3.5.4 Topographic Analysis 
To assess potential differences in the topographic distributions of the two adaptation effects and infer distinct underlying neural sources (Michel & Murray, 2012), a topographic analysis of variance (TANOVA) was conducted using RAGU (Koenig et al., 2011). This analysis compared individual N1 initial adaptation (peak amplitudes of deviants–peak amplitudes of the 2nd tones) and P2 subsequent adaptation (peak amplitudes of the 2nd tones–peak amplitude of final tones in the 4th to 30th positions) with 5,000 randomization runs. The scalp topographies for N1 initial adaptation and P2 subsequent adaptation, normalized for strength (GFP = 1), were examined (see Figure 6; for the scalp topographies for N1 subsequent adaptation and P2 initial adaptation, see Figure S2 in Supplementary Material II).
The results indicated a significant difference in the topographic maps of N1 initial adaptation and P2 subsequent adaptation (P < .05), suggesting disparate topographic distributions and underlying sources for these two adaptation effects. Specifically, the gradients of the N1 initial adaptation effect exhibited a steep incline over left superior temporal regions, while the gradients of the P2 subsequent adaptation effect were steepest over bilateral frontal regions. These findings align with the notion of initial adaptation occurring in auditory cortex regions and the model reestablishment effect in bilateral frontal regions.