Effects Of Lone-term Environmental Enrichment On The Brain Structure Of APPswe/PS1dE9Mice:an MRI Study

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by progressive dementia and, neuropathologically, by the appearance of (3-amyloid plaques (Aβ) and neurofibrillary tangles. The typically early symptom of AD is difficulty in remembering newly learned information. As the disease develops over time the symptoms will get worse, and the abnormality of patient’s cognitive function will appear. Neuroimaging studies such as magnetic resonance imaging (MRI) showed hippocampal atrophy in AD brain, and demonstrated the correlation between hippocampal atrophy and cognitive decline. Currently AD has no cure. Patients with Alzheimer’s need special attendance, since he or she who suffered the disease can’t be leaved alone. Lots of family and even our aging society are at the stake of this disease. Today the causes and treatments of AD are at the forefront of medical research.Enriched environment (EE) refers to a more novel and complex environment for laboratory animals to grow up, as compared to a standard laboratory environment (SE). EE enhances of animals’sensory stimulation, and physical/social activities. EE has been shown to be a simple and effective treatment which is able to improve the intelligence, retard aging, delay the onset of neurodegenerative disorder and benefit the recovery from brain lesions. Also it has been demonstrated that, EE treatment could improve neurogenesis and neural plasticity, and increase the number of newborn neurons in the hippocampus, reduce cognitive impairment of AD transgenic animal.In this study, we aimed to investigate whether EE treatment could cause structural changes in the brain of wild type and APPswe/PS1dE9transgenic mice. High resolution anatomical image and diffusion tensor image of the brain were acquired from wild type and transgenic mice of different ages. Four approaches were used to analyze the image data. among which deformation-based morphometry (DBM) and voxel-based morphometry (VBM) were used to analyze the anatomical image data, and voxel-based analysis (VBA) and tract-based spatial statistics (TBSS) were used to analyze the diffusion tensor image data. We look into the influence on the volume of whole brain, white matter (WM), grey matter (GM), fiber microstructure in wild type and APPswe/PS1dE9transgenic mice that raised in EE. The results demonstrated that long-term EE caused enlarged CA1and CA3hippocampal subfields, and increased fractional anisotropy (FA) in the external capsule of the APPswe/PS1dE9transgenic mice (≥6months). Those consequences suggested that EE can degrade the impairment of hippocampal neurons and external capsule nerve fibers, prevent memory deficits and improve performance on the association of fronto-parietal and tempo-frontal.