Homosexuality in body, brain and behaviour

The New York Magazine has an in-depth article on the science of sexual orientation and whether the biological factors which may make someone more likely to be gay, also make them more likely to appear gay to others.

There are now a range of established findings that suggest that gay men are likely to have a number of physical traits not shared by straight men (the findings on gay women are a lot less clear-cut it seems).

For example, a 2004 study [pdf] found that gay men were much more likely to have a counter-clockwise hair whorl (as pictured) than straight men.

Other studies have found differences in finger lengths, size of structures in the hypothalamus (a deep brain area), and on a number of psychological abilities like mental shape rotation and navigation to name but a few.

Some researchers believe that the same biological conditions that increase the chances of homosexuality, also increase the chances of some of these body, brain and mind differences.

While genetics is thought to play a part, researchers are also interested in the time when an unborn child is developing in the womb.

Interestingly, many of the differences are linked to hormone exposure in the womb and can be seen to different degrees in both gay and straight men.

One of the critical questions is still how much of the influence is to do with biological factors and how much with social influence, opportunity and freedom of expression.

The New York Magazine is a fantastic guide to the science of sexual orientation, but is also a wonderful commentary on how this research is perceived by parts of the gay community and what it might mean for gay politics.

The only slight drawback is that it repeats the ‘scientists tried to turn sheep gay’ myth, but apart from that, it’s a compelling read.

UPDATE: Discover Magazine just had a feature article on the genetics of homosexuality which accompanies this piece nicely.

Link to article ‘The Science of Gaydar’.

Mirror touches

Nature reports on a recently discovered form of synaesthesia where affected individuals actually feel a sensation when they observe someone else being touched.

Synaesthesia is a condition where senses become crossed, so people might seeing colours when they encounter numbers, or tastes when they hear certain words.

This new form of synaesthesia was found by accident, during a talk by neuropsychologist Dr Jamie Ward:

“We first came across the mirror-touch synaesthesia by chance,” says Ward. The sensation of touch was being discussed at a UCL neuroscience seminar, and someone suggested, as a thought experiment, imagining that people felt what they saw. A colleague of Ward’s objected, vigorously insisting that everyone does, in fact, feel what they see. It was the first time Ward had realised such a condition could exist.

“There may be a lot of such people around, since they are unaware that that they have the condition. They think it is normal,” says Ward. When he started to look for people who experience mirror-touch synaesthesia, he had little trouble finding them, he says.

Ward collaborated with Michael Bannisy to study the condition and they found that they affected people were more likely to confuse an observed touch with a real touch than unaffected people under experimental conditions.

They also found that people with the condition were especially sensitive to other people’s emotions, rating much higher on measures of emotional empathy.

The study is published in Nature Neuroscience but I’ve just discovered there’s also a great write-up over at The Neurophilosopher.

Link to Nature news story.
Link to write-up from the The Neurophilosopher.

Encephalon 25 hits the tubes

Edition 25 of psychology and neuroscience writing carnival Encephalon has just been published on PsyBlog.

A couple of my favourites includes GrrlScientist on why smart people don’t all make smart choices and Memoirs of a Postgrad on whether AI systems will need bodies to be truly intelligent.

It has all the latest on the last fortnight’s mind and brain writing, so head on over for more great articles.

Link to Encephalon 25.

Natalie Portman, cognitive neuroscientist

Natalie Portman is best known for her roles in Hollywood movies like Star Wars, Cold Mountain and V for Vendetta. What is less known is that she was co-author of a scientific paper on the neuroscience of child development. This is about her research.

Portman, whose real name is Natalie Hershlag, left acting to pursue a psychology degree at Harvard during 2000.

While there she was employed as a research assistant in Prof Stephen Kosslyn’s neuropsychology lab where she got involved in a study investigating the link between frontal lobe development and visual knowledge in infants.

The study investigated object permanence – the ability to understand that objects do not disappear from the world when they are out of sight, something that typically develops in the first year of life.

Researchers have argued that the frontal lobes are particularly important for this skill, but the trouble is, you can’t put babies in conventional brain scanners to easily test the idea. They just wriggle about too much.

Portman’s study, led by neuroscientist Dr Abigail Baird, used a relatively new method for measuring brain function called near-infrared spectroscopy.

This technology relies on the fact that near-infrared light can penetrate the skull, and that blood carrying oxygen, and blood that has given up its oxygen, absorbs the light differently.

The idea is that the device beams light into the frontal lobes, and you can work out how hard this area is working from how much oxygen-rich blood there is.

The advantage is that this technology is safe for children, and can be worn as a sort of high-tech hat, meaning there’s less of a problem if the child being tested moves about.

During the study, infants were shown a toy, which was then hidden under a cloth. Children who have object permanence – who know that it hasn’t disappeared – look for it under the cloth.

Children without this skill just ignore the cloth and look for something else to do, because the memory of the toy is gone.

The study tested 20 infants, every four weeks, from the ages of 5-12 months. To see what changed in the brain as the ability emerged, the researchers compared infrared light absorption from a time when the kids first looked for the toy, to an earlier time, when they just forgot that it existed when it was out of sight.

The team discovered that the frontal lobes suddenly kicked in when children develop the knowledge that hidden objects still exist, providing an understanding of which brain areas are involved in this important mental function.

The study also demonstrated that near-infrared spectroscopy could be used successfully to study the brain development of very young children.

The paper was eventually published in the journal Neuroimage, under Natalie’s real name, with the title ‘Frontal lobe activation during object permanence: data from near-infrared spectroscopy’.

It has since been cited by at least 20 different studies that have built on its findings.

And if you want to read the study in full, it is available as a pdf file at the link below.

pdf of Neuroimage paper.

Amazon tribe challenges the structure of language

Chomsky famously argued that a core property of all language was recursion – the ability to include units of meaning inside other units. Anthropologist Daniel Everett argues in an article for Edge that the language of the Pirah√£ people is not like this, and might suggest that our understanding of the structure of language needs to be re-thought.

Language researchers like Noam Chomsky and Steven Pinker are often called ‘nativists’, meaning they think our core language abilities are inherited and suggest that all the individual languages have the same underlying components.

Research based on this idea looks at the structure and neuroscience of language to try and work out the basic elements.

Chomsky and colleagues argued in a 2002 paper [pdf] that human language has only one core property – recursion, which Everett also describes in his article:

The essence of human language is, according to Chomsky, the ability of finite brains to produce what he considers to be infinite grammars. By this he means not only that there is no upper limit on what we can say, but that there is no upper limit on the number of sentences our language has, there’s no upper limit on the size of any particular sentence. Chomsky has claimed that the fundamental tool that underlies all of this creativity of human language is recursion: the ability for one phrase to reoccur inside another phrase of the same type. If I say “John’s brother’s house”, I have a noun, “house”, which occurs in a noun phrase, “brother’s house”, and that noun phrase occurs in another noun phrase, “John’s brother’s house”. This makes a lot of sense, and it’s an interesting property of human language.

Finding a language which doesn’t have the supposedly ‘universal’ property of recursion challenges the Chomsky theory and, potentially, the whole idea that a ‘language instinct’ is somehow genetically inherited.

Everett argues that the Pirah√£ language doesn’t have recursion (or numbers and few colour names), presumably partly as a result of the particular habitat that the tribe lives in.

Everett’s article is also fascinating as it describes his first encounter with the Pirah√£ as a Christian missionary, and his subsequent rejection of his missionary work and focus on linguistics.

It also describes the culture and mindset of the people and has some of Everett’s personal reflections on his research and experiences.

There’s also a video about the topic and its possible effect on our understanding of language on the same page, and a recent NPR radio show investigated the Pirah√£ controversy in more detail.

UPDATE: Many thanks to Austin for sending in a link to an enjoyable article from The New Yorker that is a fantastic guide to the language and its impact on science.

UPDATE 2: There are some fantastic comments, corrections and additional links in the comments that are definitely worth reading. Thanks to everyone who’s contributed!

Link to ‘Recursion and Thought: Why the Pirah√£ don’t have numbers’.
Link to NPR radio show.

Smuggling drugs into the brain

Open-access science journal PLoS Biology has a fascinating article on the latest developments in getting drugs across the blood-brain barrier – the body’s strict border control that keeps the brain free of foreign substances.

The blood-brain barrier is a filtering system in the capillaries, the smallest blood vessels in the brain, to prevent molecules over a certain size reaching the brain itself (click image for larger version).

This makes good biological sense as it keeps the brain free of a whole range of potential poisons and infections but is a pain for drug designers.

There are many drugs which would have an effect but can’t get from the blood into the brain because the molecules are too big.

For example, Parkinson’s disease involves the death of dopamine neurons in the nigrostriatal pathway of the brain – a key circuit for movement – which is partly why the disease causes tremor and rigidity.

The obvious thing to do would be to give people dopamine to make up for the lost neurons, but it turns out that dopamine molecules are too big to cross the blood-brain barrier. If you swallow a dopamine pill, it won’t reach the brain.

Eventually someone hit on the idea of giving people levodopa or L-DOPA – a molecule that the body eventually transforms into dopamine and is small enough to cross the barrier.

So, you swallow an L-DOPA pill, it crosses the barrier and is changed into dopamine inside the brain itself. Clever.

Substances given with the intention that the body will transform them into the desired drug are called prodrugs and finding prodrugs small enough to cross the blood-brain barrier is one method for getting round the delivery problem.

This is fine if what you’re trying to deliver can be transformed into something useful but for many drugs this isn’t possible, so other methods have to be found.

New techniques are being developed which take advantage of the fact that the blood-brain barrier makes special exceptions for certain essential proteins.

The idea is that a drug molecule will be ‘wrapped up’ in a familiar protein and so will be smuggled across the barrier, only to be released when it reaches the other side.

Other techniques involve a mechanical approach to the problem where a device is implanted to pump the drug straight into the brain. Needless to say this direct intervention approach is favoured by neurosurgeons (the armed wing of the neuroscience world).

The PLoS Biology article discusses these are other developments and looks at how this problem is now becoming a core focus of drug development as useful medicines have sometimes been invented only to be found to be unusable in practice.

Link to PLoS Biology article ‘Bridging the Blood-Brain Barrier’.

Fatherhood in the mind and brain

Both Time and Slate have just run articles on the often neglected field of fatherhood, where they report on the significant brain changes and unique psychological processes linked to male parenthood.

I sometimes think you can’t blame fathers for feeling like they’re unimportant when science has relegated them to a footnote in the parenting process.

This is slowly beginning to change and increasingly research is showing that fatherhood and impending-fatherhood has a unique effect on the mind and brain.

For example, fathers have unique hormonal changes during their partner’s pregnancy and when interacting with their child that significantly affects their brain.

And yet despite these findings, few scientists treat the physiology of fathers as a serious subject in its own right. Researchers have been investigating some of the hormonal swings in humans for almost a decade, and longer in other species; still, most of this work remains on the fringe. Between 2000 and 2006, the journal Hormones and Behavior published nearly three times as many studies of mothers as of fathers, and this year the count so far is 16 to three. A 2000 review framed research into physiological fatherhood as “an opportunity to better understand maternal behavior, by studying parental behavior in the absence of pregnancy and lactation.” Interest in how men’s bodies prepare themselves for fatherhood only seems to matter to the extent it sheds light on mothers. Meanwhile, the ways in which dads screw up their kids is a thriving area of research.

It’s also interesting how stories on fatherhood are presented.

BBC News recently reported on a new study (which I haven’t been able to track down yet, except as a press release) that looked at couvade syndrome – where fathers experience physical symptoms as their partners go through pregnancy.

This is entirely explained in terms of ‘anxiety’ and being ‘attuned’ to their partners.

This is despite the fact that researchers have been arguing for over a decade that the syndrome is equally as influenced by the biological changes brought on by fatherhood.

In contrast, the popular reporting on pregnancy and women is awash with the effects of hormones on behaviour and often ignores the psychological aspect.

In other words, women who experience changes in thinking or behaviour are described if they’re slaves to their hormones whereas symptoms in men are due to anxiety and over-identification.

It’s an interesting twist on how our stereotypes about sex roles and parenting play out in science and popular culture.

The Time and Slate articles attempt to redress the balance by examining research on the role of fathers and how their body and brains react to pregnancy and childcare.

Link to Slate article on what fatherhood does to the body and the brain.
Link to Time on the psychology of fatherhood.