SAN FRANCISCO, CALIFORNIA - Imagine not being able to tell your son's voice from that of a perfect unknown. Welcome to the life of a 60-year-old British woman known as KH. Although a handful of people have lost the ability to recognize voice after a stroke or other brain damage, researchers believe KH is the first documented case of a person who did not develop this ability first place.
The case came to light a few years ago when KH read an article in New Scientist magazine on people who can not recognize people by their faces. The article struck a chord, and she contacted the magazine, explaining that she had a similar voice recognition problem. As long as she could remember, the voices of even his closest relatives were indistinguishable. New Scientist contacted Bradley Duchaine, a cognitive neuroscientist presented in the article, and Duchaine KH invited to visit his laboratory at University College London.
A successful management consultant, KH scored average or above on a variety of memory tests and reasoning. His hearing was normal and magnetic resonance imaging (MRI) of the brain revealed no obvious flaws. She told investigators her problem was limited to recognize the voice of the people, explaining that she sometimes comes to different business customers by names so that when they called she could identify them based on who they request.
Additional tests supported the account of KH, says collaborator Duchaine Lúcia Garrido, who presented the findings here since April 13 at the annual meeting of the Cognitive Neuroscience Society. In one experiment, the researchers played 96 sentences, half of them spoken by famous actors, politicians, and other celebrities, the other half spoke by unknown voices. KH did little better than chance when asked if each voice belonged to someone famous. Even when it correctly categorize such a famous voice she identified the right celebrity less than 5% of the time, poor performance compared to the six control subjects who took the same test. KH was similarly desperate in a second experiment in which she tried to learn six new voices and distinguish them from the voice she had never heard before.
"I think it's quite new," said Jamie Ward, cognitive neuroscientist at the University of Sussex in the UK He stressed that KH performed normally when asked sex or the emotional state of a speaker, supporting the researchers' conclusion that the deficit is specific to speech recognition. The underlying neurological mechanism in the case of KH remains a mystery, but Garrido said the team hopes to use functional MRI to study how the brain responds to voice KH.
0 Komentar