How a car engine works

How a car engine works by Jacob O’Neal. I’ve recently been having engine trouble with my car about whose workings I know practically nothing. Nothing!

He has a bunch of other stuff worth checking out, too. I like this animated Cheeatah infographic and this one about porn and dopamine (whose scientific data on ‘porn viewing’ is made up, but whose graphical presentation I love).

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Social status, novelty-seeking, and dopamine

Dopamine sure seems to do a lot of things these days, doesn’t it? It’s most commonly thought to be the mechanism for prediction error which is used for reward-based learning, but it is also linked to sociability, pain, and a ton of other things.

One of its mechanisms relates to social dominance. Eight years ago, Morgan et al. published a paper concerning social dominance in monkeys. They wanted to show how there is a profound environmental influence on dopamine function, so they separated monkeys into housing blocks of four apiece. Whereas before there was little difference in dopamine (D2) levels between monkeys, after three months of living together the monkeys that had become dominant showed a more than 20% increase in dopamine receptor density, with the most submissive showing no change. Unrelated to our point, but still interesting, they also showed that the submissive monkeys were much more inclined to self-administer cocaine; the dominant monkeys were much less likely to do so.

Dopamine receptor density is therefore an environmental and cultural phenomenon – at least in monkeys. What about people? It turns out we’re pretty much the same way. If you do the same PET scan on people that you did on monkeys, their dopamine level (D2/3 in the striatum) correlates (r^2 ~ 0.5) with a measure of human social status. So we’re not that different, after all. Just remember it’s not dopamine that drives dominance, but dominance that drives dopamine. Why? Who knows?

Dopamine levels in the same area are related to other aspects of behavior besides just dominance. If you perform the same measure of dopamine receptor availability but compare it to sensation-seeking, or novelty seeking, you get an altogether different type of curve. Here we instead see an inverted U-shaped curve. Using modeling, they suggest that those with the greatest need to seek sensational activities have both low receptor availability and high dopamine occupancy. I suppose the low-sensation seekers have low receptor availability and low dopamine occupancy (ie, few binding sites along with a lower volume of dopamine to bind).

Are these two phenomena related? They both look at the receptor availability of a certain population of dopamine receptors (D2/3). But just because the dopamine receptors are the same and in roughly the same place doesn’t mean the connectivity is the same. Are these all the same circuit? Does dominance affect novelty-seeking? Someone really needs to find an animal model to start testing these propositions.

References
Gjedde, et al., 2010. Inverted-U-shaped correlation between dopamine receptor availability in striatum and sensation seeking. Link.

Martinez, et al. 2010. Dopamine type 2/3 receptor availability in the striatum and social status in human volunteers. DOI

Morgan, et al. 2002. Social dominance in monkeys: dopamine D2 receptors and cocaine self-administration. Link.

[monkey photo from]

Thinking about thinking leaves me thinking about nothing

Edge.org’s question of the year this year was a little boring, sadly. It is normally a chance to hear interesting people give interesting answers to interesting questions. This year is about the Internet. Boo, navel-gazing. As always, there’s still some interesting answers. Here’s one that I particularly liked by Steven Quartz:

Consider, for example, our tendency to reduce human thought to a few distinct processes. We’ve been doing this for a long time: Plato divided the mind into three parts, as did Freud. Today, many psychologists divide the mind into two (as Plato observed, you need at least two parts to account for mental conflict, as in that between reason and emotion). These dual-systems views distinguish between automatic and unconscious intuitive processes and slower and deliberative cognitive ones. This is appealing, but it suffers from considerable anomalies. Deliberative, reflective cognition has long been the normative standard for complex decision-making — the subject of decision theory and microeconomics. Recent evidence, however, suggests that unconscious processes may actually be better at solving complex problems.

Based on a misunderstanding of its capacity, our attention to normative deliberative decision-making probably contributed to a lot of bad decision-making. As attention turns increasingly to these unconscious, automatic processes, it is unlikely that they can be pigeon-holed into a dual-systems view. Theoretical neuroscience offers an alternative model with 3 distinct systems, a Pavlovian, a Habit, and a Goal-Directed system, each capable of behavioral control. Arguably, this provides a better understanding of human decision-making — the habit system may guide us to our daily Starbucks fix (even if we no longer like it), while the Pavlovian system may cause us to choose a pastry once there despite our goal of losing weight. But this too likely severely under-estimates the number of systems that constitute thought. If a confederacy of systems constitute thought, is their number closer to 4 or 400? I don’t think we have much basis today for answering one way or another.

Consider also the tendency to treat thought as a logic system. The canonical model of cognitive science views thought as a process involving mental representations and rules for manipulating those representations (a language of thought). These rules are typically thought of as a logic, which allows various inferences to be made and allows thought to be systematic (i.e., rational).

I tend to think that we have a further problem. Since we have ‘consciousness’ and ‘free will’, people have this feeling that we should be able to remember everything we do, and have reasons for doing it. Of course, neuroscientists know that every memory is a poor reconstruction of something that happened in the past; and further, we know that we perform actions all the time that are outside of our conscious perception, and sometimes even inaccessible to our conscious mind. Think of all those times someone mumbles a few words, then refuses to admit that they said anything at all when questioned. How weird is it that a perfectly healthy person can say something, and not remember it at all?

What it comes down to is the fact that most of our intuitions about how we work and reason and live are wrong, and even though we have some evidence of how different processing streams work in the brain, we’re a long, long way off from understanding how we think.

[picture from]

A horror movie for neuroscience

I have vague recollections of seeing a video where someone’s skull was wide open while scientists prodded it with some instrument of torture. Poke here, the person moves their mouth uncontrollably; poke there and they see everything in red. I was blown away; it was far and away one of the coolest things I’d ever seen, and is almost certainly one of the main reasons I got interested in neuroscience. I saw it in fourth or fifth grade, so I had recently been worrying that it was something of a fake. Nope! I just found out that it was Dr. Wilder Penfield who performed these experiments. He would operate on people with severe epilepsy and attempt to destroy the cells that caused the disease. Before he did that, however, he’d stimulate their brains with an electrode and ask them what they felt. Classic neuroscience right there, folks.

So watch these poor saps get their brains prodded! It is one of the coolest things you’ll ever watch.

Jammin’ on that royal jelly


[Image by Thomas Shahan via Creative Commons]

If you watched the Sapolsky video below, you know that he touched on something that we forget about: pheromones. I think people like to think that pheromones are limited to those baser animals, or insects, and that our behavior is more controlled. The idea that smells are influencing our choices all the time is not something most people realize. So here’s some neuroscience research on one of my favorite things – social insects.

We’re going to be talking about bees today, and about how bees use a pheromone known as queen mandibular pheromone (QMP) that controls their social behavior. This pheromone is a complex blend of chemicals designed to entice workers to feed and groom the queen. As the attendant bees exchange food with nest mates, they spread it throughout the colony. However, not all bees attend the queen – it is mainly young bees, with the older ones being the colony’s foragers. It’s interesting then, that reactions to QMP are age-dependent: very young bees find it attractive, while the older foragers try to stay away from it. What’s going on here?

Well, one component of QMP is homovanyllil alcohol (HVA). This chemical interferes with dopamine signaling, a neurotransmitter responsible for learning (in particular, learning aversive memories). But each bee is a little different; some like QMP more, some less. Why? Well, when you examine transcription levels of various neurotransmitter receptors, there’s no correlation between behavior and transcription levels in the brain – but there is in the antennae. In particular, Amoa1 and Amdop3 were significantly higher in bees attracted to QMP, which are an octopamine receptor and D2-like dopamine receptor activated by HVA, respectively. Futhermore, activation of AmDOP3 inhibits accumulation of a molecule known as cAMP; one effect of this lack of accumulation is that signaling of D1-type receptors are inhibited (Amdop1/2).

Here’s what you do next: stuff a bunch of QMP in the face of bees from emergence and see what changes. One effect is that Amdop1 transcription levels in the antennae fall significantly (though not Amdop2). Another effect is that bees exposed to the QMP are much more attracted to it, in every age group tested. What’s happening here? The theory is that octopamine enhances sensitivity to pheromone cues and to positive appetitive stimuli, while dopamine reinforces aversive stimuli. QMP activates AmDOP3 receptors, which in turn downregulates AmDOP1 receptors; this interference with dopamine inhibits the unattractive parts of QMP. Since Amdop3 levels correlate highly with QMP attractiveness, and since Amdop3 decreases with age, it is likely that this is a primary reason for the switch from caring to foraging behavior. After proffering that explanation, however, Amoa1 is forgotten because no developmental effect is seen.

So there you have it. Queen pheromone affects dopamine signaling behavior not just in the brain, but also at the level of primary sensory neurons. Apparently, this shift between avoidance and approach behavior among mammalian mothers and offspring is also due to dopamine signaling… Oh, and for the record, I know the picture above is a yellow jacket and not a bee, but it looks pretty sweet, doesn’t it?

Vergoz V, McQuillan HJ, Geddes LH, Pullar K, Nicholson BJ, Paulin MG, and Mercer AR. Peripheral modulation of worker bee responses to queen mandibular pheromone. PNAS 2009 106:20930-20935; doi:10.1073/pnas.0907563106

We are who we say we are

This is a good article on literary darwinism, or at least one that agrees with my preconceived notions of it. I was smitten from the line, “[Evolutionary psychology] is the Malcolm Gladwell of science: facile and glib, but so persuasive and charming that no one wants to ruin the fun.”

Evolutionary Psychology is usually just BS that sounds vaguely correct; some of it is good, but it is usually in more of an evolutionary biology sense than psychology sense. [Via]

I also found this article on how language shapes who we are to be fairly interesting. For example:

Even basic aspects of time perception can be affected by language. For example, English speakers prefer to talk about duration in terms of length (e.g., “That was a short talk,” “The meeting didn’t take long”), while Spanish and Greek speakers prefer to talk about time in terms of amount, relying more on words like “much” “big”, and “little” rather than “short” and “long” Our research into such basic cognitive abilities as estimating duration shows that speakers of different languages differ in ways predicted by the patterns of metaphors in their language. (For example, when asked to estimate duration, English speakers are more likely to be confused by distance information, estimating that a line of greater length remains on the test screen for a longer period of time, whereas Greek speakers are more likely to be confused by amount, estimating that a container that is fuller remains longer on the screen.)

A rat once beat me at five-card stud

It’s early in the morning, so I’m grumpy, and the commenting system at the London Review of Books blog isn’t working, so I’ll just post my comment here and hopefully they’ll see the trackback. I want to make a fairly general point anyway.

First off, the post is about a study that came out this week about rats gambling. Except, that’s not actually the point of the paper. All you have to do is read the introduction which says:

Here, we investigated the effects of agonists and antagonists at the D1, D2 [dopamine], and 5-HT1A [serotonin] receptors, as well as of d-amphetamine on [rat gambling] performance.

So it’s a study of the neuroreceptors and neuromodulators which regulate gambling performance and strategy. OK I think that’s a little more interesting than simply showing that rats gamble. As the author of the LRB post says, everyone knows that animals have to gamble in their daily lives. Then they go on to complain about the scientific method, I think:

But here’s the clever and the not so clever thing about science: unless all this risky living is taking place in a laboratory, it can’t be measured, and if it can’t be measured it’s just what they call, contemptuously, ‘folk psychology’. So they stick rats in a cage, give them four holes to poke into, and see if they go the ‘good’ route and choose sweeties in smaller quantities but more reliably, or the ‘bad’ route and choose less reliability in higher doses.

Wow! Someone sounds like they feel looked down upon by scientists. Here’s the deal. There’s plenty of science done in the wild. It’s called fieldwork, biologists everywhere do it. One of my friend goes out into the field to study the sexual behaviours of water striders – wacky. Anyway, in neuroscience we don’t tend to do that. That doesn’t mean that we assume everything that can’t be measured in the lab is ‘folk psychology’ though! It just means people spend a lot of time trying to think of good experiments to tease out what’s going on. ‘Folk psychology’ is generally reserved for those things that scientific knowledge says isn’t true.

They also seem offended by the fact that scientists are looking at gambling in rodents

Like patients with frontal lobe damage, says the Professor, the rats ‘just don’t learn from their experiences. They continue to choose from the “bad decks”.’ According to him the regular reward is the ‘optimal strategy’. Well, according to me and my frontal lobes, and the rats in his lab, we like lots and lots of sugar and we’re prepared to wait out a drought in order to get it. In the long run apparently we get less sugar, but that’s the Professor’s long run. Me and the rats like a little excitement in our lives. So sue us.

Why do scientists study such ‘obvious’ things? Why do we insist on reducing the exciting things in life to boring and dry concepts? Because the history of science – and psychological phenomenon in particular – is littered with the corpses of ‘obvious’ ideas that turned out to be completely wrong. Human behaviour is complicated, and animals don’t necessarily behave the same way. It would not be at all surprising, for instance, if we found that rats systematically underestimate the value of reward in some probabilistic paradigm where we don’t. That’s why we do the experiments. Please stop getting offended when we do.