Neural mechanisms of divided feature-selective attention to colour.

Feature-based attentional selection of colour is challenging to investigate due to the multidimensional nature of colour-space. When attending concurrently to features from different feature dimensions (e.g. red and horizontal), the attentional selections of the separate dimensions are largely independent. Therefore, if colour constitutes multiple independent feature dimensions for attentional purposes, concurrently attending to two colours should be effective and independent of the specific configuration of target and distractor colours. Here, observers attended concurrently to two out of four fully overlapping random dot kinematograms of different colours, and the allocation of attention to each colour was assessed separately by recordings of steady-state visual evoked potentials. The magnitude of attention effects depended on colour proximity and was well described by a simple model which suggested that colour space is rescaled in an adaptive manner to achieve attentional selection. In conclusion, different spatially overlaid colours can be attended concurrently with an efficiency that is determined by their configuration in colour space, supporting the idea that (at least in terms of hue) colour acts as a single dimension for attentional purposes.