Localizing 3D motion through the fingertips: Following in the footsteps of elephants.

Each sense serves a different specific function in spatial perception, and they all form a joint multisensory spatial representation. For instance, hearing enables localization in the entire 3D external space, while touch traditionally only allows localization of objects on the body (i.e., within the peripersonal space alone). We use an in-house touch-motion algorithm (TMA) to evaluate individuals' capability to understand externalized 3D information through touch, a skill that was not acquired during an individual's development or in evolution. Four experiments demonstrate quick learning and high accuracy in localization of motion using vibrotactile inputs on fingertips and successful audio-tactile integration in background noise. Subjective responses in some participants imply spatial experiences through visualization and perception of tactile "moving" sources beyond reach. We discuss our findings with respect to developing new skills in an adult brain, including combining a newly acquired "sense" with an existing one and computation-based brain organization.