# Quantitative Classification Model of Composite Product Image Based on Event-Related Potential
## 3 Analysis of Experimental Data
### ERP Experimental Data Analysis
#### 3.2.2 Startup Phase P300  
The ERP data from 200 ms before stimulus presentation to 1000 ms after stimulus presentation were selected for analysis in the initial phase. The topographic map of the brain area is shown in Figure 4. From the figure, it can be seen that there was obvious positive activation in the occipital area and left prefrontal lobe during the period of 200-400 ms, while there was obvious negative activation in the right prefrontal lobe during the period of 300-500 ms. As shown in Figure 5, there was an apparent P300 component during the period 200-500 ms and an obvious N400 component during the period 300-600 ms, and then there was a late positive component at 600-700 ms. According to the topographic map of the brain and the overall waveform, the energy of the left frontal area gradually increased in the period of 200-300 ms, indicating the presence of P300 components. The energy of the left frontal area increased significantly in the period of 300-500 ms, and the P300 component peaked. In addition, the energy of the right frontal area decreased significantly during the 300-500 ms period, resulting in N400 components. Late components occurred after 600 s.  
For the P300 components, we selected the average amplitude of ERP during the 300-400 ms period of the start phase for RMANOVA and took the distribution positions of brain electrodes (frontal electrodes (AF3 and AF4), superior electrodes (FC5 and FC6), occipital electrodes (O1 and O2)) as the intergroup variables and three groups of image words pairs and three types of semantic matchings as intragroup variables. The results showed that the degree of semantic matching and the position of the electrodes in the brain region had a large effect on the P300 components, and the degree of semantic matching had a significant main effect, F (2, 18) = 52.962, \(p\) < 0.001. The electrode position in the brain region had a significant main effect, F (5, 92) = 21.092, \(p\) < 0.001. There was a significant interaction effect between image word pairs and semantic matching, F (10, 10) = 5.828,\(p\) = 0.005. There was an interaction effect between semantic matching degree and brain area distribution, F (10, 10) = 4.841, \(p\) = 0.01. A paired t-test was performed for the distribution position of electrodes in the brain area. It can be seen that the average amplitude was highest at electrode AF3, which is consistent with the topographic map of the ERP, as shown in Figure 6. Therefore, electrode AF3 was selected for further analysis of the P300 components.  
For each type of image-word pair in AF3, stimulus materials with different levels of degrees of semantic matching induced P300 components with different amplitudes. The average amplitude of the P300 components induced using \"tough-round\" and \"speed-steady\" was the image inconsistent > image neutral > image consistent, while the P300 components induced using \"classic-modern\" were slightly different. The result is that image consistent > image inconsistent > image neutral. Based on the paired t-test of three groups of image words with different levels of degrees of semantic matching, it can be concluded that for the average P300 amplitude induced using \"classical-modern\" word pairs, there was no significant difference between image consistent and image inconsistent, t = 1.056, \(p\) = 0.252. The average amplitude of image neutral P300 was significantly lower than that of the image consistent and image inconsistent. The conclusion for the word pair \"tough-round\" and \"speed-steady\" was similar, i.e., image inconsistent > image neutral > image consistent. A small difference was that for the word pair \"tough-round\", there was also a significant difference between image neutral and image inconsistent, t = 2.254, \(p\) = 0.036.  
Figure 4: Topographic map of a brain area in the start-up phase.  
Figure 5: Total waveform of electrode AF3.