Studies Of Morphological Abnormality Of MCI And AD With MRI

Brain is the most complex, efficient information-processing system. The key of the brain cognition science is to investigate the physiological structure of the brain and the information-processing procedure. Brain cognition researches mainly focus on the mechanisms of cognitive activity. The cognitive functions of brain include perception, notice, memory, language, thinking, intelligence and consciousness etc. Brain cognitive disorder, behavior of mental illness, means abnormal intelligence processing of learning memory and thinking decision, which could cause severe memory impairment, aphasia and disturbance in executive functioning etc. The brain imaging technology can directly, non-invasively detect the structure and function of the brain. Especially, magnetic resonance imaging (MRI) allows researchers to investigate millimeter-sized brain activity and directly reflect the abnormal brain structure and function in cognitive impairment group. Clinically, brain imaging plays a very important role in the diagnosis and treatment of brain diseases. In the present work, MRI was used to study the differences of the brain structure with morphological analysis in normal control (NC), mild cognitive impairment (MCI) and Alzheimer’s disease (AD). The main contributions include as follows.1. Voxel-based morphometry (VBM) method was used to analyze the MRI data in NCs, MCIs and ADs. We studied the gray matter volumes of brain structure in the three groups and tried to find the abnormal cerebral structure in subjects with MCI and AD. The brain areas of significant between-groups differences mainly included parahippocampal gyrus, inferior frontal gyrus, amygdale, orbital frontal gyrus, olfactory, limbic lobe, caudate, insula, etc. From NC to MCI to AD, the gray matter in the brain monotonously decreased, which might mean MCI is the middle stage between NC and AD in the brain structural changes.2. The gray matter volumes obtained from MRI for all brain regions except the cerebellum were parcellated into 90 areas using the automated anatomical labeling (AAL) template to construct cortical networks for the three groups. The measurements of the network properties were calculated for each of the three groups respectively. The results showed that all three cortical networks exhibited small-world properties and those strong interhemispheric correlations existed between bilaterally homologous regions. Among the three cortical networks, the greatest clustering coefficient and the longest absolute path length were found in AD, which might indicate that the organization of the cortical network was the least optimal in AD. The small-world measures of the MCI network exhibited intermediate values. This finding is logical given that MCI is considered to be the transitional stage between normal aging and AD.3. The trend of cerebral structural changes was tried to investigate in MCI. At first, we measured the cortical thickness of 102 MCI subjects and the measurements were repeated three years later. After calculating the cortical thickness of the two stages in MCI, two-sample T test was used to detect the brain regions of statistically significant differences. These regions mainly included orbital frontal gyrus, olfactory, insula, parahippocampal gyrus, superior temporal gyrus, temporal pole, etc. The significant decrease of cortical thickness might be thought to be related to some recession of physiological functions, such as:memory loss, olfactory dysfunction, emotion impairment, etc.