Exploring alterations of brain networks of AD patients using WTC method

Objective: To explore the influences of different frequency bands on preprocessing of resting-state fMRI datasets used by the Wavelet Transform Coherence (WTC) method, and to study changes in the functional brain networks of AD patients. Method: Resting-state fMRI datasets of 10 AD patients and 11 healthy controls were collected in this study and time series of 90 brain regions defined by AAL (Automated Anatomical Labeling) were exacted after preprocessing. Wavelet transformation was performed for each time series, and a functional brain network were established in different frequencies (0.125Hz, 0.0625Hz) using the WTC (Wavelet Transform Coherence) method. The topology parameters of networks, containing global efficiency, clustering coefficient, average short paths length and small world property were calculated and averaged within each group. Result: The results imply that there are significant differences of topology parameters in networks of different frequencies. Likewise, statistical analysis of topology parameters of AD and HC (Healthy Controls) show that global efficiency, clustering coefficient and small world properties of AD all decreased by varying degrees, while the short path length of AD remained longer. Conclusion: Our research provides a theoretical basis for the choice of filter bands for data preprocessing in functional magnetic resonance imaging. The findings may serve as indicators for early diagnosis of AD patients.