Then, in the grand style of scientists who become research subjects themselves, he flipped the experiment, stimulating his
own cortex with a powerful magnetic field. "If the cortex was mediating an emotional response, you'd expect me to feel something," he said. "But I didn't."
Seeking the Center of Joy
If not in the cortex, where does emotion reside? Panksepp spent years using electrical probes to stimulate parts of lab animals' brains and then observing the behaviors provoked. An electrical impulse is a crude stimulation—it carries no information other than a jolt—yet in case after case, he'd stimulate a specific part of a rat's brain and get a coherent emotional response.
Through years of experimentation he found that many emotional circuits converged in a relatively primitive part of the midbrain called the periaqueductal gray, or PAG. Present in all mammals, the PAG produces raw "affects," as he calls them—our basic emotional impulses. It is the PAG that overwhelms us when we grieve, the PAG that signals the brain to bathe us in the soothing hormones of nurturance or the arousing chemicals of love. Panksepp has thus far isolated seven basic emotional drives common to humans and other mammals in sections of the PAG: Predictably, there are fear, rage, lust and separation-distress—all strong, basic drives that most of us would associate with the struggle for survival. But he has also found more subtle emotions, including the quest for nurturance, the desire to offer care and the drive to play.
In humans, these impulses make their way to the brain's higher centers, where they may be processed, modified, inhibited, magnified or even reflected upon. Other mammals lack the ability to reflect on emotion, but they feel it just the same. When you look at your dog bounding on his paws, wagging his tail and playfully panting, you can probably assume he feels happy and eager to interact; when you leave the room and he whimpers, you may conclude he feels sad. What you can't assume, Panksepp says, is that your dog will think back on that happy encounter or sad parting later in the day.
The Laughing Brain
All of which brings us to rat laughter, Panksepp's most controversial work. By tickling the rats, Panksepp and his students elicited laughterlike chirping. When they administered dopamine or electrical stimulation, the effect was the same. The conclusion: The laughter does not arise from learning or conditioning—or from having parents with an urbane sense of humor. It originates as a neurochemical action in the ancient brain structure called the PAG.
Given the origins of laughter and play, says Panksepp, they likely helped us survive and evolve. Other scientists have remarked on the value of play as rehearsal for life's challenges, from hunting to mating. Panksepp has taken it further by proving that play boosts the brain's pleasure-causing dopamine, priming us to respond to changing social situations through neurochemical cues. Play provides a risk-free opportunity to develop adaptive responses to new situations. "This process, which children do on their own, helps create a social brain," Panksepp says.
Panksepp's work suggests an emotional engine for evolution rooted in the ancient brain. Emotions originating in the PAG help animals recognize "comfort zones"—social situations that enhance survival. A pup's chance of survival, for instance, is improved if it's wired to stay near its mother—hence the separation response. Socially skilled pups tend to survive longer, says Panksepp, explaining the rat's love of play.
As Panksepp's colleague Brian Knutson puts it: "The evolutionary goal of a mammal is to survive and procreate. But mammals don't have to be aware of that goal. Your emotional status—things that make you feel good or bad—act as a shorthand."
Few neuroscientists accept so broad a proposition. University of Iowa cognitive neuroscientist and animal behaviorist Mark Blumberg calls Panksepp's assertions about rat laughter, "bordering on irresponsible." Two years ago Blumberg published a paper asserting that rats emit high-frequency chirps in response to changes in temperature and to the physical compression of their chests during rough and tumble play. "Think about laughter in humans," he says. "We don't even know what it is. To assume we know what these emotions are and
then project them onto animals is a double error. We just don't have access to the inner lives of animals."
Joseph E. LeDoux, a neuroscientist at New York University who has mapped the neural pathways of the fear response of mammals, says he admires Panksepp's study of behaviors, but hesitates to equate their feelings with emotions played out in the human realm. "I don't deny the existence of animal feelings. I just say it's impossible to know what they feel."
Those who spend time with animals in their natural settings don't have as many doubts. "There are fewer and fewer people who will say carte blanche that dogs don't have feelings," states ethologist Marc Bekoff. It may not be the same as human love, but "of course, dogs show love."
Panksepp's work is still preliminary, and years away from offering cures for human maladies, his original goal. Yet his ideas show practical promise. In looking at the chemistry of social behavior, for example, he finds that rats and dogs given overdoses of opiates lose their need for social connection and retreat to a state much like autism. Panksepp reversed the behavior in rats by treating them with the opiate-blocking chemical naltrexone. Scientists have given naltrexone to autistic humans and found encouraging signs of social alertness.
Tags:
animal behaviorists,
animal emotions,
animals,
bowling green state university,
brain imaging,
electrical stimulation,
electronic device,
emotion,
emotional lives,
glee,
guinea pigs,
human perception,
Jaak Panskepp,
lab rats,
maternal attachment,
modern tools,
neuroscientist,
new digs,
passion,
play today,
rats,
rough and tumble,
rough and tumble play,
squeals,
washington state university
