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Simran Purokayastha, Mariel S Roberts, Marisa Carrasco; Does endogenous attention compensate for spatial performance fields?. Journal of Vision 2019;19(10):265b. doi: https://doi.org/10.1167/19.10.265b.
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Purpose: Performance on visual discrimination tasks is better along the horizontal than vertical meridian (Horizontal-Vertical Anisotropy, HVA), and along the lower than upper vertical meridian (Vertical Meridian Asymmetry, VMA). Exogenous (involuntary) attention improves performance to a similar extent across isoeccentric locations. Here we tested whether endogenous (voluntary) attention, known to be more flexible, would perform a compensatory role, with the greatest benefit at the worst location. Further, we predicted that endogenous attention would improve performance at threshold levels. Methods: Observers performed a 2AFC orientation discrimination task, contingent upon contrast sensitivity, while maintaining fixation. The target could appear at any one of 4 isoeccentric locations along the cardinals. Participants were either cued towards a single location (Valid cue) or to all four locations (Neutral cue). On every trial, 4 Gabors briefly appeared simultaneously at all stimulus locations. A response cue indicated the target, for which participants reported the tilt (left or right). In Experiment 1, contrast was constant across locations. In Experiment 2, we obtained contrast thresholds for the 4 locations separately, which were independently adjusted between the main blocks to maintain 80% accuracy at each location. In both experiments, we measured accuracy and RTs for each location during both attention conditions. Results: Observers reliably demonstrated canonical performance fields. In Experiment 1, the effect of attention was more pronounced in the upper vertical meridian, compensating for poor performance at that location. In Experiment 2, observers required the lowest contrast along the horizontal, and the most at the upper vertical meridian, to attain ~80% accuracy in the neutral condition across all locations. Performance in the valid cue condition was similarly effective across locations. Conclusions: Endogenous attention alleviated PF asymmetries when stimulus contrast was constant at all locations, but not when contrast was adjusted to equate performance across locations.
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