Functional MRI studies of memory in healthy and memory-disordered people
2 Department of Physics, University of Kuopio
3 Department of Neurology, Kuopio University Hospital
4 Department of Clinical Radiology, Kuopio University Hospital
5 Functional Brain Research Unit, Helsinki Brain Research Center
Neuropsychological tests at the early stages of Alzheimer's disease, the most common form of dementia, typically show deterioration of long-term memory. Neuropathological concomitant of this failure to remember new facts and events is the atrophy of brain stuctures of medial temporal lobe such as the hippocampus. However, similar kind of memory problems can also be observed in normal aging, or other neurodegenerative diseases than Alzheimer's disease. Especially, differential diagnostics of normal aging, mild cognitive impairment and Alzheimer's disease, is often difficult.
Functional magnetic resonance imaging (fMRI) may reveal the dysfunction of the medial temporal lobe structures at the early stages of memory disorders before severe atrophy exists and medication can still alleviate the symptoms. fMRI combines the detailed structural MRI information with the sensitive neuropsychological tests that are visually presented to the patients during scanning. The brain areas that are needed to perform the certain memory task can then be detected as the blood-oxygen-level-dependent (BOLD) signal increases. In patients with Alzheimer's disease the BOLD signal of affected brain structures is presumably weaker or absent when compared to young subjects or to age-matched healthy controls and patients with other forms of dementia.
The aim of our research is to study the networks of brain activation areas during different memory tasks in young and elderly healthy subjects as well as different groups of memory-disordered patients. The specific focus of the study is the contribution of the separate medial temporal lobe substructures to different forms of declarative memory and the dysfunction of these structures in neurodegenerative diseases.
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