H.M.'s gift to science

About a year ago, scientists at the University of California, San Diego finished slicing the entire postmortem brain of one of the most famous neurological patients of all time: Henry Molaison or H.M.

The story of H.M. is probably familiar to anyone who has taken an intro neuroscience or psychology course. At 27 years of age, after suffering from increasingly severe and debilitating seizures, H.M. agreed to an experimental operation that involved the removal of large chunks of his brain's temporal lobes.

Although the surgery abated H.M.'s seizures, it left him unable to form new memories. Taking more than 50 years of behavioral and brain imaging data from H.M., scientists pieced together a basic understanding of human memory. Memory is regulated by discrete areas of the brain, rather than cells spread throughout, researchers learned. In addition, the hippocampus area, a region which was removed in H.M.'s surgery, is necessary for forming long-term memories.

In 2008, H.M. passed away, leaving his last gift to science -- his brain, which was sectioned, stained and digitized for any scientist to study. Check out video footage of the slicing and an interview with lead scientist Jacopo Annese, director of the UCSD Brain Observatory on the The San Diego Union-Tribune website.

I checked in periodically (okay, obsessively) on a live webcast of the sectioning, which has lasted more than 48 hours and included some sleep and breaks. Having cut my fair share of frozen rat and mouse brains, I can only imagine the technical challenge of cutting a human brain, and a famous one at that.

Of course, the researchers were extra careful with H.M.'s brain. They discussed whether to cut the whole brain, or to first divide it into smaller chunks that would be easier to cut. In the end, they decided to the brain whole, figuring that it would minimize tissue loss.

The scientists also expressed some concern, in an entry of the Project H.M. blog (which seems to have disappeared from the Observatory's site) that it would be challenging to slice tissue in the area of the lesion because of the extensive scarring in the temporal lobes.

Luckily, the scientists made it through the scarred area. The hardest part of sectioning is over, but the real challenges (and excitement) — of analyzing H.M.'s cells and making new conclusions about human memory — have just begun.