Why Do We Lose Memory with the Aging?

"You're getting old! You're getting old!". They chase you for each mistake involving recalling. And the truth is that indeed elders have troubles with the memory, from recalling a name to what they ate 5 minutes ago. And we're talking about healthy old persons, not experiencing Alzheimer's or other forms of dementia, or memory/cognitive abilities impairing capacities.

Now, a new research, published in the journal "Neuron", sheds light on this nasty issue: it could be caused by the loss of synapses (connections) between the brain cells.

The team led by Harvard neuroscientists, Jessica Andrews-Hanna and Randy Buckner, employed functional magnetic resonance imaging (fMRI) in order to investigate brain activity in 38 young adults, all in their 20's, and 55 elders, aged 60 or older.

The team looked at a network of brain nuclei that are active when the brain is not focused on any particular action. The fMRI images showed coordinated activity in the default network of the young people, like two brain nuclei of the network, which were turned on at the same time, even if one was frontal and the other one was at the back of the brain.

Thus, in elders brain activity was weakly coordinated. The team also checked the older persons for the presence of Alzheimer's, through a positron emission tomography (PET) scan that detects brain amyloid proteins connected to Alzheimer's.

"The PET scans were negative, suggesting that an out-of-sync default network is a part of normal aging, not a sign of disease," said Buckner.

The subjects were also investigated with diffusion tensor imaging technique, which showed that white matter (made of the axons connecting one brain nucleus to another) had been damaged in elders, directly connected with the degree of lack in coordination. It is not well known which is the importance of the default network in cognition, but its coordination makes the difference in memory and other cognitive abilities.

"Those with the least coordinated default network activity tended to get the lowest scores," wrote the researchers.

"The findings add to previous hints that the cognitive declines that happen with age result from changes in the way brain regions interact. Deteriorating white matter may turn out to be the root problem, breaking down communication links between brain regions and impairing their ability to work in a coordinated manner," said neuroscientist Adam Gazzaley, of the University of California, San Francisco.