Nap v. Med: Don't Sweat It.

"The Rememberer"

For great audio of a sleeping cat's brain listen to this episode of Radio Lab at 3 minutes and 45 seconds. Better yet, listen to the whole thing and learn many facts and theories about sleep, including one fine explanation for the evolutionary popularity of having two brain hemispheres. Titled "Sleep," it's from Season 3 (2007), but listen anyway; old Radio Labs don't die, they just grow stronger. 

The point of the sleeping cat sound: there is a storm of neuronal activity going on in the sleeping brain. Just because sleep is beautiful, doesn't mean it isn't hard work. That's true at midnight and in the middle of the afternoon, when I do my sweetest and most productive snoozing. Twenty minutes sometime between two and three o'clock and my 49-year-old brain feels fourteen again. There are coherent neuroscientific explanations, and more and more sleep scientists are describing them. For example, a Berkeley study led by psychologist Matthew Walker shows an hour-long nap dramatically boosts and restores brain power. He says, among other things, it refreshes the hippocampus' ability to form new memories. 

On the other hand, the most emailed piece in yesterday's New York Times was titled "How Meditation  May Change the Brain," by Sindya N. Bhanoo. It points to a new study published in the January 30 issue of the journal Psychiatry Research Neuroimaging  finding that people who meditated for about half an hour a day for two months had increased gray matter in their hippocampi (read "memory machines") and and reduced gray  matter in their anygdalae (read "road-rage machines.") That can't be bad. 

But which is better, napping or meditating? Neurocience has not weighed in yet. So take you're pick. If you're too type-A to snooze on the clock, go ahead and sit instead. Either way, you're doing your brain a favor.

As a bonus for those who've read this far. here's a lovely piece by novelist Cathleen Schine, in RealSimple, about the blissful benefits available to those willing and able to sleep while others work. 

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.

GPS and Your Brain: Do You Know Where You're Going, Or Just How to Get There?

Nearly all of us have an innate ability to navigate. But there are the few hundred known cases of what neurologists call "developmental topographical disorientation" (DTP), or the inability to get from here to there, even if "there" is right around the corner. This very good article, "Global Impositioning Systems," by Canadian journalist Alex Hutchinson, in The Walrus, looks at the work of neuroscientists studying DTP to learn how most of us navigate most of the time.

The piece poses there are two main navigational approaches or techniques and that while we employ both, everyone leans more heavily on one or the other. The first, which relies more on activity in the hippocampus, constructs cognitive maps based on relationships between landmarks. People who use the second, which plugs into the caudate nucleus, develop and memorize instructions (e.g. turn right at the ice skating rink and then left at the cheesesteak place). The former, hippocampus-based way, Hutchinson says, is versatile and generalizable. The second strategy, learning directions, works okay, unless the cheesesteak place is bought out by a Starbucks...which is pretty likely. Reading between the lines, Hutchinson is suggesting that people adopt the first strategy don't just know how to get from a to b, they actually know where they are, and where they're going.

The more we rely on GPS systems, Hutchinson's sources say, the less exercise the hippocampus-based system gets. Brain images show exercise of the  hippocampus makes it grow. Neglect makes it shrink.

The take home message: over-reliance on GPS may get us there, but at the cost of knowing where it's at.