How cat brains can help scientists understand cognitive decline

For decades, the scientific community has relied on laboratory mice to study human age-related brain diseases.

Now, however, scientists are beginning to explore the ageing processes of cats' brains, deciphering their remarkable similarities to human brains.

The domestic cat, often found dozing in a sunlit corner of our homes, might hold some of the answers researchers are seeking.

Evidently, as cats grow older, their brains experience changes that are surprisingly similar to those seen in humans, including atrophy and the accumulation of Alzheimer-like protein tangles.

This resemblance could illuminate the intricate processes behind age-related cognitive decline.

‘Translating time’

The Translating Time project, which began in the 1990s, initially served as a tool for developmental biologists, charting the brain development timelines of various mammals.

Now, it has expanded to track ageing, incorporating data from over 150 species to build a more comprehensive understanding of neurodegeneration.

“To address challenges in human medicine, we need to draw from a wide range of model systems,” says Christine Charvet, a comparative neuroscientist at Auburn University College of Veterinary Medicine, who presented the work.

Charvet emphasises the value of diversifying research subjects to include species like cats, lemurs, and even dogs, as each provides unique insights into the ageing process.

This approach becomes even more compelling when considering the well-known short lifespan limitations of mice, particularly in studies of neurodegenerative diseases.

Mice simply don’t live long enough to develop brain damage akin to what humans experience.

“The evolutionary mismatch between mice and men could be one reason why efforts to develop therapies to treat the disease have often fallen flat,” says Elaine Guevara from Duke University, who studies primate evolutionary genetics at Duke University in Durham, North Carolina.

“Mice don’t develop the classic hallmarks of Alzheimer’s disease,” she says.

Guevara points out that mice don’t exhibit the classic hallmarks of Alzheimer’s disease seen in humans.

“Their brains are quite different from ours,” she adds, revealing why scientists are eager to explore other, more suitable models.

Life measured in cat years

Cats, on the other hand, live longer and display ageing patterns that can be meaningfully compared to human brain deterioration.

They not only share similar environmental exposures with humans but also age along comparable biological timelines.

For instance, a one-year-old cat is equivalent to an 18-year-old human, while by age 15, a cat parallels an 80-year-old human and exhibits cognitive decline similar to that seen in elderly humans with changes in brain volume.

Charvet’s Catage Project is tapping into this potential and enlisting cat owners to contribute health data and blood samples from their pets.

So far, the project has amassed brain scans from over 50 cats, painting a detailed picture of feline neurodegeneration.

This extensive data could reveal why some brains age faster than others and offer insights into slowing down cognitive decline.

While cats become a feline gateway into understanding human ageing, researchers emphasise that a single model won't address every question.

Caleb Finch, an expert in the evolution of life history at the University of Southern California in Los Angeles, encourages further research into naked mole rats (Heterocephalus glaber), known for their unexpectedly long lifespans for small rodents and remarkably low cancer rates.

"Cats are useful, but they’re only going to be so useful. Other model systems are needed as well," says Charvet.