事象関連電位によるデルブーフ錯視の検討 : 対比過程における脳の応答について

概要

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We examined the event-related potentials (ERPs) under the condition that eight observers compared a single circle (comparison stimulus; visual angle: 1.0°) to inner circle of a concentric circle (Delboeuf illusion figure; standard stimulus) and responded to apparent size of the single circle as large or small by a key pressing. The constant method was used, and the outer circle was prepared for five kinds of diameter, constructing 3/2 (1.0°/0.67°, 1.5°/1.0°), 6/2(3.0°/1.0°), 12/2 (6.0°/1.0°), 18/2 (9.0°/1.0°) outer/inner ratios. The ERPs were obtained at four scalp sites of Fz, Cz, Pz, and Oz. The comparison stimulus was underestimated for the ratio of 3/2 and overestimated for 12/2 and 18/2, showing a transition process from assimilation to contrast. Although several components of the ERPs were emerged under the observation of Delboeuf illusion, only P2 amplitudes at Cz and Pz were proportionally changed in response to the psychometric function produced by the behavioral data. It is suggested that the P2 amplitude may covary with the transition process from assimilation to contrast when observers investigate Delboeuf figure Functional importance of the P2 amplitude is discussed along with the previous findings and the present results.
2010-03-15