Estimation of brain activity for perception of aperture problem

Abstract

Aperture problem is a psychological experiment for analyzing binding mechanism of the spatial recognition in an early stage of visual pathway. In this paper, we measure perceptual rate in the aperture experiments, and discuss the dependency between the perception and various parameters in the experiments. We also record Electroencephalograms(EEG) of subjects who are recognizing the perception. By the elec- troencephalograms(EEG) analysis, we measure reaction latency of visual evoked potential (VEP) and event related potential(ERP) related to visual pathway, and estimate the localized equivalent current dipole(ECD) in the visual pathway. I. INTRODUCTION Aperture problem (1)-(7) is a psychological experiment to analyze binding mechanism of the spatial recognition. A circular aperture that a base bar moves in the background first is displayed at a central coordinate position of a computer display. While the base bar moves to the top right corner orientation from the the lower left side as the starting point, two other circles that a flanking bar moves in the background appear at both ends of the center circle. The flanking bar, however, moves to the upper orientation from the lower side. If a subject perceived that the line joining the base bar and the flanking bar is straight, his/her recognition for orientation of the base bar's movement would be dragged with the flanking bar's movement. The subject would so perceive that the base bar's movement was changed the same upper vertical orientation as the flanking bar. We call the phenomenon per- ception. How will we perceive influence from neighboring other apertures and we depend on an experimental parameters for moving lines? Nishina et al. (2) have already discussed that the perception strongly depends on radius, distance between circles and time scale for displaying the flanking bar (shortly, the display time) by binding mechanism. In human early visual pathway, a binding mechanism performs an important function. In this paper, we affirms Nishina's results and discussed the dependence of the perceptual rate on the display time (5), (6). However, we have simultaneously noticed that the perception rate rather decreases at the display time later than 550ms. We discussed so the dependence of the perceptual rate on the display time by the visual measurement analysis, and in addition we here estimate the localized equivalent current dipole(ECD) in the visual pathway by the electroen- cephalograms(EEG) analysis (8). By two kinds of analyses, we can discuss which localization of the brain relates to the perception, and what mechanism causes the perception in the aperture problem. In the visual measurement analysis, the perceptual recognition rate is calculated with changing radius, distance between circles, display time, and speed of bar. We particularly discuss the influence of the speed of bar to the perceptual rate. Meanwhile, we argue that subjects tend to fail to recognize the perception on the long display time. We then discuss the dependence of the perceptual rate on the speed of bar by trend analysis. In EEG analysis (9)- (11), we measure the visual evoked potential(VEP) and event related potential(ERP) of the perception in order to estimate the localization of the brain activity area with changing radius, distance between circles, display time, and speed of bar. Then, we discuss the relationship between the latency of VEP and ERP by the perception and the localized equivalent current dipole(ECD) in the visual pathway. At the last, we presume which part of the brain relates to VEP and ERP for the perception, and what mechanism causes the perception.