Brain States


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When We’re In Sync, So Are Our Brains

We all know those moments. The electrifying seconds when the home team makes a goal, or bride says her vows, or the presidential favorite wins the election. The moments when an entire room full of people is feeling exactly the same way, at exactly the same time, because they share a common perspective.

The emotion runs high because everyone is riding the same roller coaster of events, each new twist and turn causing fresh reactions.   Our emotions are jerked like rag dolls.  The result looks so synchronized, it could be choreographed.

When we are all cheering for the same goal, both our bodies and our minds become synchronized.  You throw your hands up at the same time as the rest of the stadium, and your brains are also doing the same thing. In each head, the visual cortex is processing the game, the motor cortex is holding up the arms, and the attention-controlling networks are riveting us all to the events as they unfold.

And when you are rooting for the same person, the Action-Observation Network in the frontoparietal region of starts humming in synchrony with those around you.  In fact, it is this neural synchrony that allows you to share a moment with others.

That’s the implication of a study released in the Journal of Neuroscience. In it, scientists measured the blood flow to the brains of people who were watching a boxing match. In some cases, the scientists told the subjects to watch the match as they normally would. But sometimes they told the subjects to watch the match while paying close attention to a particular boxer, trying hard to simulate in their own minds the actions and emotions of that boxer.

When different subjects focused on the same boxer, their brains began to oscillate in phase with one another in the somatosensory cortex- the part of the brain that is responsible for the sense of touch. The somatosensory cortex also plays a big role in allowing you to mentally “mirror” the actions of another person, so that you can monitor them and understand their motivations.

Importantly, the brain synchrony was bigger when the subjects were paying attention to the same boxer than when the subjects were just watching the video casually. It’s the attention to the actions and feelings of another that caused the brain regions to activate – because in large part, the brain uses the same area to understand the way someone else is feeling as to feel that way itself. 

This report is one in a long line of evidence suggesting that time-locked brain activity shared by individuals is the basic process that supports interpersonal understanding.

Just think. All our moments of mutual understanding may depend on our brains being in sync with one another.

REF:

Nummenmaa L, Smirnov D, Lahnakoski JM, Glerean E, Jääskeläinen IP, Sams M, Hari R (2014) Mental action simulation synchronizes action-observation circuits across individuals. J Neurosci 34:748–757.


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Are experiences heritable?

Image

We all know that our ancestors pass their genes on to us, but what if they are also giving us something else? Evidence is mounting that we also receive an imprint of the experiences that they lived while we were nothing but a gleam in the eye.

In paper published this week in Nature Neuroscience, authors Brian Dias and Kerry Ressler, or Emory University, explore this phenomenon in mice.

They pair a particular smelly chemical with a mild foot shock in virgin adult mice, and then allow those mice to breed and procreate. Once the offspring of the original mice grow up, they give them a whiff of the same odor, and measure how much fear they show. Although the second generation has never smelled the chemical before, they behave as if they themselves had had the unpleasant experiences with it that their parents had before they were even conceived.

The second generation also had physical changes to the brain, specifically in the olfactory epithelium, which is the part of the brain that detects odors. The second generation had a much larger portion of the brain devoted to the detection of that odor than did control mice.

Could it be that they parents are somehow teaching their children that the odor is bad as they are growing up? To test this idea, the authors used two methods. First, they tested mice that were raised by foster parents who had no experiences with the odor. Still, the children responded to the odor with fear.  Second, they tested mice in the third generation. Neither they nor their parents had any experience with the odor that their grandparents had such bad associations with.  But the third generation mice still reacted to the odor fearfully.

So what is going on here? It turns out that not only the genome, but the regulation of the genome, is heritable between generations. This is referred to by biologists as epigenetics. The DNA itself is tagged as an organism lives. Some genes get big flashing arrows that declare “Hey!! This is really important!” whereas others that never really mattered are greyed out. And these annotations are passed along to offspring, right along with the A’s and T’s and G’s and C’s.

Is there evidence that such a thing could be happening in humans? Yes, actually, there are many anecdotal observations that support this idea. For instance, the grandchildren of people who experienced the Dutch famine of 1944 during the German occupation of the Netherlands are smaller than average.

So if you haven’t had kids yet, but are planning to in the future, there are now even more reasons to be careful how you live. Your grandchildren may be feeling it in the future.

Reference: B.G. Dias and K.J. Ressler  (2013) Parental olfactory experience influences behavior and neural structure in subsequent generations. Nature Neuroscience


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Early musical training gives older adults an advantage

rsz_boy_violin

Brain recordings of professional musicians have revealed that they have sharper auditory responses than non-musicians, even in late life when neural responses are declining. But what about people who played an instrument early in life and then stopped after reaching adulthood?

Travis White-Schwoch and his colleagues addressed this question by recording from the auditory brainstem of adults between the ages of 55 and 76.  The older adults fell into one of three groups: some had no musical training, others had three years or less, and some had between four and fourteen years.

As we age, one of the elements of speech that is the most difficult to encode and hear properly is a consonant-vowel transition.  This is because of how quickly the transition occurs relative to the sustained vowel sound.  (Think of how easy it is to mistake the word “vowels” for the word “bowels”.) For this reason, the group hypothesized that those with more musical training would have faster neural responses to the consonant-vowel transition syllable “da” than their non-trained counterparts.  This was true, especially when the syllable was presented in a noisy environment, which tends to slow neural responses in the auditory brainstem.

So why does it make a difference if those with musical training react a few milliseconds faster than their non-trained peers?  In short, timing is everything.  A faster reaction means a more efficient auditory system.  This study does not explore whether the musically-trained groups have comparatively fewer events of mishearing speech, but that can be a hard variable to quantify.  Having a faster reaction in the brainstem at least makes it more likely that the cortex can parse speech correctly.

It is remarkable that early musical training left a detectable trace in the brain,  despite the fact that 40 or more years had passed since the musical training ceased.  Although this study does not address the mechanisms of the change, the authors propose at least two alternatives.  It could be that early training causes a enhancement that is crystallized as the adult ages, resulting in a permanent structural change.  The authors see this as unlikely, however, given that auditory responses are known to be responsive to interventions even late in adulthood.  Another possibility is that early musical training changes the individual’s lifetime relationship with sounds, and so the tight neural timing typical of a musician is reinforced.  To state it differently, people with early musical training may be better listeners throughout their lives, more appreciative of the rhythms and tones that make up our auditory landscape.

One thing is for sure: I’m glad my mom made me practice violin everyday as a kid. She was right when she said I’d thank her later.

Reference:

T. White-Schwoch, K.W. Carr, S. Anderson, D.L. Strait, N. Kraus.   (2013) Older Adults Benefit from Music Training Early in Life: Biological Evidence for Long-Term Training-Driven Plasticity


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Sexism and sexual harassment rock the science writing world

A bizarre internet drama has been playing out in science writing circles recently. A Scientific American blogger posted about a sexist and super unprofessional email she received from an editor at Biology Online after she refused to write for them (for free). The name of her blog is The Urban Scientist. The offending editor suggested that she was, in fact, an “Urban whore”.

Scientific American pulled the blog post within an hour, but later put it back up and offered both an apology and an unsatisfying explanation that they’d pulled it because the post was not about science. They verified the e-mail and the offending editor was fired by Biology Online. Case closed.

Nah, just kidding.  When things like this happen in a professional community, there is always a backlash.  In this case, the backlash has overwhelmed the original story. Another blogger, after reading the revelation on The Urban Scientist, was reminded of her own encounters with sexual harassment in the science writing community and decided it was time to point the finger. Turns out her harasser was the Scientific American blog editor Bora Zivkovic, author of A Blog Around The Clock.  Mr. Zivkovic has many friends in the community, and many of them were shocked by the allegation and thought that Mr. Zivkovic should not have been publicly called out on his behavior because of the impact that it has on his career.

Mr. Zivkovic apologized immediately and stated that it was an isolated incident. But then at least two more women decided to state publicly that the incident was not isolated, and that. Mr. Zivkovic had harassed them as well at professional conferences. The abuse was predominately verbal – he talked at length about the unhappiness of his marriage and its lack of sexual activity, about how he was a very sexual person and was considering affairs (hint, hint).  These are fine topics to discuss with a close friend or a therapist, but they are not appropriate to hash out with someone who you’ve just met, or someone who is seeking your help in advancing their career. Which is what Mr. Zivkovic did.

Mr. Zivkovic is no longer employed by Scientific American, and he has resigned from the board of a conference that he helped to create. An editorial was published in Nature condemning Mr. Zivkovic’s behavior and stating that science cannot afford to lose women to such “boorishness.”  The Nature editorial makes the issue so simple- but in comments all around the internet, there are still fights going on, with some still doubting that what Mr. Zivkovic did was wrong.

Mr. Zivkovic’s defenders make me certain that this type of harassment will happen again, because for those people, his behavior is not perceived as being out of line. Certainly, we must acknowledge that we humans are sexual by nature.  The goal is not to rid people in power of their sexuality, but to constrain it to appropriate times and relationships. Boundaries are an important part of life, and they are indispensable in having a healthy community.


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A drug to break marijuana addiction?

At the base of the midbrain lies the ventral tegmental area, or VTA.  It is a dark, melanin-pigmented structure that is connected in a feedback loop of wiring with many other far-flung chunks of brain. It projects to and receives projections from the celebrated prefrontal cortex, the memory-forming hippocampus, and most importantly for this story, the pleasure-processing nucleus accumbens.  Although the specific numbers are debated, over half of the neurons that live there release the neurotransmitter dopamine.  And these neurons get excited by delta-9-THC, the cannabinoid present in marijuana.

This is the reward circuitry of the brain, and it provides motivation for many behaviors. Every major drug of abuse – cocaine, nicotine, alcohol, heroin, etc. –  causes an increase in the activity of the dopaminergic neurons in the VTA and the nucleus accumbens. But the  firing of these neurons also increases for natural pleasurable stimuli like food and sex.  Because of the broad activity of the neurons, it is difficult to find effective treatments for addiction to specific drugs by intervening at this level.

But Justinova and colleagues have found another possible way to intervene in marijuana addiction – at least in preliminary experiments on squirrel monkeys and rats.  Prior studies  have suggested that the effects of THC are mediated by a different type of receptor altogether: an acetylcholine receptor known as 𝛼7nAChR.

Most receptors in the brian have a primary molecule to which they respond, known as a ligand.  But receptor efficiency can be changed by other secondary molecules, known as allosteric modulators. Allosteric modulators can work in two directions: positive allosteric modulators increase the efficiency of the receptor, whereas negative allosteric modulators decrease it.

Kynurenic acid is a naturally-occuring negative allosteric modulator of the 𝛼7nACh Receptor. Justinova et. al used a molecule called Ro 61-8048 to increase the levels of kynurenic acid produced in the brain. By doings this, they reduced the efficiency of the 𝛼7nACh Receptor. This caused there to be less dopamine secreted in the VTA and the nucleus accumbens when THC was present, reducing activation of the reward circuitry in response to marijuana.

The researchers gave Ro 61-8048 to a group of squirrel monkeys that had been allowed to self-administer injections of THC. Giving the monkeys Ro 61-8048 reduced marijuana seeking behavior – i.e.,  the monkeys pressed the lever to get high fewer times after Ro 61-8048 than they did before. This is neat because monkey self-administration of THC is probably the best animal model we have of voluntary marijuana use in humans.

Importantly, the Ro 61-8048 did not affect the food-seeking behavior of the monkeys – so the pleasure-reducing effects of the drug were specific to THC, not to pleasurable stimuli in general.

The researchers also studied an animal model of marijuana relapse.  In formerly addicted, now abstinate squirrel monkeys, exposure to specific cues that signal the availability of THC can cause an increase in drug-seeking behaviors.  But Ro 61-8048 administration reduced this effect.  After treatment with Ro 61-8048, the animals were better able to resist temptations to relapse. 

So what does this mean for interventions in human drug abuse? The authors are guardedly optimistic. Although the drugs show promise in rats and squirrel monkeys, every species has slightly different biology.  Preliminary translational studies on humans will have to be done before we know whether the benefit of the drug outweighs any potential risks.

Reference:

Z. Justinova, P. Mascia, H. Wu, M.E. Secci, G.H. Redhi, L.V. Panlilio, M. Scherma, C. Barnes, A. Parashos, T. Zara, W. Fratta, M. Solinas, M. Pistis, J. Bergman, B.D. Kangas, S. Ferre, G. Tanda, R. Schwarcz, S.R. Goldberg. (2013) Reducing cannabinoid abuse and preventing relapse by enhancing endogenous brain levels of kynurenic acid.  Nature Neuroscience. 


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Oxytocin and Empathy

Note: this entry was previously published on Octopractical.

It was a beautiful day at the White Oak Pavillion at Mt. Pisgah in Eugene, OR. The sunshine was filtering through the light green usnea lichen that hung from the stately oaks.  The sky was the deep blue of Fall.  It’s no wonder that the Pavillion is one of Eugene’s top three spots for a wedding. But on this day, those gathered here were considering love from a different point of view.

Sarina Saturn, Ph. D.

Dr. Sarina Saturn, an assistant professor of psychology at Oregon State University, presented her work on the oxytocin receptor, OXTR, as a keynote speaker for the University of Oregon Institute of Neuroscience’s annual retreat. Oxytocin has a reputation as the “love molecule” and is one of the superstar molecules of neuroscience- a neurotransmitter like serotonin an dopamine that has debuted in the public consciousness as a molecule of positive psychology.  Oxytocin is actually both a hormone and a neurotransmitter.  It can act as a signalling molecule for both neuronal tissue, as in the brain, and non-neuronal tissue, such as the uterus.  It is produced in abundace in prarie voles, a species that forms near-monogamous pair bonds. It is causes uterine contractions during labor, and is thought to carry that powerful first flush of love between a mother and an infant.  It is also know to have a role in the stress response, inhibiting cortisol production.

Unlike many other neurotransmitters, there is only one receptor for oxytocin present in the human genome.  It is on the third chromosome. But not everyone has exactly the same form of OXTR.   It is mostly the same, except that at one location within the molecule, some individuals have an adenine nucleotide (or “A” of the famous four:  A, T, G and C) and others have a guanine (or “G”).  This is what is known as a single nucleotide polymorphism, or SNP (pronounced “snip”).  Since we all have two copies of the third chromosome, we each have two versions of the genetic code for the oxytocin receptor.  We can have either two A’s  (about 25% of us), and A copy and a G copy (about 50% of us), or we can have two G’s (about 25% of us).  This is one of the many points at which we humans have natural genetic variation.

Dr. Saturn is a molecular biologist turned social psychologist. She did her Ph.D. work in the lab of Joseph LeDoux, author of The Synaptic Self.  At that time, she worked on the amygdala- the so-called emotional center of the brain.  But her career now focuses on the SNP of the oxytocin receptor in humans- and her findings point to the big role of this little difference between us.  She and her colleauges have found that this single neucleotide substitution has a role in how we behave both in reaction to stress, and in situations where we need to be empathetic and “read” the emotions of others through body language.  Those of us with the GG genotype are better at reading the intentions of other people by just looking at picutre of the eyes than those of us with one or two A’s.  In addition, people with a GG genotype report feeling more empathy than their AA or AG peers.   People with two G’s are also better able to keep calm when anticipating a stressor.

In another study, Dr. Saturn and her colleauges found that a GG genotype does not just impact how empathetic a person feels. It also manifests in the person’s behavior in a way that can be observed by others.  The researchers recorded conversations between romantic partners. In particular, they recorded the behavior of one partner with he or she was listening to thier romantic partner talk about a difficult time in thier lives. This show of vulnerability is thought to consistently elicit an empathetic, prosocial reaction.  The researchers then showed the videos of the listeners to another group of people, who ranked the listener’s empathy based on viewing only twenty seconds of the listener’s behavior.  Judges rated listeners with a GG genotype as signifcantly more empathetic and prosocial than listeners with AG or AA genotypes.

“At this point, I cried for days,” said Dr. Saturn when relaying these results, “and not because I knew I would have get some cool papers out of it. I genotyped myself and I am an AA.”

But the story with oxytocin is not yet over. There is some evidence that intranasal administration of oxytocin- in addition to increasing eye-gaze and feelings of empathy towards those present, can also promote exclusionary behaviors of those in the out-group, such as ethnocentrism. There is likely some social advantage to being a carrier of the A alelle of the OXTR, net yet uncovered by research.  I wonder if this is what Dr. Saturn will investigate next.

References:

S.M. Rodrigues,*, L.R. Saslow, N. Garcia, O.P. John, D. Keltner. (2009) An oxytocin receptor genetic variation relates to empathy and stress reactivity in humans. Proceedings of the National Academy of Sciences, 106: 21437-21441. (*co-first author)

A. Kogan, L.R. Saslow, E.A. Impett, C. Oveis, D. Keltner, S.R. Saturn. (2011) Thin-slicing of the oxytocin receptor (OXTR) gene and the evaluation and expression of the prosocial disposition. Proceedings of the National Academy of Sciences, 108: 19189-19192.