For the past decade, brain researchers have been trying to prove that the brain has a false image of your hands; in fact, you experience your fingers being shorter than they are. How can that be?
Because of that sensory noise, we never experience our hands the same way, even when touching the same object ten times in a row
Peviani's recent research indicates that initially, the brain possesses accurate information about our hands; however, the resulting sensation is always based on chance. Peviani explains: 'Even the world's best darts player will not always hit the bull's eye. There is always some, albeit minimal, variation in how the player throws the dart. Now Imagine that the player is the brain, the dart is a brain signal, and the bull's eye is the image of the hand. The resulting sensation of the hand is always a bit 'off-target'. Peviani calls this sensory noise, which our brain sometimes has difficulty with.
Noise creates a distorted body image
'Because of that sensory noise, we never experience our hands the same, even if we touch the same object ten times in a row,' Peviani says. She explains: 'Maybe you are tired after a workout, you dimmed the lights in your room, or you sat in the same posture for a few hours. Even vitamin deficiency affects our brain signals. Our brain works like a computer, performing various calculations to filter out as much 'noise' as possible from each signal. This computational process makes us experience our bodies twistedly. So what's that like?
Your brain is building a kind of archive of probabilities that the brain can choose from in the future
High-level guesswork
As your brain goes through those calculations, it taps into past experiences and knowledge about your hands. Peviani explains: 'If you do a lot of typing at work or hold a cup of coffee, your brain learns about your hands based on those experiences. If you are a classical pianist or guitarist, your brain has different experiences again. Your brain is building a kind of archive of probabilities that the brain can choose from in the future. During a new experience, your brain combines all that previous information about your hands with new information and draws the most likely conclusion. But so it always remains high-level guesswork'.
Why examine hands?
'Research on hands and fingers provides quick results', Peviani says. She explains: 'Your hands and fingers move every day, much more than, say, our stomach or chest.
So knowledge about our hands might also help us understand how we experience our belly, legs and neck
Our brains keep track of every movement and position. In addition, a lot is already known about hands because more research is done here. Also, we can assume that how the brain paints a picture of our hands is similar to other body parts, Peviani explains'. 'So knowledge about our hands might also help us understand how we experience our belly, legs and neck, for example.'
Impact of the research
'And that's where it gets fascinating for me', Peviani says. People with eating disorders can also have a distorted body image; for example, they feel their bodies to be bigger than what they see in the mirror. If we understand how the brain paints a picture of our bodies, we can apply this knowledge to help people who struggle with self-perception.
How do you examine hands?
'We succeeded in recreating the brains' computational processes that create a distorted image with a computational model', Peviani says. How does that work? She continues: 'Our study involved twenty participants using virtual reality and motion tracking in our labs to explore how they perceived different parts of their hands (like knuckles and fingertips) in space even when they were not visible. Then, we developed algorithms to see how the brain puts together noisy signals and checked if these rules matched how people behave.'
Computations to describe brain activity
'If we can recreate these brain calculations, we can predict and better understand patients' behaviour and feelings. It can help us understand where things' go wrong' in someone with an eating disorder, for example. Is it due to too much noise? Or is something going wrong with how the brain processes the noise?
From observation to explanation, from explanation to tailored treatments
Peviani hopes this knowledge will allow us to personalise patient treatments even better. 'I want to be able to explain behaviour instead of just observing it. Our computational model will help us make our insights more and more detailed. That way, we can understand people better and help them to the best of our capabilities.