Is Mister Rogers a liar? That's the question for this week.

If you haven’t seen it yet, check out the entrancingly weird video, “Garden of Your Mind,” a remix of Mr. Rogers by PBS studios.

The tune is catchy. The content is laced with just enough creepiness—slightly deranged stares, spinning spirals, an out-of-context big purple bear—to keep you hooked, but ends on the empowering note, that no matter what your situation, a sanctuary of hidden ideas awaits you in your mind.

“All you have to do is think, and they’ll grow!”

A seriously liberating thought, that no matter what, a brain can always make new connections and grow throughout life. But what about that thing we all grew up hearing—that the human brain stops changing around age 20? (It is well-established that the human brain shrinks as we age.) While Mr. Rogers’ message may have been true for his intended audience—children, undergoing the spurts and flowerings of early childhood brain growth—what about us adults? No matter how hard we may think, is the adult brain just an atrophying patch of barren ground?

In short—no! Studies going back as far as the 1960s have shown that the adult brain can create new neurons. And while the research community was initially wary of these results (how could a brain change during life without disrupting the rest of the body?!), explosions in research in the last 20 years—in rodents, primates, and humans—have overwhelmingly confirmed the finding. The field of study is called “neurogenesis”—birth of neurons, and now the hot question is: what causes it? What activities or behaviors or nutrients can make a brain grow? While the field itself is too new to know what’s a cause and what’s a correlation, a series of behaviors have been linked with spurts of new neurons (but not all of them are worth trying at home).

So, without further ado, here’s a list of alternate choruses to Mr. Rogers’ song. Just fill in the blank:

“ALL YOU HAVE TO DO IS ________________, AND THEY’LL GROW.”

1) EXERCISE

The more you run, the more brain cells you grow. If you’re a mouse, anyway. In 1999, a team of researchers at the Salk Institute showed that mice who were forced to hit the gym (the hamster wheel) gained a proliferation of new cells in the dentate gyrus, an area of the hippocampus. What’s more, there were behavioral implications for these brain-blossoming mice: mice who exercised were able to remember the path through aquatic mazes much better than their non-exercising counterparts, who often got lost, panicked, and gave up.

2) BE NEAR TREES

This was a topic we covered in our Zoos show. How enriched cages—cages with trees to climb and toys to play with—actually changed the creatures inside them. Their zookeepers observed happier, more peaceful animals, and neurologists observed bushier, more neuron-filled and connected brains. This one is my favorite, because of its seeming visual logic. I know it doesn’t actually work this way, but I picture a grumpy brain taking a cue from the lush trees above it, beginning to blossom. Almost like a little kid wanting to be like the cool kids: it sprouts dendrites out of admiration. But back to the science. Researchers like Elizabeth Gould at Princeton have shown that within a matter of weeks a deprived brain will grow bushier if it is placed in an ‘enriched environment.’ Fernando Nottebohm has found similar results in birds.

3) F#$%

Make love. Do the sex. Another discovery led by neurogenesis queen Gould shows that sex can promote neurogenesis. A caution though: one roll in the hay can cause a surge in stress hormones, glucocorticoids, which destroy brain cells. It’s only with lots of sex (described by Gould as “chronic sexual experience”) that the stress hormones disappear, freeing the brain for straight-up, free-flowing spurts of brand new neurons. Oh yeah, keep in mind this has only been observed in rats.

4) SMOKE POT

A team in Saskatchewan gave rats a daily dose of a substance called HU210 (a cannaboid that looks like THC—the active ingredient in marijuana), and after ten days, they found the rate of nerve cell formation in the hippocampus had increased dramatically. Another team in Ohio found similar results. (The Ohio team is curious about a marijuana-like drug’s potential to delay the onset of Alzheimers.) That said, extrapolating to humans isn't wise. Even in rodents, it’s hard to know what’s a cause and what’s a flukey correlation: Barry Jacobs, a neuroscientist at Princeton University, found that when he gave mice actual TCH, (instead of the synthetic compound the other two studies used), there was no evidence of neurogenesis. Plus, stoners everywhere report finding it hard to remember that thing they were just thinking of… So.

5) HAVE A SEIZURE

This one is very interesting: in 1997, a group of scientists found that seizures trigger neurogenesis in rats. (Since then, multiple studies have repeated this finding.) This could explain the kind of hallucinatory and transcendent experiences sometimes described by human sufferers of epilepsy. Fyodor Dostoevsky, the famed writer happened also to be an epileptic, once described the moment right before the seizure this way:

For several moments, I would experience such joy as would be inconceivable in ordinary life... I would feel the most complete harmony in myself and in the whole world and this feeling was so strong and sweet that for a few seconds of such bliss I would give ten or more years of my life, even my whole life perhaps.

Perhaps that feeling of "the most complete harmony" was caused by the sudden proliferation of new neurons—an unruly explosion of new connections—in his mind. In this review, Matthew Tremblay at the University of Rochester further explains how aura—the perceptual strangeness such as hallucinations in light, smell, etc—right before a seizure, could be caused by the dramatically increased rate of neurogenesis associated with seizure. That much activity, however, is not good for the brain in the long run. Helen Scharfman, a neurologist at Columbia University, monitored the electrical activity of neurons birthed after a seizure and observed that they were abnormally excitable, and often wired to the wrong partners. Often, the more that there were, the more likely the person was to have another seizure."The new neurons may not be reparative but [rather] may be part of the problem,” Scharfman said.

6) THINK

Last but not least, what about ol' Mr. Rogers' promise: “Just think, and they’ll grow…” Can thinking alone promote neurogenesis? Elaine Reynolds—who has created an absolutely fantastic online resource about neurogenesis—says “there’s nothing to say that isn’t true!” She points out that it’s sort of a chicken and the egg situation: “New neurons are associated with increased cognition but do cognitive activities cause neurogenesis or does neurogenesis improve cognition?” Either way, she cites studies in which thinking alone—brain puzzles and learning new languages—can actually stave off the onset of Alzheimer's and other degenerative diseases of the brain. Thinking, it turns out, can’t hurt.

…There are more connections out there (diets low in fat and sugar, sociability, and antidepressants have been linked to neurogenesis), and it’s definitely known that nothing kills brains cells better than stress and lack of sleep. So get your sleep, make your love, do your exercise, and please post any other brain-growing findings you may come across.

May you all have a neuronally bushy week.