Temporal dynamics of Feature-Selective Attention
Visual selective attention critically supports perception and behaviour by prioritising the processing of relevant information. Attentional selection can be based on spatial locations, simple features (e.g. colour or orientation) or objects. In a series of experiments, we investigated the temporal dynamics of stimulus processing during cued shifts of feature-selective attention. We recorded steady-state visual evoked potentials elicited by overlapping fields of flickering random dots of different colour while participants detected infrequent target events embedded in the continuous stimulation. This technique allows for the assessment of the allocation of attention to each individual stimulus in a multi-stimulus display. Our results reveal that feature-selective attention involves separate mechanisms for enhancement of attended and suppression of unattended stimuli which have different temporal characteristics. An experiment investigating the time-course of feature-selective attention inside and outside the spatial focus of attention revealed that feature-selective attention is not spatially global from the outset, but that its effect spreads to unattended locations with a temporal delay. This finding reconciles previous contradictory results from classic event related potential (ERP) studies finding a hierarchic dependency between spatial and feature-selective attention and a wide range of more recent studies finding evidence for the independence of those two attentional mechanisms.