Check if any spelling and grammar errors and descriptions that can be improved in the following paragraphs from the perspective of academic papers, and rewrite them in a more professional, refined and academic way: 
Although Alzheimer’s Disease (AD) is irreversible, detecting it as early as possible (e.g., at its prodromal stage, early Mild Cognitive Impairment (eMCI)) is of great clinical importance to delay their progression. The associations between Brain Functional Connectivity (BFC) and neurodegenerative diseases have been well established, and many recent early MCI detection studies have focused on mining early brain functional changes from subjects’ BFC networks/graphs. However, few attentions have been paid on the structural information of BFC graphs for subject group classification. Due to the indistinct early symptoms and heterogeneous properties of MCI, it is worthwhile exploring the multi-granularity graph structural characteristics for early MCI identification. In this work, we investigate the potential of metric-based graph similarity learning for the task based purely on fMRI image data. A novel graph neural network named Cross Attention-based Graph Neural Network (CA-GNN) is  proposed to measure the similarity between pairwise BFC graphs with explicitly considering both their local structures and global structures. In particular, CA-GNN generates an attention mask for each of the pairwise global structure-aware representations to enhance the comparative and critical regional features in them bas Your entire response should be in English, and in all capital letters.
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