# Effect of Subject-Specific Region of Interest on Motor Imagery Brain-Computer Interface
## 3 Results and Analysis
### Neurophysiological Properties of Motor Imagery Movements  
The neurophysiological properties of EEG for Subject 3 are shown in Figure 7. The topographic map was used to evaluate the physiologically plausible results of the recorded EEG and the dissimilarity at different frequencies: alpha of 8 Hz to 12 Hz, and beta of 14 Hz to 28 Hz. The data behavior at specific frequency bands was computed using the coefficient of determination (color coded \(\mathbf{r}^{2}\)) as a function of electrode location, as in [14]. Figure 7a shows the \(\mathbf{r}^{2}\) topography map for the specific frequency component of the right-hand motor imagery compared to the rest state, correlated with the right side of the sensorimotor cortex (C3). Figure 7b displays the topographical distribution of the motor imagery tasks for the left hand; the expected spatial response for the left-hand motor imagery movement agrees with the spatial distribution for all subjects. In Figure 7c, a high \(\mathbf{r}^{2}\) value indicates a region in a specific frequency band that was activated differentially between the imaginations of both hands and the rest state for both hands. Figure 7d displays the \(\mathbf{r}^{2}\) topography for both feet motor imagery compared to the rest condition; additionally, the high \(\mathbf{r}^{2}\) value correlated with a specific frequency in feet area (Cz). It was found that the topographies of \(\mathbf{r}^{2}\) significantly discriminate between the two motor imagery conditions and were clearly restricted to the sensorimotor cortical areas involved. The Rolandic beta and mu rhythms in the human brain were observed in sensorimotor areas with frequency bands between 10 Hz and 20 Hz [15]. These frequency bands show typical responses associated with the subject's movement and motor imagery [16; 17; 18]. The topography of the frequencies  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Subject** & & **Left Hand** & **Right Hand** & **Both Hands** & **Both Feet** \\ \hline \multirow{4}{*}{Subject 1} & & Accuracy \% & 86.25\% & 91.46\% & 98.12\% & 91.45\% \\  & ITD & Sensitivity \% & 84.58\% & 91.66\% & 98.33\% & 90.00\% \\  & with ROI & Specificity \% & 87.91\% & 91.45\% & 97.91\% & 92.91\% \\  & AUC \% & 92.99\% & 97.19\% & 99.64\% & 97.20\% \\ \cline{2-6}  & & Accuracy \% & 75.00\% & 79.79\% & 80.21\% & 78.12\% \\  & ITD without & Sensitivity \% & 75.00\% & 81.66\% & 79.58\% & 74.16\% \\  & ROI & Specificity \% & 75.00\% & 77.91\% & 80.83\% & 82.08\% \\  & AUC \% & 81.91\% & 87.03\% & 88.08\% & 83.87\% \\ \hline \multirow{4}{*}{Subject 2} & & Accuracy \% & 96.66\% & 87.29\% & 90.83\% & 90.00\% \\  & Sensitivity \% & 96.66\% & 90.41\% & 91.66\% & 91.66\% \\  & Specificity \% & 96.66\% & 84.16\% & 90.00\% & 88.33\% \\  & AUC \% & 99.16\% & 94.01\% & 96.80\% & 96.02\% \\ \cline{2-6}  & & Accuracy \% & 78.75\% & 73.33\% & 72.50\% & 71.66\% \\  & ITD without & Sensitivity \% & 79.58\% & 73.33\% & 71.25\% & 71.66\% \\  & ROI & Specificity \% & 77.91\% & 73.33\% & 73.75\% & 71.66\% \\  & AUC \% & 87.53\% & 79.29\% & 80.37\% & 80.63\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Subjects’ performance using ITD with and without ROI.  
Figure 6: ROC’s of ITD for Subject 2: (**a**) without ROI and (**b**) with ROI estimation.  
associated with maximum control in the mu and beta bands were found. The locations line up with the expected sites of the peri-rolandic sensorimotor cortex. Thus, a clear and locally restricted spectrum of the channels for which participants had maximum control (i.e., the largest values of the correlation between channel location and the EEG feature) was observed. The results of this work support the notion that hand/foot motor imagery activates neural networks in the cortical hand/foot areas, which were displayed here as the blocking of mu and beta rhythms in the contralateral hand/foot areas; previous studies in [16; 17] also showed similar findings. Topography maps for subjects 3 to 13 are shown in Supplementary Figure S2.