February 2009 – Mind Hacks

On believing you died during the operation

I just found this interesting paper in the medical journal Anesthesiology on fear of imminent death or the delusion that death has actually occurred, both linked to anaesthetic intoxication.

Despite our repeated explanations that she had suffered a local anesthetic-induced complication, the patient remained convinced that she had died and come back to life. This patient had been a non-practicing Christian who believed in an afterlife. She had not had any previous experience of this kind or know of others who had had. She had had no fear of death in the preoperative period.

The article notes that the delusional belief that one has died has been linked to complications with the use of lidocaine, procainamide, and procaine.

As with the drugs used in the Anesthesiology case study, all of these are local anaesthetics. They are just intended to numb a specific area, so the patient is not ‘put under’ with globally conscious altering substances.

It’s also interesting because the delusion that one has died is also known in the psychiatric literature, usually in the context of diagnoses such as schizophrenia or after brain injury.

In these cases it is known as the Cotard delusion which is usually explained, rather unsatisfactorily, as being caused by a general emotional disconnection from the world, interpreted by the patient’s faulty reasoning system as being convincing evidence that they are dead.

The case studies from the anaesthesiology literature suggest that these beliefs can be triggered in other ways, although the exact process still remains a mystery.

If you’re put off by academic journals, give this article a try. It’s well written, short and fascinating.

Link to Anesthesiology article on death delusions.

Sir Humphrey teaches questionnaire design

Classic British TV comedy Yes Prime Minister has important lessons for those who want to interpret questionnaire data. This clip shows two civil servants discussing a policy suggestion. Bernard Woolley, who we see first, thinks the public are in favour of the policy – the minister has had an opinion poll done. Luckily senior civil servant, Sir Humphrey Appleby is there to set him straight:

Fans of cognitive biases, note that Sir Humphrey uses at least three in his illustration of a biased questionnaire: framing, priming, and acquiescence bias.

This example exaggerated, but the moral still holds : questionnaires can be designed to encourage the answers you want. People’s opinions are not objective facts like their height and weight, they change depending on the context and on how they are asked.

2009-02-27 Spike activity

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

BBC Radio 4’s science programme Leading Edge covers memory in the dock, and memory and ageing.

New Scientist discusses virtual autopsies and looks inside the skull of a suicide victim with a medical scanner.

One for Spanish language readers: El Pais discusses the neuroscience of religion and spiritual experience with an article entitled ‘Dios habita en el cerebro‘.

Seed Magazine discusses the role of the internet in the recent voodoo fMRI controversy with a mention of Mind Hacks.

Beauty affects men’s and women’s brains differently, reports Wired.

The Times discusses the increasing trend for children with behavioural problems to be given numerous psychiatric diagnoses.

Neuroscientists develop ‘wireless‘ activation of brain circuits, reports press release on EurekaAlert.

Petra Boynton covers the ‘Facebook causes cancer’ debacle and the subsequent unhelpful and misleading contribution from neuroscientist Baroness Greenfield who should know better.

A study on the social benefits of social networking is covered by The Washington Times. Does this mean Facebook cures cancer too?

New Scientist discusses the psychology and neuroscience of suicide.

BBC’s science programme Horizon recently had a programme on the neuroscience of dreaming which is available to view online for another month or so. UK residents only though unfortunately.

The Neurocritic has an excellent critique of a recent imaging study that was rather widely and poorly reported as ‘men think of women in bikinis as objects’.

Does mentioning sex help students learn about other stuff too, asks Cognitive Daily with coverage of an interesting study on exactly this.

Science News reports that people who hold negative attitudes toward the elderly have an increased risk of heart-related ailments later in life.

An interesting study on the role of the 5-HTTLPR gene in attention to fearful or positive images is appallingly spun by New Scientist with nonsense about ‘happiness genes’ and genetic basis for optimism.

The Daily Mash has a <a href="Daily Mash
http://www.thedailymash.co.uk/news/society/facebook-gives-you-short-attention-span%2c-says…–ooh-what%92s-that?-200902251602/”>satirical take on the ‘Facebook causes cancer / rots your brain’ nonsense.

Research suggesting a possible genetic flag for brain cancer is covered by Science News.

The New York Times reports on a recent small sample size but interesting study on structural brain changes found in childhood abuse victims.

Brain scans replace job interviews within five years, reports gullible Digital Journal.

Neuroanthropology reviews a bunch of great brain books for kids. Yay!

New kind of epilepsy shakes up memory, reports New Scientist who seem to have no idea that transient epileptic amnesia is not new.

Furious Seasons is essential reading at the moment – e.g. catching AstraZeneca ordering it’s Seroquel sales reps to lie about the the drug causing diabetes. In case you didn’t know journalist Phil Dawdy is entirely funded by reader donations and he’s having a fundraiser at the moment.

First gene discovered for most common form of epilepsy, reports Science Daily.

BBC News reports that Alzheimer’s plaques may have a bigger impact on the brain than previously thought.

An interesting study on the interplay between reason and emotion in buying decisions is covered by Frontal Cortex.

Warning of ghosts in the machine

Today’s issue of Science has a letter from neuroscientist Martha Farah and theologian Nancey Murphy warning against ‘non-materialist neuroscience’ becoming the new front-line in the religion wars.

Most religions endorse the idea of a soul (or spirit) that is distinct from the physical body. Yet as neuroscience advances, it increasingly seems that all aspects of a person can be explained by the functioning of a material system. This first became clear in the realms of motor control and perception. Yet, models of perceptual and motor capacities such as color vision and gait do not directly threaten the idea of the soul. You can still believe in what Gilbert Ryle called “the ghost in the machine” and simply conclude that color vision and gait are features of the machine rather than the ghost.

However, as neuroscience begins to reveal the mechanisms underlying personality, love, morality, and spirituality, the idea of a ghost in the machine becomes strained. Brain imaging indicates that all of these traits have physical correlates in brain function. Furthermore, pharmacologic influences on these traits, as well as the effects of localized stimulation or damage, demonstrate that the brain processes in question are not mere correlates but are the physical bases of these central aspects of our personhood. If these aspects of the person are all features of the machine, why have a ghost at all?

By raising questions like this, it seems likely that neuroscience will pose a far more fundamental challenge than evolutionary biology to many religions. Predictably, then, some theologians and even neuroscientists are resisting the implications of modern cognitive and affective neuroscience. “Nonmaterialist neuroscience” has joined “intelligent design” as an alternative interpretation of scientific data. This work is counterproductive, however, in that it ignores what most scholars of the Hebrew and Christian scriptures now understand about biblical views of human nature. These views were physicalist, and body-soul dualism entered Christian thought around a century after Jesus’ day.

As I’ve noted before, I remain sceptical that this will pose much of a threat, largely due to the fact that non-materialist neuroscience is not particularly new – many famous neuroscientists (including the Nobel prize-winning John Eccles) have been explicitly non-materialist with few contemporary ripples.

Unlike evolution, which bluntly contradicts what many religious texts claim, very few holy books describe any concepts of the soul that can be directly contradicted by neuroscience.

However, there is certainly some interest in the neuroscience bashing among Christian fundamentalists, who recently held their first conference on the issue. We shall have to see how successfully they manage to enthuse their flock.

Link to letter ‘Neuroscience and the Soul’.
Link to DOI entry for same.

Brain implants and cognitive side-effect trading

This week’s Nature has an interesting article on the ethics of electronic brain enhancements. It does something quite unusual for an article on technological brain enhancements – it talks about the side effects.

Brain implants and ‘neuroprosthetics’ have been widely covered by the science media in recent years owing to a number of impressive advances but very little discussion has focused on the adverse effects.

In considering the ethics of using brain implants to enhance both the damaged and healthy brain, this article actually touches on some of the research on unwanted effects of deep brain stimulation.

Many patients with Parkinson’s disease who have motor complications that are no longer manageable through medication report significant benefits from DBS. Nevertheless, compared with the best drug therapy, DBS for Parkinson’s disease has shown a greater incidence of serious adverse effects such as nervous system and psychiatric disorders and a higher suicide rate. Case studies revealed hypomania and personality changes of which the patients were unaware, and which disrupted family relationships before the stimulation parameters were readjusted.

Such examples illustrate the possible dramatic side effects of DBS, but subtler effects are also possible. Even without stimulation, mere recording devices such as brain-controlled motor prostheses may alter the patient’s personality. Patients will need to be trained in generating the appropriate neural signals to direct the prosthetic limb. Doing so might have slight effects on mood or memory function or impair speech control.

The author of the piece argues that this does not raise any new ethical questions, as many psychiatric drugs also have side effects.

However, it’s probably true to say that ethical difficulties often arise with regard to specific side effects – talking about unwanted effects in general is a bit too vague to be useful.

Risk-benefit analyses are only useful when you know both the extent and quality of the risks and benefits and this is where it truly gets interesting.

The neuropsychology literature is full of surprising findings about what sort of functions the brain performs, suggesting that specific effects, wanted and unwanted, may have to be traded off against each other.

For example, is the loss of the ability to have an unconscious emotional reaction to a loved one worth a change in pathological gambling behaviour?

This is a hypothetical example based on the role of the ventromedial cortex in both situations, but who knows what sort of effects might need to be weighed up against each other.

Nature Network has an online discussion about the issues the piece raises which also links to the weekly podcast which has an interview with the author.

Link to Nature article ‘Man, machine and in between’.

The life and times of the truth serum

I just found this fascinating photo in a 1932 book on forensic psychology in the Universidad de Antioquia’s history of medicine section. It pictures the inventor of the truth serum, Dr House, administering the drug to an arrested man in a Texas jail.

The book is called Manual de Psicolog√≠a Jur√≠dica (literally ‘manual of legal psychology’) by the pioneering forensic psychiatrist Emilio Mira y L√≥pez and is a curious mixture of psychological theory, mental tests and descriptions of what seem like strange lie-detecting contraptions.

The history of the ‘truth serum’ is recounted in a fantastic article by medical historian Alice Winter from Bulletin of the History of Medicine which describes the Dr House’s invention and the influence it had on society of the time.

Truth serum was the creation of a rural Texas physician, Robert House. House claimed that the drug scopolamine hydrobromide, which was known for erasing the knowledge of painful events, could actually be used to extract intact information. His announcement was seized upon by journalists, police, and forensic scientists as heralding a potentially transformative new technology, and was just as robustly rejected by the legal community.

Scopolamine’s identity as an extractor of “truth” was indebted to certain earlier conventions‚Äînotably, research into altered psychic states such as mesmerism and hypnotism, which sometimes were said to create a confessional state. Scopolamine, in turn, created the shoes that other chemical agents would come to fill when, later in the decade and in the 1930s, the new barbiturates sodium amytal and sodium pentothal were said to have the potential to extract “truthful” memories.

These drugs largely act by reducing inhibition, with the hope that the person will speak more freely, but they have never been found to reliably make anyone more truthful.

Alice Winter was also recently interviewed on SciAm’s Mind Matters blog, in light of rumours that one of the men involved in the Mumbai attacks had been subjected to interrogation under ‘truth serum’.

Link to Winter’s article The Making of ‘Truth Serum’.
Link to ‘What is truth serum?’ from SciAm.

The future of experimental philosophy

March’s Prospect magazine has an excellent article on ‘experimental philosophy’ that gives a good overview of an exciting new branch of philosophy as well as picking up on some of the growing criticisms and detractors.

The first half of the article covers the current methods and strands of thought in the field, discussing brain scans, trolley problems and intentionality. If you’re familiar with the ‘x-phi’ movement this is really just a well-written recap.

However, the second half tackles criticisms of the field by more established philosophers and is a useful counter-point to much of the unfettered enthusiasm which has gripped the recent media reports.

Points of disagreement include relying on the fuzzy data of brain scans, the fact that the field aims to find out about what people think in general rather than building the soundest conceptual solutions, and the accusation that it’s “a cynical step by researchers to appear cutting edge and to tap into scientists‚Äô funding”.

Ouch. If you’re not wincing already, it’s probably worth noting that this is the philosophical equivalent of saying your girlfriend looks fat in her new dress.

The piece finishes on the interesting idea that perhaps one of the field’s main contributions is to develop a context dependent philosophy that isn’t so swayed by the world view of academic thinkers.

Link to Prospect article ‘Philosophy‚Äôs great experiment’.

Match maker’s intuition

The BPS Research Digest covers an intriguing study finding that observers can reliably tell within 10 seconds whether a girl and a guy who have just met fancy each other.

The research was based on a speed dating study, which, to be honest, immediately put me off as they typically just correlate features of the individuals with their date choices – but this study is a little different.

The speed dating was used just to record videos of the daters meeting and interacting with each other, and the participants in the study were just asked to watch the videos and rate when they thought the chemistry was flowing between any particular couple.

From the BPS Research Digest write-up:

Skyler Place and colleagues made their finding using footage of couples on speed-dates. Fifty-four students observed dozens of 10-, 20- or 30-second clips of real speed dating interactions and attempted to say in each case whether each person was romantically interested in the other.

The researchers had access to the daters’ real decisions about whether they were interested in any of their speed dates, and were able to compare these with the students’ judgements.

The students performed more accurately than would be expected had they simply been guessing. They judged the interest of the male daters with 61 per cent accuracy and the female daters with 58 per cent accuracy. Their accuracy was unaffected by the length of each clip, but was higher when the clip was taken from the middle or the end of a dating interaction. Students currently in a romantic relationship outperformed those who weren’t.

I was particularly interested in the results described in the last sentence.

In the scientific paper, the researchers suggest that this “could stem in part from learning through relationship experiences. Alternatively, it is possible that the social skills necessary to succeed in finding and maintaining a relationship also support the ability to correctly perceive romantic interest.”

Link to BPSRD on perceiving the hots study.
Link to DOI entry for scientific article.

Love is ye drug

Today’s Nature has a fascinating letter from ecologist Joan Ehrenfeld who notes that Shakespeare describes how potions made from certain psychoactive plants were used to encourage reluctant lovers in one of his most famous plays.

Ehrenfeld is riffing on a recent Nature feature article that discussed the neuroscience of love, which seems to have been made open-access.

In his Essay ‘Love: neuroscience reveals all’ (Nature 457, 148; 2009), Larry Young claims that the biochemical understanding of love is not poetry. But at least one poet, namely William Shakespeare, foretold the application of drugs to manipulate the brain systems associated with pair bonding.

In A Midsummer Night’s Dream, Oberon maintains that topical applications of the juice of the wild pansy (Viola tricolor, called ‘love-in-idleness’ in the play) “Will make or man or woman madly dote Upon the next live creature that it sees” (Act 2, Scene 1). The potion proves highly effective, supplying much of the humour in the play as Titania falls in love with the donkey-headed Bottom. Shakespeare also suggests that other substances from “Dian’s bud” ‚Äî variously identified as a species of wormwood (Artemisia spp.) or chaste tree (Vitex agnus-castus, a species not native to England but long known for its anti-libidinal properties) ‚Äî could reverse the neurobiological results of the pansy. Perhaps poets have something to teach us about neurobiology and love after all.

Link to letter in Nature.
Link to Nature article ‘Being Human: Love: Neuroscience reveals all’.

Think of the children, not the evidence

The BBC’s flagship news analysis programme Newsnight featured a hefty segment on the ‘Facebook causes cancer / the end of the world as we know it’ nonsense that recently hit the headlines. The Beeb invited alarmist psychologist Aric Sigman on the show but, God bless ’em, they also invited Bad Science author Ben Goldacre who did a great job of countering the drivel. And due to wonders of the internet you can see the whole interview on YouTube.

The segment also features neuroscientist Susan Greenfield who has recently taken to warning everybody (including in the House of Lords believe it or not) about the ‘neurological dangers’ of children using the internet – based entirely on her own prejudices and in the absence of any good evidence.

She is featured in the TV report where, rather bizarrely, she admits there is no evidence but then goes on to warn of the dangers.

The debate between Goldacre and Sigman is pure TV gold, not least for watching Goldacre’s facial expressions.

Ben has also written-up the episode and put load of links and background material on Bad Science.

Link to Newsnight interview and debate.
Link to Bad Science with more on the debate.

Reigning in the extended mind

Philosopher Jerry Fodor has written a sceptical and entertaining review of a new book on the extended mind hypothesis – the idea that that we use technology to offload our mental processes and that such tools can be thought of as extensions of the mind itself.

The book in question is by fellow philosopher Andy Clark and is entitled Supersizing the Mind: Embodiment, Action and Cognitive Extension.

It’s a development of the original idea, described in Clark and Chalmer’s 1998 article called ‘The Extended Mind’, and it’s clear that Jerry Fodor is not a fan.

However, it’s probably true to say that Fodor starts from a definition of the mind which already excludes any form of information recording technology, be it a computer or a notepad, whereas the extended mind argument argues that we should rethink exactly these sorts of definitions.

The review gets a bit muddy in the middle as Fodor tries unsuccessfully to explain the difference between the confusingly similar but subtly different philosophical concepts of intentionality and intensionality in a paragraph but the article remains enormously good fun throughout.

Link to London Review of Books article ‘Where is my mind?’ (thanks Paul!)

Key to neurosurgery success

I’ve just found this remarkable CT scan in a 1997 article entitled ‘Trans-orbital penetrating head injury with a door key’.

The paper reports that “A 71-year-old-female was answering the door when she misjudged the step and fell forward impaling herself on the large key protruding from the lock.”

She was found with the key still embedded in her head and was transferred to neurosurgery where the key was removed.

Thankfully, the patient recovered with no neurological impairment and only slight difficulties with her vision.

Link to PubMed entry for the case report.

Engraved brains

Neurophilosophy has just found some beautiful neuroanatomical engravings from an 1823 book called The Anatomy of the Brain, Explained in a Series of Engravings by the pioneering brain researcher Sir Charles Bell.

Those with a slightly medical tendency may know his name from Bell’s palsy, a facial muscle paralysis that usually affects one side, and is caused by damage to cranial nerve VII.

We have discussed Bell before on Mind Hacks, when we noted that he learnt his anatomy at a London strip club – although strictly speaking, he studied at a London anatomy school which is now one of the most famous strip clubs in London.

Neurophilosophy has some more of the fantastic engravings and recounts some of the background to the book and Bell’s work.

And if you’ve seen all of them, you may want to check out another great Neurophilosophy post on a intriguing brain scanning study that suggests that the visual cortex is used as storage during working memory for visual images.

Link to Neurophilosophy on antique brain engravings.

Social influences on the drug hit

BBC Radio 4’s eclectic sociology programme Thinking Allowed recently had a fascinating discussion on how drug users learn to experience the effects of a substance and how society has an influence on the personal drug experience.

We tend to assume that drugs have fairly fixed effects but sociology has a long history of studying how users learn to manage and steer the effects of particular drugs.

The programme touches on Becker’s classic study [pdf] ‘Becoming a Marihuana User’ where he charted the informal social initiation into dope smoking in 1960s America.

Importantly, it wasn’t just the rituals that accompanied the smoking that were socially acquired, but also knowledge about what ‘counted’ as the enjoyable aspects of the drug, how to steer the effects and so on.

This is known to be particularly important for psychedelic drugs, with the so-called set and setting having a big influence over the likelihood of having an enjoyable trip.

However, the same applies to drugs such as alcohol, where the effects of having a drink varies between cultures, largely ascribed to the beliefs each culture instils about what are the likely and permissible effects of drunkenness.

This was tackled in another sociological classic, David Mandelbaum’s 1965 paper ‘Alcohol and culture’ where he described the different effects of alcohol in cultures around the world.

However, if you’re looking for a punchy overview of the field, the Social Issues Research Centre has a great page on the social and cultural aspects of drinking which I highly recommend.

These situation or culture specific effects have been tackled on the cognitive and neural level, but unfortunately I can’t access one of the key papers in the field [update: pdf], although the abstract has the main punchline:

In situations involving inter-neuronal events, these processes of adjustment may take the form of learned modifications that can be re-evoked on future occasions by events that co-occurred at the time of the original modifications.

Sensitization, defined as the enhancement of a directly elicited drug effect, though adaptive, appears to represent facilitation within a system, making the effect easier to elicit on future occasions.

Like tolerance, sensitization of a drug effect can become linked to the events that co-occurred when the effect was originally elicited, making it possible for sensitization to come under selective event control.

In other words, the article argues that learned associations have an effect on the overall experience of repeat drug taking. Of course culture can create learned associations, but changing the context can also mean certain associations are no longer triggered, leaving a great deal of room for situation specific effects.

UPDATE: Thanks to commenter dangermusic for finding a copy of the ‘key paper’ noted above. I’ve added a link into the text above or you can just grab it here as a pdf.

Link to Thinking Allowed on the sociology of drug effects.
pdf of ‘Becoming a Marihuana User’.
Link to excellent SIRC page on ‘Social and Cultural Aspects of Drinking’.

Experimental philosophy of others’ intentions

Today’s ABC Radio National All in the Mind has a fascinating discussion on how we attribute intentions to other people which covers some surprising and counter-intuitive examples of how our understanding of other people’s desires are biased by the situation.

There’s a great example depicted in this YouTube video which I highly recommend, but essentially the example is this:

A vice president of a large company goes to the CEO and says “We have a new business plan. It will make huge amounts of money for the company, but it will also harm the environment”.

The CEO says “I know the plan will harm the environment, but I don’t care about that, I’m just interested in making as much money as we possibly can. So let’s put the plan into action”.

The company starts the plan, and the environment is harmed.

The question is, did the CEO harm the environment intentionally? As it turns out, most people say yes to this question.

Now have a think about this similar scenario.

A vice president of a large company goes to the CEO and says “We have a new business plan. It will make huge amounts of money for the company, but it will also help the environment”.

The CEO says “I know the plan will help the environment, but I don’t care about that, I’m just interested in making as much money as we possibly can. So let’s put the plan into action”.

The company starts the plan, and the environment is helped.

The question is the same – did the CEO intentionally help the environment in this case.

Curiously, most people say no. Despite the CEO making the same decision in both cases.

The programme is full of many more fascinating examples of how our judgement of intention is affected by the outcome rather than the decision the person makes.

However, I wonder whether our judgements are clouded by the notion of responsibility rather than purely intention, where we place much greater social weight on responsibility for damaging actions, than beneficial ones.

This area is largely being explored by the new area of ‘experimental philosophy‘ that aims to empirically test our assumptions about traditionally philosophical issues.

Link to AITM on ‘The philosophy of good intentions’.

Car crash over before consciousness kicks in

This is a fascinating run down of an ‘anatomy of a crash’ from Australian car magazine Drive suggesting that the accident can be over before we’re even consciously aware of it happening.

This is a reconstruction of a crash involving a stationary Ford Falcon XT sedan being struck in the driver’s door by another vehicle travelling at 50 km/h.

0 milliseconds – An external object touches the driver’s door.

1 ms – The car’s door pressure sensor detects a pressure wave.

2 ms – An acceleration sensor in the C-pillar behind the rear door also detects a crash event.

2.5 ms – A sensor in the car’s centre detects crash vibrations.

5 ms – Car’s crash computer checks for insignificant crash events, such as a shopping trolley impact or incidental contact. It is still working out the severity of the crash. Door intrusion structure begins to absorb energy.

6.5 ms – Door pressure sensor registers peak pressures.

7 ms – Crash computer confirms a serious crash and calculates its actions.

8 ms – Computer sends a “fire” signal to side airbag. Meanwhile, B-pillar begins to crumple inwards and energy begins to transfer into cross-car load path beneath the occupant.

8.5 ms – Side airbag system fires.

15 ms – Roof begins to absorb part of the impact. Airbag bursts through seat foam and begins to fill.

17 ms – Cross-car load path and structure under rear seat reach maximum load. Airbag covers occupant’s chest and begins to push the shoulder away from impact zone.

20 ms – Door and B-pillar begin to push on front seat. Airbag begins to push occupant’s chest away from the impact.

27 ms – Impact velocity has halved from 50 km/h to 23.5 km/h. A “pusher block” in the seat moves occupant’s pelvis away from impact zone. Airbag starts controlled deflation.

30 ms – The Falcon has absorbed all crash energy. Airbag remains in place. For a brief moment, occupant experiences maximum force equal to 12 times the force of gravity.

45 ms – Occupant and airbag move together with deforming side structure.

50 ms – Crash computer unlocks car’s doors. Passenger safety cell begins to rebound, pushing doors away from occupant.

70 ms – Airbag continues to deflate. Occupant moves back towards middle of car.

Engineers classify crash as “complete”.

150-300 ms – Occupant becomes aware of collision.

The video of the crash test, from which is the above is taken, is also available online.

As you can see, it’s a lab-based crash test and so doesn’t capture the messiness of many real world impacts.

I checked out their figure for conscious awareness kicking in at 150-300ms and it seems to be accurate and mostly taken from the work of neuroscientist Benjamin Libet.

There’s a good 2004 review article from the Archives of Neurology that actually cites 300ms as the start of conscious awareness, some other reviews cite 200ms as a ‘rule of thumb’ figure.

Link to Drive on ‘Anatomy of a Crash’ (<a href="http://www.sentientdevelopments.com/2009/02/will-you-perceive-event-that-kills-you.html
“>via Sentient Developments).
Link to paper on ‘Neuronal Mechanisms of Conscious Awareness’.