Time as the substrate of behavioral and neural processes : dynamical systems approaches

The behavior of organisms unfolds in time as do the neural processes supporting behavior. Ultimately, the physics of organisms and nervous processes are the framework in which the temporal structure of behavior and neural representations can be articulated.

This module will present a number of concepts on the basis of which the implied constraints for the temporal structure of processes can be analyzed. Central is the concept of stability. Stability is defined as the capacity of nervous and behavioral systems to maintain or reinstate particular states in the face of random or external perturbations. Perturbations arise from the complex natural environments in which organisms behave. At the neural level, the internal complexity of the nervous systems is the major challenge to stabilization mechanisms.

Stability limits flexibility, which may be defined as the ability to change behavior or state in response to changes in the sensed environment, changes in task, or structural changes in nervous systems. Fundamentally, such flexibility requires release from stability (or instability). Learning, adaptation, and adjustements to new task requirements thus are generically accompanied by changes in stability.

Mathematically, the interplay between stability and flexibility can be formalized within the framework of dynamical systems, the attractor states of which are stable states, and whose bifurcations generate flexibility. This language can be used at two levels describing either behavioral patterns or representational states. Neurophysiologically, these two domains correspond roughly to the domains of rate vs. space coding.

The basic ideas will be illustrated in tutorial fashion through toy examples derived from the approach of "synthetic psychology" first made popular by Valentino Braitenberg. Examples from the domain of human motor behavior will then be used to illustrate the use of these ideas for the analysis of behavior. The preparation of movements and its neural basis will finally be used to illustrate the dynamical approach to representation, establishing the link to the notion of population coding.

References

Erlhagen, W., Schöner, G. (in press). Dynamic field theory of movement preparation. Psychological Review.

Thelen, E., Schöner, G., Scheier, C., Smith, L.B. (2001). The dynamics of embodiment: A field theory of infant perserverative reaching. Brain and Behavioral Sciences (target article), 24:1-33.

Erlhagen, W., Bastian, A., Jancke, D., Riehle, A., Schöner, G. (1999). The distribution of neuronal population activation ({DPA}) as a tool to study interaction and integration in cortical representations. Journal of Neuroscience Methods, 94:53-66.

Schöner G., Kelso J.A.S. (1988). Dynamic pattern generation in behavioral and neural systems. Science, 239: 1513-1520.

Schöner G. (in press). Dynamical systems approaches to neural systems and behavior. In Neil J. Smelser and Paul B. Baltes (eds). International Encyclopedia of the Social & Behavioral Sciences article