Category Archives: Neuroscience

Sugar, Obesity, and the Brain

teaspoon of sugarI’ve written about sugar in earlier posts – notably, its effect on our physiology and its addictive power. I got another dose of admonitions against this pervasive component of the American diet when reading Grain Brain: The Surprising Truth About Wheat, Carbs, and Sugar, Your Brain’s Silent Killers by Dr. David Permutter.

For most of human history, sugar made rare appearances in the diet. We simply didn’t have access to the raw materials or the technology to refine it. We only consumed a modest amount of fructose and glucose in fresh fruits and vegetables. So our bodies had to develop elaborate mechanisms to convert protein and fat to glucose and release it into the bloodstream.

Insulin provides the means to transport glucose from the bloodstream into muscle, fat, and the liver. Upon arrival, it is stored as a readily available source of fuel. However, once cells have their fill, they’ll grow insensitive to further attempts by insulin to “unlock their doors” and deposit additional glucose – a condition known as insulin resistance. Excess glucose molecules remain in the bloodstream and attach themselves to proteins, fats, and amino acids, a process called glycation. Once glycated, proteins don’t do their jobs well. Moreover, glycated proteins have been shown to create a 50-fold increase in free radical formation relative to proteins that are not glycated. Free radicals give rise to inflammation which, among other things, sparks arterial plaque formation. Plaque accumulation gives rise to coronary artery disease (CAD), Alzheimer’s disease, and stroke.

For most of us, excess weight is the only physical manifestation of too much sugar in the diet. We may find it bothersome that our clothes don’t fit as well or that we face the implied criticism from a culture that venerates thin people. But it turns out that when excess fat accumulates in adipose tissue, it’s anything but passive. Visceral fat (around the organs) secretes a large amount of cytokines that trigger inflammatory pathways. The refuse from our bodies’ immune response dumps into the liver. The liver then ups the ante on inflammatory and hormone-disrupting substances.

sugar and the brainIf the after-effects of inflammation fail to sound the alarm, perhaps loss of cognitive function might do the trick. Dr. Perlmutter notes that chronically obese individuals have been shown to have 8% less brain tissue than folks of normal weight. Chronically overweight individuals may experience a 4% drop in brain tissue. Much of this tissue loss occurs in the frontal or temporal lobe, the locus of executive decision making.

A change in diet lowers the risk of obesity, vascular disease, and inflammation linked to cognitive decline. Avoid foods and beverages responsible for the biggest surges in blood sugar – i.e., anything made with refined flour, starches (rice, potatoes, corn), liquid carbs (e.g., fruit juices, soft drinks), and, of course, added sugar, sugary sauces, and syrups. Get your carbs from whole fruits and vegetables. They’re bound up with insoluble fiber and water which slows fructose and glucose absorption to a rate the body can handle… in moderation.

Why Our Brains Are Not Computers

our brain is not a computerI used to think that our brains were like computers. After all, they process lots of input, use logic to make executive decisions, store and retrieve memories, and produce output. Yet after reading Welcome to Your Brain and watching Dr. Sam Wang’s 36-part DVD entitled Neuroscience of Everyday Life, I have a whole new perspective.

Our brains are not designed for pinpoint accuracy, like a computer. They’re in the business of keeping us alive. To that end, Dr. Wang tells us that “at any given moment, your brain is lying to you.” Here’s how…

The brain takes in huge amounts of information through its sensory processors – eyes, ears, nose, mouth, and skin. As it sifts through the input, it combines a lifetime of experience with its expectations to render judgments, store what’s useful, and discard what it deems unimportant. Speed takes precedence over accuracy.

Forty percent of our brain is sensitive to visual stimulation. A large number of brain regions can activate in response to visual signals without entering that input into consciousness. Conscious awareness may function like a spotlight that focuses on specific stimuli and ignores others. And by the time we’re cognizant of visual images, our brains have already made assumptions about what we’re looking at.

The brain’s mechanism for storing and retrieving memories also falls into the realm of not-at-all-like-a-computer. Memories get stored in shorthand based on what the brain considers important. There’s also good evidence that we erase and re-write our memories every time we recall them. And we invent details to fill in the gaps and create a more coherent story. Researchers have demonstrated this phenomenon in laboratory experiments. For example, they can show their subjects a list of words that share a consistent meaning – e.g., ice cream, honey, lollipop, sugar, candy, chocolate. When asked later if the word sweet was on the list, most folks say yes with confidence. They make a reasonable inference that the word made the list even though it did not.

The hippocampus serves as the initial repository for our memories. In the process of rewriting as we re-experience them, memories can change transition from the hippocampus to the neocortex. As this transfer occurs, some memories get separated from the context in which they occurred and get woven into the fabric of our general knowledge. For example, we’ll remember that Salem is the capital of Oregon, but we won’t recall when, where, or how we learned that fact. Dreams likely play an important role in memory consolidation.

Armed with this information, I’m more likely to adopt a generous response when others recount memories that are inconsistent with my recollection. I’ll also be wary of declaring that my historical narratives are factually true.

synaptic connectionsOur brains also play close attention to activity on all of its synaptic connections. It strengthens synapses that see frequent use (“cells that fire together, wire together”). This mechanism enables us to execute thousands of sequences in everyday life without having to think much about them (e.g., tying our shoe laces). It also weakens or removes synapses that remain dormant while others are actively used (“out of synch, lose you link”). This phenomenon is referred to as neural plasticity. It has several important practical applications:

  • If there’s a goal that you’d like to accomplish, visualize the process of attaining it in as much detail as possible and as often as possible. When your brain is wired for success, you’re far less likely to be stymied by roadblocks along the way.
  • When teaching a class, provide some initial exposure to key facts or conclusions. By preparing the brain for what’s ahead, it’s more likely to pay attention to specific pieces of information. For example, an early quiz sets the brain up for future learning.
  • If you need to study for an exam, break your preparation into several relatively small sessions (45-90 minutes). Your brain will retain information longer if it has the chance to process it between study sessions.
  • If something or someone makes you unhappy, find a way to distract yourself when the memory emerges. If you dwell on it, you simply reinforce the pain and increase the likelihood that it will keep popping up. Turn your attention to something pleasant.
  • Reappraisal is a powerful tool for transforming unhappy memories. Find a way to change the meaning of the event into something positive and forwarding. Folks skilled in reappraisal tend to be emotionally stable and resilient.

Finally, frequent small positive events have a greater cumulative effect on happiness than large positive events. For example, when people win the lottery, they typically go through an initial period of euphoria after which they revert to their former set points. To elevate your set point, eliminate daily irritants, set realistic goals and achieve them, use your character strengths, and cultivate a daily practice of gratitude.

Why Exercise is Good for the Brain

Most of us can recite the reasons why exercise is good for our bodies. Aerobic exercise strengthens our cardiovascular system and raises our metabolic rates. An elevated metabolism burns more calories which helps us maintain a healthy weight. Load-bearing exercise (a.k.a. “pumping iron”) builds muscles and strengthens bones. And a daily dose of vigorous exercise can help us sleep better at night. In SPARK: The Revolutionary New Science of Exercise and the Brain, Dr. John J. Ratey, MD gives us yet another reason to move. Exercise gets our brains to function at peak efficiency.

ready to learnTwo innovative school districts served as “demonstration plots” for the mind-body connection in active fitness programs. Teachers reported that when students in the Naperville IL or Titusville PA school districts completed a mile run:

  • They went to class alert, focused, and ready to learn.
  • They were less fidgety, tense, and moody.
  • They felt more motivated and invigorated.
  • They outperformed peers who did not participate in a fitness regimen.

The last point merits special attention. Naperville’s District 203 students placed among the highest echelons of students academically in the U.S. and abroad. Some dismissed these results given Naperville’s favorable socioeconomic standing (although District 203 compared favorably to schools with comparable demographics). Titusville serves an underprivileged population. Their students went from below average performance statewide to 17% above average in reading and 18% above average in math. Moreover, they experienced a near absence of fist fights. Both districts also reported very low rates of childhood obesity.

For the record, Physical Education (PE) at Naperville and Titusville isn’t the “stand around and wait your turn to bat a ball” kind of fitness. Nor is it a one-size-fits-all program. Kids are encouraged to find an activity they enjoy with the right level of effort to elevate their heart rates to their target zones. If kids like wall climbing, they climb walls (and enjoy their classmates’ cheers and encouragement while doing it). If they’re slow runners but manage to get their heart rates up, they’ll receive praise for working at their own paces.

The other end of the age spectrum also provides “demonstration plots.” Among elderly populations, those who are educated, confident in their ability to effect positive change (a.k.a. “self-efficacious”), and exercised exhibit the least cognition decline.

From this launching pad, Dr. Ratey’s book dives into the neuroscience behind the beneficial impact of exercise. Here’s a high-level summary:

  • Exercise elevates neurotransmitters (serotonin, norepinephrine, and dopamine) responsible for attention, perception, motivation, arousal, and mood.
  • Exercise elevates brain derived neurotropic factors (BDNF) that build and maintain brain circuitry. It strengthens our cellular machinery for learning.
  • Cells sprouted during exercise increase the attraction between neurons and their likelihood to “spark” (a.k.a., long term potentiation or LTP).
  • The most effective form of aerobic exercise calls upon the brain to acquire skills while we move. For example, partner dancing forces the brain to take another person into account. Aerobic classes that change up the patterns of movements also encourage “skill” development.
  • The mild stress of exercise activates genes that produce proteins to protect our brain cells against damage and disease.
  • The heart muscle secrets ANP during exercise which travels through the blood-brain barrier to create a calming effect. It’s an antidote for anxiety and panic attacks.
  • exercise is good for the brainWhile exercise and medication are both effective at treating depression, consistent exercise works better over the long run. In fact, a Duke University study found that every 50-minute installment of weekly exercise reduces the odds of being depressed by 50%.
  • Exercise tricks the brain into maintaining itself for survival despite the hormonal cues that it is aging.

Dr. Ratey’s anti-aging prescription for exercise: 60 minutes of aerobic exercise at least 4x per week; strength training at least 2x per week to build strong bones and ward off osteoporosis; and, 30 minutes of flexibility and balance exercise 2x per week. It may seem rather daunting, but your body and your brain will love you for it!