A retrospective editing of consciousness

A new study has found that conscious experience can be altered retrospectively, so that experience of visual information can be changed almost half a second later by manipulating where our attention is drawn.

The research, led by cognitive scientist Claire Sergent, involved asking people to stare at a centre point of a screen with two empty circles either side.

At some point, one of the two circles would fill with randomly oriented stripes for just 50ms (one twentieth of a second) and afterwards the participants were asked to say which direction the stripes were pointing in.

Crucially however, each time this happened, one of the two circles would dim either before or after the stripes appeared.

This would happen at different times – from 400ms before the stripes appeared, up to 400ms after the stripes appeared, and the dimmed circle might appear on the matching side to the stripes or on the opposite side.

Dimming one of the circles grabs your attention. It makes you instantly focus more on whichever side of space it happens.

For example, if the left-hand circle dims, it grabs your attention, and if the stripes then appear on the left, you’re more likely to make a correct judgement about which direction they’re pointing because you’re already focused on this area. But if the stripes subsequently appear on the other side, you’re distracted and you do worse.

The key discovery from this experiment was that this also happens if the dimmed circle appears after the stripes. Up to 400ms seconds after.

In other words, you perceive the original visual details that would otherwise have escaped consciousness if your attention is drawn to the area after the picture disappears. It’s like a retrospective editing of consciousness by post-event attention.

This suggests that consciousness isn’t ‘filtered’ sensory information, but an active ‘conclusion’ drawn from information distributed across senses, space and time.

Link to locked scientific study.
Link to open-access commentary from same journal.

Hallucinations caused by lightning

A 23-year-old mountain climber was hit by a lightning bolt and awoke in hospital to find herself experiencing bizarre hallucinations.

The case, reported in BMJ Case Reports, describes how the healthy young woman was mountaineering with her climbing partner when they heard heard cracking thunder and were thrown to the ground by a massive shockwave.

The air rescue team took her to hospital and she was put in a drug induced coma for three days as she was disoriented and extremely agitated.

When she awoke, her world was somewhat different.

In the evening, still awake and 6 h after extubation, strange phenomena occurred. These exclusively visual sensations consisted of unknown people, animals and objects acting in different scenes, as if in a movie. None of the persons or scenes was familiar to her and she was severely frightened by their occurrence. For example, an old lady was sitting on a ribbed radiator, who then became thinner and thinner, finally vanishing through the slots of the radiator. Later, on her left side a cowboy riding on a horse came from the distance. As he approached her, he tried to shoot her, making her feel defenceless because she could not move or shout for help.

In another scene, two male doctors, one fair and one dark haired, and a woman, all with strange metal glasses and unnatural brownish-red faces, were tanning in front of a sunbed, then having sexual intercourse and afterwards trying to draw blood from her. These formed hallucinations, partially with delusional character, were in the whole visual field and constantly present for approximately 20 h. At the time of appearance, the patient was not sure whether they were real or unreal, but did not report them for fear that she might be considered insane. However, as she was still frightened after cessation of the hallucinations, she insisted on being transferred to her hometown hospital. Over the next few days, she had increasingly better insight and later forgot about this episode.

Her brain scan showed damage to the occipital lobes, the areas at the back of the brain that are largely taken up with the visual cortex that deal with the early stages of visual perception.

Luckily, the patient survived without sustaining any serious brain damage although the article mentions that because the occipital lobe has so many blood vessels “it could be particularly vulnerable to lightning damage”.

Link to case report on lightning-strike hallucinations.

Deaf police to monitor security cameras in Mexico

Deaf police officers have been recruited to monitor security cameras in the Mexican city of Oaxaca because of their ‘heightened visual abilities’.

There’s a brief and somewhat clunky English-language news article from the local paper that describes the project:

Ignacio Villalobos Carranza, Deputy Secretary for the Ministry of Public Security of Oaxaca, said most of the monitoring of the 230 cameras is done by law enforcement officials that are hearing or speech impaired. He noted these police officers have a very strong deaf and visual sense and can better detect what is happening in different places where the cameras are located; they can often remotely read the conversations of people, to the benefit of this security system that operates 24 hours a day.

The ability to lip read conversations is a fantastic advantage, but the project raises the question of whether deaf people would actually be better at security monitoring in general.

As far as I know, there are no studies comparing hearing and deaf people on specific monitoring tasks but there is evidence that deaf people have certain advantages in visual attention.

This isn’t vision in general, such as having sharper visual acuity – where there seems to be no difference, but there is good evidence that deaf people are better at noticing things in the periphery of vision and detecting movement.

This potentially makes them perfect for the job and likely better than their hearing colleagues.

So the project turns out to be a targeted way not of recruiting ‘disabled people’ into the workforce, but of recruiting the ‘super able’. In fact, turning the whole idea of disability on its head.

There’s also a Spanish-language video report from BBC Mundo if you want more información.

Link to brief new article on the project.
Link to Spanish-language video report from BBC Mundo.

Hallucinating body flowers

A curious and kaleidoscopic case of hallucinations reported in the latest journal Arquivos de Neuro-Psiquiatria:

A 95-year-old woman, with four years of schooling, had a seven-year history of DI [delusional infestation]. In the beginning, there were itching and prickling sensations on arms and head. Subsequently, she felt small worms, with different shapes and colors, crawling through her skin or swirling around her body.

After two years, she began to see small pumpkins and flowers coming out of her body and lettuce crawling on the table. She complained of water trickling out of walls and forming puddles on the ground. Occasionally, she saw small children walking on the walls and also worms on the floor and walls.

Sometimes, the parasites set fire to small objects. She became upset with her family and physicians who did not believe her.

The belief that you are infested with hallucinatory parasites is more typically called delusional parasitosis but it is usually not linked to the florid circus of hallucinations reported here, which are more typical of Charles Bonnet syndrome.

Link to case report in Arquivos de Neuro-Psiquiatria.

Snakes on a brain

The latest Journal of Neuroscience features a study on the neuroscience behind Akiyoshi Kitaoka’s famouse Rotating Snakes illusion and to celebrate they’re made a ‘Rotating Brain’ illusion for the front cover.

This type of illusion, often called a peripheral drift illusion, was thought to occur due to slow drifting eye movements but this new study suggests that it is more likely to be explained by rapid but tiny eye movements called saccades.

Brain-shaped version of Akiyoshi Kitaoka’s “Rotating Snakes” illusion. In its usual presentation, the image consists of concentric circles of stepwise luminance gradients with curved edges, which produces a strong illusion of rotation in most observers. New evidence suggests this illusion is produced by transient oculomotor events such as microsaccades, saccades, and blinks, rather than continuous drift.

Despite the fantastic cover I expect the journal to outdo itself next time and have both an article explaining the neuroscience Brocken spectre as well as an image you can hide up a mountanside to create 20 metre tall ghost-like figures.

Link to study (via

Transplanted corneas are a window to the soul

A fascinating note on the social meaning of eyes and why people are much more reluctant to donate the cornea after death than other bodily organs.

From a recent article in the journal Transplanatation:

At the time that a patient is diagnosed as brain dead, a substantial proportion of families who give consent to heart and kidney donation specifically refuse eye donation. This in part may relate to the failure of those involved in transplantation medicine and public education to fully appreciate the different meanings attached to the body of a recently deceased person.

Medicine and science have long understood the body as a “machine.” This view has fitted with medical notions of transplantation, with donors being a source of biologic “goods.” However, even a cursory glance at the rituals surrounding death makes it apparent that there is more to a dead body than simply its biologic parts; in death, bodies continue as the physical substrate of relationships. Of all the organs, it is the eyes that are identified as the site of sentience, and there is a long tradition of visual primacy and visual symbolism in virtually all aspects of culture.

It therefore seems likely that of all the body parts, it is the eyes that are most central to social relationships. A request to donate the eyes therefore is unlikely to be heard simply in medical terms as a request to donate a “superfluous” body part for the benefit of another. That the eyes are not simply biologic provides one explanation for both the lower rates of corneal donation, compared with that of other organs, and the lack of adequate corneal donation to meet demand.

What’s interesting is that the operation to remove the cornea does no visible damage to the donor. It’s just the idea of the thing that puts people off.

Link to locked article on eyes, meaning and cornea transplants.