Hierarchical Organization of Human Visual Feature Attention Control

Attention can be deployed in advance of visual stimuli based on features such as color or direction of motion. This anticipatory feature-based attention involves top-down neural control signals from the frontoparietal network that bias visual cortex to enhance attended information and suppress distraction. For example, anticipatory attention control can enable effective selection based on stimulus color while ignoring distracting information about stimulus motion. Anticipatory attention can also be focused more narrowly, for example, to select specific colors or motion directions that define task-relevant aspects of the stimuli. One important question that remains open is whether anticipatory attention control first biases broad feature dimensions such as color versus motion before biasing the specific feature attributes (e.g., blue vs. green). To investigate this, we recorded EEG activity during a task where human participants of either sex were cued to either attend to a motion direction (up or down) or a color (blue or green) on a trial-by-trial basis. Applying multivariate decoding approaches to the EEG alpha band activity (8-12 Hz) during attention control (cue-target interval), we observed significant decoding for both the attended dimensions (motion vs color) and specific feature attributes (up vs. down; blue vs. green). Importantly, the temporal onset of the dimension-level biasing (motion vs. color) preceded that of the attribute-level biasing (up vs. down as well as blue vs. green). These findings demonstrate that the top-down control of feature-based attention proceeds in a hierarchical fashion, first biasing the broad feature dimension, and then narrowing to the specific feature attribute. Significance Statement During voluntary feature-based attention, electrophysiological and neuroimaging studies have highlighted the role of anticipatory (top-down) biasing of the sensory cortex in enhancing the selection of attended stimulus attributes, but little is known about how this is achieved. In particular, it is not clear whether attending to an attribute such as a color (blue vs. green) or motion direction (up vs. down) first biases all neural structures coding that dimension (color/motion) before biasing the specific attribute, or if the top-down signals directly bias only the attended attribute. Using EEG and multivariate decoding, we report that top-down attention control follows a hierarchical organization: first, the broader attended feature dimension is biased, which is followed by the biasing of the specific feature attribute.