Abstract
Following the studies of Ito et al. (1993, 1995), in which equilateral triangle elicited larger N1 responses compared to square and circle, we compared the effects of partial forms of triangle and circle, in order to understand the roles of three angular parts of triangle. Two groups of sharp or round figures were tachistoscopically presented to the lower visual field for eight subjects. One consisted of an equilateral triangle and its three sharp parts, the other of a circle and its three round parts. Transient VEPs were obtained monopolarly at five locations around occipital area. Subtracted waves between figure and control (blank) conditions were computed and analyzed. As a main result, any three sharp parts of triangle elicited significantly larger N1 amplitudes than did the corresponding round parts of circle, while the triangle was of a significantly larger N1 amplitude than the circle. Thus, the increase of the N1 response for equilateral triangle as compared to circle could be attributable to the N1 increases for all the three acute-angled parts of triangle.
