Assessing neuronal networks: understanding Alzheimer's disease.
Findings derived from neuroimaging of the structural and functional organization of the human brain have led to the widely supported hypothesis that neuronal networks of temporally coordinated brain activity across different regional brain structures underpin cognitive function. Failure of integration within a network leads to cognitive dysfunction. The current discussion on Alzheimer's disease (AD) argues that it presents in part a disconnection syndrome. Studies using functional magnetic resonance imaging, positron emission tomography and electroencephalography demonstrate that synchronicity of brain activity is altered in AD and correlates with cognitive deficits. Moreover, recent advances in diffusion tensor imaging have made it possible to track axonal projections across the brain, revealing substantial regional impairment in fiber-tract integrity in AD. Accumulating evidence points towards a network breakdown reflecting disconnection at both the structural and functional system level. The exact relationship among these multiple mechanistic variables and their contribution to cognitive alterations and ultimately decline is yet unknown. Focused research efforts aimed at the integration of both function and structure hold great promise not only in improving our understanding of cognition but also of its characteristic progressive metamorphosis in complex chronic neurodegenerative disorders such as AD.
Bokde
Arun L W
AL
Discipline of Psychiatry, School of Medicine and Trinity College Institute of Neuroscience (TCIN), Laboratory of Neuroimaging & Biomarker Research, Trinity College Dublin, The Adelaide and Meath Hospital incorporating the National Children's Hospital (AMiNCH), Dublin 24, Ireland.
Ewers
Michael
M
Hampel
Harald
H
D000544:Alzheimer Disease / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000209:etiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D009415:Nerve Net / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D010100:Oxygen / Q000097:blood; D049268:Positron-Emission Tomography / Q000379:methods
D010100:Oxygen