Posters

1. Give me your shape and I will tell you how you move: A case study of the ontogeny of the olive baboon

Druelle F.^1,2, Aerts P.¹, Berillon G.²

1. Laboratory for Functional Morphology, University of Antwerp, Antwerpen, Belgium

2. UPR 2147 CNRS, Paris, France

Corresponding author: francois.druelle@student.uantwerpen.be

Like clay is modeled by a sculptor, the animal’s body is shaped (largely) by locomotion. This may be understood according to 1) the biomechanical principles linking morphology, forces and energy, and 2) the behavioral and ecological contextualization. All these elements interact and are part of a changing system that implies continuous processes at both the life- and evolutionary span of time of species.

In this frame, we expect to be able to predict, from body shape, how and in which environment an animal will move and behave. Although this is feasible for animals specialized for one locomotor mode, the complexity of some locomotor profiles, such as those of primates, makes establishing and predicting these relationships more tricky, and impedes an understanding and modeling of the evolution of primate locomotion (including that of human).

In this context, we decided to setup an integrative research project on captive baboons during an early stage of development. This allowed us to investigate specifically the relationships between gradual changes in the distribution of the mass, between and within the body segments (i.e. body shape), and the changes in the manner in which baboons move quadrupedally, bipedally, and behave at the level of the posturo-locomotor repertoire. This project, at the boundary between behavior and biomechanics, aims to better understand the relationships between body shape and locomotion in primates.

Our results reveal that the global body design of baboons is governed by changes in the functional demands involved in the development of the locomotor profile. Nevertheless, despite transitioning toward locomotor autonomy, the shape of fore- and hindlimbs appear to be optimized very early for quadrupedal walking. From these findings, we assume that the ability to use different locomotor modes in varying proportions (the degree of flexibility) is a trade-off issue that is reflected in body shape. In other words, body shape, considered as a whole, as well as considering its subtleties, may be related to the complexity of the locomotor profiles and may help to predict locomotion of extinct primates.

2. Unsupervised learning of the trajectory of a moving visual target and evolution of its tracking in the non-human primate

Bourrelly C.^1,2, Quinet J.¹, Cavanagh P.² and Goffart L.¹

1. Institut de Neurosciences de la Timone, UMR 7289 Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France.

2. Laboratoire Psychologie de la Perception, UMR 8242 Centre National de la Recherche Scientifique, Université Paris Descartes, Paris, France.

Corresponding author: laurent.goffart@univ-amu.fr

An object moving in the visual field triggers a saccade that brings its image onto the fovea. It is followed by a combination of slow pursuit eye movements and catch-up saccades that keep the target image onto the fovea as long as possible. The accuracy of this ability to track the “here-and-now” location of a target contrasts with the distributed nature of the encoding processes in the brain and the variable sensorimotor delays. We studied how this performance is acquired in 6 inexperienced rhesus monkeys that we recorded during consecutive sessions. During the early exposure, the tracking is surprisingly mostly saltatory, made of saccades separated by low eye velocity episodes, demonstrating that smooth pursuit is not a spontaneous response to a moving stimulus. A joint evolution of saccade and pursuit components is observed. Across sessions, the tracking becomes less discontinuous and the smooth pursuit more prominent. This smoothing is observed at several scales, across the time course of each trial, trial repetitions and consecutive training sessions. We explain how saccades facilitate the evolution of smooth pursuit, even in the absence of stringent training constraints. Our findings create new perspectives for studying in the oculomotor system the neural mechanisms underlying implicit visuomotor learning and synchronization.

Work supported by an ERC grant (POSITION, CB), Fondation de France Berthe Fouassier (JQ) and CNRS (LG).

3. From robotics toward primate grasping and from animal grasping toward robotics

Pouydebat E.¹, Kivell T.², Dollar A.³, Gazeau J.P.⁴, Chèze L.⁵

1. Département d’Ecologie et de Gestion de la Biodiversité, UMR 7179 CNRS/MNHN, 57 rue Cuvier, Case postale 55, 75231 Paris Cedex 5, France

2. Animal Postcranial Evolution Laboratory, School of Anthropology and Conservation, University of Kent, Marlowe Building, Canterbury CT2 7NR, UK

3. Department of Mechanical Engineering and Materials Science, Yale University, 9 Hillhouse Avenue, New Haven, CT 06511, USA

4. Université de Poitiers, Institut PPrime UPR CNRS 3346, 86962 Futuroscope, France

5. Laboratoire de Biomécanique et Mécanique des Chocs, UMR_T9406, Université de Lyon, Université Lyon 1/IFSTTAR, Villeurbanne, Paris, France

Corresponding author : epouydebat@mnhn.fr

Primates are characterized by high manual dexterity. However, drawing the biomechanical link between hand morphology/behaviour and functional capabilities has been challenging. In addition, the rules and invariants of prehension movements in extant primates and most generally tetrapods are unknown. Our objectives are 1) to exploit kinematic model of thumb–index precision grip and manipulative movement in a broad sample of extant primates and fossil hominins and 2) to understand the rules and invariants of prehension movements in various extant tetrapod models, humans included, and to apply these principles to the control of robot arms with mechanical hands. First, the model show that both joint mobility and digit proportions are critical for determining precision grip and manipulation potential, but that having either a long thumb or great joint mobility alone does not necessarily yield high precision manipulation. The results suggest even the oldest available fossil hominins may have shared comparable precision grip manipulation with modern humans. Second, the behavioral, biomechanical and anatomical strategies which govern the prehension of species belonging to several groups of tetrapods are collected to create a previously non existing data base. This data base will allow us to 1) test the different existing hypotheses pertaining to the origin and evolution of prehension and 2) develop models of the reaching, grasping and return phases to be used in robotics. Indeed, the pool of kinematic data gathered will later on be used during the learning phase of robotic hand in order to develop and validate robust and versatile algorithms.

4. A head-neck-system to walk without thinking

Benallegue M.¹, Laumond J.-P.¹, Berthoz A.²

1. LAAS--CNRS Toulouse, France

2. Collège de France, Paris, France

Most of the time, humans do not watch their steps when walking, especially on even grounds. They walk without thinking. How robust is this strategy? How rough can the terrain be to walk this way? Walking performance depends on the dynamical contribution of each part of the body. While it is well known that the head is stabilized during the motions of humans and animals, its contribution to walking equilibrium remains unexplored. To address the question we operate, in simulation, a simplified walking model. We show that the introduction of a stabilized head-neck system drastically improves the robustness to ground perturbations. It significantly influences the dynamics of walking and hence to the balance. Our study is a starting point of a wider research on the involvement of vertebral limbs in the mechanics and control of the human steady gait. It also studies the benefits of such simple control schemes capable to produce complex behaviors.

5. Full integrated analysis of bipedal gait in olive baboons

Berillon G.¹, Druelle F.^1,2, Anvari Z.^1,3, D'Août K.⁴, Aerts P.^2,5, Cretual A.⁶, Daver G.⁷, Lacoste R.⁸, Lamberton F.⁹, Molina Vila P.⁸, Moulin V.⁸, Multon F.⁶, Nicolas G.⁶