Kelly Lambert: We made our first rodent car out of a plastic cereal container. Through trial and error, my colleagues and I discovered that rats can learn to drive forward by grasping a tiny wire that acts like an accelerator pedal. Soon they were steering with surprising precision to reach the Froot Loop treat.
As expected, rats housed in enriched environments – equipped with toys, space and companions – learned to drive faster than rats in standard cages. This finding supported the idea that convoluted environments raise neuroplasticity, or the brain's ability to change throughout life in response to environmental demands.
After our research was published, the rat herding story became popular in the media. The project continues in my lab with modern and improved rat remotely operated vehicles, or ROVs, designed by robotics professor John McManus and his students.
These upgraded electric ROVs – equipped with rat-proof wiring, indestructible tires and ergonomic drive levers – resemble a rodent version of Tesla's Cybertruck.
As a neuroscientist who advocates keeping and testing laboratory animals in natural habitats, it was amusing to me to see how far we had strayed from my laboratory practices on this project. Rats usually prefer dirt, sticks and stones to plastic objects. Now we made them drive cars.
But humans didn't evolve to drive either. Although our antique ancestors did not have cars, they had versatile brains that enabled them to acquire modern skills – fire, language, stone tools and agriculture. Some time after the invention of the wheel, people began to produce cars.
Although cars designed for rats are a far cry from those found in the wild, we believed that driving was an captivating way to study how rodents acquire modern skills.
Surprisingly, we found that the rats were intensely motivated to learn to drive, often jumping into the car and revving the “lever engine” before the vehicle hit the road. Why was that so?
A modern goal for joy
Concepts from beginner's psychology textbooks took on a modern, practical dimension in our rodent management laboratory. Drawing on fundamental learning approaches such as operant conditioning, which reinforces targeted behavior through strategic incentives, we trained rats step-by-step in their driver education programs.
Initially, they learned basic movements such as getting into a car and pressing a lever. However, with practice, these straightforward actions evolved into more convoluted behaviors, such as driving a car to a specific location.
Rats also taught me something profound one morning during the pandemic.
It was the summer of 2020, a period marked by the emotional isolation of almost everyone on the planet, even the lab rats. When I entered the lab, I noticed something unusual: three dog-trained rats eagerly ran to the side of the cage and jumped up, just as my dog does when asked if it wants to go for a walk.
Have rats always done this and I just didn't notice? Did they just want the Froot Loop or were they expecting just the drive? Either way, they seemed to be feeling something positive – perhaps excitement and anticipation.
Behaviors associated with positive experiences in humans are associated with joy, but what about rats? Did I see anything like joy in the rat? Perhaps so, given that neuroscience research increasingly suggests that joy and positive emotions play a key role in the health of both humans and animals.
In this way, my team and I shifted our focus from topics such as the effects of chronic stress on the brain to how positive events – and the anticipation of them – shape neural function.
Working with postdoctoral fellow Kitty Hartvigsen, I developed a modern protocol that used waiting periods to raise anticipation of a positive event. Adding Pavlovian conditioning to the mix, rats had to wait 15 minutes after placing the Lego brick in the cage before receiving the Froot Loop.
They also had to wait a few minutes in a transport cage before entering Rat Park, their play area. We also added challenges such as shelling sunflower seeds before eating.
This became our Wait For It research program. We called this modern line of research UPER – unpredictable positive responses to experiences – in which rats were trained to wait for rewards. In contrast, control rats received the reward immediately.
After about a month of training, we subject the rats to various tests to determine how the expectation of positive experiences affects their learning and behavior. We are currently peering into their brains to map the neural trace of prolonged positive experiences.
Preliminary results suggest that in a test designed to measure optimism in rodents, rats that had to wait for a reward show signs of changing their cognitive style from gloomy to bullish.
They performed better on cognitive tasks and were bolder in their problem-solving strategies. We connected this program to our lab's broader interest in behavioral medicines, a term I coined to suggest that experiences can change brain chemistry much like pharmaceuticals do.
This study provides further evidence of how anticipation can reinforce behavior. Previous work on lab rats has shown that rats pressing a bar of cocaine – a stimulant that increases dopamine activation – already feel a rush of dopamine, anticipating a dose of cocaine.
The Tale of Rat Tails
It was not only the impact of prediction on rats' behavior that caught our attention. One day, a student noticed something strange: one of the rats in the group trained to expect positive experiences had a straight tail with a bend at the end, resembling the handle of an old-fashioned umbrella.
I've never seen anything like this in my decades of working with rats. By reviewing the video, we found that rats trained to anticipate positive experiences held their tails high more often than untrained rats. But what exactly did that mean?
Curious, I posted a photo of the behavior on social media. Other neuroscientists have identified it as a milder form of the so-called Straub's tail, typically seen in rats treated with the opioid morphine. This S-shaped curl is also associated with dopamine. When dopamine is blocked, Straub's tail behavior goes away.
Natural forms of opiates and dopamine – key components of the brain pathways that reduce pain and raise reward – appear to be the hallmark components of the raised tails in our anticipation training program.
Observing tail posture in rats adds a modern layer to our understanding of rat emotional expression, reminding us that emotions are expressed throughout the body.
Although we cannot directly ask rats whether they enjoy driving, we developed a behavioral test to assess their motivation to drive. This time, instead of giving the rats the opportunity to drive to the Froot Loop Tree, they could also make a shorter journey on foot – in this case, by paw.
Surprisingly, two of the three rats chose the less productive path: turning away from the reward and running to the car to drive to the Froot Loop destination. This response suggests that rats enjoy both the journey and the rewarding destination.
Rat lessons on enjoying your journey
We are not the only team researching positive emotions in animals. Neuroscientist Jaak Panksepp famously tickled rats, demonstrating their capacity for joy.
Research has also shown that desirable, stress-free environments in rats fine-tune their brain's reward circuits, such as the nucleus accumbens. When animals are kept in their favorite environments, the area of the nucleus accumbens that responds to appetitive experiences expands.
Alternatively, when rats are kept in stressful conditions, the fear-generating zones of their nucleus accumbens expand. It's as if the brain is a piano that the environment can tune.
Neuroscientist Curt Richter also argued that rats have hope. In a study that would not be allowed today, rats swam in glass cylinders filled with water and eventually drowned from exhaustion if they were not rescued.
Laboratory rats often kept by humans swam for hours or days at a time. The wild rats gave up after just a few minutes. However, if wild rats were rescued for a low time, their survival times increased dramatically, sometimes by several days. The rescue seemed to give the rats hope and spurred them on.
The Rat Drive project opened modern and unexpected doors in my behavioral neuroscience research lab. While it's critical to explore negative emotions like fear and stress, positive experiences also shape the brain in significant ways.
As animals – human and otherwise – cope with the unpredictability of life, the anticipation of positive experiences helps raise persistence in continuing to seek life's rewards.
In a world of instant gratification, these rats offer insight into the neural rules that drive everyday behavior. Instead of pushing buttons for immediate rewards, they remind us that planning, anticipating and enjoying the ride can be the key to a fit brain. This is a lesson my lab rats taught me well.
Kelly Lambert, professor of behavioral neuroscience at the University of Richmond
This article has been republished from Conversation under Creative Commons license. Read it original article.
Image Source: Pixabay.com
