The neurochemistry of orgasm

Below is an excerpt from a review, published in this week’s Nature, of the book The Science of Orgasm (ISBN 9780801884900).

The review is by Prof Tim Spector whose work we’ve featured previously on Mind Hacks.

Spector published the results of a study in 2005 on the genetics of female orgasm which generated a range of critical commentaries.

His review tackles a new book which aims to cover the latest research on orgasm from a number of perspectives, but also gives a glimpse into the neuroscience of orgasm itself.

In my view, the best part of the book is the neurochemistry of the orgasm. Studies of paraplegic women clearly show the importance in female orgasm of multiple complex neural pathways such as the vagus nerve.

Functional brain imaging is an exciting area for study and (despite poor-quality pictures) the authors present the latest findings of multiple areas of brain activity during orgasm — which make any simplistic dopamine (stimulatory) – serotonin (inhibitory) mode of action unlikely.

They postulate a central role for areas such as the cingulate cortex, which is also where pain is perceived — linking pain and orgasm as related sensory processes. Orgasms apparently alter pain perception and increase pain thresholds, and this link may explain bizarre reports of women having orgasms during childbirth.

However, just when I was ready for the truth — a clear definition of orgasm and where it arises in the brain — I was told it was not a reflex, only a perception of neural activity and, even worse, probably a form of diffuse consciousness in an as yet undiscovered fifth dimension.

After such a careful, slow build-up of teasing and tantalizing data, I was definitely left frustrated — and wanting more.

Link to Spectors’ review (not freely available unfortunately).
Link to info on the book from the publishers.

A fruit that affects dopamine neurons

The fruit pictured on the right is called a soursop – a reportedly delicious fruit from the French West Indies that contains very small amounts of a substance that kills dopamine neurons.

Two research studies have looked at the substance – annonacin – and found it to kill off dopamine neurons in test tube trials.

Annonacin is only present in small quantities so occasionally eating soursop should be safe.

However, it is thought that the high rates of treatment resistant Parkinson’s disease in the French West Indies may be linked to high levels of soursop consumption.

Parkinson’s disease is caused by the death of dopamine neurons in the nigrostriatal pathway of the brain.

Link to neurotoxicity study on soursop.
Link to study on link with Parkinson’s disease.

Love unlimited

New Scientist has a fascinating news report on the psychology of polyamory – the practice of having multiple partners with the full consent of everyone involved.

Most Western societies have a focus on exclusively committed couples as the main family unit.

In contrast, people who are polyamorous feel themselves capable of more than one loving relationship and are often a part of a network of intimate lovers.

Crucially, lovers may not simply be sexual partners, and someone may be involved in several long-term committed relationships.

The dynamics of these relationships are bound to be different from traditional couples-based relationships, and psychologists are now starting to research how this affects the individuals and the social group.

Opinion is still divided on how successful these relationships might be in different spheres of life, although the field is really lacking in any systematic long-term studies.

So is poly more sustainable than monogamy? “Infidelity in monogamous relationships is estimated at 60 to 70 per cent, so it seems that attraction to more than one person is normal. The question is how we deal with that,” says Meg Barker, a professor of psychology at London South Bank University who presented her research into poly at the 2005 meeting of The British Psychological Society. “The evidence is overwhelming that monogamy isn’t natural,” says evolutionary biologist David Barash of the University of Washington, Seattle. “Lots of people believe that once they find ‘the one’, they’ll never want anyone else. Then they’re blindsided by their own inclinations to desire other attractive individuals. So it’s useful to know that this behaviour is natural.”

But as a mating strategy, poly may not be any better than monogamy; a person’s reproductive success may diminish if there is less pressure to be exclusive. “Jealousy is probably fitness enhancing,” Barash says. A more jealous male is likely to stick closer to his mate and prevent her from getting impregnated by other males. “A good look at human biology does not support polyamory any more than it supports monogamy,” he says. Biologist Joan Roughgarden, at Stanford University in Palo Alto, California, goes further. “Polyamory won’t last. The likelihood of being able to successfully raise children in that context is very limited. My guess is that it’s not an evolutionary advance, but a liability.”

Link to NewSci article ‘Love Unlimited: The polyamorists’.

The iris is the window to the soul

A fascinating paper just released online suggests that patterns in the iris of the eye can give an indication of personality.

The research has been led by psychologist Mats Larsson and looks at relationship between measures of personality and the ‘crypts, pigment dots, and contraction furrows’ of the iris.

BBC News covers the research, as does a post on the Living the Scientific Life blog. There’s also some excellent background material to the research on a page from Larsson himself.

The paper itself is only available to subscribers to Biological Psychology. It seems the free summary isn’t available online yet, but this is an interesting excerpt from the introduction of the paper on previous studies:

The idea that personality differences are related to iris characteristics is not new. In 1965, Cattell observed differences in cognitive styles between blue and brown eyed subjects (Cattell, 1965) and since then eye color has been found to be related to a great variety of physiological and behavioral characteristics. Dark eyed people have on average higher scores on extraversion, neuroticism (Gentry et al., 1985), ease of emotional arousal (Markle, 1976) and sociability (Gary and Glover, 1976). However, there are a number of studies that fail to replicate the personality findings, typically because the effect tends to fade after early childhood. For instance, Rubin and Both (1989) found that blue-eyed children in kindergarten and Grade 2 were overrepresented in groups of extremely withdrawn youngsters, whereas no association could be found in Grade 4 or between eye color and extreme sociability in any grade.

According to Larsson’s more recent research, a gene called Pax6 is involved in both the development of the eye, and the development of an area of the frontal lobe called the anterior cingulate cortex or ACC.

The ACC is known to be involved in attention and inhibiting automatic responses, and there’s plenty of evidence to link it to personality-relevant traits like empathy and self-control.

Larsson found that ‘crypts’ were significantly associated with five personality characteristics (Feelings, Tendermindedness, Warmth, Trust and Positive Emotions) whereas ‘contraction furrows’ were associated with Impulsiveness.

I can’t say I’m entirely clear what ‘crypts’ and ‘contraction furrows’ look like, but there’s a description on Wikipedia and you can click here to see the diagram from Larsson’s paper in a popup window.

If it comes as a surprise that the same gene could influence both the eye and brain development, it’s actually not that strange an idea based on what we already know.

The retina, like the brain, is part of the central nervous system, so genes that code for the eye could also be associated with brain development.

Furthermore, the face develops from some of the same cells as the brain during the early stages of embryo growth.

This is why disorders that cause learning disabilities are sometimes associated with distinctive facial features (e.g. Down syndrome, Williams syndrome).

One other recent development worthy of note is that governments and businesses are now set on storing iris information to use as ID.

For example, the UK government wants to encode iris information on passports and keep copies on database to use in iris recognition systems in a system that is being trialled at the moment.

This might mean that personality profiles could be generated from biometric data.

How accurate they might be remains another question, but as with any centralised population sample, the concern is that those with unusual results may be scrutinised more closely using other methods, or deemed to be ‘risky’.

Link to BBC News story “How irises ‘reveal personalities'”.
Link to Living the Scientific Life post.
Link to Larsson’s page on his research.

Virtual reality to treat combat trauma

BBC News is reporting on a AAAS presentation on how virtual reality is being used to treat soldiers who have suffered post-traumatic stress disorder (PTSD) after combat.

Symptoms of PTSD include intrusive memories, pathological avoidance of things related or loosely-related to the trauma, and persistent arousal.

Cognitive behaviour therapy or CBT is one of the most effective treatments for PTSD.

Among its key methods is to slowly reintroduce the person to things associated with the trauma, while dealing with the negative thoughts that are triggered by the situation.

This is relatively straightforward if the person was traumatised by a car crash, as cars, roads and traffic are readily available.

If the person was traumatised by war, however, it is not always feasible to expose the person to ‘low level’ combat conditions as it may be too dangerous, or the person may have been taken out of the combat zone already.

Virtual reality is a possible way of doing this without putting the soldier at risk, while being realistic enough to treat the condition.

This research is part of a project led by Dr Albert Rizzo, which was the subject of a 2005 NPR radio programme which explored the treatment and its benefits.

While the project has been running for a while, the AAAS presentation contained the latest results, which reportedly suggest a promising outcome for soldiers treated with this method.

Link to BBC News story ‘Virtual treatment for US troops’.
Link to NPR programme ‘Virtual Reality Therapy for Combat Stress’ (with audio and video).

Greetings cards for mental illness

Greetings card manufacturer Hallmark have released a new line of cards especially for the person in your life experiencing mental illness, such as depression or an eating disorder, or other traumatic and difficult times.

ABC News has a report on the cards which are designed with colours to reflect the mood of the situation and pithy messages to match:

For eating disorders: “All I want is for you to be healthy and happy with yourself. Please take it one day at a time until you are.”

For depression: “When the world gets heavy, remember, I’m here to help carry it with you.”

There’s no word on cards for psychosis or paranoia (maybe “Like you, I never trusted those neighbours and their infernal thought stealing machines”) or people detained under the mental health act (“Kafkaesque doesn’t begin to describe the situation. Have a successful tribunal”).

Perhaps I’ve found a gap in the market?

Link to Journeys cards on Hallmark website.
Link to ABC News story (via Trouble with Spikol).

Top ten psychology studies

Jeremy Dean of PsyBlog is currently doing a run down of his top ten psychology studies and will conclude the series by asking for a vote for the reader’s favourite.

He’s writing up each one as a separate article, so you get a flavour of what the study involved and how it changed our knowledge of psychology.

So far, five out of the ten have been covered and include influential studies such as the one that laid the foundations for cognitive behavioural therapy and another where euphoria was induced by experimental trickery.

The full list will be released and written-up over the coming weeks, and a vote will decide the winner!

Link to PsyBlog’s “Top Ten Psychology Studies”.