Kelly Lambert: We made our first rodent car out of a plastic grain container. Through trial and error, my colleagues and I discovered that rats could learn to drive forward by grasping a wire that acted as an accelerator. It wasn’t long before they were steering with surprising precision to reach a Froot Loop treat.
As expected, rats housed in an enriched environment – complete with toys, space and companions – learned to drive faster than rats in standard cages. This finding supported the idea that complex environments increase neuroplasticity: the brain’s ability to change across the lifespan in response to environmental demands.
After we published our research, the story of herding rats went viral in the media. The project continues in my lab with new, improved rat-operated vehicles, or ROVs, designed by robotics professor John McManus and his students.
These upgraded electric ROVs – with rat-proof wiring, indestructible tires and ergonomic driving levers – resemble a rodent version of Tesla’s Cybertruck.
As a neuroscientist who advocates for housing and testing laboratory animals in natural habitats, I was amused to see how far we have strayed from my laboratory practices with this project. Rats generally prefer dirt, sticks, and rocks to plastic items. Now we let them drive.
But humans didn’t evolve to drive either. Although our ancestors did not have cars, they had flexible brains that allowed them to acquire new skills: fire, language, stone tools and agriculture. And some time after the invention of the wheel, people made cars.
Although cars made for rats are far from everything they encounter in the wild, we believed that driving cars was an interesting way to study how rodents acquire new skills.
Unexpectedly, we found that the rats had intense motivation for their driving training, often jumping into the car and revving the “lever motor” before their vehicle hit the road. Why was that?
The new destination of joy
Concepts from introductory psychology textbooks took on a new, practice-oriented dimension in our rodent riding laboratory. Building on fundamental learning approaches such as operant conditioning, which reinforce targeted behavior through strategic stimuli, we trained the rats step by step in their driver training programs.
Initially, they learned basic movements, such as climbing into the car and pressing a lever. But with practice, these simple actions evolved into more complex behaviors, such as steering the car to a specific destination.
The rats also taught me something profound one morning during the pandemic.
It was the summer of 2020, a period marked by emotional isolation for almost everyone on the planet, even lab rats. As I walked into the laboratory, I noticed something unusual: the three row-trained rats eagerly ran to the side of the cage and jumped up like my dog does when asked if he wants to go for a walk.
Had the rats always done this and I just didn’t notice? Were they just curious about a Froot Loop, or were they anticipating the ride itself? Either way, they seemed to feel something positive – perhaps excitement and anticipation.
Behaviors associated with positive experiences are associated with joy in humans, but what about rats? Did I see something that looked like joy in a rat? Perhaps so, as neuroscience research increasingly suggests that joy and positive emotions play a crucial role in the health of both human and non-human animals.
In doing so, my team and I shifted the focus from topics such as how chronic stress affects the brain to how positive events – and the anticipation of these events – shape neural functions.
Together with postdoctoral colleague Kitty Hartvigsen, I designed a new protocol that used waiting times to increase the anticipation of a positive event. Bringing Pavlovian conditioning into the mix, rats had to wait 15 minutes after a Lego block was placed in their cage before receiving a Froot Loop.
They also had to wait a few minutes in their transport cage before entering Rat Park, their play area. We’ve also added challenges like making sure they shell sunflower seeds before eating them.
This became our Wait For It research program. We called this new line of research UPERs – unpredictable positive experience responses – in which rats were trained to wait for rewards. In contrast, control rats received their rewards immediately.
After about a month of training, we expose the rats to various tests to determine how waiting for positive experiences affects the way they learn and behave. We are currently looking into their brains to map the neural footprint of long-term positive experiences.
Preliminary results suggest that rats forced to wait for their reward show signs of shifting from a pessimistic cognitive style to an optimistic style in a test designed to measure rodent optimism.
They performed better on cognitive tasks and were bolder in their problem-solving strategies. We linked this program to our lab’s broader interest in behaviorceuticals, a term I coined to suggest that experiences can change brain chemistry in the same way pharmaceuticals can.
This research provides further support for how anticipation can enhance behavior. Previous research in laboratory rats has shown that rats that press a bar for cocaine – a stimulant that increases dopamine activation – already experience a surge of dopamine as they anticipate a dose of cocaine.
The story of rat tails
It wasn’t just the effects of anticipation on rat behavior that caught our attention. One day, a student noticed something strange: one of the rats in the group that had been trained to expect positive experiences had its tail straight up with a curve at the end, resembling the handle of an old-fashioned umbrella.
I had never seen this in decades of working with rats. When watching the video footage, we found that the rats trained to anticipate positive experiences were more likely to hold their tails up than untrained rats. But what exactly did this mean?
Curious, I posted a photo of the behavior on social media. Fellow neuroscientists identified this as a softer form of the so-called Straub tail, which is typically seen in rats given the opioid morphine. This S-shaped curl is also linked to dopamine. When dopamine is blocked, Straub tail behavior decreases.
Natural forms of opiates and dopamine – key players in brain pathways that reduce pain and increase reward – appear to be telltale ingredients of the increased tails in our anticipation training program.
Observing tail posture in rats adds a new layer to our understanding of rats’ emotional expression, reminding us that emotions are expressed throughout the body.
Although we cannot directly ask rats whether they like driving, we have devised a behavioral test to assess their motivation to drive. Instead of just giving rats the option to drive to the Froot Loop Tree, this time they could also make a shorter journey on foot – or in this case, by paw.
Surprisingly, two of the three rats chose to take the less efficient path by turning away from the reward and running to the car to drive to their Froot Loop destination. This response suggests that the rats enjoy both the journey and the rewarding destination.
Rat lessons about enjoying the journey
We are not the only team investigating positive emotions in animals. Neuroscientist Jaak Panksepp tickled rats, demonstrating their capacity for joy.
Research has also shown that desirable, low-stress rat environments retune their brain’s reward circuits, such as the nucleus accumbens. When animals are housed in their preferred environment, the area of the nucleus accumbens that responds to appetizing experiences expands.
Alternatively, when rats are housed in a stressful context, the anxiety-inducing zones of their nucleus accumbens expand. It’s as if the brain is a piano that can tune the environment.
Neuroscientist Curt Richter also advocated that rats have hope. In a study that wouldn’t be allowed today, rats swam in glass cylinders filled with water, eventually drowning from exhaustion if they weren’t rescued.
Laboratory rats often handled by humans swam for hours to days. Wild rats gave up after just a few minutes. However, when the wild rats were briefly rescued, their survival time was dramatically extended, sometimes by days. It seemed that the rescue gave the rats hope and encouraged them.
The riding rat project has opened new and unexpected doors in my behavioral neuroscience research laboratory. While it is vital to study negative emotions such as anxiety and stress, positive experiences also shape the brain in important ways.
As animals – human or otherwise – navigate the unpredictability of life, anticipating positive experiences helps fuel the perseverance to continue seeking life’s rewards.
In a world of instant gratification, these rats offer insight into the neural principles that govern everyday behavior. Instead of pressing buttons for immediate rewards, they remind us that planning, anticipating, and enjoying the ride can be the key to a healthy brain. That’s a lesson my lab rats taught me well.
Kelly Lambert, professor of behavioral neuroscience, University of Richmond
This article is republished from The conversation under a Creative Commons license. Read the original article.
