How the mouse can compute the coordinate of distant touch
Haptic sensation is traditionally associated with direct handling of an object. Yet haptic sensing can detect distant objects when the forces of touch are transmitted through feelers to a receptor organ, e.g., via the vibrissae of rodents or by sticks held by humans. What neural signals are available to compute the egocentric coordinates of distant touch? I address this issue for the thalamocortical signals that drive cortical computation. Our approach utilizes the ethologically prominent scanning sensorimotor system of rodents. I review the active nature of this system and then present new data that combines behavior with recordings of activation of tens of thousand of thalamocortical synaptic boutons. Our analysis shows how two concurrent signals, one purely encoding torque and the other encoding torque and self-motion, may be combined to compute the location of vibrissa touch at a distance.