# White Matter Network Alterations in Alzheimer's Disease Patients
## 7 Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**AAL**} & \multicolumn{2}{c}{**HC**} & \multicolumn{2}{c}{**MCI**} & \multirow{2}{*}{
\begin{tabular}{c} **\(p\)-Value** \\ **(<0.05)** \\ \end{tabular} } \\ \cline{2-2} \cline{5-6}  & **Mean** & **SD** & **Mean** & **SD** & **t** & **(<0.05)** \\ \hline Supp\_Motor\_Area\_L & 0.0412272 & 0.0020638 & 0.02617364 & 0.0018140 & 1.13384828 & 0.26328876 \\ \hline Putamen\_L & 0.0819758 & 0.0014046 & 0.0678216 & 0.0019687 & 1.14306843 & 0.25964103 \\ \hline Pallidum\_L & 0.0511135 & 0.0045694 & 0.08446744 & 0.0038844 & \(-\)1.7014911 & 0.09624379 \\ \hline Temporal\_Pole\_Sup\_R & 0.0824825 & 0.0019001 & 0.06551453 & 0.0022605 & 1.23383964 & 0.11206136 \\ \hline Frontal\_Sup\_R & 0.0726996 & 0.0020407 & 0.06041580 & 0.0019387 & 0.91334624 & 0.18313697 \\ \hline Temporal\_Sup\_R & 0.0998498 & 0.0015746 & 0.09650786 & 0.0014116 & 0.28684311 & 0.77564282 \\ \hline Precentral\_R & 0.1054495 & 0.0007850 & 0.09427731 & 0.0021882 & 0.96102214 & 0.34332614 \\ \hline Postcentral\_R & 0.0703458 & 0.0035513 & 0.05592594 & 0.0030042 & 0.83535202 & 0.40824652 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Region-of-interest-based clustering coefficient changes between HC and MCI. concentrated in precentral and postcentral gyrus, hippocampus, insula, temporal pole: superior temporal gyrus, median cingulate and para cingulate gyri, supplementary motor area, cerebellum and precneus. However, majority of alterations occurred within the network associated with limbic lobe and central and medial surfaces of AD patients. In our study, disruption of connection from hippocampus of limbic system to other region supports the need to establish the hypothesis that WM would be altered at the network level and, more specifically, regarding the connections associated with the processing of short-term memories into long-term memories [41]. In addition, we found supplementary motor area (SMA) was the only region that was affected in left and right hemisphere of the brain. The SMA is also known as Brodmann area 6, which is situated medially between primary motor cortex and medial-to-premotor cortex [42]. SMA is involved in planning of learned complex movements and in coordinating movements involving both hands and learning new motor sequences. The altered network with this region suggests either a failing motor planning system of learned movement or alternative strategy for enforcing motor response. Similarly, this study found altered connection in the parietal and temporal lobe. We overserved disruption in network associated with superior parietal gyrus and inferior parietal lobule. These regions are mainly responsible for the interpretation of sensory information, language, mathematical operations, and body image. Damage or stimulation of network in these regions can result in difficulty in processing language, undertaking mathematical operations and processing sensory information. Additionally, our study found alterations within the cerebellum network. Cerebellum system is well known for receiving information from various sensory systems, spinal cord and other parts of brain and then regulating movement. Recent clinical and neuroimaging studies reveal the involvement of cerebellum in modulation of cognition and emotion [43]. Compared to network alterations in AD versus HC, we found fewer alterations in HC versus MCI with only three edges. The altered network includes frontal, limbic, medial, central and subcortical gyri nuclei. Majority of alterations are occurred in subcortical gyri and central region. These areas are more involved in emotion and formation of memory. Additionally, we performed an integrated analysis of WM alteration using NBS and graph theoretical analysis. The detailed investigation show changes in clustering coefficient in different regions.