Cores and Surrounds: From Receptive Fields to Motives

• Interactive/Self-Organizing Systems by John Fentress, 10/4/97
  • Sounds Familiar by Lee, 10/5/97
    
    

My use of "excitatory core" was borrowed from sensory neurophysiology, as was the idea of surround inhibition.

For example: single neurons in the brain can have receptive fields that respond with "exitation" (i.e. they turn on) when events are in one place (within receptive field), but then become actively inhibited (turn off) when events occur outside the field. One value of this is that edges get sharpened in the sense that contrast between core events and their surrounds is accentuated. The next interesting tidbit is that the relative size of center and surround can shift, rather like an archery target with expanding and shrinking bulls-eye.

My interest was actually at the level of behavioral MOTIVATION. Different classes of activity can both block one another and mutually facilitate one another. It appears that mutual excitation is most likely when the systems are weakly activated. The analogy is to a central "excitatory" core that expands to encompass more than one system. As the systems become more strongly activated (e.g. as in concentrating on one task, whether fighting or mating) the individual becomes more "focussed" and surrounding (alternative) activities are blocked rather than facilitated.

All of this opens up the promise (hope) of providing a dynamic model that can account for a) when systems operate separately (as in separate pieces), b) when they are mutually facilitatory, and c) when they are mutually inhibitory. The goal of the models is to allow systems to operate BOTH autonomously (as in "pieces") and in conjunction with their neighbors (as in "relations"). In addition, the idea is that the shift from mutual facilitation to mutual blocking is a dynamic property that in part depends upon level (intensity) of activation. [A little hunger might make you fight more; if you are really hungry, fighting takes a back seat.] One further implication is that the pieces form the relations that re-form the pieces that re-form the relations, etc. Its rather like a bootstrap; hard to figure out where the invariances are.

I am not certain this addresses your question. One can use the excitatory core as a metaphor for "primary initiator" in the sense that it is what gets the system up and going. Once up and going, the system can narrow its focus (rather like concentrating one's effort and ignoring {not hearing} the telephone). Outside, potentially disruptive, events become blocked. Action integrity is preserved. Once the activity draws toward a conclusion, the "boundaries" loosen, and interconnections with other ongoing or potential activities become possible. The ongoing activity is canceled, the circuits reshuffle, and new activities become formed.

My guess is that this is a GENERAL form of biological organization, and can be applied not just to sensory systems but also to motivational (etc.) systems, and not just to integrated actions, but also to their construction (differentiation) during development. In the later case cells communicate with their neighbors, then start down a path which is preserved by isolation from their neigbors (i.e. they become relatively autonomous), then communication is restored, etc. The questions are: a) how much communication is there (quantitative), b) what kind of communication is there (qualitative), and c) who do these properties change in time. The very distinction between "pieces" and "relations" then becomes both relative and dynamic, rather than absolute and static. In other words, diagrams with immutable boxes connected by arrows do not work. The boxes have properties that influece the arrows of communication, but the communication in turn modifies the properties of the boxes, and so on.

Well, I mean't to write a short reply. I failed. Became too "self-organized" for the moment.

Thanks for your note. John

• Behavioral Motivation by Lee Dean, 10/7/97
  • Interesting! by John Fentress, 10/9/97