Your brain processes what you see and makes continuous predictions based on your experiences. This predictive process may be less refined in autistic people.
When someone throws a ball at you, you instinctively know to catch it—even before you consciously think about it. In the past, people believed that the brain worked like a camera: an image of the flying ball enters through your eyes and is then processed by your brain. After that, the brain programs a suitable action in response. However, doesn’t that process take too long? Would you still be able to catch the ball in time?
Researchers Christian Keysers, Giorgia Silani, and Valeria Gazzola reveal that the brain processes information differently than expected. Christian explains, “Your brain doesn’t simply react to what your eyes see; instead, it predicts what will happen based on your expectations and past experiences. Doing this keeps our actions in sync with the ball, even though it takes the brain several hundred milliseconds to process visual input and coordinate movement. It plans to ensure enough time to execute the action and catch the ball. The image that enters through your eyes is primarily used to verify whether your expectations align with reality. It is only when there’s a discrepancy between your expectations and what you see that your brain relies on visual input to adjust its predictions more accurately.”
Predicting others
Ms Gazzola shared, “What’s interesting is that we use our motor programs and somatosensory cortices to predict the actions of others. For instance, when you perform a physical action, like lifting a carton of milk to pour some into your coffee, you have certain expectations about the carton’s weight and how it should feel in your hand as you lift it. Typically, you don’t consciously notice the weight of the carton because your brain has already predicted it. However, if someone else has finished the milk and the carton is much lighter than you anticipated, the sudden discrepancy between your expectations and the sensory feedback will catch your attention.”
“When you see someone else do so, you don’t directly feel the weight of the carton. Still, you can make predictions using your motor programs and test them against what you see. So, you still feel surprised if the carton flies skywards much faster than you expected. We think this has to do with so-called mirror neurons, cells within your motor cortex that become active when you see someone else act. This acts as a sort of ‘shortcut,’ allowing you to use your motor programs and the predictive machinery necessary for your actions to predict the behaviour of others.”
But what about emotions? Gazzola explains: “We know that regions in our brain that are involved in our own emotions become active while we witness the emotions of others. However, how we predict the emotions of others is not fully understood. Reviewing
the literature revealed that the regions in our brain that are active when we receive a reward or punishment also become active when someone else receives a reward or punishment. Reward and punishment are therefore valuable predictors for the emotions of others.”
Complex system
Christian Keysers: “Imagine I have a button, and every time I press it, an actor starts screaming in pain. If I do this five times, your expectations change: the first time, it’s unexpected, but by the fifth time, you can predict what will happen.”
“According to the traditional theory of perception, where the brain only processes the image you see, you should see the same reaction in the brain each time. But if the outside world primarily serves to test your predictions, you’d expect a strong brain response the first time and a much smaller response the last time because you already know what will happen.”
“So what happens in the brain? Over many studies, we have seen that it’s quite complex. Some brain areas respond relatively consistently across all five times. At the same time, there are also brain regions where activity changes across the five times. In this review paper, we look at the many studies that have emerged on the topic to propose how these different brain systems organize into a coherent predictive brain. For example, if some actions become predictable, your premotor cortex knows how to act as your body. This region will then inhibit visual regions in your brain, leading to less visual input. What you perceive is no longer what you see but expect to see. Only if something unexpected happens will this inhibition become ineffective. The visual areas now show a strong response sent forwards to the premotor cortex to revise the predictions”.
Predictions and autism
It’s believed that the predictive system in people with autism is less well-tuned. This makes the world around them more unpredictable, leading to less suppressed stimuli. Christian Keysers: “Imagine standing in a crowded room with many people. Because our brain makes a lot of predictions, we can ignore most stimuli and focus only on what’s important. But when this predictive system doesn’t work well, such a busy environment can suddenly feel overwhelming.”
“The brain is complex and has the unique ability to adapt. It’s interesting to realize that your brain isn’t just a camera simply processing what comes in. Instead, your brain constantly operates based on predictions. Your brain is always ahead and continuously constructs what the world should be.”