These photomicrographs depict comparative stained sections of a healthy brain (top) and of patient EP, in which significant structures in the medial temporal lobe are heavily damaged or missing. The letters identify specific brain structures, such as EC and PRC for entorhinal cortex and perirhinal cortex, respectively, both important to memory formation and function.
Gone, But Not Forgotten
UC San Diego scientists recall EP, perhaps the world’s second-most famous amnesiacAn international team of neuroscientists has described for the first time in exhaustive detail the underlying neurobiology of an amnesiac who suffered from profound memory loss after damage to key portions of his brain.
Writing in this week’s Online Early Edition of PNAS, principal investigator Larry R. Squire, PhD, professor in the departments of Neurosciences, Psychiatry and Psychology at the University of California, San Diego School of Medicine and Veteran Affairs San Diego Healthcare System (VASDHS) – with colleagues at UC Davis and the University of Castilla-La Mancha in Spain – recount the case of EP, a man who suffered radical memory loss and dysfunction following a bout of viral encephalitis.
EP’s story is strikingly similar to the more famous case of HM, who also suffered permanent, dramatic memory loss after small portions of his medial temporal lobes were removed by doctors in 1953 to relieve severe epileptic seizures. The surgery was successful, but left HM unable to form new memories or recall people, places or events post-operation.
HM (later identified as Henry Gustav Molaison) was the subject of intense scientific scrutiny and study for the remainder of his life. When he died in 2008 at the age of 82, he was popularized as “the world’s most famous amnesiac.” His brain was removed and digitally preserved at The Brain Observatory, a UC San Diego-based lab headed by Jacopo Annese, PhD, an assistant adjunct professor in the Department of Radiology and a co-author of the PNAS paper.
Like Molaison, EP was also something of a scientific celebrity, albeit purposefully anonymous. In 1992, at the age of 70, he was diagnosed with viral encephalitis. He recovered, but the illness resulted in devastating neurological loss, both physiologically and psychologically.
Not only did he also lose the ability to form new memories, EP suffered a modest impairment in his semantic knowledge – the knowledge of things like words and the names of objects. Between 1994, when he moved to San Diego County, and his death 14 years later, EP was a subject of continued study, which included hundreds of different assessments of cognitive function.
“The work was long-term,” said Squire, a Career Research Scientist at the VASDHS. “We probably visited his house 200 times. We knew his family.” In a 2000 paper, Squire and colleagues described EP as a 6-foot-2, 192-pound affable fellow with a fascination for the computers used in his testing. He was always agreeable and pleasant. “He had a sense of humor,” said Squire.
