Rauschecker1s research, conducted over the past two and a half years, involved four rhesus monkeys, whose brain structure is similar enough to that of humans to draw valid comparisons. He and his colleagues performed microelectrode recordings on the monkeys while they listened to rhesus-specific communication sounds coming from different locations.

It was known previously that virtually all higher hearing functions take place in the auditory cortex, which is located on either side of the head, above the ears, and receives information from the inner ear and brainstem. However, the Georgetown scientists were able to define certain specialized areas within the auditory cortex that the monkeys used specifically to identify the type and location of sound‹areas that up until now had not been pinpointed.

"This is an interesting discovery for not only basic scientists, but for anyone who studies hearing and brain function," Rauschecker said. "We hope that our findings can be more widely used to help solve neurological problems that are still not understood."

Ongoing studies will examine functional specialization directly in the auditory cortex of the human brain using functional magnetic resonance imaging (fMRI). This technology allows researchers to observe brain activity in response to certain types of speech sounds and music. "Single-neuron studies in animals remain indispensable nevertheless," Rauschecker says, "if one really wants to understand in sufficient detail how our brain processes such highly complex sounds."