台大心理系

Visual attention spreads over a range around the focus as the spotlight metaphor describes. Spatial spread and local selection/inhibition are crucial factors determining the profile of the spatial attention. They are opposite effects of attention, enhancement and ignorance/suppression, and appeared to be mutually exclusive. Yet, no unified view of the factors has been provided despite their necessity for understanding the functions of spatial attention. This report provides electroencephalographic and behavioral evidence for the attentional spread at an early stage and selection/inhibition at a later stage of visual processing. Steady state visual evoked potential showed broad spatial tuning whereas the P3 component of the event related potential showed local selection or inhibition of the adjacent areas. Based on these results, we propose a two-stage model of spatial attention with broad spread at an early stage and local selection at a later stage.