Male zebra finches learn to sing a courtship song between 35 days and 100 days after hatching, at which point they are sexually mature. Area X is located in the male finch's basal ganglia, beneath the brain's cortex. Only males have the full set of circuitry that allows them to mimic sounds. Female zebra finches don't learn the courtship song and don't have a brain region similar to Area X. Humans don't have an Area X either.
"In your brain, I know that the basal ganglia is involved in your speech, but I don't know exactly which cells," White said. "If I knew which cells, I could see what the genes are. We can't do that in humans, but we can in zebra finches and we have."
Two genes that seem to be especially important are FoxP2, a "master gene" that directs many other genes to turn on and off and which is critical for both human speech and birdsong, and reelin, a gene that is suspected of causing autism susceptibility in humans. Autistic children often have language difficulties. Both reelin and FoxP2 may play a critical role in human speech and speech disorders.
"No one had ever thought that reelin has a role in vocalization," White said. "We have now found that it is likely important for vocal learning."
A study published in 2001 revealed a single mutation in FoxP2 in each member of a family in England with a severe speech disorder. Over four generations, half the members of this family had the speech and language disorder, and each of these family members had the mutation. Those family members without the disorder didn't have the mutation.
Recent neuroscience research has provided insights into the connection between the brain and our behavior, including the ways in which our behavior can influence gene expression.
"Everybody knows the brain controls our behavior, but in neuroscience, more recently, we have been learning that our behaviors also control our brain and cha
|Contact: Stuart Wolpert|
University of California - Los Angeles