Abstract: Behavior research evidence has shown that people with a negative physical self have a cognitive bias with a longer reaction time to body information than to neutral information. Chen (2005) indicated that participants with a fat negative physical self have a cognitive preference and selectively perceived body information; however, the underlying mechanism of this phenomenon has not been discussed further. Therefore, the aim of this study is to reveal the brain mechanism of negative physical self by using the event-related potential (ERP) technique.
ERPs were recorded to examine the electrophysiologic correlates of the recognition of body pictures. After completing the Negative Physical Self Scale (NPSS), based on their scores on the NPSS-Fat, 28 participants were assigned to the control group (14 normal females) or experimental group (14 females with a negative physical self). During phase one, 288 pictures were presented to the participants. The participants were asked to respond when the target picture appeared. Phase two involved the random presentation of 576 pictures, which consisted of the 288 pictures already presented in phase one and 288 new ones. The participants were requested to judge whether or not the pictures had appeared in phase one. According to the participants’ responses, the electroencephalography (EEG) of the responses to “fat pictures,” “thin pictures,” and “neutral pictures” was separately overlapped. The averaged epoch for an ERP was 1200 ms including an epoch of 200 ms for the pre-answer baseline.
ERP waveforms of both groups showed that both fat pictures and thin pictures elicited a more positive ERP deflection than did neutral pictures in the time interval of 250~1000 ms. Moreover, we found that the fat pictures elicited a more positive ERP deflection than did the thin pictures in the time interval of 750~800 ms only in the experimental group. A voltage map of the difference wave of the fat and thin pictures showed strong activity in the central frontal region. The dipole analysis (brain electrical source analysis (BESA) software) localized the generator of the difference wave (fat pictures minus thin pictures) in the right occipital lobe.
In the current study, it is indicated that the difference wave of the fat and thin pictures mainly activated the right inferior occipital gyrus, which was consistent with Uddin et al.’s (2005) functional magnetic resonance imaging (fMRI) findings that the same brain region was activated by images of one’s own face. A possible interpretation might be that body information may have activated physical self-schema in participants with a negative physical self, which might be reflected by the activation of the right inferior occipital gyrus

Key words: self schemata, negative physical self, event-related potentials, LPC