SOMATOGPS · The Body Positioning System: A GPS for somatosensory space

Reaching to an object touching the body is so commonplace that we hardly give it a second thought. However, this simple behavior is actually an incredibly complicated problem the brain must solve on a daily basis. Somatosensory information is initially represented in neural maps whose relationship with the physical body is ambiguous. Despite this, the brain can accurately pinpoint where the object is in three-dimensional space and move the reaching hand towards it. How remains a mystery, though its solution is necessary for making concrete progress on societal issues, such as designing prosthetics that can be embodied. SOMATOGPS introduces the first neurocomputational framework aimed at solving this mystery.My novel approach leverages an analogy with computations used by manmade positioning technology in order to gain insight into potential solutions. Global Positioning Systems (GPS) ingeniously turn localization into a problem of geometry, pinpointing an object on Earth by calculating its distance from multiple satellites. I propose that the brain uses a somatosensory version of GPS that I call the Body Positioning System (BPS). I hypothesize that like the GPS, the brain reduces localization to its geometry. By keeping track of the distances between each body part and their distances from a tactile object, the brain could compute a reach to the object. The main aim of SOMATOGPS is to characterize how the BPS is implemented by neural computations, from neural map to body movement. I will develop novel behavioral and neuroimaging paradigms to measure localization in two and three dimensions, model the underlying geometric computations and their neural implementation, and manipulate the geometry of the body in order to perturb these neural computations. This innovative proposal provides the first neurocomputational model of tactile localization, representing a new state-of-the-art in our understanding of somatosensory space.