Those old familiar faces.

Those old familiar faces

Some people, primarily certain victims of Alzheimer's disease, amnesia, strokes or herpes encephalitis, also suffer from prosopagnosia, a brain disorder that renders its victims incapable of visually recognizing the faces of people they know--including their family and friends. Many prosopagnosiacs claim they rely upon other cues, such as voices, in order to identify people.

Researchers at the University of Iowa College of Medicine in Iowa City have now found that the nervous system of a prosopagnosia patient does respond to familiar faces, even though the patient isn't consciously aware of it.

Daniel Tranel and Antonio R. Damasio report in the June 21 SCIENCE that they measured electrical charges on the skin of two prosopagnosia patients while the patients were each shown 50 photographs of faces, eight of which were faces of people the patients knew: family members, close friends or famous people. When the patients were shown the photographs of the people they knew, the electrical conductivity of their skin increased, even though they claimed the faces were unfamiliar. They did not respond in this way to unfamiliar faces.

The nervous system responses may mean, the researchers say, that even though the patients' ability to activate memories associated with the faces has been destroyed, the brain's records --both of faces and of associated memories--are intact.

"Our brains store different types of memories in different places,' Damasio told SCIENCE NEWS. Images of faces, he says, are stored separately from the memories associated with them. But people with prosopagnosia, which is caused by twin lesions in the part of the brain believed to control the central visual system, can't activate the associated memories, he says. And these memories must be activated, or "brought into the conscious mind,' he adds, "in order for us to consciously experience visual recognition.'