For this week's essay I chose to continue our discussion regarding dynamical system's theory (Thelan, etc) and it's usefulness in terms of helping one to understand or conceptualize a view of the nervous system as boxes within boxes. You indicated that you would like to hear more about dynamical system's theory, and although I feel that I am only a novice in terms of understanding it, I will give it a shot.

Dynamical systems is a theory, as I know it, a theory developed to describes how development occurs and how behavior emerges and changes. It has been mainly utilzed (to my knowledge) to describe motor development and the development of motor control, as in how a child develops and refines walking (much of Ester Thelen's work has been on walking and reaching development). Dynamical system's states that "behavior is an emergent property of interactions of multiple systems. Because the behavior is not specified, but emergent, the system can be said to be self organizing" (Kamm, Thelen and Jensen, 1990, page 770). This theory has arisen from works on Chaos Theory and embraces the concept that patterns (in this case behaviors) arise from the cooperativeness of many elements. MY interpretation of this is that we strive to make sense of chaos by creating systems for looking at and understanding things. In this class, our way of understanding behavior is by examining how the nervous system works as a system of boxes within boxes.

Dynamical System's theory challenges the notion that behaviors arise as a result of nervous system maturation and suggests that behaviors (specifically movement) are influenced by many factors (such as biomechanics, gravity, motivation, arousal state, as well as neuromaturation). The task itself will influence the behavior because it will provide certian constraint which will determine how the behavior is performed. For example, if a child is reaching for a round rattle, the shape of the rattle itself will influence the grasping pattern that the child uses. It's attractiveness and appeal to the child will influence if the child attends to the rattle, etc. The environment and the organism also provide additional constraints. Can the child physically move their body to get to the toy; is the lighting in the room such that the child can see the toy?, etc. IN addition, the system is said to be self organizing and self modulating in that it will organize around the task to be performed (rather that being driven by the CNS), and it will be modulated by mechanisms at all levels, influenced by systems or structures horizontally as well as vertically. It is a non-linear system.

So you see the dynamnical systems theory is similar to the box within box theory of how the nervous system guides behavior because they both realize that behavior is organized around the task (not directed from above); that there are multiple factors that influence any given behavior; and suggest that any of these factors may take precedence or set limits on a specific behavior. They both allow us to appreciate the compexity (or chaos) of the nervous system while enabling us to conceptualize its compelexity (?). In addition, they allow us to appreciate behavior within the context of real life, with it's complexities, diversity and indivdualism. Although neither discounts the concept that there is some linearity in the nervous system (ie: the individual with a spinal cord injury can not move or feel senstation from their limbs because the information to and from the higher centers can not get through); they appreciate the activity that is occuring at other levels of the nervous system (brain stem to cortex) and how this activity can drive new behaviors to emerge. For example, the idividual with a spinal cord injury who wants to move their wheel chair independently so they can get to visit their girlfriend, can learn a new behavior: using a mouth stick to operate the wheelchair switches. The "person" has not been injured but spared; the motivation to accomplish a task is apparent and the behavior is organized around the task for success.

The box metaphor does indeed proceed from many of the same concerns that motivate complexity theory generally ... particularly with the idea that most behavior arises not from a single cause but rather from an interaction among a set of influences, and that behavior can reflect more abstract objectives rather than simply particular bits of "machinery". The question, as you put it, is whether complexity theory gives us a practical way to usefully conceptually complex systems ... i.e. is it more than simply an acknowledgement that things are complex. Hopefully, we can do better than this, at least in particular cases. Recognizing the independent capabilities of brain and spinal cord (with "normal behavior resulting from an interaction among them) is one example. Can you be more specific about how this approach helps to understand emergence of motor behaviors in a way different from more traditional approaches? PG