What We Eat Is What We Think?

Consider that diet can affect your gut microbiome.  Consider also that gut bacteria produce short chain fatty acids from dietary fiber, so that diet can not only affect what bacterial species are in the gut but what products they produce.  Now, take a look at this article on the “gut-brain axis” mediated in part by lipids, including fatty acids, and this other article on a similar topic.

“We are what we eat,” indeed.  Perhaps, we “think what we eat” as well.

Prior Expectations Primes The Brain

The paper linked here shows that prior expectation of an external stimulus “tunes” the brain to expect that stimulus and thus affects the ability for that stimulus to be processed. When the expected “feature” was “task-oriented,” expecting the stimulus in advance improved participant performance. The authors also claim that: “We observed a representation of expected stimuli in the neural signal shortly before they were presented, showing that expectations indeed induce a preactivation of stimulus templates.”  In other words, the nervous system actually physically prepares for the expected stimulus so that evidence of the stimulus in a neural signal can be discerned even before the stimulus is actually presented.  This sheds light on how expectation can affect perception and, indeed, improve performance.  Abstract:

Perception can be described as a process of inference, integrating bottom-up sensory inputs and top-down expectations. However, it is unclear how this process is neurally implemented. It has been proposed that expectations lead to prestimulus baseline increases in sensory neurons tuned to the expected stimulus, which in turn, affect the processing of subsequent stimuli. Recent fMRI studies have revealed stimulus-specific patterns of activation in sensory cortex as a result of expectation, but this method lacks the temporal resolution necessary to distinguish pre- from poststimulus processes. Here, we combined human magnetoencephalography (MEG) with multivariate decoding techniques to probe the representational content of neural signals in a time-resolved manner. We observed a representation of expected stimuli in the neural signal shortly before they were presented, showing that expectations indeed induce a preactivation of stimulus templates. The strength of these prestimulus expectation templates correlated with participants' behavioral improvement when the expected feature was task-relevant. These results suggest a mechanism for how predictive perception can be neurally implemented.

Heavy Metal Music Toxicity?

By Flickr user Wok - http://www.flickr.com/photos/wok/12916031/, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=887535

It would appear that lovers of “heavy metal” music (HMML) have certain “alterations” of brain function, compared to fans of classical music (CML), and we can assume these alterations are not good because the authors of this study conclude that “The results may partly explain the disorders of behavioral and emotional cognition in HMML compared with CML and are consistent with our predictions. These findings may help provide a basic understanding of the potential neural mechanism of HMML.”

Assuming these findings can be replicated and are of relevance, the question is whether they are cause or effect. Does listening to “heavy metal” cause the alterations, or is it that people already having the alterations (for whatever reason) are prone to be HMML?  Or both – some people are predisposed to be HMML because of their neural wiring, but then listening to the music creates positive feedback to reinforce the differences?  Abstract:

The aim of this study was to investigate the spontaneous neural activity and functional connectivity (FC) in heavy metal music lovers (HMML) compared with classical music lovers (CML) during resting state. Forty HMML and 31 CML underwent resting-state functional MRI scans. Fractional amplitude of low-frequency fluctuations (fALFF) and seed-based resting-state FC were computed to explore regional activity and functional integration. A voxel-based two-sample t-test was used to test the differences between the two groups. Compared with CML, HMML showed functional alterations: higher fALFF in the right precentral gyrus, the bilateral paracentral lobule, and the left middle occipital gyrus, lower fALFF in the left medial superior frontal gyrus, an altered FC in the default-mode network, lower connectivity between the right precentral gyrus and the left cerebellum-6 and the right cerebellum-3, and an altered FC between the left paracentral lobule and the sensorimotor network, lower in the right paracentral lobule and the right inferior temporal gyrus FC. The results may partly explain the disorders of behavioral and emotional cognition in HMML compared with CML and are consistent with our predictions. These findings may help provide a basic understanding of the potential neural mechanism of HMML.

Stress, Dopamine, Wnt signaling, And Myelin Loss

Dopamine is related to major aspects of behavior, and abnormal regulation of the dopamine system is linked to depression and other mental disorders. Mice with knocked out dopamine receptors display increased anxiety and depression when confronted with chronic stress. Loss of myelin occurs with multiple sclerosis, and this study shows that chronic stress causes myelin loss in wild-type mice, while the dopamine receptor mutant mice have lower baseline (starting) levels of myelin, but in these mutant mice, myelin levels are not further decreased by stress.  Wnt signaling, which is abnormally regulated in different forms of cancer, is downregulated in the brains of stressed mice; this effect is reversed by lithium treatment (lithium can upregulate Wnt signaling), which normalizes myelin and behavior in stressed wild-type mice.  However, this effect of lithium did not occur in dopamine receptor-mutant mice.  This links the dopamine system with Wnt signaling affecting myelin levels and behavior in mice; the possibility exists that the same association occurs in humans. Stress has previously been linked to multiple sclerosis – with inflammation being one possible mechanism – but the dopamine pathway is another possibility, one that requires further consideration and study. Abstract:

Dopaminergic systems play a major role in reward-related behavior and dysregulation of dopamine (DA) systems can cause several mental disorders, including depression. We previously reported that dopamine D2 receptor knockout (D2R-/-) mice display increased anxiety and depression-like behaviors upon chronic stress. Here, we observed that chronic stress caused myelin loss in wild-type (WT) mice, while the myelin level in D2R-/- mice, which was already lower than that in WT mice, was not affected upon stress. Fewer mature oligodendrocytes (OLs) were observed in the corpus callosum of stressed WT mice, while in D2R-/- mice, both the control and stressed group displayed a decrease in the number of mature OLs. We observed a decrease in the number of active β-catenin (ABC)-expressing and TCF4-expressing cells among OL lineage cells in the corpus callosum of stressed WT mice, while such regulation was not found in D2R-/- mice. Administration of lithium normalized the behavioral impairments and myelin damage induced by chronic stress in WT mice, and restored the number of ABC-positive and TCF4-positive OLs, while such effect was not found in D2R-/- mice. Together, our findings indicate that chronic stress induces myelin loss through the Wnt/β-catenin signaling pathway in association with DA signaling through D2R.

Exercise And Mental Function

A neuroscientist describes some of the positive effects of exercise on brain function and mental activity.
 

Let’s start with one of the most practical immediate benefits of breaking a sweat: exercise combats stress. Exercise is a powerful way to combat feelings of stress because it causes immediate increases in levels of key neurotransmitters, including serotonin, noradrenalin, dopamine and endorphins, that are often depleted by anxiety and depression. That’s why going for a run or spending 30 minutes on the elliptical can boost our moods immediately—combatting the negative feelings we often associate with chronic stressors we deal with every day.

Exercise improves our ability to shift and focus attention. In my lab, we have also demonstrated that exercise improves our ability to shift and focus attention. Even casual exercisers will recognize this effect. It’s that heightened sense of focus that you feel right after you’ve gotten your blood flowing, whether it be a brisk walk with the dog or a full-on Crossfit workout. These findings suggest that if you have a big presentation or meeting where you need your focus and attention to be at its peak, you should get in a workout ahead of time to maximize those brain functions.

But my favorite neuroscience-based motivation for exercise relates to its effects on the hippocampus—a key brain structure that’s critical for long-term memory. We all have two hippocampi: one on the right side of the brain and the other on the left. The hippocampus is unique because it is one of only two brain areas where new brain cells continue to be generated throughout our lives, a process called adult hippocampal neurogenesis.

Studies in rodents demonstrated that increased levels of physical exercise can result in improved memory by enhancing both the birth rate and the survival of new hippocampal brain cells. Exercise encourages the long-term growth of hippocampal cells by immediately increasing levels of a key growth factor in the hippocampus called Brain Derived Neurotrophic Factor (BDNF. Now, when I exercise, I imagine BDNF levels surging in my hippocampi, encouraging all those new hippocampal cells to grow.

That is of course in addition to the positive effects of exercise in preventing cardiovascular disease and cancer, as well as being an important component in body weight control.

JUST NOTHING: Mind the human limits

We all know and feel the physical limits of our bodies; however, we rarely recognize and admit to the limits of our brains. 

We, as adults, make this mistake, and what is worse, we expect that our children should do the same - they should sit in school for eight hours a day without losing their focus. At the same time, we are certain that after one to two hours of intense physical activity the same kids are tired, and need at least 20 minutes of rest. So, why cannot we apply the same logic to any intensive brain activity?  

According to this article, our brains have two modes: the “focused mode,” which we use when we learn, write, calculate, or analyze something, and the “diffuse mode,” which is relaxed, day-dreaming mode when we do not think (hard). Contrary to our expectations, it seems that our intellectual potential is not achieved without the diffuse mode. In fact, the diffuse mode correlates with increased activity in the brain, as revealed by functional magnetic resonance imaging (the images show how the brain “lights up” during the diffuse mode).  

The daydreaming/diffuse mode has been utilized by scientists and artists in the past when they needed to solve  problems. For example, Thomas Edison, known for his many inventions, tried to relax to overcome a problem in his work. He would do this by switching to diffuse brain mode by getting into a state of almost falling asleep: he would doze while clutching a handful of ball-bearings. As soon as he went into too deep a sleep, his hand would relieve the grip and the noise of the falling ball-bearings would wake him up. In this relaxed state he would frequently find whatever solution he was searching for. 

Similarly, the artist Salvador Dali took a spoon in his hand when he relaxed on a chair; the moment he went napping, the spoon would fall and wake him up. This was the time when he could resume his creative work with fresh images and ideas.  Even we sometimes unintentionally benefit from the diffuse brain mode: probably all of us have had an eureka moment while relaxing under the shower or when waking up from sleep.  

There are different recommendations on how much time of diffuse mode we need per hour of focused mode, but it seems that the human brain thrives on one hour on, and 15 minutes off schedule.   Who knew that doing nothing, thinking about nothing, buying nothing, and even eating nothing is so beneficial?  

Actionable 
Allow yourself to daydream and do nothing.