Number Three
I can't resist any articles about our miraculous grey matter. A
specific place that remembers names of animals? Wow.
----------------------------------------------------------------------
'Broker' in brain puts names, faces together, researcher says
----------------------------------------------------------------------
Copyright © 1996 Nando.net Copyright © 1996 The Boston Globe
(Apr 11, 1996 5:30 p.m. EDT) -- If, like many people, you never forget
a face but are terrible with names, it's the "broker" in your brain
you should blame.
"Broker" is what scientists are calling a newly discovered brain
function that, most of the time, enables us to dip into our enormous
store of words and dredge up the correct one for a face or object.
Neuroscientists had long believed that retrieving known words was just
a two-step process: One part of your brain recognized the concept
(it's an eating utensil, or a musical instrument) and then triggered a
separate speech center that would in turn produce the specific word
("spoon" or "clarinet").
But Drs. Hanna and Antonio Damasio, renowned neuroscientists at the
University of Iowa, say they've found there's a previously unsuspected
middleman.
"We find evidence that you don't go from concepts to words nonstop,"
said Dr. Antonio Damasio in a telephone interview Wednesday. "There's
an intermediary structure that helps you go from one to the other,
like a diplomatic broker that is talking to both sides at the same
time."
Moreoever, he said, there may be as many brokers as there are
categories of words. In experiments being reported today in the
journal Nature, the Damasios and their colleagues found at least three
brokers: one that helps retrieve names of familiar people, another for
names of tools, and another for animals.
Surprisingly, the areas of the brain that act as brokers, in effect as
the brain's dictionary or thesaurus, aren't part of structures long
considered the primary speech and language areas -- Broca's and
Wernicke's areas. Instead, they are scattered about the temporal lobe
of the left hemisphere, said Damasio.
The experiments that revealed the existence of the brokers were done
in two groups of people: 127 patients who had had strokes or other
forms of brain damage, and 7 normal volunteers.
The researchers asked the brain-damaged subjects to name objects in
pictures in a standard test and found that some of them made errors
indicating a word-broker wasn't working.
Shown a skunk, for example, one said: "Oh, that animal makes a
terrible smell if you get close to it; it is black and white and gets
squashed on the road by cars sometimes."
His brain produced the right concept, but the brokering step failed,
and he couldn't recall the word. The researchers noted what part of
the brain was damaged in that patient and concluded that's where the
"mental dictionary" for animals was located.
The normal volunteers underwent PET scans, which revealed what parts
of the brain were especially active when they took various
word-retrieval tests. The "hot spots" turned out to be the same areas
that were damaged and inactive in the stroke patients who couldn't
recall certain kinds of words.
The fact that there are many brokers may explain bizarre cases of
people with brain damage who can no longer name certain categories of
words, like tools or animals, but have no trouble naming others.
Damasio said the findings might someday help people who have
difficulty thinking of certain words.
In a commentary, neuropsychologist Alfonso Caramazza of Harvard
University praised the Damasios' work and called for studies to
determine what other brokers exist. "Are abstract concepts -- justice,
evidence and ambition, for example -- also represented categorically?"
he asked.
It's not surprising that people's names are hard to dig up, Damasio
added, because "different brokers handle different levels of
complexity, and the names of specific people involve the highest
levels of complexity. When you're distracted or tired, those may be
hard to retrieve, while you'd have less trouble coming up with the
name of a tool or an animal."
The Damasios' co-authors are Thomas J. Grabowski, Daniel Tranel and
Richard D. Hichwa.
----------------------------------------------------------------------
janet
the cat's claw vines are blooming yellow.
[log in to unmask]
