1 3 Exp Brain Res DOI 10.1007/s00221-014-4011-0 RESEARCH ARTICLE Contributions of visual and proprioceptive information to travelled distance estimation during changing sensory congruencies Jennifer L. Campos · John S. Butler · Heinrich H. Bülthoff Received: 22 November 2013 / Accepted: 31 May 2014 © Springer-Verlag Berlin Heidelberg 2014 combined. In the combined cue condition, the relationship between the two cues was manipulated by either changing the visual gain across trials (0.7×, 1.0×, 1.4×; Exp. 1) or the proprioceptive gain across trials (0.7×, 1.0×, 1.4×; Exp. 2). Results demonstrated an overall higher weight- ing of proprioception over vision. These weights were scaled, however, as a function of which sensory input pro- vided more stable information across trials. Specifically, when visual gain was constantly manipulated, propriocep- tive weights were higher than when proprioceptive gain was constantly manipulated. These results therefore reveal interesting characteristics of cue-weighting within the con- text of unfolding spatio-temporal cue dynamics. Keywords Optic flow · Proprioception · Multisensory integration · Distance estimation · Self-motion · Cue conflict Introduction During everyday walking, dynamic visual information and information from the motor and vestibular systems are intrinsically linked. Understanding the interplay between these sensory signals is important for a wide variety of behaviours and applications. Studying tasks related to self- motion perception also provides a unique opportunity to better understand the mechanisms of multisensory integra- tion during causally related interactions between internal (proprioceptive/vestibular/efference) and external (visual) sensory information. A popular approach to quantifying relative cue-weight- ing has been to create a subtle conflict between the spatial or temporal characteristics of two or more sensory cues. In the context of self-motion perception, this has been done Abstract Recent research has provided evidence that visual and body-based cues (vestibular, proprioceptive and efference copy) are integrated using a weighted linear sum during walking and passive transport. However, little is known about the specific weighting of visual informa- tion when combined with proprioceptive inputs alone, in the absence of vestibular information about forward self- motion. Therefore, in this study, participants walked in place on a stationary treadmill while dynamic visual infor- mation was updated in real time via a head-mounted dis- play. The task required participants to travel a predefined distance and subsequently match this distance by adjust- ing an egocentric, in-depth target using a game controller. Travelled distance information was provided either through visual cues alone, proprioceptive cues alone or both cues J. L. Campos · J. S. Butler · H. H. Bülthoff (*) Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Spemannstr. 38, 72076 Tübingen, Germany e-mail: heinrich.buelthoff@tuebingen.mpg.de J. L. Campos (*) Toronto Rehabilitation Institute, University Health Network, 550 University Ave., Toronto, ON M5G 2A2, Canada e-mail: Jennifer.Campos@uhn.ca J. L. Campos Department of Psychology, University of Toronto, Toronto, ON, Canada J. S. Butler Trinity Centre for Bioengineering, Trinity Biomedical Science Institute, Trinity College, Dublin, Ireland H. H. Bülthoff Department of Brain and Cognitive Engineering, Korea University, Seoul 136-713, Korea