This post is, for all intents and purposes, fashionably late, given that Halloween is done and we are one-third of the way through the HallowThanksMas season. Still, it’s that time of the year when people most often have their ghost stories ready, so here’s something of a ghost story from the world of science.
Neuroscientists at EPFL have created the ghost illusion in the lab, duplicating the feeling of a presence, research that not only tells us about how the brain creates the illusion, but also has ramifications for schizophrenia.
The feeling of “a presence” is nothing new. Sometimes it is the product of sleep paralysis. The body paralyzes you at night to keep you from acting out your dreams. There are times, however, when you start to come out of your dream state and the paralyzing mechanism in your brain doesn’t immediately turn off. Individuals (and it is more common than you might think) who have experienced this have described what they call a shadowy figure at their beds pressing down on their chests. The body is still dreaming, essentially, even if your brain is waking up.
Now the team at EPFL have demonstrated the roots of the ghost illusion in the brain, creating the “presence” illusion in the lab—and no, the lab isn’t haunted.
Olaf Blanke’s research team at EPFL has now unveiled the ghost. They were able to recreate the illusion of a presence in the laboratory, and provided a simple explanation. They showed that the “feeling of a presence” actually results from an alteration of “sensorimotor” brain signals, which are involved in generating self-awareness by integrating information from our movements and our body’s position in space. In their experiment, Blanke’s team interfered with the sensorimotor input of participants in such a way that their brains no longer identified such signals as belonging to their own body, but instead interpreted them as those of someone else.
The researchers first analyzed the brains of 12 patients with neurological disorders – mostly epilepsy – who have experienced this kind of “apparition.” MRI analysis of the patients’s brains revealed interference with three cortical regions: the insular cortex, parietal-frontal cortex, and the temporo-parietal cortex. These three areas are involved in self-awareness, movement and the sense of position in space (proprioception). Together, they contribute to multisensory signal processing, which is important for the perception of one’s own body.
The scientists carried out a “dissonance” experiment. Blindfolded participants performed movements with their hand in front of their body. Behind them, a robotic device reproduces their movements, touching them on the back in real time. The result is a kind of spatial discrepancy, but because of the synchronized movement of the robot, the participant’s brain is able to adapt and correct for it….
…The participants were unaware of the experiment’s purpose. After about 3 minutes of the delayed touching, the researchers asked them what they felt. Instinctively, several subjects reported a strong “feeling of a presence”, even counting up to four “ghosts” where none existed.
As research on the brain continues, scientists have begun to unravel just how easily that energy sucking organ can fool us. Read the full story here or watch the video below.