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Alex White, Marisa Carrasco; The simultaneous and involuntary effect of global feature-based attention on motion sensitivity. Journal of Vision 2011;11(11):154. doi: 10.1167/11.11.154.
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Goal: Neural responses to attended feature values such as motion directions are boosted even at ignored locations, in line with the feature-similarity gain principle of Treue & Martinez-Trujillo (1999). Psychophysical and neuroimaging studies have also found effects consistent with the global spread of feature-based attention (FBA) (e.g., Lu & Itti, 2005; Melcher et al., 2005; Serences & Boynton, 2007). However, no study has yet provided direct behavioral evidence for involuntary changes in motion sensitivity that are simultaneous with the deployment of FBA at another location. Methods: Observers (n = 13) performed two tasks simultaneously. In the primary task, observers had to detect a speed change in one of two superimposed dot fields moving in opposite directions. In the attended conditions, the direction in which the speed change could occur was precued. In the neutral condition the speed change was equally likely in either direction. At a random time during the presentation of these primary stimuli, two dot fields appeared in the opposite hemifield. One moved randomly (0% coherence) and the other moved coherently either upwards or downwards. The secondary task was to indicate which dot field contained a coherent motion signal, but its particular direction was task-irrelevant. The amount of coherence was varied to estimate 75% correct thresholds. Results: The secondary task did not require observers to discriminate or selectively attend to the particular direction present. Nonetheless, sensitivity was highest when the direction of the secondary target matched the direction cued in the primary task. Comparison to the neutral condition revealed more enhancement of the attended direction than suppression of the unattended one. These perceptual effects of selective attention to motion direction at a distant location occur involuntarily and simultaneously with the deployment of attention, consistent with known neurophysiological phenomena.
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