Research Report Dual adaptation to sensory conflicts during whole-body rotations Iroise Dumontheil a,b, ⁎ , Panagiota Panagiotaki b , Alain Berthoz b a Institute of Cognitive Neuroscience, University College London, 17 Queen Square, Alexandra House, WC1N 3AR London, UK b LPPA, Collège de France-CNRS, 11, place Marcelin Berthelot, 75005 Paris, France ARTICLE INFO ABSTRACT Article history: Accepted 29 November 2005 A dual adaptation paradigm was used in order to study the adaptation to two conditions of conflicting visual and kinesthetic and vestibular information. Adaptation was induced in humans by modifying visual information during whole-body rotations with the help of a virtual reality set-up. Real rotations' amplitudes were factored by a gain of 0.5 or 1.5. The two conditions were associated to a visual context cue. The aim of the experiment was to provide support for either the feedback or the feedforward model of adaptive states switch. Results show that subjects could adapt to the two conditions of conflict during whole-body rotations. However, the two conflict situations have been found to differ both in their motor dynamics and in their susceptibility to adaptation, as it seems that the adaptation is more complete in the condition of gain 1.5, i.e., faster and more precise. Subjects could be divided into two groups according to their ability to use contextual information to switch between adaptive gains. The visual cues were sufficient for some subjects to switch adaptive state, which corresponds to a context-dependent dual adaptation, or feedforward model of switching. Other subjects showed a switch cost maintained across the experiment, corresponding with a stimulus-dependent adaptation, or feedback model of switching. We are suggesting that the process enabling switching between adaptive states depends on subjects' abilities to use contextual cues of certain types, and thus on their “perceptive styles”. This could explain the variability of results obtained in the literature. © 2005 Elsevier B.V. All rights reserved. Keywords: Feedback Feedforward model Dual adaptation Sensory conflict Virtual reality 1. Introduction The construction of a coherent representation of the relation- ship between our body and the environment is a challenging task for the brain, given the existence of many sensory ambiguities in the information provided by our senses. A theory has been proposed to model this system. The sensory weighting model of multisensory integration consists of three processing layers (Zupan et al., 2002). Firstly, each sensory system provides the central nervous system with information regarding a specific physical variable. Secondly, because the information available from different sensory systems is qualitatively different, sensory estimates are converted to intermediate estimates that share the same ‘units’, a process referred to as ‘promotion’ by Landy et al. (1995). This conversion is based on internal models of the relationships between sensory systems. Thirdly, because several sensory systems may provide information about the same physical variable, the final estimate is computed as a weighted average of all available intermediate sensory estimates. An interesting BRAIN RESEARCH 1072 (2006) 119 – 132 ⁎ Corresponding author. Institute of Cognitive Neuroscience, University College London, 17 Queen Square, Alexandra House, WC1N 3AR London, UK. Fax: +44 20 7813 2835. E-mail address: i.dumontheil@ucl.ac.uk (I. Dumontheil). 0006-8993/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2005.11.091 available at www.sciencedirect.com www.elsevier.com/locate/brainres