Inferring Visuomotor Priors for Sensorimotor Learning

Sensorimotor learning has been shown to depend on both prior expectations and sensory evidence in a way that is consistent with Bayesian integration. Thus, prior beliefs play a key role during the learning process, especially when only ambiguous sensory information is available. Here we develop a novel technique to estimate the covariance structure of the prior over visuomotor transformations – the mapping between actual and visual location of the hand – during a learning task. Subjects performed reaching movements under multiple visuomotor transformations in which they received visual feedback of their hand position only at the end of the movement. After experiencing a particular transformation for one reach, subjects have insufficient information to determine the exact transformation, and so their second reach reflects a combination of their prior over visuomotor transformations and the sensory evidence from the first reach. We developed a Bayesian observer model in order to infer the covariance structure of the subjects' prior, which was found to give high probability to parameter settings consistent with visuomotor rotations. Therefore, although the set of visuomotor transformations experienced had little structure, the subjects had a strong tendency to interpret ambiguous sensory evidence as arising from rotation-like transformations. We then exposed the same subjects to a highly-structured set of visuomotor transformations, designed to be very different from the set of visuomotor rotations. During this exposure the prior was found to have changed significantly to have a covariance structure that no longer favored rotation-like transformations. In summary, we have developed a technique which can estimate the full covariance structure of a prior in a sensorimotor task and have shown that the prior over visuomotor transformations favor a rotation-like structure. Moreover, through experience of a novel task structure, participants can appropriately alter the covariance structure of their prior

Ámbar cretácico de San Just (Teruel): el estudio de los insectos que convivieron con los dinosaurios

San Just es un yacimiento de ámbar español que se encuentra cerca de la población de Utrillas, en la provincia de Teruel. Este yacimiento es rico en masas de ámbar que contienen variadas bioinclusiones, principalmente insectos. Se localiza en la Formación Escucha, en la cuenca del Maestrat, y tiene una edad Albiense Medio (Cretácico temprano). Desde 2003 se han realizado una prospección y dos excavaciones paleontológicas. Hasta ahora, se han descrito varios géneros y especies de insectos de los órdenes Isoptera, Thysanoptera, Hemiptera, Hymenoptera y Diptera, y un género y especie de ácaro oribátido. Además, en San Just se encontró la tela de araña más antigua conocida, la cual contiene una asociación de artrópodos atrapados. La Administración regional realiza una protección especial del yacimiento debido a su alto valor científico.San Just is a Spanish amber outcrop located near the village of Utrillas (Teruel Province). This outcrop is rich in amber pieces containing varied bioinclusions, mainly insects. It occurs in the Escucha Formation, in the Maestrat Basin, and is Middle Albian in age (Early Cretaceous). Since 2003 one prospection and two paleontological excavations have been carried out. Several genera and species of insects of the orders Isoptera, Thysanoptera, Hemiptera, Hymenoptera and Diptera, and one genus and species of an oribatid mite, have been described up to now. In addition, from San Just is the earliest known spider web, which contains an association of trapped arthropods. The regional Administration specially protects San Just due to its high scientific value.Este artículo es una contribución del proyecto del Ministerio de Ciencia e Innovación: CGL2008-00550/BTE: “El ámbar del Cretácico de España: un estudio pluridisciplinar”