Zooming In and Out: Selective Attention Modulates Color Signals in Early Visual Cortex for Narrow and Broad Ranges of Task-Relevant Features

Research on feature-based attention has shown that selecting a specific visual feature (e.g., the color red) results in enhanced processing in early visual cortex, providing the neural basis for the efficient identification of relevant features in many everyday tasks. However, many situations require the selection of entire feature ranges instead of just a single feature value, and recent accounts have proposed that broadly tuned attentional templates are often critical for guiding selection in cluttered visual scenes. To assess the neural implementation of such broad tuning of feature-based attention, we here recorded frequency-tagged potentials in human observers (male and female) while participants attended to narrow or broad ranges of colors of spatially intermingled dot fields. Our results show clear increases in the signal strength for the attended colors relative to unattended colors for both narrow and broad color ranges, though this increase was reduced for the broad-range condition, suggesting that limits in the breadth of attentional tuning arise at early processing stages. Overall, the present findings indicate that feature-selective attention can amplify multiple contiguous color values in early visual cortex, shedding light onto the neural mechanisms underlying broad search templates. More generally, they illustrate how feature-based attention can dynamically "zoom in" and "zoom out" in feature space, mirroring models of spatial attention.