Scientists at Karolinska Institutet have pinpointed a specific brain rhythm, the alpha wave, that fundamentally shapes our sense of body ownership. This groundbreaking research, detailed on ScienceDaily.com, reveals how these brain oscillations act as an internal clock, determining what our brain perceives as part of our physical self.
The seemingly effortless feeling that your hand belongs to you is, in fact, a complex neurological feat. Our brains constantly evaluate a torrent of sensory data, meticulously distinguishing between self-generated sensations and external stimuli to construct a coherent bodily self. This intricate process is vital for daily function and self-perception.
Disruptions in this delicate balance can profoundly impact individuals, particularly in conditions like schizophrenia where the sense of self is often fragmented. Understanding the underlying mechanisms of body ownership, therefore, holds significant implications not only for neuroscience but also for clinical applications and technological advancements.
Alpha waves as the brain’s internal clock
The study, published in Nature Communications from Karolinska Institutet, involved 106 participants. Researchers combined behavioral experiments with brain recordings (EEG), brain stimulation, and computational modeling. Their focus was on how visual and tactile signals merge to create the experience that a body part belongs to oneself.
This phenomenon, known as the sense of body ownership, was further investigated. Their findings showed that the speed of alpha waves in the parietal cortex plays a critical role. This brain region processes sensory information, and the frequency of its alpha activity dictates how accurately individuals perceive their body as their own.
Mariano D’Angelo, lead author and researcher at the Department of Neuroscience, Karolinska Institutet, explained: “We have identified a fundamental brain process that shapes our continuous experience of being embodied.” To explore this further, participants engaged in the well-known “rubber hand illusion.”
In this setup, a fake hand is visible while the participant’s real hand remains hidden. When both hands are simultaneously touched, many participants begin to feel the rubber hand as their own. The illusion’s strength directly correlates with the timing precision between the visual and tactile inputs.
From illusion to real-world applications
The research revealed that individuals with faster alpha wave frequencies were more adept at detecting subtle timing differences between what they saw and felt. Their brains processed sensory information with enhanced accuracy, leading to a sharper and more reliable sense of body ownership. Conversely, those with slower alpha frequencies exhibited a wider “temporal binding window.”
This wider window meant visual and tactile signals were more likely to be perceived as simultaneous, even when slightly out of sync. This reduced precision blurred the lines between self-related sensations and external input, weakening the boundary of the body from its surroundings. The team further used non-invasive electrical brain stimulation to modulate alpha rhythms, directly influencing participants’ body ownership perception.
Professor Henrik Ehrsson, senior author of the study at Karolinska Institutet, highlighted the broader implications: “Our findings help explain how the brain solves the challenge of integrating signals from the body to create a coherent sense of self.” This understanding is crucial for advancing the design of prosthetic limbs, making them feel more like a natural extension of the body, and for developing more immersive and realistic virtual reality experiences.
The research, a collaboration between Karolinska Institutet and Aix-Marseille Université, paves the way for deeper insights into how our brains construct our physical self. By regulating the precise timing of sensory information, alpha oscillations are not just background noise; they are fundamental architects of our embodied existence, offering new avenues for therapeutic interventions and technological innovation.
