A YouTube video of a rat carrying a cheesy slice of pizza many times its size in the New YorkCity subway, braving the risk of getting trampled on, attracted millions of views back in 2015.
Ever wondered what keeps rats happy, apart from pizza? Young rats love cartwheels, burrows, and tunnels, say researchers. Being raised in an enriched environment with lots of toys and peers to mingle with not only keeps them stimulated but also changes their brain. They tend to develop more connections in the hippocampus, the part of the brain that facilitates learning and memory, compared to rats that have no such enriching experiences.
Sumantra Chattarji, professor of neurobiology at the National Centre for Biological Sciences (NCBS), Bengaluru, says, “Even a month of social interactions, playtime, exercise, and sensory stimulation can make a two-month-old rat a better learner.” Other studies by Chattarji and his team of researchers have found that if these young rats are stressed for ten days, they lose those connections in the hippocampus. “Strikingly, the amygdala, another part of the brain which is known as the emotional hub, will actually grow more connections, providing an explanation for why stress causes unstable mood and high anxiety,” says Chattarji. “Stress is quite devastating because it is a double whammy for the brain. Even as it damages the hippocampus, it makes the amygdala stronger. So the rats lose the ability to learn from and remember daily experiences, and they become more anxious and fearful. Together these stressful experiences leave a lasting scar in a young rat's brain,” says Chattarji, who has been studying the effects of stress on the brain for the last 20 years.
Chattarji’s lab found that if rats are first exposed to one month of a stimulating environment—lots of playtime, social interactions, and physical exercise—they can combat the ill effects of stress. Animals raised in an enriched environment are hard-wired to be more resilient, as shown by the increased levels of connections between brain cells and molecules that strengthen memories in their hippocampus.
“Chronic stress impairs memory formation. It particularly affects the formation of spatial and declarative memories that include memories about facts and events,” says Giselle Fernandes, one of the research scholars in the project. She found that rats raised in a positive or enriched environment do not form these deficits in memory even after they are stressed. “An enriched environment helps them cope with future stress better,” says Fernandes. “I found that environmental enrichment can strengthen the hippocampus, the seat of learning and memory in the brain. And then, this strengthened hippocampus is refractory to any bad influence from stress.”
One of the memory tests Fernandes used involved giving rats a foot shock while at a particular location so that they attach an emotional significance to that spot. “The rat is then required to remember that location at some future time,” she said. “Putting it in a person's context, it is akin to remembering a dangerous place or object. For instance, learning to avoid touching a hot iron, poking a bee's hive or a snake's pit. This sort of learning and memory are important as it helps you predict and avoid future mishaps. Rats raised in a stimulated environment performed better in that test, whether or not they were stressed. This shows enrichment enhances memory significantly.”
So what is the takeaway from these studies for humans? The findings from these studies could be an eye-opener for young parents. “How we can draw lessons from animal studies and help our children to flourish is what I am mulling these days,” says Chattarji. “I am not making any judgments. I am just bringing in the science to tell people why too much pressure on young brains does not make sense when it comes to our education system. We need to rethink how best to use the brain’s natural ability to learn and grow in a healthy and stimulating environment—and not subvert it with the kind of pressure and demands being made by our current education system.”
Indian children are massively overburdened with their school curricula. “Much of what they are expected to learn in school is mostly rote learning—repeated exposure to long lists of dry facts, often devoid of any social or emotional relevance,” says Chattarji.
The environment a child is raised in plays a pivotal role in sculpting the brain. “The wiring of the brain occurs mostly in the early years. During this period, brain cells constantly make connections and withdraw them, and then eventually stabilise over time. Social experiences and exposure to sensory stimuli such as light, sound, and touch can go a long way in forming new connections,” he says.
Music, drama, painting and social interactions are great ways to stimulate the brain. “However, today's children are often deprived of opportunities that are beneficial for a young brain. Instead, there is increasing pressure on them to do long hours in classrooms and coaching classes—to blindly mug up things and then regurgitate them under pressure in endless exams. It is just counterproductive. That is what modern neuroscience tells us,” says Chattarji. “Encourage your child to make friends. Expose them to a range of different environments and hands-on experiences. Enrich their brains, and the long-term benefits for their mental health will be obvious. It is like farming—if the land is enriched with nutrients early on, whatever you plant there later will grow well.”
Both sensory overload and sensory deprivation are bad for the brain. Under stressful conditions, the hippocampus struggles to learn and remember, while the hyperactive amygdala makes the individual anxious. Unlike other organisms in the animal kingdom, humans are not born with innately hard-wired brains that enable them to readily respond to various situations. “A baby zebra knows how to run away from a lion—it does not have the luxury of 'learning on the job' because it will become the lion’s lunch!” says Chattarji. “Human beings are different. It takes time for us to learn through experiences. We are heavily dependent on our families and social groups to acquire the necessary skills to survive and flourish in the real world.”
The human brain has an amazing ability to rewire itself based on a person's experiences. The capacity of the brain to create new neurons and neural connections in response to environmental changes, injury or disease is described by neuroscientists as 'neuroplasticity'. Brain plasticity allows us to acquire and store new information.
“Plasticity can be good and bad. Environmental and social enrichment has hugely positive effects on the young brain. But, the 'plastic' brain is equally vulnerable to bad experiences—such as stress and addiction,” cautions Chattarji.
The cerebral changes in people who have encountered a lot of childhood stress are quite visible, says Dr Sagar Mundada, a consultant psychiatrist at Healthspring, Mumbai. “In people who have been subjected to too much childhood stress, the prefrontal cortex (the rational brain) and the limbic system that includes the amygdala do not develop properly, and hence they don't function well,” he says. These are the parts that are supposed to deal with stressful situations. Such people also develop more connections in their amygdala and hence even mild stress will be perceived by their brain as big stress. “When a stressful event occurs, the amygdala and the prefrontal cortex should work in tandem to give a balanced response. In people who have been under a lot of childhood stress, the amygdala is hyperactivated, and they are not able to look at things from a rational context,” says Mundada.
Sandeep Mohan, a 30-year-old executive, working with an MNC is a classic victim of constant childhood stress. An IIM graduate, Mohan would get very upset when he failed to meet his targets. “His bosses were fine with the fluctuating results, but Mohan would get stressed,” says Mundada. From Mohan's detailed history, Mundada found that as a child, Mohan was always under a lot of pressure from his parents. He was always a winner, excelling in academics and co-curricular activities. A perfectionist, he would constantly worry about the expectations of his parents and teachers. He also developed exam phobia. “Apart from that, there was an element of child sex abuse from one of his uncles,” says Mundada. “He never opened up to his parents about these things as he perceived them to be disciplinarians.”
At work, if something did not work out, Mohan would get so upset that his daily routine would be hit. “He could not take rejection at all. The relentless stress left him with panic attacks and anxiety. Now he is on medication,” says Mundada.
Bullying is often a cause for childhood stress. So are unresolved conflicts, especially when a child does not dare speak up. “If any of these have happened in your childhood, there is a strong likelihood that your stress-coping mechanism has been disrupted,” says Mundada. What kind of help is available for such victims of childhood trauma? “The age at which the patient comes to the doctor decides how severe its impact has been on his brain,” says Mundada. “Options are many if he is seeking help in his childhood. If he is coming as an adolescent, a combination of therapies and medicines would work for him. But, if he is an adult now and the stress has been there since long, medication could be the only option.”
Some names have been changed.