Researchers have identified a new mechanism that can make memories stronger and more precise during the aging process. The findings come from researchers at the Harvard Stem Cell Institute (HSCI).
The brain has billions of neurons at birth and new ones aren`t formed—except in the hippocampus. Over time, neural stem cells are constantly being formed in the hippocampus, which causes a struggle between the new and old neurons. The hippocampus is the area of the brain responsible for new memories, and the continued creation of new neurons helps keep similar memories separate.
When aging, older neurons become stronger and more abundant—this causes the formation of new neurons to become more difficult. Neural stem cells then become less effective, which can lead to age-related memory loss. Essentially, with fewer new neurons, the brain is less efficient at separating and retrieving memories.
For the study, the researchers over-expressed a transcription factor known as KLF9 in older neurons in mice. This caused for the elimination of one-fifth of the dendritic spines—a storage site synaptic strength that helps transmit electrical signals to the neuron—and increased new neurons and activated neural stem cells.
When the researchers restored the expression of KLF9 back to normal, the old dendritic spines restored and reformed competition. Additionally, the neurons which integrated into the hippocampus were found to still be present.
They further discovered that in the mice with increased neurogenesis, there was less overlap between the two neuron populations and older mice exhibited better memory precision.
Study corresponding author, Dr. Amar Sahay, concluded, “We believe that by increasing the hippocampus’s ability to do what it supposed to do and not retrieve past experiences when it shouldn’t can help.” The researcher’s findings may be beneficial in treating conditions that affect the brain including post-traumatic stress disorder (PTSD), mild cognitive impairment, and even age-related memory loss.
Robbins, H. L., “Making memories stronger and more precise during aging,” Harvard Stem Cell Institute, Sept 1 2016; http://hsci.harvard.edu/news/making-memories-stronger-and-more-precise-during-aging, last accessed September 7, 2016.
McAvoy, K. M. et. al., “Modulating Neuronal Competition Dynamics in the Dentate Gyrus to Rejuvenate Aging Memory Circuits,” Neuron, DOI: http://dx.doi.org/10.1016/j.neuron.2016.08.009, http://www.cell.com/neuron/fulltext/S0896-6273(16)30501-3, last accessed September 7, 2016.