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 do have persistent emotions, despite not having a declarative memory of what caused the emotion in the first place.”
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 skies.
14. False Alarms
Usually, it’s fun to sit in the bleachers. Maybe it’s the altitude, but there’s something easygoing about the patrons up there—bleacher bums dress casually, bring snacks, and seem to have a pretty good time. That also goes for the upper decks of a Broadway theater.
It was a rainy fall evening in Manhattan. Jude Law was playing a particularly well-dressed and anguished Hamlet at the Broadhurst Theatre on Broadway. The views from the upper decks were good and not obstructed. By the time the prince saw ghostly visions of his father, a pack of cellophane-wrapped Twizzlers was being passed around the last row.
That’s when the problem started. One patron wasn’t amused. Every Twizzler extraction prompted her to whip her head around and shoot icy glares. Then two people nearby slid a box of Good&Plenty out of a backpack. Even the most gingerly shake of the carton produced a loud sigh from the woman. Yet it was the Goobers at stage right that sent the lady over the edge. Without sugarcoating it, she went nuts. “Stop eating.” It was a whisper-yell, accompanied by a little fist bang on the armrest—but it was loud enough so that heads turned, up and down the aisle.
It’s possible that junk food is this woman’s pet peeve—maybe she’s a dentist or a personal trainer, and it qualifies as a “professional annoyance.” Maybe there’s some cognitive overlay that we could never guess. Or, perhaps a more depressing explanation is that this particular person suffers from a genetic predisposition to getting annoyed.
Sarina Rodrigues is a neuroscientist in the Psychology Department at Oregon State University. Her research points to one way in which genetics could play a role in irritability and what that could mean for treating annoyance. Rodrigues is broadly interested in how our brains process emotions, and her approach is to study oxytocin. It is a chemical that acts as both a neurotransmitter and a hormone and has been implicated in trust, generosity, romantic attachment, and sex. In prairie voles (Microtus ochrogaster), oxytocin has been shown to work sort of like Cupid’s arrow. When oxytocin was injected into the brain of a female vole, she rapidly fell for the nearest he-vole around.{50}
Oxytocin is manufactured in the hypothalamus region of our brains; it acts locally to help brain cells communicate over short distances and travels far afield to places such as the uterus and the heart, where it acts as a hormone. Like all hormones, oxytocin doesn’t do anything without a receptor. The receptor is a protein sticking out of the membranes of cells. When oxytocin wafts by, it engages with the receptor, which sets off a chemical cascade inside the cell. Like a car key, it doesn’t do much on its own, but with a turn, it activates a lot of sophisticated machinery.
Not all cells have all receptors. This is partly why certain hormones have specific effects—because they can interact only with certain cells. And some cells have more receptors than others: in places where reactivity is crucial to keeping us alive, such as where nerves and muscles meet to control our movements, a muscle cell can have ten thousand receptors per square micron.
There are receptors for oxytocin in cells all over the body, from the heart to the nervous system. Oxytocin fits into only one specific receptor, Rodrigues says. It’s as if oxytocin turns on only one make of car, which makes life simpler for the researchers studying it. The oxytocin receptor is coded by a gene on chromosome three. Rodrigues and her colleagues wanted to know whether a variation in this gene had any affect on a person’s behavior—specifically, on a person’s reaction to stress.
Oxytocin calms us down when we’re stressed, Rodrigues says. “It plays a key role in attenuating how much our emotional centers of the brain activate. It can actually calm the brain down. It can also lower heart rate responses during psychosocial stress.”