More of HM

Henry Molaison's digitized brain.

Here is another story about HM, this one, in the November Esquire, even longer and more thorough than the one I pointed to in my last post. It is by Luke Dittrich, who happens also to be the grandson of William Beecher Scoville, the surgeon who removed Molaison's hippocampus. This piece sheds some interesting light on Scoville and on the fascinating work of UC San Diego neuroanatomist Jacopo Annese, director of the Brain Observatory. Anesse was in charge of freezing HM's brain just after the experimental subject died two years ago. Then he thinly sliced it and took high-resolution images of each section to record it at a single-neuron level. The images will be digitized and reconstructed to make a publicly-available, explorable, 3-D rendition of what is already the most studied brain in history.

One thing has been bugging me a little, though. Why did the ambitious Scotville decide to remove both lobes of HM's hippocampus in the first place? Wouldn't it have been prudent to first remove one side and see if the seizures stopped? Was Scotville really just trying to quell HM's seizures, or was he also putting himself on the neuroscience map by revealing the function of those then-still-mysterious parts of the limbic system? If the latter, it deepens HM's already unfathomable martyrdom.

WE Remember, Because HM Forgot

Henry Gustav Molaison

So many big moments in the history of neuroscience are the products of efforts to understand or treat epilepsy. Look for instance at this fine recent story by Mo Costandi in the Guardian memorializing one of the most important figures in the field, a man who for decades was known simply as HM. Henry Molaison (whose full name was only released upon his death two years ago) had been dogged by seizures since childhood and was so desperate to shake them that, in 1953, he agreed to have his hippocampus removed. His surgeon knew HM's seizures were originating there, but no one knew what the side effects would be. The surgery had its intended effect; his seizures were reduced from dozens a year to about two. But in exchange for that gain, he lost the ability to make new memories, a condition known as severe anterograde amnesia.

The main character in Memento, the excellent movie about an amnesiac driven to keep progressing into the future by preserving his past with Post-Its, annotated Polaroids, and tattoos, was purportedly modeled after Molaison.

Before Molaison, most neuroscientists believed memory to be distributed all through the brain.  The first paper about the case, published by Molaison's  surgeon, William Beecher Scoville, and neuroscientist Brenda Milner (both at the Montreal Neurological Institute) showed that though even without his hippocampus Molaison could still retain small amounts of information for short periods of time, he couldn't store them anywhere before they were supplanted by new ones. This suggested, for the first time, that memory has distinct long- and short-term components. Memory research has never been the same, and today no one doubts the central role of that weird little seahorse-shaped part of the limbic system known as the hippocampus in creating and quickening new memories; it is now arguably the most intensively studied part of the brain.

Molaison died two years ago, at 82, but his brain (still being studied at the Brain Observatory UC San Diego) is still revealing secrets about the nature of memory and what makes it work--and cease working.

It's hard to say where memory research would be today if it weren't for Molaison and his epilepsy; possibly decades behind where it is now.  Let's not forget him...or the many other courageous and generous patients with epilepsy who shed so much light on this field.