Neuroscience
A 22-year-old epilepsy sufferer with no known psychiatric problems has described the eerie feeling that a shadow-like person is mimicking her actions, when really no-one is there. She had the experience when, prior to surgery, Swiss researchers applied electrical probes to the left temperoparietal junction region of her brain. This area is known to be involved in multisensory integration and in distinguishing the self from others.
When the patient was lying down and the probe was applied, she felt as though a figure was behind her. “He is behind me, almost at my body, but I do not feel it”, she said. When she sat upright and embraced her knees, she described the unpleasant sensation that the shadow-like man was now also sitting and was clasping her arms. During a language-task in which she was asked to read out words on cards, she said “He wants to take the card; he doesn’t want me to read”.
The woman’s perceptions resemble those reported by some psychiatric and neurological patients – in particular she didn’t realise the figure was an illusion of her own body – and Shahar Arzy and colleagues concluded their findings may help understand the mechanisms behind experiences like paranoia and alien control. “It is notable that hyperactivity in the temporoparietal junction of patients with schizophrenia may lead to the misattribution of their own actions to other people”, they said.
Incidentally, the practice of exploring brain function in epilepsy sufferers prior to surgery is hardly new – the celebrated Canadian neurosurgeon Wilder Penfield famously charted some of the first somatosensory maps by observing patients’ responses when he stimulated parts of their exposed brain with an electric probe.
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Arzy, S., Seeck, M., Ortigue, S., Spinelli, L. & Blanke, O. (2006). Induction of an illusory shadow person. Nature, 443, 287.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
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Neuroscience
Shadow illusion casts light on psychotic experience
A 22-year-old epilepsy sufferer with no known psychiatric problems has described the eerie feeling that a shadow-like person is mimicking her actions, when really no-one is there. She had the experience when, prior to surgery, Swiss researchers applied electrical probes to the left temperoparietal junction region of her brain. This area is known to be involved in multisensory integration and in distinguishing the self from others.When the patient was lying down and the probe was applied, she felt as though a figure was behind her. “He is behind me, almost at my body, but I do not feel it”, she said. When she sat upright and embraced her knees, she described the unpleasant sensation that the shadow-like man was now also sitting and was clasping her arms. During a language-task in which she was asked to read out words on cards, she said “He wants to take the card; he doesn’t want me to read”.
The woman’s perceptions resemble those reported by some psychiatric and neurological patients – in particular she didn’t realise the figure was an illusion of her own body – and Shahar Arzy and colleagues concluded their findings may help understand the mechanisms behind experiences like paranoia and alien control. “It is notable that hyperactivity in the temporoparietal junction of patients with schizophrenia may lead to the misattribution of their own actions to other people”, they said.
Incidentally, the practice of exploring brain function in epilepsy sufferers prior to surgery is hardly new – the celebrated Canadian neurosurgeon Wilder Penfield famously charted some of the first somatosensory maps by observing patients’ responses when he stimulated parts of their exposed brain with an electric probe.
__________________________________
Arzy, S., Seeck, M., Ortigue, S., Spinelli, L. & Blanke, O. (2006). Induction of an illusory shadow person. Nature, 443, 287.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
Link to related Digest item.
Link to discussion of issues raised by this research.
- Targeted Brain Stimulation Provokes Feelings Of Bliss
It's hard to fathom how our subjective lives can be rooted in the spongy flesh of brain matter. Yet the reality of the brain-mind link was made stark half way through the last century by the Canadian neurosurgeon Wilder Penfield. Before conducting...
- The Alien Awakened By A Rubber Hand
What happens if you administer a tactile illusion to a brain-damaged patient whose hand is out of their control? A team of researchers has done just that, figuring that illusions could offer new insights into complex neuropsychological disorders. The...
- Tongue-tied: When Bilinguals Switch Languages Involuntarily
People who can communicate in more than one language – bilinguals - are intriguing to psychologists. A new study focuses on how bilinguals switch between tongues – how come they don't mix up words from different languages? A prevailing view is...
- Who Replaced All My Things?
Capgras syndrome – in which the patient believes their friends and relatives have been replaced by impersonators – was first described in 1923 by the French psychiatrist J.M.J. Capgras in a paper with J. Reboul-Lachaux. Now Alireza Nejad and Khatereh...
- Rabbit Illusion Tricks The Brain Too
Like a kind of neural Voodoo doll, there’s a representation of our body in our brain, so that when we’re touched on, say, our left arm, the brain’s representation of our left arm is activated. So what do you think would happen in a tactile illusion...