The Science of Social Interaction
Story posted February 14, 2003
Could studying social behavior in goldfish lead to a discovery of what causes autism? The answer is - maybe- though the route is not direct if it exists at all. Like so much in science, understanding why begins with a lot of time and effort, and with the realization that much in the natural world is connected and small steps in one area can lead to surprise developments in another.
The same basic brain chemical affects aggressive behavior in birds and hamsters, stimulates courtship in amphibians, and affects pair bonding in vols. It's even been called "the monogamy drug." Bowdoin's Richmond Thompson, assistant professor of psychology and neuroscience, has proved for the first time that this chemical can affect the way human's perceive social stimuli, and he recently set out to find out if it affects social behavior in goldfish.
Though scientists have studied a related hormone in many other animals, no one had yet looked at vasopressin's effect on social behavior in humans. Thompson's study is the first to show a causal link between vasopressin and social behavior.
In a study soon to be published in the journal Psychoneuroendocrinology, Thompson, with the help of his Harvard collaborator Scott Orr and Shiva Gupta '01, demonstrates that vasopressin affects the way men respond to facial expressions. They had some subjects inhale vasopressin and others inhale a placebo and then showed them a standard series of photographs of faces. Some of them showed happy expressions, some showed neutral expressions and others showed angry expressions. After showing the subjects the photographs, Thompson recorded their physical reactions.
Given a related chemical's ability to affect aggressive behaviors in other species, they predicted that the vasopressin would affect responses to the angry photographs. They found to their surprise that the hormone didn't affect the response to the threatening stimuli, but instead affected responses to the neutral faces. It created an effect similar to that seen in the control group when they looked at angry faces. Thompson is cautious to draw any conclusions from this very preliminary investigation, but he surmises that vasopressin could be in some way affecting the perception process.
"It may presdispose an individal to perceive a neutral or ambiguous stimulus as aggressive," he said. If this is true, it would be consistent with the ideas that breakdowns in the vasopressin system are related to difficulties in interpreting social stimuli, which could be related to disorders such as autism. A recent study by other scientists has shown that patients with autism have a mutation of the gene that codes for the vasopressin receptor. In addition, a 1999 study showed that individuals with personality disorders with high aggressive tendencies also tend to have higher levels of vasopressin in their brain than do individuals with personality disorders without high aggressive tendencies. These studies show corollary relationships between vasopressin and social/personality disorders, but Thompson's preliminary study will be the first to show causal effects.
Thompson plans to expand the study to include women and to add another component: He'll ask the subjects to describe their perceptions of the faces they see (previously physiological changes were measured, not perceptions).
Meanwhile, as he waits for publication of the article on the first human study and waits for the grant to begin the next, Thompson and technician James Walton are hard at work studying vasotocin in gold fish.
Though not directly linked, the current research in goldfish, Thompson's past and upcoming research in humans, and the research of other scientists into analogous systems in other species are all building blocks to greater understanding of the vasopressin/vasotocin system.
Vasopressin and vasotocin, the analogous chemical in fish, circulate throughout the body, as do traditional hormones, but they're also released by neurons in specific regions in the brain, where they serve as neuromodulators.
As a neuromodulator, vasotocin seems to affect sexual or aggressive behavior, but scientists aren't sure exactly how: it could be altering how social cues are perceived, or it could be affecting arousal or performance. They also don't know where in the brain vasotocin is creating these affects.
The goldfish is a good model for vasotocin research because scientists know a great deal about the exact effect that particular social stimuli have on goldfish behavior. Since Thompson knows what to expect, he'll be able to see exactly what effect vasotocin is having and where in the goldfish brain it's working. In a fish, Thompson can look at vasotocin from the molecular to the behavioral level.
In addition, studying similar systems across a range of species is important to show evolutionary development of systems and to allow scientists to develop general principles for use in biological research. Seeing how the vasotocin system works in newts, birds, fish, and even how the related system works in humans demonstrates the range of possibilities of evolutionary brain structure - function and relationships, Thompson said.
"If you only study one species, you can't really extrapolate very well or very far what happens in other species, including or humans," he said.
In earlier research in newts, Thompson demonstrated that vasotocin stimulated courtship behavior by affecting their behavioral responses to pheromones, which are chemical cues used for social communication by many species, including both newts and goldfish. In newts, he was able to establish a model for vasotocin's effect on the way such chemical stimuli are processed. The goldfish are an ideal organism in which to test the generality of his ideas.
But the first step is to discover whether vasotocin affects social behavior in goldfish at all. Thompson's research into this question has just begun and will continue through the summer and beyond.
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