## 2 Method
### Analysis
#### 2.4.2 ERP  
EEG data were pre-processed using EEGLab [44]. EEG data were first downsampled to 250 Hz (each time point covering 4 ms), bandpass filtered (0.1-30 Hz) and re-referenced to average reference. The data from two electrodes (E62, E63) on the facial surface mainly for the detection of eye-movement artifacts and those near the tragus (E23, E55) were deleted from the dataset, and the data from the remaining 61 channels were entered into further analysis. The channel layout on the scalp surface is shown in Figure 1.  
Artifacts were removed from the data by performing independent component (IC) analysis. After decomposition, ICs were checked by visual inspection, and those judged to reflect blink and motion artifacts based on scalp distribution and temporal fluctuation were removed from the data, resulting in removal of on average 3.9 ICs. EEG data were epoched to \(-\)100-700 ms after stimulus onset and baseline-corrected with \(-\)100 to 0 ms as the baseline. Because the data were downsampled to 250 Hz, each epoch contained 200 time points. The trials in which EEG exceeded \(\pm\)75 \(\upmu\)V were excluded from further analysis and visually checked afterwards. After pre-processing, 69.7 trials on average were retained for further analyses. In self condition, 69.4, 71.0, 70.8 trials were retained for original, enhanced and degraded versions, whereas in familiar condition, 67.8, 69.1, and 70.3 trials for original, enhanced and degraded versions, respectively. Conventional ERP Analysis  
ERP was computed by averaging the epochs of the same condition. All the eligible trials were used for computation of ERP to increase the signal-to-noise ratio. Previous studies revealed the effect of facial familiarity on early visual components in left and right occipito-temporal regions [9; 13; 19; 20]. The mean amplitude of P100 was measured in bilateral occipital sensors (E39 for the right and E35 for the left) within 100 to 140 ms after stimulus onset. The left and right occipito-temporal clusters each included five electrode locations (E40, E42, E45, E44, E43 for the right cluster, and E27, E28, E30, E31, E32 for the left cluster) following the previous ERP studies on face processing. The following analyses were carried out for averaged ERP waveform across the five electrodes included in each cluster. The mean amplitude of N170 was measured in bilateral occipito-temporal sensor clusters within 140 to 200 ms after stimulus onset. The mean amplitude of P250 was quantified as averaged amplitude from 200 to 270 ms after stimulus onset in bilateral occipito-temporal sensor clusters. Several ERP studies on self-face recognition found the effect of self-relatedness in the long-latency positive component (LPC) [13; 45]. Thus, the average amplitude of LPC was measured as averaged amplitude from 500 to 700 ms after stimulus onset in bilateral occipito-temporal sensor clusters. The mean amplitudes were entered into an ANOVA with the within-participant factors of Hemisphere (left-right) x Identity (2) \(\times\) Version (3). The significance threshold was set to 0.05. Statistical analyses were carried out by R Analytic Flow (ef-prime Inc., Tokyo, Japan) and anovakun (retrieved from [[http://riseki.php.xdomain.jp/index.php?ANOVA%E5%90%9B](http://riseki.php.xdomain.jp/index.php?ANOVA%E5%90%9B)]([http://riseki.php.xdomain.jp/index.php?ANOVA%E5%90%9B](http://riseki.php.xdomain.jp/index.php?ANOVA%E5%90%9B)), accessed on 10 July 2021). When ANOVA revealed significant interaction, its source was examined by simple main effect analysis. Time Series Analysis by Cluster Permutation Statistics  
We searched for the temporal windows within which the conditional difference is statistically significant. ERP waveforms at occipito-temporal clusters were compared between the self and other familiar faces for original, aesthetically enhanced, and degraded versions by cluster-permutation statistics [46]. In this procedure, \(t\) value is computed at each time point by paired \(t\) test between the ERP waveforms of the two conditions (Identity; Self vs.