So long, and thanks for all the fish, suckers

SciAm’s Mind Matters blog has a completely fascinating post on the common assumption that humans have the the most complex brain of all the animals. Compared to a whale, however, our brain is smaller and has even less cortical folds. Does that mean they’re smarter?

The article is by neuroscientist R. Douglas Fields and takes a comparative look at brain size, relation to body size, and function across the species.

It turns out, we’re perhaps not quite so special as we like to believe. Even on the ratio of brain to body size, humans are beaten by the humble tree shrew.

We humans pride ourselves on our big brains. We never seem to tire of bragging about how our supreme intelligence empowers us to lord over all other animals on the planet. Yet the biological facts don’t quite square with Homo sapiens’ arrogance. The fact is, people do not have the largest brains on the planet, either in absolute size or in proportion to body size. Whales, not people, have the biggest brains of any animal on earth.

Just how smart are whales? Why do they have such big brains? Bigger is not always better; maybe the inflated whale brain is not very sophisticated on a cellular level. We’re closer to answering such questions now, for a couple of recent papers address them squarely. What they find is helping separate fact from fiction.

It turns out that while whales have bigger brains, humans have more neurons. Nevertheless, whales have more glial cells.

Glial cells were traditionally thought to do nothing more than support and insulate the neurons, but it’s becoming increasingly clear that they’re actually part of the brain’s processing system (although they’re exact role is far from clear).

So maybe there’s a lot more to the whale brain that it first appears.

Link to ‘Are Whales Smarter Than We Are?’.

The resistence of memory in hypnotic amnesia

Research just published in neuroscience journal Neuron has discovered some of the brain networks behind post-hypnotic amnesia. Importantly, the study might give us an insight into how memories are repressed from consciousness.

Psychogenic amnesia is a type of memory disorder where there is no brain damage to explain the memory loss. Unlike amnesia after brain injury, which usually causes an inability to form new memories, psychogenic amnesia typically results in the person being unable to remember past events.

Most memory research involves comparing how well people recognise or recall information that they’ve been shown earlier.

One of the difficulties in studying psychogenic amnesia is that you’re never sure whether the memories you’re asking about were taken in, but are inaccessible, or whether the person simply didn’t register the information in the first place.

Amnesia caused by hypnosis is remarkably similar to psychogenic amnesia in many ways, but has the advantage of being temporary and reversible.

This is important because it allows researchers to show people information, then induce hypnotic amnesia and check memory, and then reverse the effects and check memory again.

The final memory check shows that the person genuinely took the information in to start with, so you know that the amnesia was for memories that were definitely there already.

Post-hypnotic amnesia is where a suggestion is given during hypnosis that the person won’t remember a specific event after the hypnosis is over. Because hypnotisability varies between individuals, it doesn’t work for everybody, but for those who experience this type of temporary memory loss, the effect can be quite dramatic.

In an initial session, researchers showed high and low hypnotisable participants a 45 minute film which they were told to remember.

A week later, they were put in an fMRI scanner, hypnotised and told to forget the film when the hypnosis was over. Crucially, they were told that their memories would return when given a specific command.

They were then scanned while being asked “yes/no” questions about both the film itself and other details about the initial session (such as whether the door to the testing room was open).

Unlike facts about the film, the participants were never told to forget these other details, allowing the researchers to test how specific the amnesia was.

The ‘hypnosis resistant’ low hypnotisable participants were equally good at recalling facts about the film and the testing session.

For high hypnotisable participants, although they were good at remembering session details, they were no better than chance at answering the questions about the film. In other words, they would have got the same number of questions right if they flipped a coin – suggesting their memory was quite impaired.

When given the command to remove the amnesia, the high hypnotisable participants could then recall the film as well as the others.

(Partly owing to the scepticism about hypnosis, the researchers also tested another group of people who were told just to pretend to be hypnotised. They performed quite differently – vastly exaggerating their memory difficulties – indicating that the high hypnotisable participants weren’t faking or ‘conforming’).

When trying to recall information when post-hypnotic amnesia was in effect, activity in the temporal lobes and occipital lobes was reduced, while activity in part of the frontal lobes increased.

The areas of the temporal and occipital lobes are known to be involved in dealing with factual and visual information, while the frontal lobes are known to be involved in coordinating other brain areas.

In this case, they seem to be inhibiting the function of other areas, perhaps preventing recall and explaining the amnesia.

Interestingly, when the amnesia was reversed, brain circuits involved in long-term memories became more active as the participants were able to answer questions.

This study might explain how psychogenic amnesia works. Perhaps this syndrome results from the same brain mechanism being ‘locked’ in place, persistently ‘repressing’ memories.

In fact, there’s a whole range of apparently neurological problems but where the person has no recognisable brain damage. These usually get diagnosed as conversion disorder and can involve everything from blindness to paralysis.

Two studies have just come out which point in the same direction as this hypnosis study.

In one, several patients with structurally normal brains were found to have under-activation in certain areas corresponding to their conversion disorder paralysis.

In another, when a patient with conversion disorder was asked to recall the traumatic event which triggered her paralysis, brain activation suddenly dropped in the brain areas that controlled movement in her immobile limbs.

What these studies are suggesting is that problems can arise in the operation of seemingly intact brains that can lead to what appear to be neurological problems.

An analogy might be that while the roads are intact, traffic jams can still bring a city to a standstill. The trick, of course, is to get the traffic flowing again.

The more we understand about how the flow gets disturbed, the more likely we are to help patients get things running smoothly again.

Link to abstract of post-hypnotic amnesia study.
Link to write-up of study from Science News.

Why we love (and flirt)

Time magazine has a couple of articles on the psychology of love, sex and attraction. The first looks at the science of love, from thoughts to hormones, and the second at what we know about flirting.

The love article is a more in-depth look at the topic of the two articles, and touches on studies that have taken place everywhere from the delivery room to the brain scanner.

It’s a little basic in places (e.g. it uses the dopamine = reward line a little uncritically), but is otherwise an interesting read.

A deep voice, also testosterone driven, can have similarly seductive power. Psychology professor David Feinberg of McMaster University in Ontario studied [pdf] Tanzania’s Hadza tribesmen, one of the world’s last hunter-gatherer communities, and found that the richer and lower a man’s voice, the more children he had. Researchers at the University of Albany recently conducted related research [pdf] in which they had a sample group of 149 volunteers listen to recordings of men’s and women’s voices and then rate the way they sound on a scale from “very unattractive” to “very attractive.” On the whole, the people whose voices scored high on attractiveness also had physical features considered sexually appealing, such as broad shoulders in men and a low waist-to-hip ratio in women.

This suggests either that an alluring voice is part of a suite of sexual qualities that come bundled together or that simply knowing you look appealing encourages you to develop a voice to match. Causation and mere correlation often get muddied in studies like this, but either way, a sexy voice at least appears to sell the goods. “It might convey subtle information about body configuration and sexual behavior,” says psychologist Gordon Gallup, who co-authored the study.

The flirting article is, rather predictably, a bit more light-hearted and largely talks about theories rather than evidence.

You’re probably better off trying your luck with the guide to flirting from the Social Issues Research Centre that looks at what sociology can tell us about being playfully alluring.

Link to Time article ‘Why we love’.
Link to Time article ‘Why we flirt’.
Link to Social Issues Research Centre guide to flirting.

Sensory Processing and Neurotopographics

While we’re on the subject of art and neuroscience I recently discovered a couple of pieces that caught my interest.

The picture is a piece by Sandra Dawson called ‘Sensory Processing’ which has combined a cap used for EEG recordings of the brain with comforting objects and materials.

I recycled two EEG caps, cut up pyjama bottoms which were freeform crocheted with the leads and black yarn, with iPod headphones
symbolizing synaesthesia with output from the eye going to the ear.

It’s called “Sensory Processing” and is meant to evoke sensual comforts (music, flannel) that are perceived and processed by the brain; only with my hat, it’s abstracted and externalized into fashionable form so that viewers ponder connections.

It’s part of a show currently on at the Femina Potens gallery in San Francisco until January 28.

The other piece is one I saw at the weekend called Neurotopographics and is a collaboration between artist Antoni Malinowski, architect Bettina Vismann and neuroscientist Hugo Spiers.

It takes inspiration from the recent discovery of three types of neurons that seem specialised for spatial awareness and navigation.

Place cells provide a ‘you are here’ signal; grid cells signal information about distances travelled and head direction cells provide a sort of internal compass.

So far, these have only been discovered in rats, but Spiers and his collaborators have created a film of how they might operate in humans.

In fact, they’ve created three films which run simultaneously:

The resulting artwork – which will be on show at the Gimpel Fils Gallery from 18–21 January – follows the journey of a person through space, in this case the gallery itself. The actor is filmed from two camera viewpoints: a static wide angle position, which records movement and spatial position, similar to a surveillance camera; and from a dynamic point of view, filmed out of the perspective of the actor’s eyes, recording the subjective impressions of the space and his journey through it. The films will be simultaneously projected onto the gallery walls and combined with a two-dimensional animation displayed on the floor representing assumed brain cell activity patterns.

Rather annoying, the website only works properly in Explorer, but the film from the observational point of view and the firing of the cells can be experienced online.

Link to Femina Potens gallery.
Link to Neurotopographics website.

Not seeing the wood for the dendritic trees

The LA Times has an article by Jonah Lehrer arguing that we can’t solely understand the mind and brain by reductionism – the process of working out smaller and smaller components of what we’re trying to study.

He argues that an approach that uses only measurement will never capture the complexity of subjective experience and that cognitive science needs to rediscover the value of first-person experience if it is to truly capture human thought and behaviour.

Lehrer suggests that the arts might be a way of re-addressing the balance:

The question, of course, is how neuroscience can get beyond reductionism. Science rightfully adheres to a strict methodology, relying on experimental data and testability, but this method could benefit from an additional set of inputs. Artists, for instance, have studied the world of experience for centuries. They describe the mind from the inside, expressing our first-person perspective in prose, poetry and paint. Although a work of art obviously isn’t a substitute for a scientific experiment — Proust isn’t going to invent Prozac — the artist can help scientists better understand what, exactly, they are trying to reduce in the first place. Before you break something apart, it helps to know how it hangs together.

Virginia Woolf, for example, famously declared that the task of the novelist is to “examine for a moment an ordinary mind on an ordinary day … [tracing] the pattern, however disconnected and incoherent in appearance, which each sight or incident scores upon the consciousness.”

In other words, she wanted to describe the mind from the inside, to distill the details of our psychological experience into prose.

Woolf and her fellow ‘stream of consciousness’ writers, however, were latecomers to this particular challenge.

The phenomenologist philosophers, most notably Karl Jaspers and Edmund Husserl, were attempting to chart the subjective structure of the mind in the early 1900s.

While scientific psychology has been the dominant research paradigm for the past century, there has been a small but dedicated band of psychologists, psychiatrists and philosophers who have attempted to continue the project.

In particular, psychiatry and clinical psychology involve the application of science to help patients who report disturbances in their subjective mental states, so this area has always been particularly influential in these areas.

In fact, it’s seeing something of a resurgence, with special issues of scientific journals being published on the topic.

Of course, Lehrer’s main point, that we ignore subjective experience at our peril, is exactly the thinking that led to the eventual death of behaviourism in the first half of the 20th century.

That’s not to say that behaviourism was worthless. Far from it. Many of the theories are still as valid today, but as with reductionism, beware when any tool becomes an ideology.

Art is another way of approaching an understanding of first-person experience of course, which is why Lehrer is arguing its benefit to cognitive science.

As it goes, I’m working on something similar at the moment, as I’m going to be co-teaching a course on cinema and the phenomenology of psychosis with psychiatrist Andrea Raballo and psychologist Frank Laroi at the next European Congress of Psychiatry, so look out for some musings on the topic in the coming weeks and months.

Link to LA Times article ‘Misreading the mind’.
Link to previous Lehrer article on art and science.

Wired on suicides of AI leading lights

Wired magazine has a feature article on the life, work and tragic deaths of two of the leading lights of Artificial Intelligence: Chris McKinstry and Push Singh.

Singh was a young researcher at MIT’s AI lab while McKinstry was considered a maverick and most of his AI work was conducted independently.

Both had a significant impact on the field as personalities and took a similar line in trying to make AI more focused on dealing with ‘common sense’ knowledge, rather than applying neural networks to complex pattern-recognition and transformation tasks as was more common at the time.

Interestingly, it seems from the Wired article that their ideas are experiencing something of a renaissance.

Tragically, both took their own lives. We covered the sad event of McKinstry’s death back in 2006, and the Wired article discusses the somewhat less clear circumstances surrounding the death of Singh.

Link to Wired article ‘Two AI Pioneers. Two Bizarre Suicides’.

Avalanches and Gnarls Barkley psychiatry mashup

Laptop Punk has created a mashup of two curiously complementary music videos: Gnarls Barkley’s Crazy and The Avalanches’ Frontier Psychiatrist.

The original version of Frontier Psychiatrist is a turntable satire on clich√©s about psychiatry and mental illness taken from films of the 1950s, that include mental illness being dangerous, psychiatrists having couches and patients being ‘crazy as a coconut’.

In contrast, Crazy gives us the modern voice of someone who’s lost their mind, but suggests that being betrayed in love is the greater madness.

When combined, they make an unlikely couple, but the musical mix works well and the contrast is wryly appropriate.

Link to Gnarls Barkley / Avalanches mashup.

Test your corpus callosum

I’ve just discovered a wonderfully simple finger touch procedure that can test the function of your corpus callosum, a key brain structure that connects the two cortical hemispheres.

It is called the ‘cross lateralization of fingertips test’ and was used in a 1991 study by Kazuo Satomi and colleagues.

It relies on the fact that different hemispheres are responsible for the movements and sensations from each hand.

In other words, each hand is connected to a different side of the brain, and, to allow you to co-ordinate both hands, the brain passes information between the two sides by using the corpus callosum.

The corpus callosum is the largest structure in the brain and works like a huge bundle of white matter ‘cables’, connecting different areas.

If this structure gets damaged, a patient might have trouble with coordinating their hands, preventing them from matching sensations on one hand with movement on the other, because the information doesn’t get to where it’s needed.

The test works like this: you need to ask someone to close their eyes and put their hands face up.

You then touch one of their fingertips with a pencil, and with the opposite hand the participant needs to touch the corresponding finger with thumb of the same hand.

For example, if you touched their right ring finger, they would need to touch their left ring finger with their left thumb, as shown in the diagram above.

You need to do this on both hands, with them always touching the corresponding finger on the opposite hand.

It’s important that the person keeps their eyes closed, because as soon as they look, they get information from the eyes, which goes to both hemispheres.

Patients who have damage to the corpus callosum (either because of acquired damage or because it just hasn’t developed) usually can’t do this test, because of the disruption in communication between the two hemispheres of the brain.

Of course, just to be sure its not a problem with movement or sensation in one hand only, the patient is also asked to do another quick test where they’re asked touch the exact finger you just touched.

For this part, the sensation and movement happen in the same hand, so information doesn’t need to cross the corpus callosum.

The test was shown to me by Dr Emma Barkus, who researches what neurological tests can tell us about psychosis and unusual experiences.

Link to Wikipedia page on the corpus callosum.
Link to abstract of Satomi and colleagues study (thanks Emma!).

The inner body

NPR’s radio show Talk of the Nation has a discussion with Sandra and Matthew Blakeslee, authors of a new book on the neuroscience of the body and movement.

If you’re interested in the ideas of embodied cognition that we covered the other day, the discussion touches on many of the major findings in cognitive science that are feeding into this important area.

The book, called The Body Has a Mind of Its Own, has a website which is somewhat sparse on readable excerpts but does have links to some more interviews about the topic.

The host of the NPR programme is a bit taken by the idea of ‘body maps’ (called sensory or somatotopic maps in the scientific literature), where areas of the body are literally mapped by the brain to represent sensation and movement, and the Blakeslees get asked lots of variations on the question ‘how do body maps explain x, y and z’.

Of course, somatotopic maps are only one part of a complex brain system that perceives the outside world and allows us to act within it, but I wonder whether this is a sign that ‘body maps’ might be the new ‘mirror neurons’ and become a popular explanation for everything from winning the World Cup to finding a partner.

Either way, Sandra and Matthew Blakeslee do a great job of explaining the science and trying to draw out some of the complexities.

Link to NPR discussion.
Link to The Body Has a Mind of Its Own website.

Power and consciousness with John Searle

Philosopher John Searle, most widely known for his ‘Chinese Room‘ thought experiment, is profiled in an article for The Times.

The article is partly a review of his new book Freedom and Neurobiology, and partly a look back at the work and experiences which have shaped his current views on mind, brain and society.

Searle, like Daniel Dennett, tries to avoid the technical jargon that haunts some philosophical literature and is known for penning accessible material even when writing for academic journals.

The article is written by fellow philosopher David Papineau who doesn’t seem awfully keen on Searle’s new ideas.

Link to Times review and article on Searle.

An ode to ibuprofen

A lyrical tribute to the pain killer ibuprofen, written by poet Matt Harvey.

The poem was written for BBC Radio 4’s Saturday Live, as they had Dr Stewart Adams on the programme discussing his discovery of the drug.

The Telegraph has a great article on its discovery, which includes the fact that he tested the drug on himself to try and shift a troublesome hangover.

I Prefer Ibuprofen

Life is so much easier with effective analgesia

The purpose of pain is to say to the brain:
Ow! Houston we’ve got a problem…
But once we’ve got the message we don’t need it again and again…

What do we want? Symptom Relief!
When do we want it? Now!

When you’ve had enough of it there’s just no need to suffer it
Just pop a little caplet and Ibuprofen will buffer it

I’ve had a go with Aspirin, Codeine and Paracetamol
With Solpadeine, Co-codamol, with Anadin and Ultramol
I love them all, I really do, but I prefer Ibuprofen

There are other non-steroidal anti-inflammatory drugs around
Your NSAID’s these days are quite thick on the ground
There‚Äôs Naproxen, there’s Nabumetone
and, of course, there’s Indomethacin
Each with much to offer us. But I prefer Ibuprofen

I love the way the compound sticks its cheeky little hand in
The way it blocks the enzyme that creates the prostaglandin

Reducing fever, inflammation, and mild to moderate pain

Yes I know it isn’t curative, in anyway preventative
But to dwell on what it doesn’t do is anally retentative
I know it doesn’t treat the cause, the cause will still be there
But it lends a hand, it puts the ‘pal’ back into palliative care.

It does exactly what you’d expect it to say it would do if it came in a tin

Link to more poems by Harvey.
Link to Telegraph article on the story of ibuprofen.

Questioning the cognitive

American Scientist has two great reviews that tackle books on perhaps the most important theory of psychology: that the mind can be understood as an information processing system.

This theory is known as the ‘cognitive approach’ and it assumes that the mind and brain can be usefully described as systems that transform and interpret different types of information.

For example, information from light that falls on the 2D surface of the retina is processed to allow us to recognise objects and judge depth in 3D.

The advantages this approach is that it easily allows for a scientific experimental approach (unlike some Freudian ideas) and accepts that we have internal mental states and are not just our behaviour (unlike behaviourist theories).

You can see from the success of cognitive psychology, cognitive neuroscience, cognitive linguistics and so on and so on that it’s been a very widely adopted idea.

The first review is of the epic book Mind as Machine: A History of Cognitive Science by Margaret Boden (sample chapter available online as a pdf).

I’m a firm believer in history telling us as much about a theory as the empirical evidence and this book looks at the development of the information processing approach.

One of my favourite analyses in this area is from Douwe Draaisma who noted in his book Metaphors of Memory that we borrow ideas from technology to explain the mind.

Past models of the mind used fluids, pressures and vapours (Freud’s psychodynamic theories were inspired by thermodynamics), whereas now we use metaphors related to computers.

The other book review tackles Language, Consciousness, Culture: Essays on Mental Structure, a new book by Ray Jackendoff.

Cognitive ideas generally describe how the mind works, and while everybody assumes that the brain is the organ that supports the mind, how these two map together is the subject of much debate.

One approach is functionalism, which suggests that anything that functions like the mind is the mind, regardless of what supports the function – be it a biological brain or digital computer.

In other words, the mind is just information processing, and is not solely a type of information processing that can only be completed by a brain.

The book under review defends a functionalist approach to the mind and language, while the reviewer, George Lakoff (known for his own theories about how metaphors shape thought), gives it a hard time.

More importantly though, both are informative reviews in their own right.

Link to Harman review of Mind as Machine: A History of Cognitive Science.
Link to Lakoff review of Language, Consciousness, Culture.

2008-01-18 Spike activity

Quick links from the past week in mind and brain news:

The BPS Research Digest covers some more amazing studies that find that our names are linked to our choices and performance.

Games console chip to be used for MRI analysis reports io9. Mostly cool for the beautiful MRI tractography image.

Furious Seasons covers a new study that finds placebo outperforms antipsychotics in treating aggression in patients with learning disabilities.

A series of studies that suggest we have little conscious access to the workings of our own mind are collected by PsyBlog.

Time magazine has a great article on how siblings of autistic children adapt and interact in the family.

Why should not old men be mad? 3QuarksDaily has a poignant W.B. Yeats poem.

Science News covers two novel studies into the genetics of autism.

Tracing the history of syphilis. Advances in the History of Psychology covers a recent controversy over the origins of what was once one of the major causes of madness.

The Observer covers the case of Howard Dully, who had a lobotomy at the age of 12 and later created a moving, powerful and unmissable radio programme about his experiences.

Deric Bownd’s looks at an interesting argument that cooperation and choosiness necessarily evolved together.

Film footage of the ice pick lobotomy, which Dully was subjected to, is discovered by Neurophilosophy, as part of an upcoming documentary.

Phenomenology and Cognitive Science makes a special double issue on Dennett’s heterophenomenology freely available online.

The BrainWave neuroscience and arts festival kicks off in New York in April and The Neurocritic has a preview.

The Onion report an astounding case where neuroscientist discover that half of a 26-year-old’s memories are Nintendo-related.

Does too much dreaming lead to depression? The Mouse Trap discusses an intriguing hypothesis.

The first chapter of a new book The Philosophy of Social Cognition has been posted online.

My Mind on Books lists some recent and forthcoming books on the self to look forward to.

Can artificial life help us solve the mind-body problem? Brain Hammer investigates with a link to Pete Mandik’s full-text paper.

Cognitive Daily has another fantastic demonstration on how older people adapt to blurred vision.

Effect of antidepressants exaggerated due to buried data

The New England Journal of Medicine has just published a study that found the effectiveness of 12 of the most popular antidepressants has been exaggerated because pharmaceutical companies have been ‘hiding’ data from negative drug trials.

Known as the ‘file drawer effect‘, it involves submitting only positive results to be published in scientific journals.

This type of selective publishing was recognised as a pervasive problem in medicine, and to try and combat this, a rule was introduced that required all clinical trials to be registered before they began.

This means no-one could claim that a negative study didn’t occur and others could try and track down the data if needed.

The researchers in this new study decide to do exactly this. They examined the American Food and Drug Admistration (FDA) register and requested data from all 74 trials of the most commonly used antidepressant drugs.

They then compared the results from all the trials, to just the trials that had been published in the medical literature.

The findings are quite shocking:

A total of 37 studies viewed by the FDA as having positive results were published; 1 study viewed as positive was not published.

Studies viewed by the FDA as having negative or questionable results were, with 3 exceptions, either not published (22 studies) or published in a way that, in our opinion, conveyed a positive outcome (11 studies).

According to the published literature, it appeared that 94% of the trials conducted were positive. By contrast, the FDA analysis showed that 51% were positive.

In other words, when all the studies are examined, there’s only about 50-50 chance that a scientific study of an antidepressant drug will find it more effective than placebo in treating depression.

The Wall Street Journal has a good write-up of the study, from which I’ve also taken the graph below. It describes which antidepressant drugs have their apparent effect most boosted by the hiding of negative findings.

As we live in the age of ‘evidence based medicine’, doctors will used the available evidence to decide which drugs to prescribe.

Needless to say, distortions in the published results can affect individual patients owing to the effect on doctors decision-making.

Link to abstract of study.
Link to good write-up from the Wall Street Journal.

Can stress stop the menstrual cycle?

Inkling has an interesting article on the effect of stress on the menstrual cycle that investigates the received wisdom that stress can prevent periods.

It turns out the scientific studies have found no conclusive answer as they’ve returned mixed results, but this may be because they don’t adequately distinguish between physical stress and psychological stress.

A range of physical health problems are known to halt menstruation. Malnutrition is a common example and this is why women with anorexia often don’t have periods.

Of course, physical and psychological stress go hand in hand, but one study that looked at healthy young women under a great deal of psychological stress, but no major physical health problems, found no alteration in the menstrual cycle.

So Ellison examined female juniors at Harvard who were preparing for the MCAT [Medical College Admission Test] and compared their anxiety levels (and ovulation schedules) to women who were not preparing for the MCAT. In order to make sure there were no other factors at play, all the women were otherwise physically healthy, were not using any oral contraceptive pill that would change hormone levels, and all reported normal ovulation…

But despite the significant increase in stress, there was no change in ovulation or periods in either group. No matter how stressed these students were about the upcoming exam, they continued to have a visit from Aunt Flow right on schedule. This was even the case during the final days and weeks leading up to the MCAT exam, when the subjects described intense stress levels that only Harvard pre-meds can sustain. The study was published in the December 2007 issue of the American Journal of Physical Anthropology.

There’s more on the effects of stress on menstruation in the article.

Link to Inkling article ‘Of Stress and Periods’.