Brain States

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Mathematics Anxiety and Brain Stimulation


It’s a familiar feeling to many.  Try to calculate a tip, and your brain seems to freeze.  Attempt to figure out a relative’s age from the year they were born, and your neurons seem to dart around nervously and elude you. Just thinking about a math test makes you feel nauseous.  If you’ve experienced any of these episodes, then you may have math anxiety.


It’s a bizarre phenomenon in which any problem having anything to do with numbers induces negative feelings, and even activates the part of the brain that is associated with feeling pain. It’s thought that the negative feelings take up too many of the brain’s resources, leaving little left over for actually tackling the problem.  Performance goes down, and that only validates the feeling of inadequacy. It’s a vicious cycle.

In a recent article published in the Journal of Neuroscience, researchers used transcranial electric stimulation (tES) on individuals with high math anxiety while they took a simple math test. They had to answer “true” or “false” to a series of arithmetic equations, such as 6 + 2 = 16.  The researchers measured reaction times for their answers.  Another group of individual with little or no math anxiety was intended as a control.

Each study participant had to take the test twice: once with brain stimulation, and once without. The stimulation was applied to the dorsolateral prefrontal cortex (dlPFC). The dlPFC is an area that is implicated in so-called executive control- a function that enables an individual to regulate emotions generated elsewhere in the brain.  Before and after each test, the participants gave a saliva sample, from which cortisol, a hormone that indicates stress levels, was measured.

The researchers were unsurprised to find that people with math anxiety did better at the test when they were receiving stimulation to the dlPFC than when they were not. This fits with the idea that the PFC is regulating emotions, and by enhancing positive emotion while diminishing negative emotions, individuals were able to overcome their anxiety and increase their reaction times. Additionally,  they showed a decrease in cortisol levels, indicating less stress, after taking the exam while having their brain stimulated compared to when they took the test without.

The surprise came later, when the researchers realized that the brain stimulation had actually had the opposite effect on people with little or no math anxiety.  They did worse on the exam when receiving the same brain stimulation, rather than better. They had higher cortisol levels, indicating more stress.  Rather than being a simple control group, it turned out that the same type of stimulation exerted completely different effects on the two groups  – speeding up those who were slow, but slowing down those who were fast.

It’s tempting to speculate about how this effect works. Perhaps for those with no math anxiety, the prefrontal cortex is acting as a helpful cheerleader. When that cheerleader is taken away, performance drops. For those with math anxiety, the prefrontal cortex is acting like an naysaying bully. When that bully is eliminated, performance goes up.  It’s a lovely story, but it’s just that.

This is the first report we have that the effects of transcranial electric stimulation are not one-size-fits-all, but rather, depends on the traits of the person being stimulated. It’s a huge finding, indicating that scientist need to think in more nuanced ways about the experimental design.

Reference: Cognitive Enhancement or Cognitive Cost: Trait-Specific Outcomes of Brain Stimulation in the Case of Mathematics Anxiety. Amar Sarkar, Ann Dowker, and Roi Cohen Kadosh. (2014). Journal of Neuroscience 34(50): 16605-16610.

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The signature of happiness

How do we know what someone else is feeling? Clues about the emotions of others can come in various forms. Facial expression can be a dead giveaway, but we can also make inferences from body posture, or even from seeing or reading about the situation that caused the emotion.  An interesting problem in neuroscience is how these very different cues about the emotions of others can all lead to the same ultimate realization: She’s happy; he is sad.

In a paper published this week in the Journal of Neuroscience, Amy Skerry and Rebecca Saxe sought to find the region of the brain that is responsible for these empathetic realizations, regardless of the origin. They did this by showing people different types of media that relayed emotion: a short video clip from a movie, or an animated clip that showed a geometric figure experiencing prosocial or antisocial action from its fellow geometric shapes.  For instance, in the figure below, a woman makes a sad face, and then a red circle is excluded from a group of purple triangles, squares, and pentagons (so sad! poor circle).


The authors then trained a computer program to look at the fMRI brain scans of people during each emotional media presentation, and guess which emotion was being conveyed.  Importantly,  the program was trained to discriminate the emotional states based on one type of media (facial expression, say) and then was tested on data for the other type of media (animated situations).  The scientists were looking for brain regions that had such distinct neural response to the emotional state that the computer program could recognize it no matter which media type the person had seen to make the inference. To qualify, the program had to perform significantly better than chance on data from that region.

Following data from previous studies, the authors homed in on the prefrontal cortex, or PFC. This is not surprising, as the prefrontal cortex is a particularly “thinky” part of the brain, responsible for, among other things, future planning and impulse control.  But the PFC is large (it’s basically everything in your forehead region) and has many functions. Specifically, it seemed to be the medial part of this structure, or MPFC, that held the key to invariant recognition of emotional states, regardless of how they were communicated.  Further subdividing, the authors found that data from both the dorsal (upper) MPFC and middle MPFC reliably allowed the computer program to perform above chance.




Skerry and Saxe then asked another question. Would these same brain regions represent emotions the same way when it was the self experiencing that emotion, rather than another? To determine the answer, the participants in the study were told that they were either winning money (happy 🙂 ) or losing it (sad 😦 ). They then had the computer program guess, based on neural response, what emotion they had induced in the individual.  Here, the middle MPFC still held reliable information, whereas the dorsal MPFC no longer did.

This study succeeded in identifying a region of the brain that has an particular response to particular emotions, regardless of how the brain whether it was perceived visually or merely implied, and regardless, even, of whether it was the self or someone else experiencing it. While the current study dealt only in binary (good or bad, happy or sad) it remains an open question whether these findings hold for more complex emotions like greed, jealousy, or gratitude.

Reference: A Common Neural Code for Perceived and Inferred Emotion. Amy E. Skerry and Rebecca Saxe. (2014) Journal of Neuroscience, 34(48): 15997-16008

Intro image by Dietmar Temps, all other images adapted from above.


Diet and Memory: Cocoa-derived flavonoids improve hippocampal function in older adults


The hippocampus is an hugely important structure.  Small in size and buried in the medial temporal lobe, it packs an oversize punch. When it starts to decline as we age, certain facts may become difficult to recall. When inputs to the structure are strangled, Alzheimer’s Disease is a likely outcome. And if it is totally removed, as it was for Henry Molaison in a 1950’s attempt to cure his epilepsy, the brain is no longer able to form new memories.


Just as a country can be divided into states, the hippocampus can be divided into regions. One of these, the dentate gyrus (or DG), shows the most consistent  changes as we age.  Inspired by a study done on mice in which ingestion of epicatechin, a molecule derived from cocoa solids, increased the branching of neurons in the DG, Adam Brickman and his colleagues in  Scott Small’s lab at Columbia University decided to pursue the question of whether adding cocoa flavanols to the diet of adults aged 50-69 could improve DG functionality.

The authors divided the study participants into groups. Some of the participants got 900 mg of cocoa flavanols per day, whereas others took only 45 mg per day.  After three months, the two groups were tested for their performance on a memory test designed specifically for this study to target the DG.


Adults in the high-flavanol group were significantly better at the test, with reaction times that were almost a full second quicker than adults in the low-flavanol group.  In addition, subjects in the high-flavanol group had significantly higher cerebral blood volumes in the DG, indicating that the DG had better blood supply for these individuals.  Also, the amount the blood volume had changed to the DG was closely associated with how much the subjects had improved their reaction times on the memory test.  Big increases in blood supply meant big decreases in reaction time – and both could be brought about by the ingestion of flavanols.

Chocolate, of course, isn’t the only food that provides dietary flavanoids. Many fruits such as blueberries and raspberries also provide these important phytonutrients.  This study confirms a bit of common sense – that a healthy diet leads to healthy aging.

Reference: Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults (2014) Adam M Brickman, Usman A Khan, Frank A Provenzano, Lok-Kin Yeung, Wendy Suzuki, Hagen Schroeter, Melanie Wall, Richard P Sloan & Scott A Small. Nature Neuroscience, 17 1798-1803.

All images adapted from above.