# Quantitative Classification Model of Composite Product Image Based on Event-Related Potential
## 3 Analysis of Experimental Data
### ERP Experimental Data Analysis
#### 3.2.4 Target Phase P300  
In the target phase, ERP data from 200 ms before stimulus presentation to 1000 ms after stimulus presentation were selected for analysis. The topographic map of the brain area is shown in Figure 8. From the figure, it can be seen that there was significant positive activation in the occipital area within 100-300 ms and significant negative activation in the apical area within 300-500 ms. The amplitude of the electrode POZ is shown in Figure 9. According to the topographic map of the brain and the overall waveform, the energy in the occipital area increased gradually during the period 100-200 ms, indicating the presence of P300 components; during the period of 200-400 ms, the energy in the occipital area increased significantly, and the P300 component peaked; in addition, the energy in the superior area decreased significantly during the period of 300-500 ms, and the N400 component peaked. The P300 component is significantly related to working memory updating, while the N400 component is related to semantic processing and semantic conflicts. The P300 component is explained here. As subjects were asked to judge the stimulus materials presented in the initial phase based on the image vocabulary, they will recall the image style corresponding to the stimulus materials presented before making a judgment, so the P300 component appears. Figure 7: N400 component waveforms of three pairs of image words at electrode F8. Green dashed rectangles mark the 350–500-ms time window. For the P300 components, the average amplitude of the ERP in the target period of 200-300 ms was selected for RMANOVA, and the distribution positions of the brain electrodes (frontal electrodes (AF3 and AF4), top electrodes (FC5 and FC6), occipital electrodes (POZ and O1)) were taken as intergroup variables, three groups of image-word pairs (classical-modern, tough-round and speed-steady) and three types of semantic matchings (image consistent, image neutral and image inconsistent) were used as within-group variables. The results show that the degree of semantic matching and the position of the electrodes in the brain region had a larger effect on the P300 components, and the degree of semantic matching had a significant main effect, F (1.954, 31.123) = 8.626, \(p\) = 0.001; the distribution position of the electrodes in the brain area had a significant main effect, F (5, 15) = 14.717, \(p\) < 0.001. There was a significant interaction between image word pairs and semantic matching, F (7, 16) = 9.838, \(p\) = 0.001; there was an interaction effect between the degree of semantic matching and the position of the electrode distribution in the brain area, F (10, 10) = 8.066, \(p\) = 0.001. The paired t-test of the electrode distribution in the brain area shows that the average amplitude at electrode POZ was the highest, while that at electrode FC5 was the lowest, which is consistent with the topographic map of the ERP, as is shown Figure 10. So the electrode POZ was selected for further analysis of the P300 components. Figure 8: Brain area topographic map at the target stage. Figure 9: Total waveform of electrode POZ. The amplitude of P300 triggered by different types of image words in the electrode POZ differed to some extent. For the \"classical-modern\" word pairs, the amplitude of P300 triggered by image neutral was the highest, followed by the amplitude of image consistent and image inconsistent. For the \"tough-round\" word pair, the amplitude of P300 triggered by image inconsistent was highest, followed by image neutral, and the amplitude of image consistent was lowest. For the word pair \"speed-steady\", the amplitude of induction from image consistent was highest, followed by image neutral, and the amplitude of induction from image inconsistent was lowest. Based on the paired t-test of three groups of image words under different degrees of semantic matching, it can be seen that the P300 waveform shows significant differences for the three groups of image word pairs.