SPATIAL SCALING OF END-STOPPED PERCEPTIVE FIELDS - DIFFERENCES IN NEURAL BASES OF END-ZONES, FLANKS AND CENTERS

Length and width spatial interactions associated with a small test lin e centered on a rectangular background were measured at 0, 5 and 10 de g retinal eccentricities. Results indicated an elongated central regio n of summation with antagonistic flanks and end-zones comparable to ea rlier results [Yu, C. & Essock, E. A. (1996). Vision Research 36, 2883 -2896]. The extent of the end-zones, flanks and centers (length and wi dth) exhibited significantly different spatial scaling, which was stee pest for the end-zones (E(2) = 0.45 deg), less steep for the flanks (E (2) = 0.77 deg) and least steep for the centers (E(2) = 2.05 deg). Per ceptive fields measured with concentric circular stimuli showed center and surround scaling equivalent to center and flank scaling, respecti vely, in line target experiments. These results suggest that: (1) psyc hophysical end-stopping and flank-inhibition reflect different underly ing cortical neural processes; and (2) the spatial interactions appare nt on the conventional Westheimer paradigm are partly governed by cort ical factors. Copyright (C) 1996 Elsevier Science Ltd.