## 6 Performance and Discussion  
### ROI Selection and Its Importance  
Table 4 presents the clinical ROIs found on \(t\)-test group comparison between participating class domains; it lists the important brain regions identified using AAL matching. There were majorly six clusters to distinguish the voxel intensities, with Left Temporal Inferior Lobe, both Right and left Thalamus, left and right Amygdala, left Fusiform, left Insula, and right Hippocamp being the prominent ones for CN versus AD, at \(p<0.001\), whereas left and right Hippocamp, Temporal mid lobe, right Parahippocampal region were highlighted as dense cluster for CN versus MCI. Details of all the clusters and numbers of voxel detected are presented in Supplementary files. The ROIs identified using ADNI datasets are clearer and larger whereas GARD datasets are smaller and dimmer, (please see Figures 4 and 5) which may be due to the difference of MRI acquisition protocol [41], still the regions like the hippocampus, Amygdala, Temporal lobe, Thalamus are commonly deteriorated during AD/ADD and MCI/mAD (please see Tables 2 and 3, the T-value measures the size of the difference relative to the variation in the group data. A higher T-value supports our null hypothesis of group difference condition. SD of T represents the standard deviation measure of T-value and mean-T, the mean value of all T-values for voxels in its cluster). As it is believed that the loss of memory is mostly related to the limbic system including its subcortical structures like Hippocamp, Amygdala, more prominent in the left hemisphere [42]. However various cortical structures including frontal, Parietal, Temporal lobes are also affected during neurodegeneration [43; 44]. Hence, it is wise to state that overall brain structures associated with memory are affected during the AD memory dysfunction phase.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Region from ROI\_CL**} & \multirow{2}{*}{**\# of Voxels**} & \multirow{2}{*}{**Mean T**} & \multirow{2}{*}{**\# of Cluster**} & \multicolumn{1}{c}{**Selected Region for ROI**} \\  & & & & \multicolumn{1}{c}{**-AAL (Alphabetically)**} \\ \hline
**Insula\_L** & 508 & 3.5646 & 1 & **Amygdala\_L** \\ \hline
**Amygdala\_L** & 256 & 7.602 & 1 & **Amygdala\_R** \\ \hline
**Amygdala\_R** & 329 & 6.5708 & 2 & **Fusiform\_L** \\ \hline
**ParaHippocampal\_R** & 138 & 6.9469 & 2 & **Hippocampus\_L** \\ \hline
**Hippocampus\_R** & 60 & 7.6221 & 2 & **Hippocampus\_R** \\ \hline Olfactory\_R & 46 & 3.8332 & 2 & **Insula\_L** \\ \hline Temporal\_Pole\_Sup\_R & 30 & 5.5589 & 2 & **ParaHippocampal\_L** \\ \hline
**Thalamus\_R** & 1020 & 5.2492 & 3 & **ParaHippocampal\_R** \\ \hline
**Thalamus\_L** & 981 & 4.4001 & 3 & **Temporal\_Inf\_L** \\ \hline Hippocamp\_L & 13 & 6.2737 & 4 & **Temporal\_Inf\_R** \\ \hline
**Temporal\_Inf\_L** & 1148 & 4.6223 & 6 & **Temporal\_Mid\_R** \\ \hline
**Fusiform\_L** & 490 & 3.9798 & 6 & **Temporal\_Pole\_Sup\_L** \\ \hline
**Temporal\_Mid\_L** & 405 & 4.2446 & 6 & **Thalamus\_L** \\ \hline
**Temporal\_Inf\_R** & 440 & 4.3544 & 7 & **Thalamus\_R** \\ \hline Temporal\_Mid\_R & 238 & 4.7228 & 7 & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Voxel values for each AAL anatomic region from each cohort \(t\)-test of ADNI dataset for ROI_AAL selection. Bold represents the area from ROI_CL selected for ROI_AAL.