The first word on nouns and verbs

Since humans learned to speak, they have put their words into two basic categories, nouns and verbs. Nouns denote objects; verbs refer to actions. Dictionaries of specialized words have been added by bankers, lawyers, scientists, and clergy, but this core distinction remains.

Birds sing, but sings don't bird, in any language.

Scientists would really like to know how our brain arranges words into meaningful sentences, how it does grammar. "Knowing this would help us understand how the brain organizes knowledge," says Alfonso Caramazza, Daniel and Amy Starch Professor of Psychology at Harvard University.

Caramazza is one of many people who look for clues to this organization in brain-damaged people. Those with injuries in certain areas under the left temple often show difficulties producing nouns. Others who suffered trauma on the front left side of the brain may struggle with verbs. He describes one case of an injury to the front left side that resulted in such a deficit. Closer examination revealed a small area of the brain that was not getting enough blood. When the medical team restored blood flow, that patient regained the ability to produce and comprehend verbs.

Working with Kevin Shapiro, an M.D.-Ph.D. graduate student, Caramazza is trying to pinpoint the difficulties such patients face when processing nouns and verbs. For example, some of them find it tough to use these words in a sentence. They can say "the sails" but not "he sails."

With the assistance of Lauren Moo at the Harvard Medical School, Caramazza used an MRI brain scanner at Massachusetts General Hospital in Boston to obtain images of brain activity while volunteers spoke short phrases and sentences. Other researchers have done such scanning experiments, but this is the first time that specific brain sites were seen to be activated by either nouns or verbs, but not both.

"For the first time we were able to identify areas of the brain where no overlap occurs between production of nouns and verbs," Caramazza maintains.

The experiments were described in the online edition of the Proceedings of the National Academy of Science (http:// www.pnas.org) on Jan. 16, 2006.