What makes you feel that your hand is yours? It might seem obvious, but the brain’s ability to tell self from non-self is a complex process. Using a combination of behavioral experiments, brain recordings (EEG), brain stimulation, and computational modeling with a total of 106 participants, researchers from Karolinska Institutet investigated how the brain combines visual and tactile signals to create the feeling that a body part belongs to oneself – a phenomenon known as the sense of body ownership.
Their experiments showed that the frequency of alpha waves in the parietal cortex, the brain region that processes sensory information from the body, determines how precisely we perceive our body as our own. “We have identified a fundamental brain process that shapes our continuous experience of being embodied,” explains lead author Mariano D’Angelo, researcher at the Department of Neuroscience, Karolinska Institutet. “The findings may provide new insights into psychiatric conditions such as schizophrenia, where the sense of self is disturbed.”
Participants took part in the Rubber Hand Illusion, a classic method for studying the sense of body ownership. When touches on a visible rubber hand and the participant’s hidden real hand were synchronized, many reported feeling that the rubber hand was part of their body. But when the timing was off, that feeling faded.
The study found that individuals with faster alpha frequencies were more sensitive to timing differences between the seen and felt touches. They noted smaller timing differences, as if their brains operated at higher temporal resolution, resulting in a more precise sense of body ownership. In contrast, slower alpha frequencies were linked to a broader ‘temporal binding window,’ causing the brain to treat more asynchronous visual and tactile signals as if they occurred together. This reduced temporal precision made it harder to separate self-related sensations from external ones, weakening the distinction between body and world.
To test whether alpha frequency directly causes these perceptual effects, the researchers used non-invasive electrical brain stimulation to slightly speed up or slow down participants’ alpha waves. The results showed that adjusting the alpha frequency in this way also changed how precisely people experienced body ownership and how precisely they perceived visual and tactile stimuli as simultaneous.
In other words, faster rhythms allow the brain to match sight and touch more precisely, strengthening the feeling that a body part is truly yours. Slower rhythms blur that timing, making it harder to separate self from surroundings. The findings are published in Nature Communications.
StepUp Note
Rhythmic brain waves are an important part of StepUp to Learn. As we move our bodies in rhythm, we have a greater sense of our personal body space: what parts of my body are moving, and when and how are they moving. Different exercises are done at different movement speeds. This helps us create and control the purposeful movements that we use for all learning. When we see a child “find” the rhythm of an exercise, we see that the rhythmic movement creates a space for the learning that goes with the exercise. Rhythm makes the learning stick!
Note by Nancy W Rowe, MS, CCC/A
Reposted from Karolinska Institutet