WASHINGTON (dpa-AFX) - A new study, published in the journal Alzheimer's & Dementia: The Journal of the Alzheimer's Association, helps explain why a patient with Alzheimer's fails to recognize their loved ones.
Inside the brain's hippocampus, a region important for memory, there's a small area called CA2, which helps us remember people and social interactions. The neurons in this area are surrounded by thin, mesh-like structures called perineuronal nets, which help keep brain connections stable and support long-term memory, especially memories involving people we know.
Researchers at the University of Virginia studied what happens to these nets in mouse models of Alzheimer's disease. They found that as the disease worsens, these protective nets weaken and eventually break down, even though the neurons themselves remain intact. Interestingly, this damage occurred without the usual amyloid plaques seen in Alzheimer's, suggesting another cause for memory loss.
The loss of these nets matched the mice's loss of their ability to recognize familiar faces. Young mice were able to recognize familiar mice, but by six months old, they no longer could tell the difference between familiar and new ones.
To test if the nets directly cause memory problems, scientists removed a key component called aggrecan from the CA2 region in healthy mice. Within weeks, the mice lost their social memory similar to those with Alzheimer's.
When the researchers later used an enzyme to temporarily dissolve the nets, the mice again lost social memory but once the nets regrew, their memory came back. This showed that restoring the nets can also restore lost memories.
Finally, the team tested MMP inhibitors, the drugs which are already being studied for cancer and arthritis, to see if they could protect the nets. The treatment worked, preventing net breakdown and preserving the mice's social memory.
Overall, the findings suggest that protecting or repairing these brain 'nets' could one day help people with Alzheimer's keep their social memories for longer.
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