# Parallel Mechanism of Spectral Feature-Enhanced Maps in EEG-Based Cognitive Workload Classification
## 3 Parallel Mechanism of Spectral Feature-Enhanced Maps
### The Structure of Parallel Mechanism
\[Min(A_{n}^{is})=Min(A_{\theta_{n}}^{1*},A_{\theta_{n}}^{2*}\cdots,A_{\theta_{n}}^{ i*}\cdots,A_{\theta_{n}}^{64*},A_{\theta_{n}}^{1*},A_{\alpha_{n}}^{2*}\cdots,A_{ \alpha_{n}}^{i*}\cdots,A_{\alpha_{n}}^{64*},A_{\beta_{n}}^{1*},A_{\beta_{n}}^{2* }\cdots,A_{\beta_{n}}^{i*}\cdots,A_{\beta_{n}}^{64*}) \tag{7}\]  
\[A^{ri}_{\ n}=\frac{A_{\alpha}^{ir}-Min(A_{\alpha}^{ir})}{Max(A_{\alpha}^{ir})- Min(A_{\alpha}^{ir})} \tag{8}\]  
\(Max\big{(}A_{n}^{i*}\big{)}\) is the maximum value of \(\theta_{n}^{*},\ \alpha_{n}^{*}\) and \(\beta_{n}^{*}\) in the No. n trail; \(Min\big{(}A_{n}^{is}\big{)}\) is minimum value of \(\theta_{n}^{*},\ \alpha_{n}^{*}\) and \(\beta_{n}^{*}\) in the No. n trail. Substituting Equation (5) into Equation (8), the final feature-enhanced equation and spectral feature-enhanced maps are obtained as follows:  
\[A^{ri}_{\ n}=\frac{(e^{Min(-0.15A_{n}^{i})}-e^{-0.15A_{n}^{i}})\cdot(1+e^{Max (-0.15A_{n}^{i})})}{(e^{Min(-0.15A_{n}^{i})}-e^{Max(-0.15A_{n}^{i})})\cdot(1+e^ {-0.15A_{n}^{i}})} \tag{9}\]  
\[\begin{array}{l}\theta_{n}^{\prime}/\alpha_{n}^{*}/\beta_{n}^{\prime}=\\ \left[\begin{array}{ \begin{table}
\begin{tabular}{c c} \hline
**Notation** & **Explanation** \\ \hline \(\theta_{n}\) & The spectral values in the frequency bands of theta (4–7 Hz) \\ \(\alpha_{n}\) & The spectral values in the frequency bands of alpha (8–13 Hz) \\ \(\beta_{n}\) & The spectral values in the frequency bands of beta (13–30 Hz) \\ \(A_{n}^{i}/A_{\theta_{n},\alpha_{n},\beta_{n}}^{i}\) & The spectral values recorded by No. \(i\) channel electrode at 4–7 Hz, 8–13 Hz and 13–30 Hz of the No. \(n\) trail \\ \(A_{n}^{i*}/A_{\theta_{n},\alpha_{n},\beta_{n}}^{i*}\) & The spectral value in No. \(i\) channel electrode at 4–7 Hz, 8–13 Hz and 13–30 Hz of the No. \(n\) trail \\ \(A_{n}^{ii}/A_{\theta_{n},\alpha_{n},\beta_{n}}^{i}\) & The final enhanced spectral value in No. \(i\) channel electrode at 4–7 Hz, 8–13 Hz and 13–30 Hz of the No. \(n\) trail processed by Equation (9) \\ \(\theta_{n}^{*}\) & The spectral values in the \(\theta\) (4–7 Hz) frequency bands processed by Equation (5) \\ \(\alpha_{n}^{*}\) & The spectral values in the \(\alpha\) (8–13 Hz) frequency bands processed by Equation (5) \\ \(\beta_{n}^{*}\) & The spectral values in the \(\beta\) (13–30 Hz) frequency bands processed by Equation (5) \\ \(Max\left(A_{n}^{i*}\right)\) & The maximum value of \(\theta_{n}^{*}\), \(\alpha_{n}^{*}\) and \(\beta_{n}^{*}\) in the No. \(n\) trail \\ \(Min\left(A_{n}^{i*}\right)\) & The minimum value of \(\theta_{n}^{*}\), \(\alpha_{n}^{*}\) and \(\beta_{n}^{*}\) in the No. \(n\) trail \\ \(\theta_{n}^{\prime}\) & The enhanced \(\theta\) (4–7 Hz) frequency bands \\ \(\alpha_{n}^{\prime}\) & The enhanced \(\alpha\) (8–13 Hz) frequency bands \\ \(\beta_{n}^{\prime}\) & The enhanced \(\beta\) (13–30 Hz) frequency bands \\ \hline \end{tabular}
\end{table} 
Table 1: The explanation of variables. Figure 4: (a) 3D image of the \(\theta\) channel; (b) 3D image of the feature-enhanced \(\theta^{\prime}\) channel; (c) 3D image of the \(\alpha\) channel; (d) 3D image of the feature-enhanced \(\alpha\)’ channel; (e) 3D image of the \(\beta\) channel; (f) 3D image of the feature-enhanced \(\beta\)’ channel.