WHILE ANDREW AND I WERE pretty sure we could figure out how to scan a dog’s brain, we had neglected to consider a minor, though important, detail: Where? The Dog Project needed a home.
The lab had been captivated with the “big question”—figuring out what goes on in a dog’s brain. Details like the type of brain scanner, or where to find it, were just that: details. Up until this point, I hadn’t been concerned. The best part of being a scientist is when the ideas are coming so fast and furious that you can’t even write them down. You don’t have time to worry about details. They just get in the way.
But eventually we had to confront the practical aspects of pulling this off. And the first detail was finding an MRI facility that would let us bring dogs into its scanner.
Yerkes National Primate Research Center, located about a mile from the main Emory campus, was our first choice for the MRI scanning. Nestled in a valley lined with southern pines, Yerkes seemed ideal. It was a short drive from the lab, so we could easily move our equipment there. And because it was off the main street, it was also quiet and peaceful. The last thing we wanted was to scare a potential canine subject with a trip through a busy intersection. From a dog’s perspective, I imagined Yerkes would look like a walk in the woods.
Yerkes also specialized in the study of animals—primarily monkeys. Andrew and I congratulated each other on our good fortune. We had come up with the idea of scanning the brain of a fully awake dog, and one of the premier facilities for the study of animals turned out to be right in our backyard. In fact, there are only eight such facilities in the United States. Yerkes even had an MRI scanner dedicated specifically to the study of animals. A friend and colleague of mine, Leonard Howell, was director of the Yerkes Imaging Center and invited us to take a look at how they scan monkeys’ brains.
Although the Yerkes MRI center is unusual in the sense that it was purposely built for the study of how primate brains function, it is actually not that unusual to have such a facility at a veterinary school or even at a high-tech veterinarian hospital. Any and all medical diagnostic tests performed on humans are now also done on animals. The challenge with obtaining an MRI of an animal, however, is that the subject must remain absolutely still. In a veterinary setting, this means sedating the animal with medication. But sedating an animal means that you can no longer study how the brain functions.
Leonard had pioneered a new approach to studying monkeys’ brains. Instead of sedating the monkeys, he had figured out how to scan their brains while fully awake. This was a big deal to neuroscientists. When you administer drugs that render the subject unconscious, you change brain function in a major way. How this happens is not really understood. While the unconscious state is interesting for its own sake, most neuroscientists spend their time trying to figure out how the conscious brain works. Having conscious subjects, animal or human, is critical.
Working with monkeys is a dangerous business. Monkeys are mean. Not if-you-don’t-give-me-food-I’ll-ignore-you mean. More like if-you-don’t-give-me-food-I-will-rip-it-from-your-hand-and-eat-your-finger-and-chew-off-your-face-for-dessert mean. This presents certain logistical problems for scanning their brains, especially if they are to remain fully awake.
What’s more, because they are closely related to humans, diseases can pass between the species with ease. For instance, HIV, the virus that causes AIDS, is believed to have originated in African chimpanzees. Monkeys harbor a strain of the herpes virus that is fatal to humans, which can be passed along if, for example, one spits on you, which monkeys often do. The monkeys also have to be protected from us. If humans can catch diseases from monkeys, the opposite is also true. Monkeys are particularly susceptible to tuberculosis. For all of these reasons, scientists must take extraordinary safety precautions to work around monkeys.
Andrew and I made special arrangements to see how Leonard and his team scanned the brains of fully awake monkeys. After registering at the security desk, we were escorted through a series of keyed doors and deposited in a changing room.
“You need to gown up,” Leonard’s assistant instructed. “From this point forward, everyone must be fully protected. This means gown, face mask, and eye shield.”
The so-called eye shields covered our faces entirely and were claustrophobic. They also had a tendency to fog up. The face masks were the surgical type. The combination of shield and mask made speech about as effective as talking into a pillow.
Our first stop was the training lab. Three oven-sized stainless steel boxes lined one wall. They resembled small refrigerators, but the hasp-type handle suggested something akin to a pottery kiln.
“These are the training boxes,” the assistant said. Opening one revealed a sterile interior with white enameled walls and a cubby for devices allowing tubes and wires to snake out to various pieces of monitoring equipment.
On the other side of the room sat an upright tube constructed from PVC plumbing material. A foot in diameter and three feet tall, the top end was capped with clear Plexiglas. A four-inch slot was cut in the center of the cap, and a plastic shelf sat below the slot.
The assistant explained, “This is the restraint device. The monkey has a collar around its neck that fits into the slot. With its head poking through, it rests its chin on the shelf.”
Andrew pointed to a pair of hoses that were attached to the bottom of the device. “What are these for?”
“Waste drainage.”
Pushing the resulting image out of my mind, I asked, “How do you get the monkeys to go in there?”
The assistant pointed to a metal rod on the wall. “That affixes to their collar, and then we can steer them into the device from a safe distance.”
So far, none of this was looking appropriate for the Dog Project. I kept silent, though, still eager to learn anything that might be useful for us. The device kept the monkey from escaping, but it wasn’t clear what would keep its head still.
The assistant pulled a pink block of foam from a shelf.
“This is how we immobilize the head,” he explained. “First, we make a mold of the monkey’s head, which is then used to make a positive cast with plaster. From that, we use a gel-type material to make a soft cast, which fits snugly around its head. We cut holes for the eyes, nose, and mouth. This gets clamped to the restraint device.”
“And the monkeys cooperate with this?” I asked.
“They learn,” he replied. “We shape their behavior through rewards. It takes about six months to train a monkey to go into the restraint device.”
“What are the boxes for?” Andrew asked.
“Those are conditioning boxes. Once the monkeys are trained to go into the restraint device, the whole rig is placed in the box. We then train them with lights and sounds.”
“Trained for what?” I asked.
“To get addicted to drugs.”
Right. Leonard’s research group was studying the biology of drug addiction. To understand addiction, you need to look at the whole process, from the first time somebody uses a drug to the point he becomes addicted. Because it is unethical, obviously, to get people addicted to drugs, Leonard uses monkeys as a stand-in.
The assistant continued. “Once they are trained to associate cues with drugs, we take the whole rig to the MRI scanner so we can see what is going on in their brains while they are craving drugs. Are you ready to go down to the scanner?”
I couldn’t wait to get out of there.