 3 c/d, 100% contrast, 30 ms duration, 60 ms cue-line SOA) and uncued conditons. In E1 horizontal lines cues appeared within the left and right line halves at eight spatial locations. In E2 vertical lines appeared within the upper and lower line halves at eight spatial locations. Results. In E1 a tonic leftward bisection error was significantly modulated by cues. Right cue potency exceeded left cue potency. Cues located inside line boundaries were equally potent, but those located outside were ineffective in modulating bisection error. In E2 a tonic upward bisection error was modulated by cues. Downward cue potency exceeded upward cue potency. Again, cues located outside the line boundary were ineffective; unlike E1, cue potency varied with location inside the line. Conclusions. Cues modulate tonic biases of spatial attention in both horizontal and vertical dimensions. Cue potency is strongest for cues which antagonize the tonic biases. Cues effects are exerted in object-referenced coordinates.
Meeting abstract presented at VSS 2012
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