Brain States


Leave a comment

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.

Math-Anxiety-500

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.


Leave a comment

The signature of happiness

https://www.flickr.com/photos/deepblue66/13147918413/in/pool-happy-face

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).

F1.large

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.

rsz_f4medium

 

 

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.


2 Comments

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.

nn.3850-F1

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.

rsz_1rsz_nn3850-f3

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.


1 Comment

Parenting Behaviors are Controlled by Specific Neurons in Mice

Source: FancyMice.com

Parents of newborns can likely sympathize with the diametrically opposed behaviors that mice and rats display towards young pups. On one hand, there is the urge to care for the pups by nesting with and grooming them. On the other hand, there is a darker urge: to go on the attack.

For laboratory mice, the urge that wins out is largely determined by both sex and mating status. Both virgin and mated adult females primarily care for young with very little attacking. This is true for males that have mated, too- especially if it has been about three weeks since they mated, which coincides with the gestation period for mice. Virgin males, however, are more moved by the darker urges- and with solid evolutionary reason. If they haven’t mated, then there is no possibility that the pups are theirs.

At Harvard University, Zheng Wu and his colleagues set out to find the neural circuits that control these behaviors. Their results were published this week in the journal Nature.

Mice, like many other species, use the vomeronasal organ to sense pheromones given off by others of their species, and pheromones can be a powerful cue in motivating social behaviors.  Wu and his colleagues tested the idea that these pheromonal inputs could be triggering the pup-directed aggression in virgin males.  They compared virgin males with intact, healthy vomeronasal organs to males who had impaired vomeronasal function thanks to a genetic mutation in a key pheromone receptor. Amazingly, they found that the virgin males who couldn’t smell the pheromones were not aggressive toward pups, and actually started to build nests and care for them.

The researchers next wanted to find the neural populations that could underlie parenting behaviors. They identified a set of neurons in the medial preoptic area that became active in females and sexually experienced males after they started parenting. These same neurons stayed silent in virgin males. The medial preoptic area is a part of the hypothalamus, which is one of the areas that the vomeronasal organ sends information to.

Although the medial preoptic area is small, it still contain many different types of cells. Which ones were responsible for getting the mice to act like parents? To answer this question, the scientist looked at the types of neurotransmitters made by cells in the preoptic area, and concluded that the cells active during parenting overlapped the most with cells that make a small neurotrasmitter known as Galanin.

Wu and colleagues investigated the role of these neurons using two opposing manipulations.

In the first set of experiments, they destroyed these neurons using modern genetic targeting tools. When they destroyed the cells in virgin females, they abruptly switched from caring for pups to attacking them. This suggesting that at least for  virgin females, these neurons act as the switch between these two opposing behaviors.  For sexually experienced males and females, loss of the galanin-positive neurons only resulted in a loss of parenting behaviors without an increase in aggression.

In the second set of experiments, the researchers activated the galanin-positive neurons by making them sensitive to light. Whenever a virgin male made contact with a pup, the researchers shined light through a optic fiber onto these neurons, thus turning them on. When the neurons were active, virgin males only attacked the pups about 10% of the time – but if the researchers left the light off, the same mice would attack over 90% of the time.

In mated male fathers, the same light-induced activity in the neurons caused a marked increase in grooming of the pups.

The authors concluded that the neural circuits to care for or attack young pups co-exist simultaneously in the mouse brain, and which circuit is active depends largely on a social context – working through a set of hypothalamic neurons.

Parental care is required for newborns to survive in many species. This is especially true for mammals, because our young are born relatively helpless and require adult intervention to move and find food.  Between species,  it varies widely how much of the care is provided by the mother or the father.  This work demonstrates that both sexes have the neuronal architecture necessary for effective parenting.

There is good reason to believe that humans have a similar set of neurons controlling parenting behaviors, because other neurons in the medial preoptic area have been shown to have conserved functions across mammal species.  This work sets the stage to investigate other fascinating questions, such as whether the function of these neurons is disrupted in postpartum depression.

REFERENCE: Galanin neurons in the medial preoptic area govern parental behaviour. (2014) Zheng Wu, Anita E. Autry, Joseph F. Bergan, Mitsuko Watabe-Uchida & Catherine G. Dulac. Nature 509, 325–330.


Leave a comment

What Can Dreams Tell Us About Consciousness?

893666_45846960To understand the nature of consciousness is perhaps the holy grail of neuroscience, not to mention philosophy and psychology. Although we are a long way off from that goal, current studies can give us some insight into our own awareness by examining and manipulating the brain during lucid dreaming.

In lucid dreaming, the dreamer is aware that he or she is dreaming while the dream continues. Lucid dreaming is also associated with several other dream states, including being able to control the dream or taking on a third person perspective. The dreamer may experience dream events,  but also have access to waking memories.

Scientists have reported that the brains of people who are in a state of lucid dreaming exhibit a phenomenon known as phase synchrony. This means that the neurons in the brain are synchronizing with each other and firing with a particular common frequency. Oscillations (or colloquially, waves) of certain frequencies are grouped together and named with greek letters, and different frequencies correspond with different states. For example, the characteristic frequency for a state of relaxed wakefulness is in the alpha band of about 8-13 Hz.  During lucid dreaming, there is an increase in the gamma band of frequencies, corresponding to about 40 Hz. This increase happens especially in the frontal an temporal lobes of the brain.

For many years, scientists have wondered whether these synchronized brain waves are a cause of the self-awareness in lucid dreams, or a consequence.  A new study out this week, spearheaded by neuroscientist Ursula Voss, sought to address this question by passing alternating current at a variety of frequencies between two electrodes placed on the surface of the scalp. Voss and her team waited until their human volunteers were dreaming in a state of REM sleep for at least two minutes before starting to apply the current, which they hoped would entrain the neurons in the brain to the same frequency as they used for stimulation. After stimulating for 30 seconds, they woke the dreamers up and asked them questions about their dreams.

When the scientists stimulated the brain with a 25 or a 40 Hz current, similar to what is observed in gamma waves, the subjects reported an increase in lucidity compared to other stimulation frequencies. Here is how one subject described it:

“I was dreaming about lemon cake. It looked translucent, but then again, it didn’t. It was a bit like in an animated movie, like the Simpsons. And then I started falling and the scenery changed and I was talking to Matthias Schweighöfer (a German actor) and 2 foreign exchange students. And I was wondering about the actor and they told me ‘yes, you met him before,’ so then I realized ‘oops, you are dreaming.’ I mean, while I was dreaming! So strange!”

This study represents a huge moment for neuroscience, because it is the first report that transcranial stimulation is capable of causing an alteration in conscious awareness. Moreover, this study suggest that brainwaves of the 40Hz band are not simply a feature of higher cognitive functions, but can actually cause them. Strange indeed.

Reference: Induction of self awareness in dreams through frontal low current stimulation of gamma activity. (2014) Ursula Voss, Romain Holzmann, Allan Hobson, Walter Paulus, Judith Koppehele-Gossel, Ansgar Klimke & Michael A Nitsche. Nature Neuroscience. 


Leave a comment

Fear Perception Depends on Heartbeat Cycle Timing

Print

It always amazes me how much our reactions to the world depend on our internal states, even when those states are outside of our conscious awareness. Though we don’t typically consider it a sense like hearing or seeing, the visceral sense is real: there are tons of receptors inside us, monitoring our internal physiology at all times.

One example is the baroreceptors that monitor the pressure inside our arteries as the heart pumps blood through them. The baroreceptors have a major role in the regulation of blood pressure, as one might expect. However, recent research has revealed that information from these internal receptors is also being used when we process emotional stimuli.

Sarah Garfinkle and colleagues investigated this phenomenon recently by showing people images of human faces, either displaying the emotions of fear, disgust, or happiness, or in a neutral state of repose. The facial expressions were embedded in a stream of scrambled images, and were flashed by so quickly that they were at the limit of conscious perception: each frame occupied the screen for a mere 70 milliseconds, or less than a tenth of a second. The facial expressions were timed to coincide with the cardiac cycle, either landing at systole (between the “lub” and “dub” of a heartbeat, when arterial pressure is high) or at diastole (between heartbeats, when arterial pressure is low).

Afterward, participants were asked to identify which face they had seen in a lineup of three faces. In general, the participants were pretty bad at this test, getting it right only about half the time. But for fearful faces especially, participants were much better at picking out the face they had seen when they saw it in the middle of the heartbeat, rather than between them. Being at the “right” time with respect to the heartbeat pushed detection of the fearful face over the edge from subconscious into consciousness.

So people were better able to detect a fearful face when it came in the middle of a heartbeat, but what about how people thought of the face they saw? The scientists assessed this in a separate experiment, at the same time doing functional neuroimaging on the participants to see what their brains were doing. Again, they showed participants a fearful face, either timed to coincide with systole or diastole. This time, the face was on the screen for a bit longer, so the participants were sure to detect it. Afterward the experimenters asked the participants to rate the intensity of the emotion they saw.

Again, the results depended on the heartbeat cycle timing: if the face was presented in the middle of a heartbeat, participants rated it as more fearful than if it was presented between heartbeats.  The difference was not just perceptual, but also was evident in the activity of a brain structure called the amygdala. The amygdala is known be involved in the processing of emotion, and this area was more active when the participants saw the fearful face at systole than at diastole.

Interestingly, this effect was less marked for individuals who were anxious. People with high anxiety conditions like PTSD are more responsive to fearful stimuli, regardless of when it comes with respect to the cardiac cycle.

This work is just one example of the dynamic feedback between our physiological and emotional states. For decades, neuroscientists have debated the nature of emotions: does nervousness cause butterflies in the stomach, or do butterflies in the stomach create the feeling of nervousness? Which comes first, the physiological or the psychological? We may never have a clear-cut answer to this question, because the there may not be a clear-cut answer. It seems that the road between the body and the mind is a two-way street.

Reference: Fear from the Heart: Sensitivity to Fear Stimuli Depends on Individual Heartbeats. (2014) Sarah N. Garfinkel, Ludovico Minati, Marcus A. Gray, Anil K. Seth, Raymond J. Dolan, and Hugo D. Critchley. Journal of Neruoscience 34(19): 6573-6582

 


Leave a comment

Musical Improvisers Have Better Connections Between Brain Regions

Playing the piano

There’s a difference between a classical pianist who sits down to play Beethoven’s Moonlight Sonata and a jazz pianist with hours of improvisational experience who is comfortable making up a melody in front of an audience.

The difference, it turns out, can be seen as well as heard. Seen by a brain scanner, that is.

The effects of long-term musical practice on the brain are well documented, but scientists have only begun to explore how the type of musical training can change the neural effects. In a study out this week in the Journal of Neuroscience, Ana Luísa Pinho and colleagues set out to investigate the neural basis of musical creativity, or improvisation.

The scientist put 39 professional pianists into a MRI scanner and assessed brain activity and connectivity as the pianists improvised tunes on a keyboard placed on their laps. The musicians also filled out a questionnaire on the number of hours they rehearsed classical music and practiced improvisation in an average week.

Pinho and her colleagues found that the more a musician practiced improvisation, the greater the connectivity between certain brain regions was as they improvised. The highly connected brain regions were areas that have to do with planning, abstract reasoning, and movement control – specifically, the dorsolateral prefrontal cortex, the presupplementary motor area, and the dorsal premotor cortex.  This result supports the idea that there may be no specific brain region that generates creative thought: rather, creativity may be generated by a distributed network of brain regions working in symphony.

Surprisingly, at the same time that the connectivity between these areas increased, the overall activity of prefrontal brain regions decreased according to how much a musician had practiced improvisation. This decrease in the activity of areas used for planning and cognitive control suggests there there is a degree of automation during extemporaneous playing when one is practiced at it.

This may reflect the subjective experience of improvisers – that when they are performing, they are not thinking hard, but are in a state of flow.  The improvisational playing feels automatic, despite being unique and creative.

Improvisation requires a musician to build up a library of musical phrases and motifs over time, to be accessed when playing and put together in new and expressive ways.  Creativity requires training. This work suggests the intriguing possibility that creativity can, to some extent, become automatic to the brain.

Related postEarly musical training gives older adults an advantage

ReferenceConnecting to Create: Expertise in Musical Improvisation Is Associated with Increased Functional Connectivity between Premotor and Prefrontal Areas (2014) Ana Luísa Pinho, Örjan de Manzano, Peter Fransson, Helene Eriksson, and Fredrik Ullén. J Neurosci 34(18): 6156-6163