Multisensory coding of body and space

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Imagine you are driving a car and ill-advisedly lean over to get something out of the glove box all the while holding on to the steering wheel with one hand. During this maneuver your eyes, head and body change their positions relative to each other and deviate from the aligned positions that they have while you are sitting upright and looking straight ahead. This is a dangerous thing to do because your perception of the relative positions of objects and your position on the road is altered by this unusual posture. The goal of this proposal is to develop a comprehensive model of how information about the arrangement of the body affects perceptual judgements. I will develop three themes: (1) THE BODY'S CONTRIBUTION TO PERCEIVED ORIENTATION. There are three main cues to how we know our orientation relative to the world: visual cues (e.g., the direction of the sky and ground), the direction of gravity (sensed by the inner ear) and the internal representation of the orientation of the body. The "body" in fact comprises several components - the eyes, head, neck, torso, limbs and pelvic regions -- that are flexible relative to each other within anatomical constraints. I expect the arrangement of these components to influence the perception of orientation. (2) LOCALIZATION ON THE BODY. My recent work has found errors in localizing a touch on the arm that are related to eye position. These errors suggest, surprisingly, that touch is coded relative to a visual representation of the body surface. I expect to find similar errors in localizing touches on the back and face (which cannot normally be seen) but which might be reversed because of our customary use of mirrors. (3) THE MOVING BODY. An important function of touch is to interpret the world using active exploration. Is the information obtained by active exploration also stored visually and hence vulnerable to eye-position related errors? My research program recognizes the body as fundamental to cognition. Knowing how the body is coded and how it affects perceived location and orientation is critical not only to understand how the brain works but also for the design of workspaces where information from multiple channels is integrated, for example when driving a car.