N1 component of event-related potential evoked by simple composite figures in the lateral occipital cortex

Since Sugawara and Morotomi (1991) first reported that illusory contour (IC) figures, or Kanizsa square inducers (KSI), evoked a significant N1 component, the first visually evoked negative component of event-related potentials (ERPs), in the lateral occipital cortex (LO), many ERP studies have confirmed their finding, and these studies showed that Kanizsa-type inducers alone evoked a relatively large N1 in the LO, even when the inducers are oriented to not form an IC (see Murray and Herrmann, 2013). In the present study, we used non-IC simple composite figures composed of several elementary shapes (e.g., triplet squares or quadruplet circles) as visual stimuli, and found that the composite figures evoked a significant N1 comparable to that evoked by KSI in the anterior LO, whereas solitary elementary shapes did not. Thus, it appears that the LO is activated by not only an IC but also the compositeness of figures, which implies that the LO might analyze the geometrical relationships among multiple 2D shapes that compose a single composite figure.