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Melissa Saenz, Geoffrey M. Boynton, Christof Koch; Combined effects of spatial and feature-based attention in human visual cortex. Journal of Vision 2006;6(6):599. https://doi.org/10.1167/6.6.599.
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© ARVO (1962-2015); The Authors (2016-present)
Spatial and feature-based attention are known to modulate cortical visual responses, but little is known about how these (or other) forms of attention interact when combined. Using fMRI in humans, we measured the individual and combined effects of spatial and feature-based attention. Subjects (n=5) viewed two circular apertures of moving random dots presented to the left and right of central fixation. The test side had one field of dots moving either upward or downward. The other side had two overlapping fields of dots moving upward and downward. Subjects performed a threshold-level speed discrimination task on one of the three dot fields at a time. We measured the modulation in the response to the test field under three attention conditions. In the spatial condition (S), attention alternated between the test field and the field with the same motion direction on the other side (block design). In the feature-based condition (F), attention alternated between the fields with the same and opposite motion directions both on the other side. In the S+F condition, attention alternated between the test field and the field with the opposite motion direction on the other side. In areas V1, V2, V3, V3A, V4, and MT+, the response modulation caused by changing both the attended location and the attended feature (S+F) equaled the sum of that caused by changing the attended location (S) or the attended feature (F) alone. Thus, spatial and feature-based attention mutually reinforce their effects in the earliest stages of cortical visual processing.
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