The quantum nature of attention: a time-resolved fMRI study P Scalf1, E St. John-Saaltink2, H Lau3, F De Lange2 |
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1Psychology, University of Arizona, AZ, United States |
| When directed to multiple spatial locations, attention has traditionally been thought to be simultaneously distributed among them (Eriksen & St James, 1986, Perception & Psychophysics 40 (4): 225–240). Rhythmic presentation of spatially disjoint targets at optimal frequencies improves their detection, however, suggesting that covert attention may in fact be rapidly cycled between attended locations (Landau & Fries, 2012, Current Biology, May; Van Rullen et al., 2007, PNAS, 104 (49), 19204-19209 ). We used time-resolved fMRI (TR = 88 ms) to investigate whether attending to multiple visual items results in serial rather than simultaneous enhancement of their representations in visual cortex. We measured extrastriate signal evoked by stimuli in the four quadrants under three conditions. A simultaneous, 400 ms, 25% increase in luminance of all four items served as a model for simultaneously distributed attention. A sequential, 100 ms, 100% increase in luminance for each item served as a model for sequentially allocated attention. We compared these with an attended condition, in which participants monitored the four items (whose luminance did not change). The phase of evoked BOLD response changed predictably across the visual field under sequential and attended conditions (p <.05), but was constant under simultaneous conditions. |
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