Multijoint movement without internal models

Thomas Buhrmann has been working on a model of arm movement that, contrary to widespread assumptions, can compensate for the complex and dynamic inter-joint torques without the need for a central control using internal models. This work has been just published and can be accessed for free:

Buhrmann T and Di Paolo EA (2014) Spinal circuits can accommodate interaction torques during multijoint limb movements. Front. Comput. Neurosci. 8:144. doi: 10.3389/fncom.2014.00144.

SCOPE

The model shows how a combination of the musculo-skeletal complex non-linear dynamics and spinal control circuits can produce smooth arm movements where the torque produced in one joint due to movement around the other is actively compensated without the need of a central control by the brain. It lends support to the plausibility of alternative hypotheses of motor control, such as the equilibrium-point hypothesis, that do not rely on internal representations or models.

Non-representational sensorimotor knowledge

Close your eyes and follow the contour of the table in front of you. When you reach the end of it, do you think you would be able to continue moving your hand along the same imaginary line as if the table went on a little further? Most people would not have any problem doing this for a wide variety of conditions (body posture, distance and angle with respect to the table, etc.) Given this variety of circumstances, traditional approaches to perception and motor control postulate when we’re no longer in contact with the table, we must be using some form of representation that keeps guiding the arm along the same invisible line in a robust manner.

Model-eps-converted

Together with Thomas Buhrmann, we have demonstrated that representations are not necessarily the only explanation, and that indeed it is possible to attune the movement of your arm to the world without at any point involving any internal models or representations, but simply by a shaping of dynamical sensorimotor transients. The “memory” of the direction of movement is kept in the whole agent-environment system in a way that generalizes across various relative positions and angles of movement.

Manifolds2b-eps-converted

For more information see:

Buhrmann, T. and Di Paolo, E. A. (2014). Non-representational sensorimotor knowledge. In A.P. del Pobil et al. (Eds.): From Animals to Animats 13, Proceedings of the 13th International Conference on Simulation of Adaptive Behavior, SAB 2014, LNAI 8575, pp. 21–31, NY, Springer Verlag.

Two recent papers looking at the micro and macro aspects of enaction

Egbert, M. D., Barandiaran, X. E., & Di Paolo, E. A. (2012). Behavioral metabolution: The adaptive and evolutionary potential of metabolism-based chemotaxis. Artificial Life, 18(1), 1-25. doi:10.1162/artl_a_00047.

Abstract

We use a minimal model of metabolism-based chemotaxis to show how a coupling between metabolism and behavior can affect evolutionary dynamics in a process we refer to as behavioral metabolution. This mutual influence can function as an in-the-moment, intrinsic evaluation of the adaptive value of a novel situation, such as an encounter with a compound that activates new metabolic pathways. Our model demonstrates how changes to metabolic pathways can lead to improvement of behavioral strategies, and conversely, how behavior can contribute to the exploration and fixation of new metabolic pathways. These examples indicate the potentially important role that the interplay between behavior and metabolism could have played in shaping adaptive evolution in early life and protolife. We argue that the processes illustrated by these models can be interpreted as an unorthodox instantiation of the principles of evolution by random variation and selective retention. We then discuss how the interaction between metabolism and behavior can facilitate evolution through (i) increasing exposure to environmental variation, (ii) making more likely the fixation of some beneficial metabolic pathways, (iii) providing a mechanism for in-the-moment adaptation to changes in the environment and to changes in the organization of the organism itself, and (iv) generating conditions that are conducive to speciation.

Froese, T. and Di Paolo, E. A. (2011). The enactive approach: Theoretical sketches from cell to society. Pragmatics and Cognition, 19, 1-36.

Abstract

There is a small but growing community of researchers spanning a spectrum of disciplines which are united in rejecting the still dominant computationalist paradigm in favor of the enactive approach. The framework of this approach is centered on a core set of ideas, such as autonomy, sense-making, emergence, embodiment, and experience. These concepts are finding novel applications in a diverse range of areas. One hot topic has been the establishment of an enactive approach to social interaction. The main purpose of this paper is to serve as an advanced entry point into these recent developments. It accomplishes this task in a twofold manner: (i) it provides a succinct synthesis of the most important core ideas and arguments in the theoretical framework of the enactive approach, and (ii) it uses this synthesis to refine the current enactive approach to social interac- tion. A new operational definition of social interaction is proposed which not only emphasizes the cognitive agency of the individuals and the irreducibility of the interaction process itself, but also the need for jointly co-regulated action. It is suggested that this revised conception of ‘socio-cognitive interaction’ may provide the necessary middle ground from which to understand the confluence of biological and cultural values in personal action.

Keywords: adaptivity, autonomy, cognition, enaction, sense-making, social interaction

And watch out for a couple of forthcoming papers in the participatory sense-making saga!