An event-related brain potential study of visual selective attention to conjunctions of color and shape

What cognitive processes underlie event-related brain potential (ERP) effec ts related to visual multidimensional selective attention and how are these processes organized? We recorded ERPs when participants attended to one co njunction of color, global shape and local shape and ignored other conjunct ions of these attributes in three discriminability conditions. Attending to color and shape produced three ERP effects: frontal selection positivity ( FSP), central negativity (N2b), and posterior selection negativity (SN). Th e results suggested that the processes underlying SN and N2b perform indepe ndent within-dimension selections, whereas the process underlying the FSP p erforms hierarchical between-dimension selections. At posterior electrodes, manipulation of discriminability changed the ERPs to the relevant but not to the irrelevant stimuli, suggesting that the SN does not concern the sele ction process itself but rather a cognitive process initiated after selecti on is finished. Other findings suggested that selection of multiple visual attributes occurs in parallel.