Human feature-based attention comprises two spatio-temporally distinct processes

Human feature-based attention comprises two spatio-temporally distinct processes D Gledhill¹, C Grimsen², M Fahle³, D Wegener⁴
¹Clinical Psychology and Rehabilitation, University of Bremen, Germany ²Institute for Human-Neurobiology, University of Bremen, Germany ³ZKW, University of Bremen, Germany ⁴Brain Research Institute, University of Bremen, Germany Contact: d.gledhill@uni-bremen.de
Feature-based attention (FBA) represents the orienting of attention towards a specific stimulus feature and facilitates its processing throughout the visual field. Current hypotheses on the neuronal mechanisms underlying FBA include the feature-similarity gain model by which FBA selectively enhances the response of neurons representing specific feature attributes (as e.g. ‘red’ or ‘moving upward’), and the dimensional weighting account, which proposes attention-dependent weighting of the task-relevant dimension (e.g. colour or motion). Both hypotheses have gained experimental support, but they contradict each other regarding the representation of non-attended feature attributes within the attended feature dimension. We investigated this issue by recording event-related potentials (ERPs) during performance of a complex delayed-match-to-sample task. Our findings clearly indicate that in the human brain, FBA in fact consists of two processes, one specific for the feature attribute, and another one specific for its dimension. ERPs of both FBA processes showed spatially independent attentional modulations particularly about 150 – 200 ms following stimulus onset and were characterized by distinct spatiotemporal activation patterns. Dimension-specific effects first emerged over frontal electrodes and then spreaded towards parieto-occipital electrodes. Attribute-specific effects developed on top of these dimension-specific effects, but were restricted to parieto-occipital electrodes.

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