Rat race project could hold lessons for human mental health

RICHMOND (Virginia) • The girls cannot hide their excitement as they are taken out to the racing arena.

"Black Tail" is up first, taking a few seconds to sniff her surroundings before placing her paw on a lever and zooming away.

After storming to the finish line, she devours a well-earned piece of Froot Loop cereal hanging on a "treat tree".

Black Tail is one of the University of Richmond's rat drivers - a group that first dazzled the world with their ability to operate tiny cars back in 2019.

Now, the rodents serve as ambassadors for the school's behavioural neuroscience laboratory, headed by Professor Kelly Lambert.

"It gets people's attention about how clever and teachable these animals are," explained Prof Lambert.

The idea of racing rodents started out as a playful challenge from a colleague.

But far from being a novelty act, the rats are part of a boundary-pushing project exploring ways in which environmental enrichment sculpts the brain - and could in turn hold potential for solving human mental health challenges.

For Prof Lambert, one of the great failings of modern medicine has been its inability to cure mental illness through drugs, even as pharmaceutical companies have reaped huge profits.

These pharmaceutical approaches have faced increasing scrutiny since a landmark study published last month questioned the theory that chemical imbalances, especially a lack of serotonin, cause depression.

Instead, Prof Lambert sees behaviour therapy as the key to treating the mind, which is where studying fellow mammals comes in.

"Our brains are changing, from the womb to the tomb," she said.

"If we have some type of engaging life, this is probably important and related to depression."

A previous experiment of hers had split rats into groups of "workers", who were assigned an effort-based reward task of digging through dirt mounds for a Froot Loop - and a control group of "trust fund" rats that were simply handed treats.

When challenged with stressful tasks, the worker rats persisted longer than those conditioned to remain in a state of what psychologists call "learned helplessness".

And when tasked with swimming, the worker rats showed greater emotional resilience, as shown by a higher ratio of the hormone dehydroepiandrosterone to cortisol in their droppings.

Rats that learnt to drive also had biomarkers of greater resilience and lowered stress - which Prof Lambert suggests might be linked to the satisfaction of acquiring a new skill, like a human mastering a new piano piece.

"They make pathways that they take over and over again in the wild, and we wanted to see if they could continue to have this great navigational skill in a vehicle," explained research lab specialist Olivia Harding.

Training was not simple: The team first tried having the rats nudge the driving control with their snouts, before finding that they preferred to stand on their hind legs and use their front paws.

Early car models required the rats to touch wiring in the front, left or right of the car, completing a mild electric circuit that corresponded to movement direction.

Now, though, they get around in fancier rides with levers designed by a roboticist.

However, just like people, not all rats have similar interests: While certain rats seemed eager to drive just for the fun of it, others did so just for treats, and there were those that could not be coaxed into participating at all.

AGENCE FRANCE-PRESSE