The findings, published in today's Journal of Neurology, show that when the man had a small section of his brain removed to control his epileptic fits, he could no longer recall the names of his friends, his family or even the hospital where he was staying.
The patient, a 47-year-old carpenter, could remember common nouns, such as names of fruits, vegetables and animals, but was unable to remember proper nouns, such as names of famous people, friends and acquaintances. He not only forgot the names he knew, but he could not memorise new names.
"This shows that there may be different neural networks involved in processing proper names and common names in the brain," said Dr Reiko Fukatsu, author of the study, who studied the case at Tohoku University in Sendai, Japan, and is currently a visiting scientist at Baycrest Centre for Geriatric Care in Toronto.
Dr Fukatsu said the case showed that an area in the brain's front, or rostral, left temporal lobe plays a crucial role in processing proper names, but appears to have no other effect on verbal function. A portion of the man's rostral left temporal lobe was removed during the surgery.
The man's impairment, known as proper name anomia, mainly affected his ability to retrieve names from his memory. He could point to the correct photo when he was given the name of an individual, and when he was shown photos of acquaintances he could provide information about them. However, he could not, in most cases, remember their name.
Dr Fukatsu said the carpenter's problem was probably far removed from the problem many people experience when they forget names they have just been told at a drinks party.
But she insisted: "This does suggest that the tip of the left temporal lobe plays an important role in remembering the names of people we meet."