Today's NYT has thoughtfully provided more strangeness for my prurient delectation:
They are eerie sensations, more common than one might think: A man describes feeling a shadowy figure standing behind him, then turning around to find no one there. A woman feels herself leaving her body and floating in space, looking down on her corporeal self.
Such experiences are often attributed by those who have them to paranormal forces.
But according to recent work by neuroscientists, they can be induced by delivering mild electric current to specific spots in the brain. In one woman, for example, a zap to a brain region called the angular gyrus resulted in a sensation that she was hanging from the ceiling, looking down at her body. In another woman, electrical current delivered to the angular gyrus produced an uncanny feeling that someone was behind her, intent on interfering with her actions.
“The research shows that the self can be detached from the body and can live a phantom existence on its own, as in an out-of-body experience, or it can be felt outside of personal space, as in a sense of a presence,” Dr. Brugger said.
Scientists have gained new understanding of these odd bodily sensations as they have learned more about how the brain works, Dr. Blanke said. For example, researchers have discovered that some areas of the brain combine information from several senses. Vision, hearing and touch are initially processed in the primary sensory regions. But then they flow together, like tributaries into a river, to create the wholeness of a person’s perceptions. A dog is visually recognized far more quickly if it is simultaneously accompanied by the sound of its bark.
These multisensory processing regions also build up perceptions of the body as it moves through the world, Dr. Blanke said. Sensors in the skin provide information about pressure, pain, heat, cold and similar sensations. Sensors in the joints, tendons and bones tell the brain where the body is positioned in space. Sensors in the ears track the sense of balance. And sensors in the internal organs, including the heart, liver and intestines, provide a readout of a person’s emotional state.
Real-time information from the body, the space around the body and the subjective feelings from the body are also represented in multisensory regions, Dr. Blanke said. And if these regions are directly simulated by an electric current, as in the cases of the two women he studied, the integrity of the sense of body can be altered.
As an example, Dr. Blanke described the case of a 22-year-old student who had electrodes implanted into the left side of her brain in 2004.
“We were checking language areas,” Dr. Blanke said, when the woman turned her head to the right. That made no sense, he said, because the electrode was nowhere near areas involved in the control of movement. Instead, the current was stimulating a multisensory area called the angular gyrus.
Dr. Blanke applied the current again. Again, the woman turned her head to the right. “Why are you doing this?” he asked.
The woman replied that she had a weird sensation that another person was lying beneath her on the bed. The figure, she said, felt like a “shadow” that did not speak or move; it was young, more like a man than a woman, and it wanted to interfere with her.
When Dr. Blanke turned off the current, the woman stopped looking to the right, and said the strange presence had gone away. Each time he reapplied the current, she once again turned her head to try to see the shadow figure.
When the woman sat up, leaned forward and hugged her knees, she said that she felt as if the shadow man was also sitting and that he was clasping her in his arms. She said it felt unpleasant. When she held a card in her right hand, she reported that the shadow figure tried to take it from her. “He doesn’t want me to read,” she said.
Because the presence closely mimicked the patient’s body posture and position, Dr. Blanke concluded that the patient was experiencing an unusual perception of her own body, as a double. But for reasons that scientists have not been able to explain, he said, she did not recognize that it was her own body she was sensing.
Six years ago, another of Dr. Blanke’s patients underwent brain stimulation to a different multisensory area, the angular gyrus, which blends vision with the body sense. The patient experienced a complete out-of-body experience.
When the current flowed, she said: “I am at the ceiling. I am looking down at my legs.”
When the current ceased, she said: “I’m back on the table now. What happened?”
Because the woman’s felt position in space and her actual position in space did not match, her mind cast about for the best way to turn her confusion into a coherent experience, Dr. Blanke said. She concluded that she must be floating up and away while looking downward.
[T]he sense of body integrity is rather easily duped, Dr. Blanke said.
Um, I don't really have anything to add, I just wanted to share this as yet another example of the precariousness of normalcy.