October 2009 – Mind Hacks

Liberation psychology graffiti

I’ve just seen my first genuine piece of psychology graffiti. The picture is from a wall in Universidad de Antioquia and the graffiti is promoting a conference on the application of ‘liberation psychology’ to preventing violence and helping the victims of violence in Colombia.

The text in Spanish is roughly translated as “We propose a scientific endeavour committed to historical reality and the problems and aspirations of the people” and is a quote from social psychologist and Catholic priest Ignacio Martín-Baró.

Martín-Baró was working in El Salvador during its bloody civil war and was using social psychology to research the opinions and views of the people and was producing results contrary to the propaganda of the army and government.

He was murdered by the El Salvadorian army in 1989 but he has had a massive influence on psychology and public policy in Latin America.

This in part was due to his strong belief in social psychology as an applied discipline to improve the society and the conditions of the poorest and most deprived.

While liberation psychology itself is typically associated with the left, one of Martín-Baró’s legacies is the practice of using social psychology for social improvement, something which is widely accepted in Latin America, regardless of political orientation.

It may seem strange that a conference is being advertised through graffiti, but political graffiti is common on the university campus and ranges from spray painted slogans to huge colourful murals.

If you’re interested in learning more about liberation psychology, The Psychologist had a 2004 article discussing both the discipline and Martín-Baró.

Link to The Psychologist article on liberation psychology.

2009-10-30 Spike activity

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

<img align="left" src="http://mindhacks-legacy.s3.amazonaws.com/2005/01/spike.jpg" width="102" height="120"

ABC Radio National’s All in the Mind has an interesting discussion on addiction and free will. I recommend the extended version here.

The New York Times has an excellent personal account of psychosis.

There’s an awesome post on a new study about how phantom limbs can contort into impossible configurations at Neurophilosophy.

New York Magazine covers songs used in ‘war on terror’ torture and musicians’ protests over the use of their material.

How do we perceive speech after 150 kisses? Talking Brains covers an interesting conference poster.

BoingBoing reviews a new book on the use of psychedelic drugs throughout history.

There’s an in-depth review of ‘The Spirit Level: Why More Equal Societies Almost Always Do Better’ in the London Review of Books.

Furious Seasons covers a new study [pdf] in JAMA on how atypical antipsychotics cause massive weight gain in children.

A slide show from Discover Magazine outlines the social factors in obesity or ‘how to make your friends fat’.

Scientific American Mind has a short report on a randomised controlled trial on how empathy in doctors reduces the duration of the common cold.

The excellent Neuroskeptic has a careful analysis of recent studies and discussion on the best antidepressant.

NeuroPod has just released it’s latest podcast. Direct mp3 link here.

Philosopher Gordon Marino writes an excellent piece on melancholy thinker S√∏ren Kierkegaard and issues of despair, depression and meaning in The New York Times.

Dr Petra has a fantastic sex research Q&A that covers a range of unquestioned or misreported pieces of ‘common knowledge’ and the evidence from the scientific literature.

The mighty BPS Research Digest discusses a fascinating study where a patient had an unexpected panic attack while being brain scanned, allowing an insight into the neural processes of panic.

Scientific American discusses asexuality, people who simply aren’t interested in sex. Another great piece from Jess Berring’s regular column.

An intriguing study on whether self-deception is genuinely possible is discussed by PsyBlog.

Language Log discusses the hypothesis that words for mother and father (e.g. mama and papa) are so similar across languages because it’s the first sounds children make and parents just assume their children are referring to them. As always, read the comments.

There’s a good piece on the neuroscience of obesity over at Dana’s excellent online magazine Cerebrum.

The New York Times has a good piece on the role of dopamine in motivation and wanting, dismissing the ‘reward system’ clich√© as old hat. Although it is seemingly unaware that this theory is not new and that the media have been mainly responsible for the gross dopamine = pleasure oversimplification.

Recent studies on the inaccurately named ‘brain scan mind reading’ approach are discussed by New Scientist.

Monkey brain surgeon

Online t-shirt company Psycho Reindeer have this fantastic monkey brain surgeon t-shirt with which you can proudly display your brain tinkering tendencies.

It’s only $14 and looks kinda funky.

If you do have a monkey by the way, it’s best not to let them do neurosurgery with a screwdriver as the t-shirt suggests.

I always make sure that they’re involved purely in an advisory capacity.

Link to monkey brain surgeon t-shirt.

Apply a female pigeon

The first neurology book printed in English was called ‘De Morbis Capitis’ and appeared in 1650. An old article from the Archives of Neurology discusses the book and has a lovely excerpt where it discusses numerous bizarre-sounding cures for brain diseases.

The full title of the book is the wonderful “DE MORBIS CAPITIS; Or, Of the chief internal Diseases of the HEAD. With Their Causes, Signes, Prognosticks, and Cures, for the benefit of those that understand not the Latine tongue”.

It was written by the country physician Robert Pemell who outlines the best rural neurological knowledge of the time.

This part from the Archives of Neurology article that discusses some of the ‘cures’ is both delightful and frightening in equal measure:

Ingredients in other remedies are marjoram, hyssop, lavender (a stimulant), rosemary, thyme, cinnamon, and nutmeg. Animal extracts included the brain of a hare, “much commended as having a peculiar property for the Paralyticall.” Diet is an important component in both the treatment and prevention of disease. Patients with paralysis, a disorder caused by an overabundance of thick humors, are counselled to “abstain from all gross and flegmatic meat…”

Physical remedies are also described by Pemell. Some are simple. “Make a noise in the ears of the (epileptic) party; for hereby the faculties are more stired up.” “Let the soles of the feet be well rub’d, and bathed with salt and vinegar.” Some are more elaborate. Apply “a female pigeon (the fethers being first leptick; for hereby the fit is abated, and the venomous vapours are drawn away.”

Link to PubMed entry for Archives of Neurology article.

Five minutes with Meg Barker

Meg Barker is a psychologist who specialises in understanding non-conventional sexuality and relationships. As well as being a researcher, Meg is also a psychotherapist where she puts her research into practice to help people overcome sex and relationship difficulties.

Having completed a great deal of research on bisexuality and ‘BDSM’ culture, Meg also has a particular interest in ‘polyamory‘ and non-monogamous relationships and has recently co-edited a forthcoming book on the topic with psychologist Darren Langdridge which attempts to understand the diverse experiences of non-monogamous relationships.

She’s also been kind enough to talk to Mind Hacks about her work and interests.

Continue reading “Five minutes with Meg Barker”

Social networks of murder

I’m just reading a long but gripping study that used social network analysis to look at murder as a social interaction between gangs in Chicago to understand how stable networks of retaliation are sustained over time.

However, I was struck by this bit in the introduction, which really highlights the social nature of murder:

But we know that murder is not in fact such a random matter. It is first and foremost an interaction between two people who more often than not know each other: approximately 75% of all homicides in the United States from 1995 to 2002 occurred between people who knew each other prior to the murder (Federal Bureau of Investigation, selected years).

We also know that the victim and offender tend to resemble each other socially and demographically (e.g., Wolfgang 1958; Luckenbill 1977). Young people kill other young people, poor people kill other poor people, gang members kill other gang members, and so on. Thus, contrary to stratification theories, a particular murder is not so much the outcome of the differential distribution of attributes as it is an interaction governed by patterns of social relations between people similar in stature and status.

It’s an amazing paper which combines a social network analysis drawn from police murder records with field work that involved talking to gang members to understand their perception and use of violence.

Link to PubMed entry for ‘Murder by structure’.
Link to DOI entry for same.

An illusory interlude

I just found a some curious case reports on two people who had hallucinations in everyday life owing to unrecognised narcolepsy, but not realising it, they assumed their hallucinated episodes had genuinely occurred.

Unlike in psychosis, where affected people often believe that their hallucinations are real, people who have narcolepsy and have hallucinations are usually able to realise they were triggered by the condition.

In this case, the people were unaware that they had a tendency to hallucinate and so the boundaries between hallucination and reality began to blur.

The 45-year-old technical manager had a multi-year history of daytime sleepiness… He frequently had curious experiences during the day ‚Äì the neighbour throwing litter into the patient’s bin; his wife throwing precious objects away. Sometimes he saw himself trying to clean dirt on the side of a ditch. These memories and experiences were confusing. They gave rise to a surprised and suspicious state of mind.

Improbable and incomprehensible things happened, leaving him in doubt. Sometimes he gave sensitive-paranoid interpretations to the events, he also denounced the neighbour for filling his bin. His paranoidity drove his psychiatrist to the diagnostic conclusion of a delusional psychosis.

Recently he had a severe conflict with his chief on account of a vivid experience of having had sexual intercourse with the chief’s wife, which he mentioned to colleagues. Remembering every detail, he was convinced that his story was true, but the reactions of those around him gradually convinced him that this experience could be a hallucination.

The man was eventually referred to a sleep clinic, diagnosed with narcolepsy and successfully treated.

The other case is of a young woman who hallucinated that she had been sexually assaulted on a bus – an experience so vivid that she reported it to the police with numerous details of the offender.

She later realised that that she could have been wrong and as part of the court case for making a false police report she was medically assessed and also diagnosed with narcolepsy after a sleep lab assessment.

Link to PubMed entry for case reports.

Tracked with pain

Today’s Nature has an excellent piece about an increasing and currently not well-researched trend for fMRI brain scan ‘neurofeedback’ treatments, where the patient is shown a visual representation of the activity of a certain brain area in the hope of learning to control it.

In this case, the big idea is that a patient with chronic pain is shown real-time activity in their anterior cingulate cortex, an area in the frontal lobe associated with the ‘unpleasantness’ of pain (rather than just its physical sensation), and they can see when they doing something to successfully reduce the activity and can try and learn to do it reliably.

The article looks at the work of Sean Mackey who researches the area but is appropriately skeptical about a number of companies who have recently sprung up offering this as a treatment, despite the lack of firm evidence.

As you may recall, this premature commercialisation is a bit of a pattern with fMRI research, as you can also buy the services of companies offering ‘lie detection’ and ‘neuromarketing’ despite a similar lack of evidence for their usefulness.

However, the piece also looks more generally at the neuroscience of pain which is, if you’ll excuse the pun, becoming a hot area, both as the understanding of pain moves away from the idea that it happens ‘in the body’ to the idea that it is handled by numerous brain circuits, each which may be involved if different aspects of the experience and our behavioural reaction to it.

In some of his other work, Mackey’s laboratory has used fMRI to explore these connections between pain processing and cognitive processes. Fear of pain, for example, can increase the pain itself, and Mackey’s group studied some of the brain regions involved in this anticipation. In another study he showed that watching someone else in pain activates brain areas that are fairly distinct from those active during one’s own pain. And in unpublished work he has found that romantic love can lessen the experience of pain. Mackey says these connections demonstrate how strong an influence conscious thought may have over pain processing.

Link to Nature article ‘Shooting pain’.

Visual illusions can be caused by imagination

A fantastic study just published in Cognition reports that the motion aftereffect illusion, where staring at something constantly moving in one direction causes illusory movement in the opposite direction when you look away, can be caused just by imagining that the movement is happening.

The effect is occasionally called the ‘waterfall illusion’ because it can be triggered by staring at a waterfall for a few minutes and then looking at the nearby bank, which will seem as if it is moving upward, in the opposite direction to the falling water.

It was traditionally explained by the fact that direction-specific motion-detecting neurons in the brain’s visual areas ‘habituate’ or adapt to constant movement by slowly becoming less active, as if they barely need to keep reporting with the same vigour because they’re just detecting more of the same.

According to this explanation, when you look away, these ‘habituated’ neurons are caught off guard and the neurons that look out for motion in the opposite direction are relatively stronger and so, until the balance is readdressed, give the impression that the world is moving contrary to your past experience.

As with most of these things, it turns out not to be quite so simple, but the effect is so easily invoked that it is used widely in vision and motion research.

One of the key findings in this area is that visual imagery activates some of the same areas as actually seeing what you’re thinking of. In other words, the brain seems to simulate the visual experience actually in the visual system.

Or at least, that’s what it looks like from the brain scans, but just because the same areas are active during both tasks, it doesn’t mean the same neurons are being used. It could be completely different processes at work that just happen to share the same neural office space.

So here’s the cool bit. This new study, led by psychologist Jonathan Winawer, asked participants to briefly view a moving pattern. It only appeared briefly, not long enough to cause the effect, and then disappeared.

Then were then shown the same pattern, without any movement, and were asked to imagine that it was moving in the same way. After a short while, the pattern was replaced by a picture of motionless dots, and they were asked to indicate if they saw the dots moving in a particular direction.

If the effect appeared, participants should see the dots moving in the opposite direction.

The participants were asked to imagine different directions and types of motion and then were given the same task but where they didn’t need to imagine anything, as the pattern moved by itself.

As expected, the moving pattern caused a clear motion aftereffect, but rather wonderfully, the effect appeared after participants had simply imagined the movement. It wasn’t as strong but it was clearly there.

They researchers also asked the participants after which direction would they expect the dots to go in, to check they hadn’t heard about the effect or were just doing what they thought was expected of them, and they couldn’t reliably give the correct direction that the effect would cause.

This provides good evidence that when imagine visual experiences we’re actually running a simulation in the same parts of the brain that are used to actually see the world.

Link to PubMed entry for study.
pdf of full text paper.

Brain stories and neuronovels

n+1 has an excellent article on how neuroscience is making an increasing appearance in novels, not only as a subject, but also as a literary device to explore characters and explain their motivations.

It marks the start of the trend from Ian McEwan‚Äôs Enduring Love and notes that in more recent years books such as Richard Powers‚Äôs The Echomaker, Mark Haddon‚Äôs Curious Incident of the Dog in the Night-Time and Rivka Galchen’s Atmospheric Disturbances have all drawn heavily from the medical and brain science literature for their main hooks.

What makes so many writers try their hands and brains at the neuronovel? At the most obvious level, the trend follows a cultural (and, in psychology proper, a disciplinary) shift away from environmental and relational theories of personality back to the study of brains themselves, as the source of who we are. This cultural sea change probably began with the exhaustion of ‚Äúthe linguistic turn‚Äù in the humanities, in the 1980s, and with the discredit psychoanalysis suffered, around the same time, from revelations that Freud had discounted some credible claims of sexual abuse among his patients. Those philosophers of mind who had always been opposed to trendy French poststructuralism or old-fashioned Freudianism, and the mutability of personality these implied, put forth strong claims for the persistence of innate ideas and unalterable structures.

And in neuroscience such changes as the mind did endure were analyzed in terms of chemistry. By the early ‚Äô90s, psychoanalysis‚Äîwhether of a Lacanian and therefore linguistic variety, or a Freudian and drive-oriented kind‚Äîwas generally considered bankrupt, not to mention far less effective and more expensive than the psychiatric drugs (like Prozac) that began to flow through the general population‚Äôs bloodstream. The new reductionism of mind to brain, eagerly taken up by the press‚Äîespecially the New York Times in its science pages‚Äîhad two main properties: it explained proximate causes of mental function in terms of neurochemistry, and ultimate causes in terms of evolution and heredity.

It’s really well researched piece and neatly outlines the play between literature, science writing, culture and neuroscience through the development of numerous popular novels in the area.

Link to n+1 article ‘The Rise of the Neuronovel’.

Dramatic sexuality changes after brain disturbance

The Neurocritic has compiled a collection of interesting neurological studies where a number of patients seems to have experienced a profound change in their sexual preferences as a result of brain disturbance.

One of the most well-known of these studies is a recent case of a man who was convicted of paedophilia late in life, but was later found to have a brain tumour, and on removal of the tumour his sudden interest in children disappeared. It reappeared again when the tumour once more began to grow.

The case has raised questions about free will and self-determination in light of the fact that such morally reprehensible acts seemed only to occur when a tumour was affecting brain function.

It’s importantly to mention that brain damage rarely causes such tragic events, although sexual difficulties, in general, are not uncommon. Problems can range from difficulties with arousal and enjoyment, to behavioural disturbances and inappropriate behaviour.

In some rare cases, preferences themselves seem to be affected, although it’s never clear whether it’s actually that the person has different desires, or whether they always had them but now are, perhaps, less able to stop themselves acting on them.

It’s easier to think that damage has changed people’s desires when the behaviour markedly unusual, such as this case of a man who was, to put it bluntly, screwing the coin return tray of a public telephone after brain deterioration.

But one thing we know from the forensic literature and cases of healthy people who accidentally die during sexual practices (for example, these two), is that no matter how strange the attraction seems to you, someone is out there expressing it.

Not all of the cases of changes sexuality after brain damage are where people act outside of the norm, of course. In one, admittedly, not brilliantly detailed case, an apparently exclusively homosexual man found he developed heterosexual attraction after a stroke.

Sadly, this area is massively under-researched so we really know relatively little about how different aspects of desire, emotional attachment and sexual behaviour are handled by the brain, but these case studies give us a window into the possibilities.

Link to The Neurocritic on ‘Unusual Changes in Sexuality’.

Face of the giant panda sign

I’ve just discovered a curious medical finding that can be detected on MRI brain scans called the ‘face of the giant panda sign’ where, quite literally, it looks like there’s a panda face in the middle of the brain, indicating a specific pattern of neural damage.

The image you can see on the left is the ‘face of the giant panda sign’ that appeared in a brain scan of a patient with multiple sclerosis who started showing unusual sexual behaviour and is taken from a 2002 study. Click the image if you want to see the whole scan.

The pattern is apparently caused by “high signal in the tegmentum, normal signals in the red nuclei and lateral portion of the pars reticulata of the substantia nigra, and hypointensity of the superior colliculus”.

It is most associated with Wilson’s disease, a genetic condition which causes a toxic build-up of copper in the body, but obviously can appear in other disorders as well.

Thanks to Twitter user @sarcastic_f for alerting me to this.

It’s not just pandas that appear in brain scans of course, the Virgin Mary has also been known to make an appearance.

Link to PubMed entry for MS study.
Link to brief description from Neurology.

A poster to remember

While strolling through town the other day, I came across this fantastic memory and brain-themed poster.

It’s from the University of Antioquia’s museum who are holding an art and literature competition to celebrate 200 years of Colombian independence.

Click the image for a bigger version or hit the link below if you want to see it in all its glory.

Link to bigger version.

2009-10-23 Spike activity

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

<img align="left" src="http://mindhacks-legacy.s3.amazonaws.com/2005/01/spike.jpg" width="102" height="120"

The single best article you’ll read on technology and the brain for a while is published in The Times. 300 words of sense.

The Sydney Morning Herald covers an inattentional blindness study in mobile phone users and asks ‘Did you see that unicycling clown?’ I’m more interested to know whether the unicycling clown saw the psychologist following him around all day.

Apart from the fact that she seems to be labouring under the misapprehension that the right temporal parietal junction is not used for anything else (it is) there’s an excellent TED talk by Rebecca Saxe on ‘theory of mind‘ and the neuroscience of inferring others’ mental states.

Neurophilosophy covers on how electrodes planted into the open brain of an awake patient reveals the neural dynamics of speech. Accompanied by an equally as awesome image.

The anthropology song is featured on Neuroanthropology.

The Neurocritic finds an intriguing film about a professor who believes she has found a way of determining scientifically whether someone is in love.

Philosopher Stephen Stich gives four lectures on ‘Moral Theory Meets Cognitive Science’ which are collected at 3 Quarks Daily.

Dr Petra has been upgraded!

Another good TED talk, this time by Beau Lotto on what optical illusions tell us about perception.

Science News on research that a gene involved in vocal cord development may be a factor in a inherited speech disorder.

There’s a brief Q&A on the science of persuasion over at Nature.

The BPS Research Digest covers some heart-warming research on how a heated room makes people feel socially closer.

You can read a free taster issue of November’s The Psychologist here. Enjoy!

Scientific American’s Mind Matters blog has a great piece on making errors and learning.

Another good Neurophilosophy post, on how immediate goal kicking performance in American ‘foot’ ‘ball’ affects the perception of how big the goal seems.

Science News reports that ‘People can control their Halle Berry neurons‘. Neurons? I have enough trouble trying to control my Halle Berry thoughts. Don’t think of Catwoman. Damn.

The National Alliance on Mental Illness (NAMI) is an American nonprofit, grassroots, self-help, support and advocacy organization of consumers, families, and friends of people with severe mental illnesses that happens to receive 75% of its funding from Big Pharma, according to The New York Times.

Cognitive Daily asks What does it take to get kids to eat healthy foods? Personally, I bribe them with cans of Red Bull.

There’s on excellent piece on how antidepressant sales are rising despite depression diagnoses falling in the UK over at Neuroskeptic. Apparently, longer-term treatment is now the norm.

FAILBlog has a hilarious duck phobia fail.

To the bunkers! H+ Magazine reports on robots controlled by human brain cells. Let’s hope they’re not the Halle Berry neurons.

Slashdot commentor kindly lists all the Doctor Who references to robots controlled by organic brains.

I found this great article on drug counterfeiting from a 1961 edition of Popular Mechanics.

BoingBoing has an interesting snippet on a new NIH study which will deploy robo-calling for boozers and stoners. Press 1 if you’re taking a bong hit?

Happy belated Fechner Day.

Language Log asks ‘Is irony universal?’. Rather ironically, asked by Americans. Also some interesting observations in the comments from Danny O’Brien.

Insecurity + power = boss rage, according to a new study covered by Neuronarrative.

The New York Times has a piece by David Brooks who marvels at how “damned young, hip and attractive” neuroscientists are. I would just like to disavow this dreadful stereotyping and point out that, like myself, many competent neuroscientists look pretty rough and find being deeply unfashionable quite groovy (by still using words like ‘groovy’ for example).

Size zero culture in Ancient Rome

We often think that pressure on young women to be thin is a modern phenomenon, but a fascinating letter to the Journal of the American Academy of Child and Adolescent Psychiatry published in 2000 noted that this is not a new development. The authors cite evidence from Ancient Rome showing a similar cultural pressures were widespread:

Garner et al. (1985) wrote about the present ‚Äúunprecedented emphasis on thinness and dieting‚Äù which is one factor responsible for the increase in anorexic and bulimic disorders. It is generally believed that dieting in pursuit of a thinner shape and slimness as a standard for feminine beauty are modern attitudes. However, a clear account can be found in the ancient comedy Terence‚Äôs Eunuchus.

Terence (Publius Terentius Afer) (c. 190‚Äì159 BC) was a Roman comic poet. His 6 surviving comedies are Greek in origin but describe the contemporary Roman society. Eunuchus was probably presented in 161 BC. In this comedy, a young man named Chaerea declares his love for a 16-year-old girl whom he depicts as looking different from other girls and he protests against the contemporary emphasis on thinness: ‚Äúhaud similis uirgost uirginum nostrarum quas matres student demissis umeris esse, uincto pectore, ut gracilae sient. si quaest habitior paullo, pugilem esse aiunt, deducunt cibum; tam etsi bonast natura, reddunt curatura iunceam. itaque ergo amantur.‚Äù (She is a girl who doesn‚Äôt look like the girls of our day whose mothers strive to make them have sloping shoulders, a squeezed chest so that they look slim. If one is a little plumper, they say she is a boxer and they reduce her diet. Though she is well endowed by nature, this treatment makes her as thin as a bulrush. And men love them for that!) Then he describes the girl he loves: ‚Äúnoua figura oris . . . color uerus, corpus solidum et suci plenum‚Äù (unusual looks . . . a natural complexion, a plump and firm body, full of vitality). So he opposes vividly the typical thinness of the girls of these times to the blossomed body of the girl he loves.

This Roman pressure on girls to diet to meet the social expectations for thinness represents a clear precedent for the current emphasis on thinness. It is clear that in Ancient Rome, as in today‚Äôs society, there were multiple factors related to the development of body image concerns which today are often a precursor to eating disorders. These include cultural pressures to strive to develop and maintain a particular body shape in order to be considered attractive and then valued as a woman. Here, Terence mentions Chaerea‚Äôs preference for a plumper girl, while mothers usually wished their daughters to be thinner. Although the media influences that today are critical in influencing images of a perfect body were not present in Ancient Rome, it is clear from this part of the text that pressures concerning appearance existed long before the 20th century.

Link to PubMed entry for letter.

Time is of the essence

New Scientist has an excellent article on how the brain makes sense of time and looks at why certain intense experiences seem to trigger the perception that time has slowed down.

It covers David Eagleman’s well-known study where he dropped people 30 metres into a safety net and while falling, asked them to read off numbers that were flashing by too fast for normal perception.

The idea was that if time really did ‘slow down’, or rather, if the brain became ‘over-clocked’ and the resolution of time perception genuinely became more fine-grained, the participants could read off some of the digits that they couldn’t normally make sense of. As it happened, they couldn’t, suggesting that time slowing effect is an illusion and not an effect of the brain going into overdrive.

The piece also has an interesting discussion of how cognitive scientists are using the wagon wheel effect to study time perception in the brain. This is where after a certain speed, spokes on a wheel seem to starting moving backward.

This has been used to work out the brain’s ‘refresh rate’, but it turns out that this is unlikely to be a global process because when looking at two such objects moving at exactly the same rate, only one of them might be subject to the effect.

This suggests that the brain might have many clocks, perhaps each assigned to a different task:

The case for discrete perception is far from closed, however. When Eagleman showed subjects a pair of overlapping patterns, both moving at the same rate, they often saw one pattern reverse independently of the other. “If you were taking frames of the world, then everything would have to reverse at the same time,” says Eagleman.

VanRullen has an alternative explanation. The brain processes different objects within the visual field independently of one another, even if they overlap in space, he suggests. So the RPL [right inferior parietal lobe] may well be taking the “snapshots” of the two moving patterns at separate instances – and possibly at slightly different rates – making it plausible that the illusions could happen independently for each object.

This implies that there is not a single “film roll” in the brain, but many separate streams, each recording a separate piece of information. What’s more, this way of dealing with incoming information may not apply solely to motion perception. Other brain processes, such as object or sound recognition, might also be processed as discrete packets.

Link to NewSci piece ‘Timewarp’.