Konstantina Kilteni

Our brain is constantly bombarded with touches that we generate ourselves, from scratching our heads to rubbing our eyes. Yet, our brain effortlessly distinguishes such self-touches from similar touches applied to our body by other people or objects. Computational theories of motor control suggest that the brain predicts the self-touches on the basis of our movements, and uses these predictions to attenuate the self-generated somatosensory input. However, the details of this process remain poorly understood, due to i) little to no insight into the temporal profile of predictions, and ii) studies often conflating feedback and prediction in one and the same event. Building on recent behavioral and neuroimaging findings from our lab, this project will use cutting-edge magnetoencephalography to delineate somatosensory processing during movement, rather than after receiving the self-touch (WP1), and experimentally omit the somatosensory feedback to isolate the contributions of predictive signals (WP2). Finally, we will combine state-of-the-art structural and functional magnetic resonance imaging data with perceptual psychophysics in a large sample to pinpoint the brain areas that implement these self-touch predictions (WP3). Taken together, this project will answer fundamental questions about self-touch, with important clinical relevance for disorders in which the distinction of self-touch from external touch is disturbed, such as schizophrenia.

Tickle is one of the most enigmatic human sensations: we do not know how a touch can turn into tickle, and why our brain responds to other people’s tickles but not to our own. To date, there is no theory that can satisfactorily explain why touch on certain body areas feels more ticklish than on others, and why some people are more prone to be tickled compared to others. Despite this fundamental knowledge gap, experiments on tickle perception have been extremely scarce, and there is currently no active research on the topic at an international level.In TICKLISHUMAN, I propose a new interdisciplinary approach to understand the neuroscience of human tickle perception, based on modern haptic technology, somatosensory psychophysics, multivariate pattern analyses of neuroimaging data, brain stimulation, and advanced statistical modelling techniques. First, my team and I will establish a stimulation protocol that optimally induces tickle sensations, and we will identify their neural profile. Building upon my findings on how the brain differentiates between self-generated and externally generated touch, we will delineate the body maps where the perception of tickle is amplified and we will determine the brain mechanism that cancels self-generated tickle sensations. Finally, we will model individual differences in tickle perception as a function of central, peripheral, personality, and demographic characteristics. TICKLISHUMAN has the strong potential to radically transform our scientific and popular thinking about the social, motor, and clinical neuroscience of tickle. The novel insights from the project will permit to explore the very undervalued clinical and functional implications of tickle in the next decades, including its use as a cognitive biomarker in schizophrenia and autism, and its evolutionary function across species.