09 February 2023
Touching our hand immediately tells us that it is our own instead of a stranger's. Hand-to-body movements elicit some of the earliest and ubiquitous sensorimotor experiences in life, taking place already in the uterus. These experiences continue throughout the entire lifespan with a frequency of up to 800 self-touches a day.
Self-touch is arguably one of the richest sensorimotor experiences, providing a tight contingency between motor, proprioceptive, and tactile information from both the touching and the touched body parts. Yet, the specific mechanisms behind the binding of self-touching actions with inner and outer sensations remain elusive. Previous accounts emphasize the convergence of proprioceptive and tactile signals from the touching and the touched body parts.
In this work, EMERGE partners from Ludwig Maximilian University of Munich and collaborators hypothesise that proprioceptive information is not necessary for self-touch modulation of body-ownership. Because eye movements do not rely on proprioceptive signals as limb movements do, the authors developed a novel oculomotor self-touch paradigm where voluntary eye movements generated corresponding tactile sensations.
They then compared the effectiveness of eye versus hand self-touch movements in generating an illusion of owning a rubber hand. Voluntary oculomotor self-touch was as effective as hand-driven self-touch, suggesting that proprioception does not contribute to body ownership during self-touch. Self-touch may contribute to a unified sense of bodily self by binding voluntary actions toward our own body with their tactile consequences.
Source: Antonio Cataldo, Massimiliano Di Luca, Ophelia Deroy, Vincent Hayward, Cataldo et al., iScience 26, 106180, 2023. doi: 10.1016/j.isci.2023.106180
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