How Dogs Love Us: A Neuroscientist and His Adopted Dog Decode the Canine Brain (10 page)

We still needed a physical mockup of the scanner to train the dogs in. Many universities that house MRIs for brain research have mock scanners. There are many situations where it makes sense to train people in the scanner before actually scanning their brains. Brain-imaging studies of children, for example, must first teach kids to lie still in the scanner by using a simulator. Because the MRI can be frightening, it is very helpful to allow children to get used to the environment before they go into the real scanner.

It isn’t surprising that a few companies have cropped up to sell mock scanners. The price tag, however, is steep. When we embarked on the Dog Project, the going rate for a mock scanner was about $40,000. Since we had no funding, this wouldn’t be practical. Besides, I couldn’t see spending so much money for what amounted to an empty tube with a few speakers inside to simulate the noise.

But how much of the real MRI would we need to simulate? Did we need something that could fill an entire room, like the real scanner? Or could we get away with a simple tube? After all, the dog was going to be inside only the scanner.

Mark came to the hospital to check out the MRI facility and determine how much of the actual MRI we would need to simulate for dog training. He hopped up on the patient table and lay down, putting his head in the birdcage. With the press of a button, the table glided into
the center of the magnet. A quick thumbs-up indicated he was good to go. We went through a few quick brain scans so that Mark could get an idea of the types of noises and how loud they were.

Mark came out of the scanner with a big grin on his face and proclaimed, “This is completely doable.”

“Do you think we need a mockup of the entire scanner?” I asked.

“No, just the patient table and the tube will be fine.”

This was good news, because we were going to have to build the simulator ourselves. The mock scanner would have three elements: a tube to simulate the inside of the scanner; an exact model of the birdcage, which the dog would have to shimmy into; and a sound system to play recordings of the scanner noise at the appropriate loudness.

I was looking forward to this. Constructing a simulator would let me dust off some woodworking equipment that had been lying dormant in the garage. It’s fun to build stuff.

To simulate the inside of the scanner, we needed a tube of the right diameter. The MRI bore measured sixty centimeters, or two feet, in diameter—larger than any tubing you would find at your local hardware store. That is, however, a common diameter of concrete pillars used in the construction of buildings. These pillars are made by pouring concrete into molds sold under the trade name Sonotube. Andrew made a few calls to construction supply houses around Atlanta and soon located a twelve-foot-long, two-foot-wide Sonotube.

“Do they sell it by the foot?” I asked him.

“Nope,” Andrew replied. “We have to buy the whole piece.”

“How much?”

“About a hundred bucks.”

“How long is the MRI bore again?”

“Six feet.”

“This is great,” I said. “We can do this NASA style.”

Andrew looked puzzled.

“In the old days,” I explained, “NASA always launched two spacecraft for their missions. The reason was that most of the cost of a project was in the design and development. Once those were achieved, the added cost of a second spacecraft was minimal. Plus, it added a level of protection if one craft failed. If we need to buy twelve feet of Sonotube, we might as well just cut it in half and build two simulators. We’ll give one to Mark to use at CPT, and I can keep one at home to test on Callie.”

Building the main tube didn’t require much beyond cutting the Sonotube in half. Andrew and I found everything else we needed at the local Home Depot. We bought two folding tables to mount the tubes on. A sheet of plywood and some lumber would serve as the patient table inside the tube. We did the construction in my garage on a Saturday.

Even though the result looked nothing like an actual MRI scanner on the outside, the important part for the dog was the interior of the tube. Andrew had obtained all the measurements from the real scanner. All we had to do was duplicate the height and width of the patient table when fully inserted into the MRI bore. To test it, we took turns crawling into the simulator. We both agreed it felt just as claustrophobic as the real thing.

Andrew and I building the MRI simulator.
(Helen Berns)

Building a mockup of the birdcage was a little more complicated. It is a peculiar shape, a cylinder about a foot long and a foot in diameter. Because it lies on its side, the cylinder rests in a cradle that attaches to the patient table inside the MRI tube. Andrew took exact measurements of the real coil and made a full-scale tracing of the ends of the birdcage. We transferred the tracings to some plywood and used a jigsaw to cut out exact replicas of the ends of the coil. Wood dowels were used to simulate the cage of the coil and also to hold the ends of the birdcage together. We bent a thin sheet of plywood into a semicircle and glued it inside the whole construction. For humans, this would form the cradle where the head rests. The dogs would need to shimmy their whole body into the coil and assume a sphinx position.

Callie kept a respectable distance from the simulator. She wasn’t afraid of it, but she wasn’t treating it like a toy either.

Just for fun, I tried to coax her into the tube, but she wanted nothing to do with it. Even with a dog treat inside, she still wouldn’t go in. The whole thing was just too foreign. Plus, it was elevated on a table, and she did not like being placed on a table. Too much like a visit to the vet.

Maybe the birdcage would be an easier place to start.

We began by placing the birdcage on the floor. I wanted Callie to sniff it out on her own terms. After a few minutes, she became bored and walked away. This was a good sign: she was getting used to it and didn’t view it as a threat. Next, I lay down on the floor and put
my head in the birdcage. Callie still wasn’t ready to jump in with me. But a little peanut butter on my lips changed her mind. She bounded onto my chest and stuck her head in to lick it off.

Since she seemed to be having fun now, I dabbed a little peanut butter inside the coil to get her to go in by herself. She happily lapped it up. To avoid smearing the whole birdcage with peanut butter, I switched over to dog treats.

Each time she stuck her head in the birdcage, I moved the treat a little farther back. I wanted to see if she would assume the sphinx position in the birdcage, but I had no idea how to do that. As much as I loved Callie and secretly hoped that she was going to be subject number one, I was afraid that she was too ill behaved for the experiment.

I e-mailed Mark some pictures of the mock scanner. In the last photo, Callie lounged next to the head coil.

Much to my delight, it was Mark who suggested using her.

“She looks comfortable with it,” he wrote. “Why not make Callie the first subject?”

I test the mock head coil, while Callie investigates.
(Helen Berns)

9

Basic Training

C
ALLIE LOOKED GOOD AT HOME
,
but how would she do in an unfamiliar environment? She showed no fear of the head coil, a sign she would be able to adapt to novel tasks. But there was only one way to find out for sure.

Helen, eager to see how Callie would do with the training, helped me load her into the car, and the three of us headed to CPT with the head coil to see Mark work his magic.

Helen entered with Callie, while I placed the head coil on the floor.

Mark looked at it and nodded. “This should be easy. Did you bring treats?”

From puppy training, I knew that soft treats are best. You can cut them up into tiny pieces so the dog doesn’t fill up too quickly. And the dog can consume them easily without getting distracted by crunching on a hard biscuit. The only treats I could find around the house were some hot dogs that had been pushed to the back of the refrigerator. I had no idea how long they’d been there, but they smelled okay, and Callie loved them. I handed Mark a baggie full of sliced-up hot dogs.

“First,” he said, “let’s start with the clicker.”

A training clicker is a small device about the size of a USB flash drive that, unsurprisingly, makes a loud
click
when pressed. Dogs can hear the clicker from across the room. The advantage of using one is that it always makes the same sound, which is not the case with vocal commands. Because it’s almost impossible to screw up, the clicker is a useful tool for beginners like me. Its operation is simple: when the dog does something correct, you click. For this to work, however, you first have to teach the dog that a click equals a reward. This is classic classical conditioning. Just like Pavlov.

Callie tracked the bag of hot dogs as I handed it to Mark. Then she dutifully sat at his feet, tail sweeping the floor. Mark clicked and immediately gave her a piece of hot dog. Callie got even more excited. She could barely sit.

At this point, what Callie was doing was unimportant. Mark periodically clicked and handed her a reward. He was establishing the association of each click with a transfer of reward, making it a conditioned stimulus. It didn’t take long. A dozen click-rewards, and Callie understood the association. With the meaning of the clicker established, Callie was ready to learn a behavior. I could immediately see how the clicker was going to make this easier.

Mark explained another advantage of using the clicker. “We are going to shape her behavior. Initially, anything Callie does that is close to the desired behavior will be rewarded. The clicker makes it absolutely clear to her that she has done something correctly. This way, she won’t get conditioned to just my voice or your voice.”

The clicker gives instantaneous feedback, making it clear to a dog that she has done something good without wasting time fumbling for the treats. Unlike a human, a dog’s memory for what she has just done appears to be very limited. The longer the interval between the desired behavior and the subsequent reward, the less likely the dog will make the association. This phenomenon is called
temporal discounting
. Research in rats suggests that a reward given four seconds
after a desired behavior is roughly half as effective as one given immediately. If the handler is deeply involved with the dog, using hand signals and vocal commands, he might not be able to give a reward for a while. This is especially true of complex behaviors. The clicker solves this problem by giving instantaneous feedback.

Mark was beginning to lure Callie into the head coil. Reaching into the coil with a hot dog in one hand and the clicker in the other, Mark had already succeeded in getting Callie to place her nose inside. Each time she did so, Mark clicked, praised her, and gave her a bit of hot dog.

With every click-reward, Mark pulled the food back a little bit, shaping her behavior gradually. Within ten repetitions, he had Callie crouching in the coil with her snout poking out the other end. Some gentle pressure on her rump indicated that she should lie down in the coil. As soon as she did, Mark clicked and exclaimed, “Good coil!” Callie wagged her tail and licked the hot dog from his hand.

I couldn’t believe how quickly Mark had gotten Callie where she needed to be.

“How is the positioning?” he asked.

Callie was lying down in a sphinx position in the coil. Her paws hung over the near edge. She would need to move back a little bit.

“We’ll want her head in the center.” Mark nudged her back an inch and clicked.

“You can shape her behavior at home too,” he said. “I think she’ll do really well with this.”

A woman walked into CPT with a border collie.

“This is Melissa Cate,” Mark said. “Melissa runs some of our agility classes at CPT. She’s interested in volunteering her dog for the MRI.”

“Mark told me about the Dog Project.” Pointing to her dog, she said, “This is McKenzie.”

McKenzie was Melissa’s three-year-old border collie. Melissa
had begun agility competitions a few years earlier with her boxer, Zeke, who had reached the highest ranks. Zeke was now eight years old and slowing down a bit, so Melissa had gotten McKenzie as a puppy to keep competing in agility. They had been going strong ever since.