ITHACA, N.Y. -- Cornell University biologists have shown how chemicals produced in a core region of the brain shared by all vertebrate animals (including humans) make males act like males, females like females -- and some males something like females.
James Goodson and Andrew Bass, who studied a fish species that produces two types of males for their report in the Feb. 17, 2000, issue of the journal Nature, say that brain processes responsible for social behavior typical of females, for example, aren't necessarily linked to the female's sex at all.
"This is a clear demonstration of how the action of neurochemicals can modulate the electrical or neurophysiological output of the brain as it establishes a social behavior," said Bass, professor of neurobiology and behavior, in an interview.
"We have also shown that there can be a neurochemical dissociation -- an uncoupling -- between an animal's gonadal sex and the regulation of behaviors typical of a sex," said Goodson, a postdoctoral fellow in Bass' neurobiology laboratory.
The part of the brain studied by Goodson and Bass is the preoptic area-anterior hypothalamus, a section of the basal forebrain, which neurobiologists say has been "conserved" throughout the evolution of vertebrates. The functions and structure of this conserved brain region are strikingly similar in fish, amphibians, reptiles, birds and mammals, including humans. The neurochemicals credited with sex-related social behaviors are isotocin and vasotocin in fish and are essentially the equivalents of oxytocin and vasopressin, respectively, in mammals.
The fish that made the neurochemical finding possible is the plainfin midshipman (Porichthys notatus), best known for its singing in shallow salt water at mating time. Most of the noise comes from male midshipman fish of the type I variety, which vocalize for hours under rocks to attract females. When type I males' courtship songs are successful, female
Contact: Roger Segelken
Cornell University News Service