Healthy Brain, Happy Life (7 page)

TAKE-AWAYS: BRAIN PLASTICITY

•  The brain is made up of only two kinds of cells: neurons (brain cells) and glia (supporting cells).

•  Brain plasticity is the ability of the brain to change in response to the environment. Raising rats in enriched environments results in a thicker cortex, more blood vessels, and higher levels of certain neurotransmitters and growth factors.

•  Training as a London taxicab driver results in brain plasticity. Cab driver recruits who studied and passed the difficult qualifying examination had larger posterior hippocampi, a structure known to be involved in spatial memory, than those who did not pass the exam.

•  Areas of the brain recruited when you lean a second language include the inferior frontal gyrus on the left side and parts of the parietal lobe on the left side. Language in general is controlled by the left side of the brain.

•  Music activates the parts of the brain involved in reward, motivation, emotion, and arousal, which include the amygdala, orbitofrontal cortex, ventral medial prefrontal cortex, ventral striatum, and midbrain.

•  The prefrontal cortex is the command center of the evolved human brain and supervises all executive functions.

•  Enriching your olfactory environment with lots of different smells stimulates the growth of new brain cells in the olfactory bulb, a key part of the brain responsible for our sense of smell.

BRAIN HACKS: HOW DO I ENRICH MY BRAIN?

You may not have time to go live in Disney World or France for the next few months, but the great news is that you can start to enrich your brain with these Brain Hacks, most of which take no more than four minutes per day.

•  
Motor cortex Brain Hack:
Go online and teach yourself a new dance move from the
So You Think You Can Dance
website and then practice it for four minutes to your favorite music.

•  
Taste cortex Brain Hack:
Try a cuisine that you have never tried before: Laotian, African, Croatian, and Turkish come to mind. Be adventurous! And here is another taste cortex Brain Hack for extra credit: Try eating a meal in complete darkness and see how the lack of visual input affects your sense of taste. It should change your experience of the meal and allow a pure taste sensation to come through.

•  
Cognitive Brain Hack:
There are so many fun possibilities to enrich your brain. Here are just a few: Watch a TED talk on a topic you know nothing about. Listen to a story from the
Moth Radio Hour
, a storytelling program with a wide range of topics. Listen to a popular podcast that you have never listened to before. Read a story from the section of the newspaper that you never read—for me it would be finance or sports.

•  
Visual cortex Brain Hack:
The next time you go to a museum, pick a piece of artwork that you are not familiar with and just sit quietly and get lost visually in it for at least four minutes. In reality, it could take hours to really explore a new piece fully; you can get a great start, though, in just four minutes. A hack for this hack is to simply find a new piece of art online and explore it visually on your computer. Both will stimulate your visual cortex.

•  
Auditory cortex Brain Hack:
Go to iTunes, the YouTube music channel, Pandora, Spotify, or whatever music site you like and listen to a really popular song from a genre of music you never listen to or in a different language. Try to understand why it might be number one for that genre.

•  
Olfactory Brain Hack:
The main difference between regular sommeliers (who can differentiate many different scents and describe them so precisely) and you or me is one thing: practice. Take just a few minutes to sit and smell your most odorous meal of the day. It might be breakfast with a rich, aromatic cup of coffee and the deep comforting smell of toast fresh from the toaster, or it might be your dinner of chicken tikka masala from your favorite Indian restaurant. Before digging in, take a few minutes to smell the food and try to really notice the different aromas and try to describe them. This will start to tune you in more to your olfactory senses.

SOLVING THE MYSTERIES OF MEMORY:
How Memories Are Formed and Retained

A
fter spending my senior year back at U.C. Berkeley in Diamond’s lab, I completed my senior thesis, which focused on examining the brain sizes of rat babies after placing rat mothers in enriched environments. I then graduated with high honors and I knew I wanted to go to graduate school and learn how to become a neuroscientist myself. My time in the Jaffard lab in Bordeaux had also piqued my interest in the brain basis of memory. After all, memory is one of the most common categories of brain plasticity. We know that every single time we learn something new, something in our brain changes. But for me, at the beginning of graduate school, the question was
how
does the brain change. I was also interested in another question: Could we find a way to visualize what was happening the moment something was learned?

The many facets of memory intrigued me. In an intuitive way, I understood that when the brain learns something new, it must change. But where was this happening? What are the challenges to learning something new? And what did learning have to do with memory? My hunch was that all these questions had to do with how memories are structured and formed in the brain. When I was accepted into the graduate program for neuroscience at U.C. San Diego, I wanted to discover everything there was to know about memory; it turns out I was about to become involved in one of the most dramatic and far-reaching areas of neuroscience research.

A SEISMIC SHIFT IN OUR UNDERSTANDING OF MEMORY AND THE BRAIN

U.C. San Diego had a top-notch neuroscience faculty, including Larry Squire and Stuart Zola-Morgan, two neuroscientists whom I had first learned about in Jaffard’s course on memory. I didn’t know it the day I accepted the offer, but I was soon going to be in the eye of the firestorm over memory function that Jaffard had described in class.

The late 1980s was an electric time to be studying memory. A gigantic memory mystery had emerged in the field centering on the question of a specific brain region that was really critical for memory. This mystery had actually started thirty years earlier, with the most famous amnesic patient ever studied, a man known as H.M.

At the heart of this groundbreaking discovery in the 1950s was a neuroscientist named Brenda Milner, a Brit who got her degree at Cambridge University and was working at McGill University in Montreal, Canada. Milner, an assistant professor at the time, had been working with the eminent neurosurgeon Wilder Penfield, who specialized in brain surgery for serious cases of epilepsy that did not respond to drug treatment. This surgical intervention involved removing the hippocampus and amygdala from the side of the brain where the specialists thought the seizures started. Milner was testing Penfield’s epilepsy patients before and after their brain surgery to see if removing the hippocampus and amygdala had any adverse effect on their brain function. She found mild memory impairment for spatial information if the right hippocampus was removed and mild verbal memory impairments if the left hippocampus was removed, but these deficits were considered acceptable given that the surgeries greatly reduced or eliminated the devastating epileptic seizures that these patients had been suffering for years before the operation.

And then the team was absolutely flabbergasted when Penfield treated two new patients with the same brain surgery and got completely different results: After surgery, these patients showed profound and devastating memory deficits. Penfield and his colleagues had done more than a hundred similar operations with only mild memory impairments. They immediately wrote an abstract and addressed the unusual and disturbing findings in a presentation that was to be discussed at a meeting of the American Neurological Association in Chicago in 1954.

You might ask, what was known about the brain basis of memory in those days? In fact, the prominent theory of the time was championed by a famous Harvard psychologist named Karl Lashley, who had done a series of experiments in rats through which he tried to understand how memory was organized in the brain. He first taught the rats a maze and then systematically damaged different parts of the outer covering of their brains, or cortex, to see which area, when damaged, would lead to the most severe memory impairment for performance in the maze. What he found was that the location of the damage did not seem to make any difference. Instead he found that only when he damaged enough of the cortex did he see a memory deficit emerge. Based on these findings he concluded that memory was not localized to any particular part of the brain. Instead he believed memory was so complex that a large cortical network was involved and only when you damaged a significant part of that network would the memory system fail. This prominent view at the time made the striking memory deficits that Milner and Penfield saw even more puzzling because the memory issues they observed seemed connected to the removal or damage of specific brain regions.

Several hundred miles away in Hartford, Connecticut, another neurosurgeon by the name of William Scoville read the abstract Penfield and Milner had submitted for the American Neurological Association conference and immediately contacted Penfield. Scoville had been treating a young man with such severe epilepsy that he, with the consent of the patient’s family, had decided to do what he referred to as a “frankly experimental operation.” Scoville removed the hippocampus and amygdala on both sides of the patient’s brain, not just one. Scoville was correct about the reduction of epileptic seizures that took place, but immediately after the patient woke up it became clear that he, like Penfield and Milner’s patients, had a profound memory deficit. He didn’t know it at the time, but Scoville’s patient (H.M.) was to become the most famous neurological patient ever studied.

Remember, this surgery took place at the height of the era when neurosurgeons were using brain operations—such as frontal lobotomies and procedures that damaged parts of the frontal and temporal lobes—to cure various psychiatric diseases like schizophrenia and bipolar disorder. This practice is referred to as psychosurgery. It’s difficult to imagine what the mind-set was like at that time to believe it was okay to experiment with taking out parts of people’s brains, even if it was supposed to be for their own good.

Scoville not only attended the 1954 meeting of the American Neurological Association but also presented a paper describing his patient H.M. Scoville then invited Milner to Connecticut to study patient H.M. She immediately jumped at the opportunity.

Milner has described herself as a “noticer,” and her observations and testing of patient H.M. and nine other of Scoville’s patients helped reveal something completely radical in our understanding of how memory works in the brain. H.M. was the easiest to test and evaluate because most of Scoville’s other patients suffered from various psychiatric disorders, including schizophrenia and bipolar disorder. While she found H.M.’s intelligence to be quite high (and even improved a small amount after his surgery), he had a profound inability to remember anything that happened to him. He could not remember any of the hospital staff or doctors he came in contact with at the hospital (including Milner herself), could not find his way to the bathroom in the hospital or remember the location or address of the home his family moved to after his operation. Despite this profound inability to remember anything new, he knew his parents and the layout and location of his childhood home, and had apparently normal memories of his childhood. This meant that the operation carried out on H.M. impaired his ability to lay down new memories but spared his general intelligence (for example, he still continued to enjoy doing crossword puzzles—though he could do the same one over and over) and generally spared his memories of events that occurred before his operation.