Humans share a great deal of similarities with our chimpanzee cousins, including our use of stone tools, our love of fruit, and the fact we both pass the mirror test. But for the many ways we are strikingly alike, humans have one heartbreaking difference lurking in our brains: we develop Alzheimer’s disease, as no other primate can.
However, researchers have recently discovered the first signs of cognitive decline, similar to Alzheimer’s, in chimpanzees – an early stage that, for some mysterious reason, seems to progress no further. This self-limiting action, in so close a relative, may point to a way of avoiding Alzheimer’s in humans. And now scientists are looking at chimp brains for clues.
Researchers out of Kent State were granted full access to a bank of 20 brain samples, collected by the National Chimpanzee Brain Resource from chimps who had died naturally in captivity between 37 and 62 years of age. They looked for elevated levels of amyloid beta, a protein that breaks down quickly in healthy human brains, but doesn’t in cases of Alzheimer’s. Extra amyloid beta leads to an accumulation of plaques between neurons. Plaques cause another protein, tau, to collect into tangles that affects healthy brain cells, and hence, cognition.
“Interestingly, traces of amyloid beta were higher in chimp blood vessels than in plaques — that’s not what typically happens in humans. A build-up of amyloid beta deposits in the brain’s blood vessels does occur in humans (a condition known as cerebral amyloid angiopathy), but the predominant effect of amyloid beta in our species is the production of excess plaque. ‘This suggests that amyloid buildup in the brain’s blood vessels precedes plaque formation in chimpanzees,’ noted study co-author Melissa Edler.”
Amyloid beta’s presence in chimps’ blood instead of their brains might be an indicator of why they don’t seem to experience severe cognitive decline and we do. But the scientists on the team acknowledge that this tiny spark of possibility needs to be fanned into a flame with full research – that must be done in an ethical manner with the help of our furry brethren. Until then, the attempt to unravel the terrifying mystery of the human brain will continue.