Something exciting happened in the world of neuroscience last week. Scientists at the University of California in San Diego made a 3-D model of the brain of H. M., the late Henry Gustav Molaison.
In the field of brain science, interesting patients often become more famous than their researchers. This was the case with Phineas Gage, the man who had a railroad spike jammed up his head. Gage’s personality changed when his frontal lobes were severely damaged by the trauma. Oliver Sacks, one of my personal heroes, took advantage of how interesting it is to study brain issues through afflicted patients in his many books. My favorite of his stories, “An Anthropologist on Mars”, shows Temple Grandin, an doctor of animal science who now has a few books of her own. It is hard to create human laboratory experiments in neuroscience because no one seems to want to have their brain cut up while they’re still using it. These case studies have therefore been critical to growth in the field, especially before the widespread use of PET scans, MRI machines, CT scans, EEGs, and others that are being invented as I type.
The importance and fame of patient H. M. was no exception. H. M. was 27 in 1953 when he had surgery to remove two finger-sized pieces of brain, including his hippocampus. This procedure was supposed to provide relief from his extreme epilepsy. The surgery fixed his epilepsy and H. M. retained many aspects of his former identity, such as his former long-term memories, his motor skills, his passion for crossword puzzles, and his language and perception skills. Unfortunately, he lost his ability to form new explicit memories, as well as most of the memories from 1-2 years before his surgery. When he worked his crossword puzzles, he could accurately answer questions related to events before 1953, but he had trouble answering questions related to events after his surgery. H. M. is famous for eventually learning to add facts to his old, pre-amnesiac memories. For example, he was able to answer a crossword question about the Salk vaccine, which was invented in 1955, because he could remember when polio was a big deal. He could learn new facts as long as he had old connections he could anchor them to. He was also able to learn new motor and perceptual skills: he was able to learn how to trace an outline between two stars while watching his hand in the mirror (a hard task for almost anyone) (Carey, 2010). He helped scientists realize how many different forms of memory there are.
Scientists learned and continue to learn from H. M. In 1992, his brain was scanned under a MRI machine for the first time, revealing the extent of his 1953 surgery (Carey, 2008). The lesion was symmetrical, but less extensive than the surgeon had intended. Parts of the hippocampus appeared to still be intact, but other areas of the brain were damaged further than anyone had expected.
On December 2, 2008, H. M. died from respiratory failure in his nursing home in Connecticut. Scientists always remarked upon his generosity and patience, especially since he viewed them as strangers (Carey, 2008). His generosity continued even after his death. Last week, UC San Diego unveiled an unprecedented study in which H. M.’s brain was cut into 2,401 slices on a livestream, analyzed, and then re-built using the digital images (Annese et al, 2014).
There’s a very important pathway called the EC that connects the hippocampus to the rest of the brain. While H. M.’s hippocampus underwent much less damage than previously believed, the scientists at UC San Diego realized that his EC had been almost completely decimated (Annese et al, 2014). This explained his memory problems. In addition, there was damage to the amygdala and other cortexes (Annese et al, 2014). These may have been the cause of H. M.’s slightly dampened emotions and his trouble reporting pain, hunger, or thirst. The model also revealed cortical damage that was not related to the surgery. Scientists theorize that it was due to age and hypertension (Annese et al, 2014).
H. M.’s brain is going to continue to benefit the fields of memory, aging, and emotion for years to come. The 3-D model of his brain is the first in human history (Annese et al, 2014). It’s remarkable that H. M. was able to retain much of his former self and even start consolidating new facts. The resilience and complexity of the human brain never ceases to amaze.
If you want to read more:
Annese, J., Schenker-Ahmed, N., Bartsch, H., Maechler, P., Sheh, C., Thomas, T., Kayano, J., & Ghatan, A. (2014). Postmortem examination of patient h.m.’s brain based on histological sectioning and digital 3d reconstruction. Nature, doi: 10.1038/ncomms4122
Carey, B. (2008). H. m., an unforgettable amnesiac, dies at 82. The New York Times, Retrieved from http://www.nytimes.com/2008/12/05/us/05hm.html?pagewanted=1
Carey, B. (2010). No memory, but he filled in the blanks. The New York Times, Retrieved from http://www.nytimes.com/2010/12/07/science/07memory.html?ref=health&_r=1&