fMRI and Voxel-based Morphometry in Detection of Early Stages of Alzheimer's Disease

Abstract

Alzheimer’s disease (AD) is the most common form of dementia in older adults. Loss of memory is the usual first symptom and different brain regions are involved to this pathological process. The aim of the study was to investigate the organization of cortical areas responsible for visual memory and determine correlation between memory impairment and atrophy of memory specific brain regions in early stages of AD. Voxel-based MR-morphometry was used to evaluate brain atrophy and functional MRI was used to detect specific brain regions responsible to visual memory task in patients with Alzheimer's disease and in control group. FMRI was performed on Siemens Magnetom Symphony (1.5 T ) with the use of Blood Oxygenation Level Dependent technique (BOLD), based on distinctions of magnetic properties of hemoglobin. For test stimuli we used blocks of 12 not related images for "Baseline" and 12 images with 6 presented before for "Active". Stimuli were presented 3 times with reduction of repeated images to 4 and 2. For functional and morthometric data post-processing we used SPM8. Patients with Alzheimer's disease showed less activation in hippocampal formation (HF) region and parahippocampal gyrus then the control group (p<0.05). The study also showed reduced activation in posterior cingulate cortex (p<0.001). Voxelbased morphometry showed significant atrophy of grey matter in Alzheimer’s disease patients, especially of both temporal lobes (fusiform and parahippocampal gyri); frontal lobes (posterior cingulate and superior frontal gyri). The study showed correlation between memory impairment and atrophy of memory specific brain regions of frontal and medial temporal lobes. Reduced activation in hippocampal formation and parahippocampal gyri, in posterior cingulate gyrus in patients with Alzheimer's disease correlates to significant atrophy of these regions, detected by voxel-based morphometry. The use of functional MRI and voxel-based morphometry provides the way to find alterations in brain function on early stages of AD before the development of significant irreversible structural damage.