Me and my shadow

Induction of an illusory shadow person

Stimulation of a site on the brain's left hemisphere prompts the creepy feeling that somebody is close by.

The strange sensation that somebody is nearby when no one is actually present has been described by psychiatric and neurological patients, as well as by healthy subjects, but it is not understood how the illusion is triggered by the brain^{1, 2}. Here we describe the repeated induction of this sensation in a patient who was undergoing presurgical evaluation for epilepsy treatment, as a result of focal electrical stimulation of the left temporoparietal junction: the illusory person closely 'shadowed' changes in the patient's body position and posture. These perceptions may have been due to a disturbance in the multisensory processing of body and self at the temporoparietal junction.

The patient was a 22-year-old woman of normal psychiatric history who was undergoing evaluation for surgical treatment of epilepsy (see supplementary information). We identified an area on the left temporoparietal junction in her brain (Fig. 1a) where focal electrical stimulation repeatedly produced a feeling of the presence of another person in her extrapersonal space.

a, Three-dimensional surface reconstruction of the left hemisphere of the brain from magnetic resonance imaging. Subdural electrodes were implanted in the brain of an epileptic patient undergoing presurgical evaluation¹⁰. The locations at which focal electrical stimulation evoked different responses are shown (red, motor; blue, somatosensory; green, language; pink, site where 'feeling of a presence' could be induced (arrow)); stars indicate the epileptic focus. Since undergoing a left-temporal lobectomy, the patient has been free of seizures. b–d, Drawings showing relative positions and postures of the patient's body (white) and that of the illusory person (shaded) during cortical stimulation (illustrations, M. Boyer).

Reference : Nature 443, 287(21 September 2006) | doi:10.1038/443287a; Received 19 July 2006; Accepted 25 August 2006; Published online 20 September 2006

Do the laws of nature last forever?

The universe might make more sense if they don't, argues leading theorist Lee Smolin

In science we aim for a picture of nature as it really is, unencumbered by any philosophical or theological prejudice. Some see the search for scientific truth as a search for an unchanging reality behind the ever-changing spectacle we observe with our senses. The ultimate prize in that search would be to grasp a law of nature - a part of a transcendent reality that governs all change, but itself never changes.

The idea of eternally true laws of nature is a beautiful vision, but is it really an escape from philosophy and theology? For, as philosophers have argued, we can test the predictions of a law of nature and see if they are verified or contradicted, but we can never prove a law must always be true. So if we believe a law of nature is eternally true, we are believing in something that logic and evidence cannot establish. ...

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Evidence of brain activity raises issues for neurologists.

'Vegetative' patient shows signs of conscious thought

The question of whether outwardly unresponsive patients may in fact be aware of their surroundings is one of the most heated debates in clinical neuroscience, with huge implications for the way such patients are diagnosed and treated. In a remarkable study published last week, researchers report that a patient who meets all the criteria of being in a 'vegetative state' can perform mental tasks on request. But the case highlights the difficulty of probing the mental state of an individual who cannot communicate, and of drawing any general conclusions about his or her condition.

Adrian Owen of the Medical Research Council's Cognition and Brain Sciences Unit in Cambridge, UK, and his colleagues used functional magnetic resonance imaging (fMRI) to scan the brain of a 23-year-old woman left in a vegetative state after a car accident in July 2005. Such patients do not respond to their surroundings, and doctors have always assumed that they are completely unaware of them. Previous brain-scanning studies have failed to detect more than reflex reactions to stimuli such as sound or pain.

Bringing the dodo back to life

Dodo skeleton find in Mauritius

At first glance the Mauritian coat of arms looks like any other, until one notices that the creature on the left is a dodo rampant. The concept of a rampant dodo is so deliciously absurd that it's hard not to giggle. For all the evidence we have suggests that the dodo was singularly cumbersome and defenceless. Hence, maybe, its Latin name, didus ineptus. The Dutch, who settled the previously uninhabited island in the early 17th century, referred to the dodo as the walgvogel, or "ghastly bird." This was apparently because, no matter which way you cooked it, its flesh was as tough as old boots. However, that didn't stop the colonisers hunting the poor dodo down. Scientists say they have discovered part of the skeleton of a dodo, the large, flightless bird which became extinct more than 300 years ago. One of the team in Mauritius said it was the first discovery of fully preserved bones which could give clues as to how the bird lived its life. Last year, the team unearthed dodo bones in the same area, but said the current find was more "significant". The bird is thought to have been hunted to extinction by European settlers. No complete skeleton has ever been found in Mauritius, and the last full set of bones was destroyed in a fire at a museum in Oxford, England, in 1755. Scientists recently declared that they could reconstruct a dodo from DNA. Not as a motionless exhibit to display in the Mauritian Institute, but a living, breathing resuscitation, from beyond the grave.