Extreme Imagination Helps Explain Consciousness
POSTED ON JUNE 5, 2019, BY DANIEL COSSINS
When you are absorbed in a novel, what does your mind’s eye see? For many of us, it is a foggy, low-contrast approximation of the scenes described, no matter how evocatively they are written. Not so for Clare Dudeney. “When people describe things, especially gory things, I visualize them so vividly it’s like I’m experiencing them first-hand,” she says. “A few years ago, I was on the train reading a passage about someone who got a nail stuck in their foot and I passed out.” Dudeney is one of an unknown number of people with this ability, known as hyperphantasia. Mental imagery is inherently private. It is hard to articulate what you see in your own mind’s eye, never mind get a sense of how it compares with everyone else’s. But we now know it differs wildly between individuals. Some people find it impossible to picture their own bedroom, while others, like Dudeney, can call to mind images as sharp as they appear at the cinema. These extremes of imagination are intriguing. A better grasp of what is going on in the brains of people who experience them could help tease out the role of mental imagery in emotion and mental health – and may be promising territory in the search for treatments for various psychological disorders. “Sometimes I think we know more about outer space than we do our own minds,” says Emily Holmes, a clinical neuroscientist at Uppsala University in Sweden. “And mental imagery is a frontier ripe for exploration.” Arguably, our powers of imagination explain above all else why our species has come to dominate the planet. Various studies have since shown that calling to mind a mental image is in neurological terms a fuzzy form of visual perception. In other words, it can be measured and investigated. One of the first to do so was Joel Pearson, a cognitive neuroscientist at the University of New South Wales in Sydney. In 2008, he and his colleagues developed a way to test the strength of people’s mental images. The technique takes advantage of a phenomenon called binocular rivalry in which people perceive one image despite their left and right eyes being shown different images at the same time. This effect exists because people create a picture in their mind, based on the image that was flashed up first, says Pearson, which primes them to perceive it again when faced with two images at once. “What you imagine literally changes the way you see the world,” he says. Our brains are constantly predicting what we will see, generating signals from non-visual parts of the brain that feed into the visual cortex, where they are combined with information from the eyes to produce an image. “It’s a pure form of internal conscious perception,” says Pearson. “So, by studying mental imagery, I believe we can figure out how the brain uses feedback signals to create consciousness. We can unlock the secrets of how we experience the world.
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