A team of researchers led by Paul Thompson, an associate professor of neurology at UCLA, has used a novel three-dimensional neuroimaging technique to compare the volumes of hippocampi of patients with Alzheimer’s Disease to those of patients with mild cognitive impairment (MCI).
In the study, published recently in the neurology journal Brain, the researchers report that the pattern of cell death in the CA1, CA2 and CA3 regions of the hippocampus closely follows that of the dissemination of neurofibrillary tangles, a characteristic pathology of the condition. The hippocampus, which is on the medial (inner) surface of the temporal lobe, is involved in memory, a cognitive function that is severely affected in Alzheimer’s.
The authors of the study conclude that hippocampal volume is an accurate predictor of clinical diagnosis of Alzheimer’s, and can be used to track the progression of the disease. This should be extremely useful in the clinical setting, as MCI always precedes the onset of Alzheimer’s (but not all patients with MCI develop Alzheimer’s).
The above animation, from an earlier study by the same team, shows the progressive loss of gray matter over a one-and-a-half-year period in Alzheimer’s patients. Gray matter contains neuronal cell bodies, whereas white matter consists largely of nerve fibres, which are insulated by a fatty substance called myelin. This fatty is not continuous along the length of the nerve fibre: there are unmyelinated regions called Nodes of Ranvier at regular intervals along the axon. These increase the conduction velocity of nervous impulses, which ‘jump’ from one node to the next, in a process called saltatory conduction. Polio is a virus which damages myelin, affecting the ability of nerve fibres to propagate electrical signals.
- Tracking Alzheimer’s Disease, a review by Thompson’s team, to be published in PNAS later this year.