PERCEPTUAL RANKING VERSUS VISUAL-EVOKED POTENTIALS FOR DIFFERENT LOCAL FEATURES IN TEXTURE SEGREGATION

Purpose. To validate recent reports of specific visual evoked potentia ls associated with preattentive texture segregation (tsVEPs) and to qu antitatively compare perceptual segregation strength and tsVEP amplitu des across different local features. Methods. Four local features were selected: crossed vs noncrossed, line segments differing in orientati on by 90-degrees, U-shapes differing in orientation by 90-degrees, and U-shapes differing in orientation by 180-degrees. The two variants of each local feature were spatially arranged in a checkerboard pattern; for the first three features this led to pop-out of a ''preattentive checkerboard.'' In seven subjects, perceptual segregation strength was assessed using ranking, and tsVEPs were recorded in these and three a dditional subjects. Results. Statistically significant tsVEPs were obt ained for the features crossed vs noncrossed and 90-degrees-line segme nts. Ranking results and tsVEP amplitudes were highly correlated (P < 0.001); the order of perceptual ranking and the order of tsVEP amplitu des were identical; 180-degrees-U-shapes had lowest ranking, mean tsVE P amplitude was 0.1 muV, close to noise. Line segments had maximal ran king, tsVEP amplitude was 1.5 muV. Conclusions. The results suggest th at tsVEPs quantitatively reflect the activity of cortical mechanisms i nvolved in texture segregation across various local features.