Figure 1.

(A) Common experimental design for neurophysiological studies of attention. The outline squares are continuously present and mark the two locations at which the solid square can be flashed. (B) Example occipital ERPs recorded in a paradigm of this nature (data from ref. 42). Note that the C1 wave (generated in area V1) shows no attention effect, whereas the P1 and the N1 waves (generated in extrastriate cortex) are larger for the attended stimuli. (C) Single-unit responses from area V4 in a similar paradigm (data from ref. 23). Note that the response is larger for attended compared with ignored stimuli. (D) Single-unit responses from area V1 (data from ref. 23) showing no effect of attention.