outbursts.
One way to find out the role of a particular part of the brain structure is to see how people behave without it. Occasionally, this happens: parts are essentially “removed” because of a stroke or some other brain injury. There are also many cases where brain areas are removed as a procedure in a medical therapy. Some neurosurgeons have removed part of a patient’s anterior cingulate cortex in order to treat psychiatric disorders such as major depression, schizophrenia, aggression, anxiety, and substance abuse. Cingulotomy, as it is technically known, has also been used on patients with chronic pain.
“Cingulotomy evolved as a better solution than frontal lobotomy,” says neuroscientist Ron Cohen of Brown University. “The idea was that rather than do the whole removal of the frontal cortex”—a procedure that brought about a rainbow of psychological changes—surgeons “would try to get this area that was more specifically tied into the emotional systems and pain systems and things like that.”
Most of the studies on patients who have undergone cingulotomy focus on whether their main symptoms were relieved. Cohen conducted one, however, that actually looked at the changes in emotional states in patients who elected to have the surgery.{49} The patients in this study were being treated for intractable pain. After the surgery, researchers gave them standard personality questionnaires and mood-measurement tools like the ones Denson used with his subjects.
Most of the patients did get relief from their pain following surgery, according to the authors. None experienced severe negative emotional side effects from their surgery. Yet there did appear to be personality changes. The families of many of the patients reported that after surgery, the patients tended to be perceived as being more relaxed or laid back. “In some cases,” the authors wrote, “These changes were described as mild apathy and a lack of initiative after surgery.” The patients themselves tended not to be aware of major personality changes, other than reporting less emotional tension, anger, and pain.
Howard Wilkinson performed the surgeries on the patients in Cohen’s study. He is a neurosurgeon at Massachusetts General Hospital in Boston. Wilkinson has performed numerous cingulotomies, mostly to control chronic pain. He says patients who have the surgery still feel pain, it simply doesn’t bother them as much. “A constant, chronic, ongoing irritation or pain fades away,” says Wilkinson, “and people are less annoyed by the pain.”
Wilkinson’s study didn’t look specifically at whether postoperative patients were less likely to be annoyed in general, “but they did seem calmer,” he says. “The emotional state seemed slightly flatter.”
This fits with Cohen’s ideas of the role of the cingulate as a gateway to annoyance. All of the disorders that cingulotomy is used to treat involve what Cohen calls an “obsessive, ruminative loop.” When the surgery works, Cohen says that it breaks the loop and allows people to live with, if not actually to ignore, the stimulus they are obsessing over, whether it’s something unpleasant, such as pain or fingernails on a blackboard, or even when it’s pleasant, like gambling or taking cocaine.
Of course, this “calmer” state makes it seem that it’s not only annoyances that cingulotomy patients are less bothered by. Still, when neuroscientists trace the pathways of annoyance in the brain, as they are certain someday to do, it’s likely that the anterior cingulate cortex will be an important part of the route.
Another way to get at how the brain processes annoyances is to look at patients with amnesia. Never mind the amnesia depicted in Hollywood movies, where the hero suddenly remembers he’s a super spy. This is genuine amnesia, where people can form no new memories at all.
One of the best-studied cases of amnesia was a patient known only by the initials H.M. while he was alive. Henry Gustav Molaison died in 2008 at the age of eighty-two. When he was a child, he was hit by a bicycle. The accident caused him to start having severe seizures. When he was twenty-seven, surgeons removed a portion of his brain as a way to bring the seizures under control. The operation was a success, but it left Molaison with a very unusual problem. He couldn’t form any new memories.
You could walk into a room where Molaison was sitting, introduce yourself to him, chat for a minute or two, leave the room, return a few minutes later, and he’d have no memory whatever of having met you. To make things even stranger, he remembered lots of details from his life before the surgery—just nothing new that happened.
It turns out that one portion of the surgical procedure involved removing a part of Molaison’s brain known as the hippocampus, as well as some nearby related brain structures. It’s a region that appears to be crucial for consolidating memory. It’s not as if Molaison had no memory at all. He could hold a conversation, which meant remembering what someone had just said to him, but storing that memory, remembering the conversation for more than a minute or two, is impossible without a hippocampus and its neighboring brain regions.
Since scientists identified Molaison’s problem, they have found many more patients with damage to this part of the brain who experience the same memory deficits. Yet the kinds of memories that are lost without a hippocampus are what psychologists call declarative memories, memories for things such as names, faces, facts, and figures. Declarative memories require a conscious, thinking brain.
There are other kinds of memories that don’t require this kind of conscious thought. Think of how you learned to ride a bicycle. You don’t say to yourself, “Okay, step over the seat, hold onto the handlebars, put one foot on the pedal, push off, start peddling, don’t fall over.” No, you simply get on and ride. Remembering that a flame can burn you also does not use much of your conscious brain. Remembering that dark alleys can be dangerous places is more of an emotional memory. Even if you’ve never been attacked in a dark alley, a feeling of danger is associated with it.
So, what kind of memory is involved in remembering that someone or something was annoying? Although the definitive study has yet to be performed, neuroscientist Daniel Tranel of the University of Iowa thinks he knows the answer. Tranel works with a lot of amnesic patients. Consider, he says, the following scenario: “You are flying on a long-distance trip, say, three or four hours, and in the row ahead of you are a mother and her small baby. The baby begins to cry, on and off. At first, you are not much bothered, hoping that the crying will subside. But it doesn’t subside and keeps up for the next two hours, with the baby crying out in a very annoying way every so often. This gets more and more annoying and prevents you from sleeping, working, and otherwise relaxing and enjoying your trip.”
Now, Tranel asks, what would happen if you had severe damage to your hippocampus? “First, you would not remember the baby crying from one time to the next, because the time between cries is at least many minutes and beyond the time frame for which you can retain new declarative knowledge. You would, however, become annoyed. Despite not having any declarative memory of the baby or of the fact that the baby has cried before (many times), you would have built up an emotional response to this.”
In other words, each time the baby cried, you would experience the emotion of annoyance, and that emotional response could persist and even strengthen to the point where you would be very annoyed. “In that respect, your response is like that of a normal person, that is, extreme annoyance. Unlike a normal person, however, you do not have any declarative memory of the cause of your annoyance.” So you’d be annoyed, but you wouldn’t know exactly why. “This prediction is based on some of our recent work with amnesic patients,” says Tranel, “which has demonstrated that the patients
Larry Squire at the University of California, San Diego, agrees with Tranel’s conclusions. Squire says the part of the brain that is essential for forming and retaining these emotional memories is the amygdala. The amygdala is another part of the limbic system, that portion of the forebrain that also contains the cingulate cortex.
So if the amygdala or some other part of the limbic system is damaged, does that mean, in Tranel’s hypothetical scenario, that the airline passenger would remember that there was a crying baby on his flight but will not feel annoyed by its intermittent crying? Yes, says Squire. “We did that experiment a long time ago with monkeys.” He removed a portion of a monkey’s amygdala and then compared monkeys lacking amygdalas with those whose amygdalas were intact. “We tested them on various emotional reactivity, fearful stimuli. It was only the monkeys without the amygdalas that showed any abnormality on that test.”
There’s one other scenario to consider here. What if, in addition to missing your hippocampus, you’re missing your cingulate cortex as well, and once again, let’s say, you are sitting behind that annoying baby?
The missing hippocampus would prevent you from remembering the last time the baby cried, and the missing cingulate would presumably keep you from becoming annoyed each time you heard it. So, in this scenario, the plane ride with the squalling baby would be, if not bliss, at least no worse than any other plane ride in today’s crowded
