Researchers have said that deterioration of a small, wishbone-shaped structure deep inside the brain could help provide earliest clues to cognitive decline, long before healthy older people exhibit clinical symptoms of memory loss.
The longitudinal study found that the only discernible brain differences between normal people who later developed cognitive impairment and those who did not were changes in their fornix, an organ that carries messages to and from the hippocampus, and that has long been known to play a role in memory.
Lead author Evan Fletcher, a project scientist with the UC Davis Alzheimer's Disease Center, said that their results suggest that fornix variables are measurable brain factors that precede the earliest clinically relevant deterioration of cognitive function among cognitively normal elderly individuals.
The study found that degeneration of the fornix in relation to cognition was detectable even earlier than changes in the hippocampus.
The study was conducted over five years in a group of 102 diverse, cognitively normal people with an average age of 73.
The researchers conducted magnetic resonance imaging (MRI) studies of the participants' brains that described their volumes and integrity.
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A different type of MRI was used to determine the integrity of the myelin, the fatty coating that sheaths and protects the axons.
The researchers also conducted psychological tests and cognitive evaluations of the study participants to gauge their level of cognitive functioning.
The participants returned for updated MRIs and cognitive testing at approximately one-year intervals.
Over time about 20 percent began to show symptoms that led to diagnoses with either mild cognitive impairment (MCI) and, in a minority of cases, Alzheimer's disease.
The research has been published online in JAMA Neurology.