Brian Alexander writes:
The student naval aviator was flying in formation — a high pressure maneuver anytime, but especially when you're still trying to make the grade — when he suddenly started laughing. Hysterically laughing. Laughing so hard he endangered the flight.
This wasn't the first time the man had broken out in uncontrollable laughter at a seemingly strange moment. In fact, the young pilot had been waking up other members of his household in the middle of night as he, sound asleep, broke out in peals of laughter.
As it turned out, the pilot, who showed no other symptoms when he was documented with the problem in 1997, was experiencing a rare form of epileptic episode called gelastic seizure. The main symptom of a gelastic seizure is uncontrolled laughter.
Laughing or crying at inappropriate moments, or out of context to one's circumstances — crying in the middle of a lecture, for example, or laughing at a funeral — is something most of us experience at least once.
However, as the case of the pilot illustrates, there can be a variety of underlying causes for these ill-timed outbursts. Multiple sclerosis, ALS (Lou Gehrig's disease), stroke, Alzheimer's disease, Parkinson's disease or any number of conditions can cause brain lesions or damage the communications between different parts of the brain. The result is pathological laughing or crying, also sometimes called involuntary emotional expression disorder. Now, Cleveland Clinic researchers are testing an experimental treatment, a combination of two medications, dextromethorphan and low-dose quinidine, to help control the involuntary outbursts.
However, involuntary emotional expression disorder turns out to be something of a misnomer. In fact, true laughter and most crying are never voluntary, according to Robert Provine, author of "Laughter: A Scientific Investigation," and a professor of psychology and assistant director of the neuroscience program at the University of Maryland, Baltimore County
"All laughter is unconscious," he said. "You do not chose to laugh the way you chose to speak."
In the book, Provine relates an amazing tale of an incident that took place in 1962, in Tanganyika (now Tanzania). A group of schoolgirls began laughing. Other girls saw and heard their laughter and they started laughing. Soon, the entire school was giggling uncontrollably, so much so that school had to be dismissed. This epidemic of uncontrollable, contagious laughter went on for six months.
When someone with a brain lesion or neuron damage suffers fits of laughter or crying without feeling especially happy or sad, a skilled neurologist can point to a cause. Explaining why an otherwise healthy person might break into tears or start laughing is more difficult.
Dr. Josef Parvizi, a Stanford University neurologist who studies seizures and pathological crying and laughing, agrees that outbursts of laughter or crying are not really under our complete control, no matter how much we think they are.
Our brains are a dynamic set of interconnected structures with wiring forming a system that has evolved over millions of years, Parvizi said. The idea that human beings can exert complete control over this system the way we can program a computer is a relic of old-fashioned hubris and moralizing.
Crying and laughter depend on flexible interplay between these brain structures, some of which are evolutionarily ancient. That interplay often takes place without our conscious selves knowing anything about it, just as our brain tells our hearts to beat. So, just as something like a nerve communication foul-up can create a harmless momentary heart flutter, the brain regions involved in laughing or crying could evoke a sudden outburst.
Just as nerve communications cause our hearts to beat without us being aware of it, the sight of someone falling down the stairs can evoke a loud guffaw before we can stop it.
Neuroscientists have found that they can evoke crying jags by stimulating a structure called the subthalamic nucleus. When scientists used electrodes to stimulate a region called the anterior cingulate, they got smiles. By turning up the juice, they triggered long, hearty laughter. Yet the patient did not "feel" especially funny.
Most laughter is not the result of a joke, Provine said. It's a form of social communication which is embedded in our brains. When chimps wrestle, they laugh. When mice are tickled, they laugh.
In reality, humor is a mystery, at least in the way it affects the brain. While it's acceptable to laugh at slapstick and jokes, it's not OK to laugh at funerals. One is socially acceptable; the other isn't. Yet both can trigger laughter and we're powerless to stop it.
This is not to say that our cortex, the reasoning part of our brains, cannot exert some control over an urge to cry or laugh. But although we tend to regard human beings as having free will, what we really have is some limited ability to deny or to act upon our brain's desires.
"What the brain will want to do is not free," Parvizi said. "The fact I want ice cream at this moment is out of my control." He may or may not help himself to ice cream, but he can't prevent his brain from wanting it.
Our conscious brain tries to control these desires according to the norms of our culture as we learn through experience what our emotional response ought to be to various situations.
"The circuitry that controls emotional expression first processes what is outside, the situation," he said. "Then it relates this particular situation to past experiences and how the brain has learned to respond. Then it triggers the emotional response. It's all to some extent involuntary and spontaneous." Nobody knows exactly why this system might malfunction in the absence of a disease or injury.
But clearly something has gone momentarily haywire.
When such an inappropriate response is triggered, like when we are listening to great aunt Judy's eulogy, Parvizi said about the best we can do is chalk it up to a "glitch" and hope the relatives don't boot us out of the will.