Because dogs have basal ganglia and limbic systems that look almost the same as ours, such a map could be applied to dog brains to help determine what a dog is feeling.

In the upper left portion of the circumplex are the emotions with high arousal and negative valence. The usual behavioral manifestation of these emotions is avoidance or retreat from whatever caused them. However, the close proximity of emotions like fear, anger, and frustration in the circumplex make that quadrant difficult to map in the brain. Despite having similar levels of valence and arousal, those emotions feel quite different from one another. Although much is known about the fear system of the brain, almost nothing is known about rage or frustration.

The upper left quadrant would remain uncharted territory in the Dog Project because of the ethical problems with inducing those types of emotions in our dogs.

In contrast, the upper right quadrant of the circumplex model is well understood and seemed like an excellent place to begin mapping the dog brain. These are the emotions that are maximally enjoyable: very good and very exciting. These positive emotions are also associated with a specific behavior seen in all animals. If something is good and exciting, every animal—dog, rat, human—will approach it. Panksepp calls this the seeking system. In the brain, we know that approach behavior, as well as the corresponding positive emotions, is associated with activity in a tiny part of the basal ganglia called the nucleus accumbens. In humans, when we observe activation in this region we can deduce that the person is experiencing a positive emotion and very likely wants whatever is making them excited.

Although I couldn’t know for sure, when Callie saw me with the bag of hot dogs, her nucleus accumbens was probably lighting up like a Christmas tree. Wagging her tail and running toward me was a classic approach behavior. This led me to assume that she was experiencing joy and excitement. But only through fMRI would we know what she truly felt.

13

The Lost Wedding Ring

UNLESS WE CAME UP WITH a solution for the head movement problem, the Dog Project would grind to a halt. We had two choices: either train the dogs to hold their heads still or come up with a better chin rest.

Mark was confident we could train the dogs. Considering that we needed the dogs to move less than two millimeters in every direction, this struck me as a significant obstacle. As I worked with Callie, I couldn’t even discern movements that small. She could easily move a few millimeters while I was looking away, and I wouldn’t even know. The alternative, a more restrictive chin rest, didn’t appeal either. I didn’t want to encase the dogs’ heads in plastic like what Andrew and I saw at Yerkes.

We were at an impasse.

Movement during a scan causes ghosting, but movement between scans causes a different problem. At the beginning of a series of scans, we have to set the boundaries of the scan, called the field of view (FOV). As Callie demonstrated during the dress rehearsal, she didn’t always place her head in the same position in the head coil. Because of the inconsistency of her head placement, sometimes she was in the FOV, but most of the time she wasn’t. All but one of the images were empty.

We had a few tricks we could do with the functional scans that would help with the movement problems. An easy fix for ghosting is to shorten the time it takes to acquire an image of the brain. By shortening the scan time, it makes it less likely the subject will move during that period. But the only way to shorten the scan is to take fewer slices. Each slice through the brain takes roughly sixty milliseconds. For humans, it usually takes thirty slices to cover the whole brain, for a total of two seconds. Fortunately, dogs have smaller brains than humans, so we don’t need as many slices. But if we get fewer slices, the FOV shrinks, and the between-scan movement becomes a bigger problem. With a small FOV, we might miss the brain entirely if the dog didn’t put her head in the correct location.

We needed a solution to both the within-scan and between-scan motion.

The problem was the chin rest. The foam bar provided feedback to the dogs about where to place their heads in the up-down direction, but left them free in the left-right and forward-backward directions. We needed something that would guide the dogs to place their heads in exactly the same position every time they went into the coil and would keep them there for the duration of the scan.

Atlanta had caught a week of unseasonably warm weather that January. It was a good opportunity to get outside, and I figured a change of scenery might generate some new ideas about the movement problem. So Kat and I piled the girls and the dogs into the minivan and headed down to the river for some hiking.

The Chattahoochee River originates in the northeast corner of Georgia, in the foothills of the Blue Ridge Mountains. From there, it flows southwest toward Atlanta, picking up volume along the way. Eventually, the “Hooch” flows all the way to the Gulf of Mexico. Much of the area around the Chattahoochee is national forest, and we were fortunate to live only a mile from the river. It was a great place to hike or mountain bike or just relax on the banks and watch wildlife.

Our favorite spot was Sope Creek—a rushing stream that tumbles down to the river over a series of granite boulders. In the decade before the Civil War, a ferry shuttled people and lumber across the Chattahoochee where the creek met the river. Next to the creek, the ruins of an antebellum paper mill had been overtaken with kudzu, the aggressive southern version of English ivy. We spread out our towels beneath the ruins while Helen and Maddy jumped from rock to rock across the creek. It had rained a few days earlier, so the flow was higher than usual.

Lyra, despite her golden retriever genes, would wade into the water only until it touched her belly. Since she had no interest in swimming, I let her off-leash. She just milled about, sniffing rocks and plants and nosing around for bits of food other people had left behind.

I looked at Callie. Her prey instinct was on red alert. She sat stiffly at the end of the leash, head like a periscope, twisting in lightning-fast jerks toward every sound and motion in the woods. She looked up at me and whimpered. I didn’t need an MRI to know what she wanted. She wanted to be off-leash like Lyra.

Figuring she would hang around the picnic spread that Kat had been setting up, I reached down to unclip her. The world seemed to spin down. As I pulled back on the leash clip, Kat screamed out in slow motion “Nooooo!”

With the opening of the clip, everything kicked into high speed. With that telltale click, Callie knew she was free.

She never looked back. Like a cheetah, Callie arched her back and released all of her pent-up energy into a massive sprint. Until that moment, I’d had no idea she could swim. But what it really looked like was a twenty-pound stone skipping across the creek. In three bounds, before anyone could react, she had hopped across the water and disappeared into the woods on the other side.

“Dad!” Helen screamed. “Callie is running away!”

I jumped into the creek. The current was strong, so I faced upstream and crab-walked as fast as I could, grabbing on to boulders for support. It must have taken at least a minute to wade across, and I could mentally tick off the distance that Callie was covering with each second.

The other side of the creek was thick with kudzu and poison ivy, but a thin path headed downstream toward the Chattahoochee. If Callie made it that far, her next stop would be the Gulf of Mexico. I couldn’t bear the thought of losing another dog so soon. Never mind that the only dog in the world that had voluntarily sat for an MRI, even if only a dress rehearsal, had just escaped because of my own stupidity.