ERP studies of selective attention to non-spatial features

ABSTRACT This paper concentrates on electrophysiological data concerning selective attention to nonspatial attributes (spatial frequency, color, shape, orientation, etc.), and the way these attributes are combined into a unified percept, so that it becomes identified as an object. Feature-based and object-based mechanisms of the brain as investigated with ERPs are analyzed. An overview is provided of studies reporting the differ- ential activation of two cortical subsystems of the visual brain, the so-called dorsal, or "Where," and ventral, or "What" systems, in conditions in which stimulus attributes must be selectively attended to separately and/or conjointly. Efforts are made to demonstrate the task-related rel- ative segregation and complex interactions of the aforementioned systems during the separate or con- joint processing of stimulus attributes.