If you flinch when watching a gruesome injury on screen, it is because your brain is actively simulating the pain as if it were happening to you, scientists have discovered.
A new study reveals that parts of the brain previously thought to process only vision contain hidden “body maps” that trigger echoes of physical sensations when watching others.
The research, published in the journal Nature by academics from the University of Reading, Free University Amsterdam and the University of Minnesota, explains that the brain’s visual processing areas are organised according to a map of the body.
This organisation allows what a viewer sees to trigger phantom touch sensations, effectively stimulating the brain to simulate the on-screen experience.
Baked brains
To understand how visual information activates the sense of touch, researchers developed novel methods to analyse brain activity in 174 participants while they watched films including The Social Network and Inception.
They found that brain regions traditionally considered purely visual showed patterns reflecting sensations on the viewer’s own body, similar to the maps usually found in touch-processing areas. In effect, the machinery the brain uses to process touch is “baked in” to the visual system.
“When you watch someone being tickled or getting hurt, areas of the brain that process touch light up in patterns that match the body part involved,” said Dr Nicholas Hedger, lead author from the University of Reading. “Your brain maps what you see onto your own body, ‘simulating’ a touch sensation even though nothing physical happened to you.”
The study found these maps align with visual information in two ways. In dorsal (higher up) regions of the visual system, body maps match where things appear in the field of view; for instance, parts tuned to face sensations align with the upper parts of a visual scene. In ventral (lower down) regions, the maps match the specific body part being viewed, regardless of where it appears on screen.
Researchers believe the findings could have clinical applications for understanding conditions such as autism, offering new ways to measure sensory processing mechanisms by simply having patients watch films rather than undergo exhausting traditional tests.
