The Racist Brain?

Is the human brain... a racist?

There are some worrying indications that it could be. After all, the cerebrum is largely composed of so-called "white" matter, and the only black area is a little 'ghetto' at the bottom called, shockingly, the substantia nigra...!

Seriously though. There's a paper just out in Nature Neuroscience from Kubota et al that looks at The Neuroscience Of Race. It's a fine review as far as it goes, but to me at least, it really shows up the limits of contemporary neuroscience.

We are told that

A network of interacting brain regions is important in the unintentional, implicit expression of racial attitudes and its control. On the basis of the overlap in the neural circuitry of race, emotion and decision-making, we speculate as to how this emerging research might inform how we recognize and respond to variations in race and its influence on unintended race-based attitudes and decisions.

So there have been studies investigating which bits of American's brains activate in response to looking at photos of black people vs. white people. It emerges that "a network of interacting brain regions" light up. But so what?

Sure, the brain reacts differently to seeing people of different races. Of course it does - it reacts differently to everything, so long as we can perceive a difference; that's how we perceive a difference. And of course race, a deeply emotive issue in American politics and culture, activates 'emotional' parts of the brain - that's how it's emotive.

The included studies all scanned Americans and (presumably) mostly college students. Now most American college students are not active racists, and indeed I'd imagine that their emotional brains are more likely to be worrying self-referentially about racism than about the actual race of the stimuli. No-one seems to have scanned card-carrying members of the KKK. Furthermore, "race" in these studies almost always means "blackness". What about Latinos, Asians?

So what have we learned?

I don't think we've learned much about race. "Race" after all is a confused mixture of emotions, attitudes and beliefs. These differ greatly from person to person, and even the same individual may experience conflicting feelings in different contexts. Kubota et al note this and say that it may explain the mixed findings (black faces activate the amygdala more than white in some studies, not in others) but I'd have said that in this case, only inconsistent results are credible.

What does it tell us about the brain? I'd say not much. The authors weave a neat little narrative - in response to seeing black faces, the amygdala and other emotional areas activate as a negative emotional response; the ACC then detects this racist response and sees that it's unacceptable, and the DLPFC then suppresses it like a parent hurriedly interrupting a young child who's making a faux pas.

But all the elements of this story - the automatic, emotional amygdala, the supervisory DLPFC - are borrowed from other neuroscience studies so at best the race literature confirms these theories but it doesn't even really do that, because there are many other possible interpretations.

I'd say that we need to know much more in terms of the 'basic' neuroscience of emotion, attitudes and beliefs because we can tackle the hornet's nest of race in the brain.

Kubota JT, Banaji MR, and Phelps EA (2012). The neuroscience of race. Nature neuroscience, 15 (7), 940-8 PMID: 22735516

This Is Your Brain On Ethics - Really

A new study published in Social Cognitive and Affective Neuroscience offers a look at the neural correlates of ethical decision making: Differential Neural Circuitry and Self-Interest in Real versus Hypothetical Moral Decisions

There have been quite a few studies using neuroimaging to measure activations associated with tackling hypothetical moral dilemmas but what makes the new paper interesting is that the participants were faced with a real moral choice. Well, mostly real.

The task was called "Your Pain, My Gain". The participants were put in the MRI scanner and given £20 at the start of the experiment. Then they could spend some of the money to help save another person from getting electric shocks. The more they spent, the less severe the pain administered to the victim. Video footage of the victim receiving the shocks was then played to the decider, and the process repeated.

Selfish people could choose to keep more of the cash, if they could handle the guilt of knowing that they were shocking their poor victim. At the end of the study, the remaining sum was multiplied by a random factor of between 1 and 10, meaning that there was, potentially, £200 at stake - a serious amount of money.

Actually, the task was a sham - as these experiments usually are. All of the 'shock' videos were pre-recorded, there was no victim, so the decision to keep the money had no effect. But the experimenters tried to make it as believable as possible (out of 18 volunteers, 4 were skeptical, and they were excluded).

There was also a comparison task, which was the same idea, but the participants were told it was purely hypothetical, and would have no real consequences.

The fMRI data showed (although note, some of these did not use multiple comparisons correction) that both the 'real' and hypothetical tasks activated a 'shared moral network':

Although both the hypothetical and the real tasks also led to different patterns of individual activation as well - the authors write:

hypothetical moral decisions mapped closely onto the imagination network, while real moral decisions elicited activity in the bilateral amygdala and anterior cingulate—areas essential for social and affective processes.

Hmm. To be honest the results are a bit messy but the method is extremely interesting. I've written before about the need to keep it real when it comes to stimuli in fMRI experiments so this is important: hypothetical moral dilemmas are no substitute for the real thing. Personally I'm holding out for someone to replicate the Milgram experiment in the MRI scanner although I'm not sure anyone would get ethical approval for that nowadays...

Feldmanhall O, Dalgleish T, Thompson R, Evans D, Schweizer S, and Mobbs D (2012). Differential Neural Circuitry and Self-Interest in Real versus Hypothetical Moral Decisions. Social cognitive and affective neuroscience PMID: 22711879

The Almond of Horror

Remember the 90s, when No Fear stuff was cool, and when people still said "cool"?

Well, a new paper has brought No Fear back, by reporting on a woman who has no fear - due to brain damage. The article, The Human Amygdala and the Induction and Experience of Fear, is brought to you by a list of neuroscientists including big names such as Antonio Damasio (of Phineas Gage fame).

The basic story is nice and simple. There's a woman, SM, who lacks a part of the brain called the amygdala. They found that she can't feel fear. Therefore, it's reasonable to assume that the amygdala's required for fear. But there's a bit more to it than that...

The amygdala is a small nugget of the brain nestled in the medial temporal lobe. The name comes from the Greek for "almond" because apparently it looks like one, though I can't say I've noticed the resemblance myself.

What does it do? Good question. There are two main schools of thought. Some think that the amygdala is responsible for the emotion of fear, while others argue that its role is much broader and that it's responsible for measuring the "salience" or importance of stimuli, which covers fear but also much else.

That's where this new paper comes in, with the patient SM. She's not a new patient: she's been studied for years, and many papers have been published about her. I wonder if her acronym doesn't stand for "Scientific Motherlode"?

She's one of the very few living cases of Urbach-Wiethe disease, an extremely rare genetic disorder which causes selective degeneration of the amygdala as well as other symptoms such as skin problems.

Previous studies on SM mostly focussed on specific aspects of her neurological function e.g. memory, perception and so on. However there have been a few studies of her "everyday" experiences and personality. Thus we learned that:

Two experienced clinical psychologists conducted "blind" interviews of SM (the psychologists were not provided any background information)... Both reached the conclusion that SM expressed a normal range of affect and emotion... However, they both noted that SM was remarkably dispassionate when relating highly emotional and traumatic life experiences... To the psychologists, SM came across as a "survivor", as being "resilient" and even "heroic".

These observations were based on interviews under normal conditions; what would happen if you actually went out of your way to try and scare her? So they did.

First, they took her to an exotic pet store and got her to meet various snakes and spiders. She was perfectly happy picking up the various critters and had to be prevented from getting too closely acquainted with the more dangerous ones.

What's fascinating is that before she went to the store, she claimed to hate snakes and spiders! Why? Before she developed Urbach-Wiethe disease, she had a normal childhood up to about the age of 10. Presumably she used to be afraid of them, and just never updated this belief, a great example of how our own narratives about our feelings can clash with our real feelings.

They subsequently confirmed that SM was fearless by taking her to a "haunted asylum" (check it out, even the website is scary) and showing her various horror movie clips, as well as through interviews with herself and her son. They also describe an incredible incident from several years ago: SM was walking home late at night when she saw

A man, whom SM described as looking “drugged-out.” As she walked past the park, the man called out and motioned for her to come over. SM made her way to the park bench. As she got within arm’s reach of the man, he suddenly stood up, pulled her down to the bench by her shirt, stuck a knife to her throat, and exclaimed, “I’m going to cut you, bitch!”

SM claims that she remained calm, did not panic, and did not feel afraid. In the distance she could hear the church choir singing. She looked at the man and confidently replied, “If you’re going to kill me, you’re gonna have to go through my God’s angels first.” The man suddenly let her go. SM reports “walking” back to her home. On the following day, she walked past the same park again. There were no signs of avoidance behavior and no feelings of fear.

All this suggests that the amygdala has a key role in the experience of fear, as opposed to other emotions: there is no evidence to suggest that SM lacks the ability to experience happiness or sadness in the same way.

So this is an interesting contribution to the debate on the role of the amygdala, although we really need someone to do equally detailed studies on other Urbach-Wiethe patients to make sure that it's not just that SM happens to be unusually brave for some other reason. What's doubly interesting, though, is that Ralph Adolphs, one of the authors, has previously argued against the view of the amygdala as a "fear center".

Links: I've previously written about the psychology of horror movies and I've reviewed quite a lot of them too.

Justin S. Feinstein, Ralph Adolphs, Antonio Damasio,, & and Daniel Tranel (2010). The Human Amygdala and the Induction and Experience of Fear Current Biology

Inception for Dummies

If you haven't watched Inception yet, don't read this post. It's great and I don't want to spoil it for you. So stop. You didn't though, did you, you're still reading this right now. Well, I warned you.

Inception as everyone knows is about people who can hack into other people's dreams to access their subconcious. The plot concerns their attempts to achieve, well, inception - putting an idea into someone's mind, which makes what they usually do, stealing secret ideas, seem easy by comparison.

The problem is that it's easy to plant an idea, but the victim always knows that it's an external imposition - they don't really believe it. Leonardo DiCaprio comes up with the plan of going into the victim's subconcious's subconcious, and planting an emotional idea about his father, in order to lead him to conclude, on his own, that he should break up his father's business empire. I'm not sure what Freud would have thought of this plan.

Could you actually do this? Well. Hacking into people's dreams is high fantasy: we have absolutely no idea how you'd do that, and in the movie the only explanation we get is that it involves fancy machines and unspecified drugs. It's safe to say no-one will be gatecrashing your dream party any time soon.

But here's one way to achieve the same kind of effect, inspired by two recent papers: this one that I wrote about in my last post, finding that electrical stimulation of the hippocampus produces temporary amnesia, and this one covered at Neurophilosophy, finding that stimulating a mouse's lateral amygdala at the same time as playing it a noise makes it fear that noise.

Simple fear conditioning happens in the amygdala, not the hippocampus (although conditioned fear to some partiuclarly complex stimuli, like places, does.) So assuming you were a neurosurgeon with a desire to do some inception and no ethical scruples whatsoever, here's what you might decide to do.

Knock your victim out with a sedative. Keep them unconscious while you implant electrodes in their hippocampus and their amygdala. Wake them up, but make sure that you constantly stimulate their hippocampus to disrupt it, from the moment they awake. This will leave them fully aware, but will mean they'll have no subsequent concious memory of what you do, because such concious declarative memories depend upon the hippocampus.

Now, you condition them to fear something, by showing it to them whilst stimulating their lateral amygdala. (To be honest, you could just give them a slap in the face and it would probably be just as effective - but that would be a bit unrefined. This is a high-tech evil medical procedure, not a common punch-up.) Maybe you could make them scared of the face of a business rival who you don't want them to cut a deal with. Or you could make a terrorist leader abhor the symbols of his own ideology. The possibilities are endless.

Once you're done, sedate them again and return them to their house. Yeah, you'd have to do this all in the course of one night, but no-one said Inception was going to be easy. With any luck, they'll wake up with no concious recollection of anything, but with the emotional conditioning still intact.

The lack of memory is of course crucial: if they remembered what had happened, they'd realize that the conditioning was an external imposition, and wouldn't be swayed by it. And they'd bust you to the cops, obviously. But without that concious knowledge as to the true source of the feelings, they'd have no alternative interpretation of the fear they now feel - they'd take it as their own, and really start to dislike whatever it was you'd made them afraid of, constructing elaborate rationalizations along the way. The dream is real...

This Season's Hottest Brain Regions

Are you a budding neuroscientist who's not sure which part of the brain to specialize in? Or perhaps you're a purveyor of media neuro-nonsense who's wondering which area to namedrop as being the key to sex / intelligence / politics next?

Well, wonder no more, because Neuroskeptic can now exclusively reveal which parts of the brain are hot, and which are not, right now (thanks to the high-tech method of searching PubMed and counting the papers published referring to eight major brain regions, each year from 1985 to 2009.)

The hippocampus stands out as an extremely hot region with both a huge number of papers and rapid growth over 25 years. So it's probably a good place to build a career... but on the other hand, the market may be saturated already, and it shows some signs of flatlining in the past few years. The cerebellum has long been popular, but growth has been extremely slow lately.

To better highlight the growth curves here's the same data but normalized to the year 2000 (so "2" means twice as many papers as in 2000, etc.)

This shows major differences. The orbitofrontal cortex and cingulate cortex are both undergoing massive growth at the moment. The amygdala and parietal cortex are pretty hot too. By contrast, the cerebellum and the caudate are stuck in the scientific doldrums.

Why are the patterns so different for different parts of the brain? That's a big question which hopefully will get discussed in the Comments. I suspect that the recent rise of the cingulate cortex and the orbitofrontal cortex, however, has much to do with the rise of fMRI (i.e. within the last 10 years, mostly), which allows them to be easily studied in humans for the first time.

Both of these areas are quite difficult to study with older technologies like EEG, because of their location within the head. That said, the same problem applies to plenty of other regions, but the orbitofrontal and cingulate cortex are also difficult to study in lab rats and mice, because it's not clear which parts of the rodent brain map onto which parts of the human brain in these regions. By contrast, things like the cerebellum and caudate nucleus have exact rodent equivalents, perhaps making them more attractive to early researchers.

In the Brain, Acidity Means Anxiety

According to Mormon author and fruit grower "Dr" Robert O. Young, pretty much all diseases are caused by our bodies being too acidic. By adopting an "alkaline lifestyle" to raise your internal pH (lower pH being more acidic), you'll find that

if you maintain the saliva and the urine pH, ideally at 7.2 or above, you will never get sick. That’s right you will NEVER get sick!

Wow. Important aspects of the alkaline lifestyle include eating plenty of the right sort of fruits and vegetables, ideally ones grown by Young, and taking plenty of nutritional supplements. These don't come cheap, but when the payoff is being free of all diseases, who could complain?

Young calls his amazing theory the Alkavorian Approach™, aka the New Biology™. Almost everyone else calls it quack medicine and pseudoscience. Because it is quack medicine and pseudoscience. But a paper just published in Cell suggests an interesting role for pH in, of all things, anxiety and panic - The amygdala is a chemosensor that detects carbon dioxide and acidosis to elicit fear behavior.

The authors, Ziemann et al, were interested in a protein called Acid Sensing Ion Channel 1a, ASIC1a, which as the name suggests, is acid-sensitive. Nerve cells expressing ASIC1a are activated when the fluid around them becomes more acidic.

One of the most common causes of acidosis (a fall in body pH) is carbon dioxide, CO2. Breathing is how we get rid of the CO2 produced by our bodies; if breathing is impaired, for example during suffocation, CO2 levels rise, and pH falls as CO2 is converted to carbonic acid in the bloodstream.

In previous work, Ziemann et al found that the amygdala contains lots of ASIC1a. This is intriguing, because the amygdala is a brain region believed to be involved in fear, anxiety and panic, although it has other functions as well. It's long been known that breathing air with added CO2 can trigger anxiety and panic, especially in people vulnerable to panic attacks.

What's unclear is why this happens; various biological and psychological theories have been proposed. Ziemann et al set out to test the idea that ASIC1a in the amygdala mediates anxiety caused by CO2.

In a number of experiments they showed that mice genetically engineered have no ASIC1a (knockouts) were resistant to the anxiety-causing effects of air containing 10% or 20% CO2. Also, unlike normal mice, the knockouts were happy to enter a box with high CO2 levels - normal mice hated it. Injections of a weakly acidic liquid directly into the amygdala caused anxiety in normal mice, but not in the knockouts.

Most interestingly, they found that knockout mice could be made to fear CO2 by giving them ASIC1a in the amygdala. Knockouts injected in the amygdala with a virus containing ASIC1a DNA, which caused their cells to start producing the protein, showed anxiety (freezing behaviour) when breathing CO2. But it only worked if the virus was injected into the amygdala, not nearby regions.

This is a nice series of experiments which shows convincingly that ASIC1a mediates acidosis-related anxiety, at least in mice. What's most interesting however is that it also seems to involved in other kinds of anxiety and fear. The ASIC1a knockout mice were slightly less anxious in general; injections of an alkaline solution prevented CO2-related anxiety, but also reduced anxiety caused by other scary things, such as the smell of a cat.

The authors conclude by proposing that amygdala pH might be involved in fear more generally

Thus, we speculate that when fear-evoking stimuli activate the amygdala, its pH may fall. For example, synaptic vesicles release protons, and intense neural activity is known to lower pH.

But this is, as they say, speculation. The link between CO2, pH and panic attacks seems more solid. As the authors of another recent paper put it

We propose that the shared characteristics of CO2/H+ sensing neurons overlap to a point where threatening disturbances in brain pH homeostasis, such as those produced by CO2 inhalations, elicit a primal emotion that can range from breathlessness to panic.

Ziemann, A., Allen, J., Dahdaleh, N., Drebot, I., Coryell, M., Wunsch, A., Lynch, C., Faraci, F., Howard III, M., & Welsh, M. (2009). The Amygdala Is a Chemosensor that Detects Carbon Dioxide and Acidosis to Elicit Fear Behavior Cell, 139 (5), 1012-1021 DOI: 10.1016/j.cell.2009.10.029

Panic! In the fMRI Scanner

Continuing the theme of interesting single case reports, I was pleased to see a paper about brain activity in someone who suffered a panic attack in the middle of an fMRI brain scan experiment.

The unfortunate volunteer, a 46 year old woman, was taking part in an experiment looking at restless-leg syndrome. The scan lasted 40 minutes, and everything was going smoothly until quite near the end, when out of the blue, she had a panic attack.

Obviously, the scan had to be abandoned - as soon as the volunteer pressed the emergency "panic button", they stopped the scan and got her out of the MRI. (This kind of thing is why we have such buttons!) However, they decided to see what happened in the woman's brain as the panic started using the data they acquired up to that point.

Here's what they found: the top graph here shows her heart rate. It starts increasing a bit and then spikes, which shows exactly when the attack occurred. What about the brain? Well, amygdala and left insula activity sort of increase around this time. A bit. If you stare at the lines hard enough.

If you believe they did, it makes sense because the amygdala is known to be involved in anxiety (amongst other things) while the insula is responsible for the perception of the body's internal state, which is rather out of whack during a panic attack.

What doesn't make sense is the middle temporal gyrus bit, which was statistically the only part of the brain where activity was significantly correlated with heart rate (in whole-brain analysis). That region is not believed to have anything to do with panic, and to be honest, it's probably just a fluke.

This is only the second published report about panic during fMRI. There was one previous paper from 2006 about an attack in someone with a history of panic, which also found amygdala activation. But there are sure to be others out there which haven't made it into print - anxiety and panic during scans is not unheard of (the scanner is rather claustrophobic). It would be interesting to get more data on this, because it's obviously rather hard to research real-life panic attacks, on account of them being unpredictable.

Spiegelhalder, K., Hornyak, M., Kyle, S., Paul, D., Blechert, J., Seifritz, E., Hennig, J., Tebartz van Elst, L., Riemann, D., & Feige, B. (2009). Cerebral correlates of heart rate variations during a spontaneous panic attack in the fMRI scanner Neurocase, 1-8 DOI: 10.1080/13554790903066909

Trauma Alters Brain Function... So What?

According to a new paper in the prestigous journal PNAS, High-field MRI reveals an acute impact on brain function in survivors of the magnitude 8.0 earthquake in China.

The earthquake, you'll remember, happened on 12th May last year in central China. Over 60,000 people died. The authors of this paper took 44 earthquake survivors, and 32 control volunteers who had not experienced the disaster.

The volunteers underwent a "resting state" fMRI scan; survivors were scanned between 13 and 25 days after the earthquake. Resting state fMRI is simply a scan conducted while lying in the scanner, not doing anything in particular. Previous work has shown that fMRI can be used to measure resting state neural activity in the form of low-frequency oscillations.

The authors found differences in the resting state low-frequency activity (ALFF) between the trauma survivors and the controls. In survivors, resting state activity was increased in several areas:

"The whole-brain analysis indicated that, vs. controls, survivors showed significantly increased ALFF in the left prefrontal cortex and the left precentral gyrus, extending medially to the left presupplementary motor area... [and] region of interest (ROI) analyses revealed significantly increased ALFF in bilateral insula and caudate and the left putamen in the survivor group..."

They also reported correlations between resting activity in some of these areas and self-reported anxiety and depression symptoms in the survivors.

Finally, survivors showed reduced functional connectivity between a wide range of areas ("a distributed network that included the bilateral amygdala, hippocampus, caudate, putamen, insula, anterior cingulate cortex, and cerebellum.") Functional connectivity analysis measures the correlation in activity across different areas of the brain - whether the areas tend to activate at the same time or not.

Now - what does all this mean? And does it help us understand the brain?

The fact that there are differences between the two groups is neither informative nor surprising. "Resting state" neural activity presumably reflects whatever is going through a person's mind. Recent earthquake survivors are going to be thinking about rather different things compared to luckier people who didn't experience such trauma. It doesn't take a brain scan to tell you that, but that's all these scans really tell us.

But these weren't just any differences - they were particular differences in particular brain regions. Does that make knowing about them more interesting and useful?

Not as such, because we don't know what they represent, or what causes them. So living through an earthquake gives you "Increased ALFF in the left prefrontal cortex" - but what does that mean? It could mean almost anything. The left prefrontal cortex is a big chunk of the brain, and its functions probably include most complex cognitive processes. Ditto for the other areas mentioned.

The authors link their findings to previous work with frankly vague statements such as "The increased regional activity and reduced functional connectivity in frontolimbic and striatal regions occurred in areas known to be important for emotion processing". But anatomically speaking, most of the brain is either "fronto-limbic" or "striatal", and almost everywhere is involved in "emotion processing" in one way or another.

So I don't think we understand the brain much better for reading this paper. Further work, building on these results, might give insights. We might, say, learn that decreased connectivity between Regions X and Y is because trauma decreases serotonin levels, which prevents signals being communicated between these areas, which is why trauma victims can't use X to deliberately stop recalling traumatic memories, which is what Y does.

I just made that up. But that's a theory which could be tested. Much of today's neuroimaging research doesn't involve testable theories - it is merely the exploratory search for neural differences between two groups. Neuroimaging technology is powerful, and more advanced techniques are always being developed. What with resting state, functional connectivity, pattern-classification analysis, and other fancy methods, the scope for finding differences between groups is enormous and growing. I'm being rather unfair in criticizing this paper; there are hundreds like it. I picked this one because it was published last week in a good journal.

Exploratory work can be useful as a starting point, but at least in my opinion, there is too much of it. If you want to understand the brain, as opposed to simply getting published papers to your name, you need a theory sooner or later. That's what science is about.

Lui, S., Huang, X., Chen, L., Tang, H., Zhang, T., Li, X., Li, D., Kuang, W., Chan, R., Mechelli, A., Sweeney, J., & Gong, Q. (2009). High-field MRI reveals an acute impact on brain function in survivors of the magnitude 8.0 earthquake in China Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0812751106