## 4 Experiment and Results
### Exp. #3: Channel Selection for Emotion Classification  
Research has shown that emotions, and their related brain signals, are associated with the frontal lobe of the cerebral cortex; therefore, the frontal EEG electrodes were often used in the emotion classification research. In this experiment, the effect of channel selection on the recognition rate of the emotion classification system is assessed. The selection of eight and 14 channels is in accordance with our previous work [3]. The reduced eight channels were selected because they are positioned on the frontal and the near frontal area of the cerebral cortex (frontal parietal and anterior-frontal), while the reduced 14 channels were chosen in accordance with the channels available in the BCI Emotiv device. The channel descriptions and the results of this experiment are depicted in Table 4. BPNN was used for the classifier, and the experiment was repeated five times.  
Table 4 shows the recognition rate of the reduced eight and 14 channels compared to the recognition rate of the full 32 channels. One-way ANOVA was used to compare the recognition rate of using the complete and the reduced number of EEG channels. The \(p\)-value of the combined arousal and valence recognition rate was \(p\) = 0.3 (\(p\) > 0.05), while for the arousal emotion recognition rate, \(p\) = 0.485 (\(p\) > 0.05), and for the valence emotion recognition rate, \(p\) = 0.548 (\(p\) > 0.05); this finding shows that the reduced eight and 14 channels did not significantly differ from that of the complete 32 channels. This experiment showed that the 14 channels in the BCI equipment are sufficient to conduct emotion classification, with only slight differences compared to that of the 32 EEG channels. However, this experiment ignored the possibility that the signal quality of the BCI equipment might be lower than that of the medical-grade EEG. This experiment also shows that when the research calls for fewer electrodes to reduce the complexity and computation cost, the use of eight electrodes from the frontal, frontal parietal and anterior-frontal regions would be sufficient.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **\(\boldsymbol{\Sigma}\)** \\ **Channel** \\ \end{tabular} } & \multirow{2}{*}{**Channel Name**} & \multirow{2}{*}{**Description**} & \multicolumn{2}{c}{**Maximum Recognition Rate 1**} & \multicolumn{2}{c}{**Mean \(\pm\) SD Recognition Rate**} \\ \cline{4-7}  & & & & **Arousal (\%)** & **Valence (\%)** & **Arousal (\%)** & **Valence (\%)** \\ \hline \multirow{2}{*}{8} & F3, F4, F7, F8, F9, F1, F52, & Frontal + Frontal Parietal & \multirow{2}{*}{74.45} & \multirow{2}{*}{74.06} & \multirow{2}{*}{73.38 \(\pm\) 1.93} & \multirow{2}{*}{73.52 \(\pm\) 1.13} \\  & AF3, AF4 & & & & & \\ \hline \multirow{2}{*}{14} & AF3, F3, F7, FC5, T7, P7, O1, & \multirow{2}{*}{BCI channel} & \multirow{2}{*}{75.94} & \multirow{2}{*}{76.02} & \multirow{2}{*}{74.81 \(\pm\) 0.71} & \multirow{2}{*}{75.00 \(\pm\) 0.82} \\  & AF4, F4, F8, FC6, T8, P8, O2 & & & & & \\ \hline \multirow{2}{*}{32} & all channels & DEAP EEG channel & \multirow{2}{*}{74.22} & \multirow{2}{*}{77.58} & \multirow{2}{*}{72.83 \(\pm\) 4.04} & \multirow{2}{*}{70.95 \(\pm\) 9.86} \\ \hline \hline \end{tabular}  
* Shown is the maximum recognition rate from 5 repeated experiments.  
\end{table}
Table 4: Channel selection and description.