The Rochester Review, University of Rochester, Rochester, New York, USA
But what of the oft-maligned snake? Inept at outmaneuvering the labyrinths favored by those earlier researchers, the humble snake has been consistently consigned to the ranks of "lower animals."
Until now, that is.
Rochester neuroscientist and herpetologist David Holtzman has discovered that snakes, their bean-size brains notwithstanding, are not the mental midgets they were once thought to be. In short, he has shown that a snake can actually learn a lot more than the earlier maze experiments ever indicated.
Holtzman uncovered this nugget with the assistance of 24 corn snakes, bright orange and red critters that can grow to lengths of up to four feet. Members of a species native to the shadowy pine forests of the southeastern United States, Holtzman's captive-bred snakes turn to thoughts of hiding when they're exposed to bright, wide open spaces.
The professor has created just such an environment in the windowless depths of Meliora Hall. His arena, a black plastic tub roughly the size of a child's wading pool, clearly rubs his reptilian colleagues the wrong way, psychologically speaking. Holtzman and his research team (student assistant Timothy Nyberg '00 and former research assistant Anita Stone) capitalized on the animals' urge to seek a dark, cozy nook--among a snake's strongest instincts--to find out if they could be taught the truth that would set them free.
As Holtzman's corn snakes were to learn, they had but one means of escape: a series of holes in the bottom of the arena, most of which were closed off with masking tape. What the researchers found was that snakes could use the arena's visual cues (large red cards pasted to its walls) and its tactile cues (tape on the floor) to figure out which of the holes was offering deliverance.
"When a snake is first placed in the arena, it tends to circle around the edge, looking for a way out," says Holtzman, an assistant professor of brain and cognitive science. But once given a nudge in the right direction, snakes can learn relatively quickly how to find the exit.
By the end of the experiments, a few of the brainier ones had become real smart asps: Perhaps agitated at finding that a previously open hole had been sealed off, some responded by using their teeth to peel away the tape that stood between them and their goal.
In the matter of teaching old snakes new tricks, Holtzman found that there do appear to be a few age-based differences as to which cues snakes use in extricating themselves from the arena. Young snakes--say, those ages six months to a couple of years--seemed more adaptable and resourceful, using a variety of clues to find their way to the exit. Their elders, perhaps more set in their ways, seemed to rely much more heavily on the visual cues, becoming a tad befuddled if the brightly colored card marking the exit hole was moved.
"Actually, one of the interesting findings from our studies is that snakes do use vision to locate places," says Holtzman. "They don't just rely on the chemical cues picked up by flicking their tongues out, as many snake biologists assume."
The experiments within the arena were surveyed by overhead video cameras that tracked the snakes by picking up on the tiny foil hats fitted to their noggins to make them more visible to the camera's eye. The snakes couldn't be observed directly during experimentation because the presence of a person could provide unintended cues, distorting the findings. Instead, Holtzman or, more often, Nyberg, the self-described "minion," lurked just out of sight behind the black curtains that wall off the arena, watching the snakes on closed-circuit television and using a computer to analyze and catalog their movements.
Holtzman--who's been happily surrounding himself with snakes since age 5 and working with them professionally since 1984--thinks it's about time his slithery colleagues got their due.
"People don't give snakes and other reptiles enough credit," argues their champion, clad in a T-shirt bearing the likeness of a large lizard. "They're not so much 'below' us as they're just different."
For his part, Nyberg, a junior from Barrington, Rhode Island, who's double-majoring in brain and cognitive science and psychology, admits he was a bit leery of the corn snakes when he joined Holtzman's lab last year. "It took a little getting used to," he says, "but these guys are really pretty docile. They rarely hassle you." Sounding like a true convert to
Holtzman's cause, he adds, "Sometimes one even gets a hint of personality. I enjoy telling people that I work with snakes. It's great as a conversation-starter."
Sitting in his office, which is adorned not only with the typical professorial trove of books and jumble of papers but also an old piñata and a velvety black sombrero, Holtzman ticks off reasons he thinks people dislike snakes, and shoots down each in turn. "People think snakes don't serve any useful purpose, but actually they have a valuable ecological role, helping to keep rodent and insect populations under control. And then there's the texture. People think they are slimy, but in fact they're smooth and dry, even leathery. Also, snakes appear to move quickly, but in fact any person can outrun a snake."
Holtzman should know firsthand about this last point: In addition to his research with snakes in the lab, he also does some fieldwork in Rochester-area parks, chasing snakes around in the interest of studying how they orient themselves in the wild and how best to ensure the survival of endangered species. (There are a few snakes in jeopardy in New York state, Holtzman notes, but he concedes that most of these being poisonous varieties, there isn't exactly a groundswell of support for their conservation.)
Holtzman's respect for his snakes' "otherness" extends to the experiments he conducts with them. He criticizes the validity of the aforementioned maze studies because they don't confront snakes with a situation they might encounter in the natural world. "In the real world, a snake has no cause to run through a maze," he points out.
"One of the most interesting new discoveries in neuroscience and cognitive science is that new nerve cells, neurons, can be formed in some brain regions in adult higher-order vertebrates, including primates," says Nyberg.
These preliminary findings of adult neuronal growth in humans appear to hold for some other species, too, including some of the snake's close relatives, who are strikingly more successful at it than we are. Learning to store food engenders brain growth in birds, as much as doubling the number of hippocampal cells. In lizards, if the hippocampus is cut away, it can grow back--and skills lost when the lizard went under the knife return as if by magic.
It's Holtzman's theory that what holds for snakes, lizards, and birds may also hold for their evolutionary descendants--us. If he and his colleagues come to understand the mechanisms that govern neurogenesis in adult snakes, lizards, and birds, it could offer new therapies for the treatment of people afflicted by brain damage--whether from accidents, strokes, or neurodegenerative diseases such as Alzheimer's and Parkinson's. This work could also help us to better pin down the as-yet fuzzy notion that babies who grow up in stimulating environments develop more robust brains than do their less-stimulated peers.
The behavioral studies indicating that snakes can learn were just the first tentative steps toward making connections with humans, Holtzman says. After all, in order to test the hypothesis that snakes' brains grow in response to learning, you first have to determine that your subjects are, in fact, learning something.
With that now proved, Holtzman and Nyberg are beginning to examine whether lessons learned in the snake pit actually spur the growth of new neurons. Using a variety of markers to gauge brain growth, they're homing in on the snake's hippocampus, a region several millimeters in size that rests squarely atop its finger-nail-width brain. They also plan to tinker with the hippocampus to determine how learning is affected.
If Holtzman's hunches are right, and his reptilian pals keep on cultivating their gray matter, maybe he'll have to start thinking about exchanging those little foil caps for mortarboards.
It turns out that snakes are a lot smarter than anyone thought. In fact, more than one corn snake in David Holtzman's lab has proved itself a real smart asp.
ack in the 1950s, scientists bent on cataloging the intelligence of all the world's creatures rightly gave high marks to animals capable of impressive feats--rats that could work their way efficiently through mazes, homing pigeons able to wing it back over enormous distances, salmon swimming thousands of miles toward their native streams.
imply stumbling into the right hole isn't proof positive that the snakes are learning something, though. "The speed with which they find the goal is one of the measures that shows they're learning," Holtzman says. "On average, on the first day of training they take over 700 seconds to find the correct hole and then go down to about 400 seconds by the fourth day. Some are actually very fast and find it in less than 30 seconds."
ranted, it's unlikely that a snake will ace the SAT or join Animal Mensa anytime soon. But the findings still come as a surprise even to some who study reptiles, and certainly to those less-informed among us who lump them in with the world's "lower" life forms.
he rap snakes have had to take as "cunning" and "vile" has a lot more to do with us than with them, Holtzman says, submitting as evidence what happens during his reptilian show-and-tell sessions at area schools. He estimates that fewer than one percent of the kindergartners who encounter his snakes are afraid of them, but that percentage steadily increases with older students. Teachers, he says, are almost uniformly petrified. "It's a learned reaction, one that's grounded in misperceptions."
elieve it or not, there are those who remain unmoved by Holtzman's passionate defense of snakes. (These ranks include his mother, who merely "tolerated" her son's reptilian fascination; dad, a fish biologist, was less squeamish.) These unconvinced souls are advised to consider that Holtzman hopes his work may someday have major implications for people, too--in the form, possibly, of therapies to grow new gray matter in the heads of those who've suffered brain damage.
n short: The familiar maxim that we're born with all the brain cells we'll ever have (frequently referred to in scientific circles as the "no-new-neuron" dogma) is now widely regarded by scientists as untrue. It's now known that humans are able to produce limited numbers of new neurons related to the sense of taste and smell, as well as new cells in the hippocampus, the seat of memory and spatial learning.
ssentially, our end goal is to find out whether learning improves the survival of neurons, and, as in birds, whether the learning actually promotes further brain growth," Holtzman says.
The story about astronaut Jim Pawelczyk '83, in the Fall issue of Rochester Review, was also by Steve Bradt '96.
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