# Predicting Architectural Space Preferences Using EEG-Based Emotion Analysis: A CNN-LSTM Approach
## 4 Data Analysis and Model Development
### ERP Component Analysis
#### 4.2.2 ERP Components (N100, N200, P300, LPP)  
We used MATLAB R2024b's EEGLAB and FastICA for preprocessing, analyzing windows from \(-0.2\) s before stimulus onset to 1.0 s after [26; 169]. This interval encompasses early sensory responses (N100 and N200), resource allocation (P300), and sustained emotional processing (LPP). To reduce noise, we applied a 40-point moving average filter. Table 13 outlines each ERP component's typical time range. Figure 9 shows the average waveforms for each ERP component, derived from the EEG signals recorded by the parietal (Pz, P3, and P4) and occipital (Oz, O1, and O2) electrodes. These waveforms illustrate the neural responses under preference and non-preference conditions. Specifically, the following points summarize the main characteristics and implications of each ERP component's waveform:  
* N100 (80-120 ms): after stimulus onset, preferred stimuli exhibit an initial negative deflection (N100) followed by a positive rebound, indicating a heightened sensory attention, whereas non-preferred stimuli show a more stable negative amplitude (see Figure 9a). * N200 (180-350 ms): preferred stimuli display a sharp positive-to-negative transition, suggesting a strong recognition of relevant stimuli, while non-preferred stimuli show a delayed negative amplitude, indicating mismatch detection (see Figure 9b). * P300 (250-500 ms): for preferred stimuli, a robust positive peak around 300 ms reflects the processing of significant stimuli, whereas non-preferred stimuli show an initial positive deflection followed by a negative shift (see Figure 9c). * LPP (300-700 ms): preferred stimuli maintain a continuous positive amplitude, signifying a high emotional engagement, while non-preferred stimuli remain at a negative level, indicating a weaker emotional processing (see Figure 9d). Collectively, these results show preferred stimuli invoke stronger responses across early sensory processing, resource allocation, and emotional evaluation, whereas non-preferred stimuli elicit relatively weaker and sometimes delayed responses. This confirms that architectural images can reliably differentiate user emotion at the neural level, offering crucial insights for future model training and affective design. To examine whether ERPs were elicited in response to architectural stimuli, paired \(t\)-tests were conducted on data collected from 40 participants, with a focus on the ERP components N100, N200, P300, and LPP. The results revealed statistically significant differences between preferred and non-preferred conditions in the early ERP components (N100 and N200). These findings suggest that early attentional responses and the detection of aversive stimuli may vary depending on the type of architectural space presented. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component** & **Time Window(s)** & **Key Domain** & **Meaning** \\ \hline N100 & 0.08–0.12 & Early sensory stage & Immediate perceptual response \\ \hline N200 & 0.18–0.35 & \begin{tabular}{c} Attention \\ shift/mismatch \\ detection \\ \end{tabular} & \begin{tabular}{c} The reallocation of \\ resources for \\ unexpected stimuli \\ \end{tabular} \\ \hline P300 & 0.25–0.50 & Cognitive evaluation & \begin{tabular}{c} Assigning \\ significance to stimuli \\ \end{tabular} \\ \hline Late positive & 0.30–0.70 & \
\begin{tabular}{c} Emotional \\ maintenance \\ \end{tabular} &
\begin{tabular}{c} Sustained emotional \\ processing or valence \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Event-related potential component analysis windows. In contrast, no significant differences were observed in the later ERP components (P300 and LPP), possibly because of the relatively short stimulus duration or individual variability. This outcome implies that late-stage cognitive and affective processing may have been less pronounced under the experimental conditions. Future studies incorporating prolonged stimulus exposure or additional environmental factors may help clarify these late ERP responses.