Good Starter Biological Model of Brain and Behavior

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Beyond the Computer Metaphor: Behaviour as Interaction – Paul Cisek, 1999

Summary
We need to step back from the input-output metaphor of computationalism and ask what kind  of information processing the brain does, and what is its purpose.  The answer, suggested numerous times throughout the last hundred years, is that the brain is exerting control over its environment.  It does so by constructing behavioral control circuits which functionally extend outside of the body, making use of consistent properties of the environment including the behavior of other organisms. These circuits  and the control they allow are the very reason for having a brain.

Behavior as Control – “”Behavior Is the Control of Perception.”
We begin with a fundamental premise: The brain evolved…The evolution of a biological system such as the brain is…a rich source of constraints for anyone theorizing about how the brain functions and about what it does. It is a source of insight that is too often overlooked…we should expect to gain insight into the abilities of modern brains by considering the requirements faced by primitive brains, and the sequence of evolutionary changes by which these primitive brains evolved into modern brains.Definition of “Living” – Actively Seeking Homeostasis.
…The earliest entities deserving of the term “living” were self-sustaining chemical systems……all theories of early life agree that living systems took an active part in ensuring that the conditions required for their proper operation were met. This means that

  • Any changes in critical variables such as nutrient concentration, temperature, pH, etc. have to be corrected and brought back within an acceptable range.  This is a fundamental task for any living system if it is to remain living.
  • Mechanisms which keep variables within a certain range are usually called “homeostatic” mechanisms
  • Mechanisms generated by evolution are products of a long sequence of modifications and elaborations, all of these performed within living organisms
  • Because the modified organisms have to continue living, evolution does not have full freedom to redesign their internal mechanisms.  Consequently, the modern form of these mechanisms is strongly constrained by their ancestral forms.

Our theories should be similarly constrained.  Therefore, an understanding of the fundamental architecture of the brain can greatly benefit from an understanding of the kinds of behaviors and mechanisms  present at the time when that fundamental architecture was being laid down.

The second kind of homeostasis should not be any more surprising than the first.  If evolution can exploit reliable properties of biochemistry, then it should also be able to exploit reliable properties of geometry and statistics.  That the second kind of homeostasis involves a mechanism which effectively extends its action past the membrane, moving the organism through the environment, does not make it do something other than homeostasis.  Both kinds of mechanisms ultimately serve similar functions – they maintain the conditions necessary for life to continue. They may be described as control mechanisms.Behavior = Control In The Local Environment
Mechanisms whose control extends out through the environment had to exploit consistent properties of that environment.  These properties include statistics of nutrient distributions, Euclidean geometry, Newtonian mechanics, etc.  Today we call such mechanisms “behavior”.

In both cases, the functional architecture takes the form of a negative feedback loop, central to which is the measurement of some vital variable.  Fluctuations in the measured value of this variable outside of some “desired range” initiate mechanisms whose purpose is to bring the variable back into the desired range.

The alternative “control metaphor” being developed here may now be stated explicitly: the function of the brain is to exert control over the organism’s state within its environment .

Briefly, rather than viewing behavior as “producing the right response  given a stimulus”, we should view it as “producing the response that results in the right stimulus ”.  While the first viewpoint has a difficult time deciding what is “right”, the second does not:

  • Animals have physiological demands which inherently distinguish some input (in the sense of “what the animal perceives as its current situation”) as “desirable”, and other input as “undesirable”.  A full stomach is preferred over an empty one; a state of safety is preferred over the presence of an attacking predator
  • This distinction gives motivation  to animal behavior – actions are performed in order to approach desirable input and avoid undesirable input
  • It also gives meaning to their perceptions – some perceptions are cues describing favorable situations, others are warnings describing unfavorable ones which must be avoided.
  • The search for desirable input imposes functional design requirements on nervous systems that are quite different from the functional design requirements for input-output devices such as computers. In this sense, computers make poor metaphors for brains.

Re-Examining the Problem of Meaning
…Perception, Cognition, and Action. These disciplinary boundaries then spill over into large-scale brain theories, yielding a model of the brain with distinct modules separated by putative internal representations.

  • The Perceptual module is separated from the Cognitive module by an internal unified representation of the external world
  • The Cognitive module is separated from the Action module by a representation of the motor plan. These boundaries help to limit the volume of literature that scientists are

Meaning comes long before symbols in both phylogeny (evolutionary history of a species) and ontogeny (developmental history of an individual).  Animals interacted with their environment in meaningful ways millions of years before they started using symbols. Children learn to interact with their world well before they begin to label their perceptions. The invention of symbols, in both phylogeny and ontogeny, is merely an elaboration of existing mechanisms for behavioral control.

…issues that are more fundamental from a biological perspective.

  • In order to survive, organisms have to take an active part in controlling their situation and keeping it within desirable states
  • For an organism to exert control over its environment, there must exist predictable relationships between an action and the resulting stimulation (“motor-sensory” relationships
  • both physiology and behavior can function adaptively only if there exist reliable properties in the organism’s niche which may be exploited toward its survival
  • Biochemical control exploits reliable properties of chemistry, diffusion, fluid dynamics, etc., while behavioral control exploits reliable properties of statistics, geometry, rules of optics, etc.

Affordances
Affordances are opportunities for action for a particular organism.…perception of the world is based upon perception of affordances, of recognizing the features of the environment which specify behaviorally relevant interaction.

An animal’s ecological niche is defined by what its habitat affords.  These relationships between animals and their habitats may be considered precursors to meaning (=)

  • properties of the environment which make adaptive control possible and which guide that control.
  • They make it possible for an organism to establish a behavioral control loop
  • which can be used to approach favorable situations and avoid unfavorable ones.

Because these properties tend to come packaged along with semi-permanent physical objects, we can speak of the “meaning” that these objects have to the organism in question.  However, the crucial point is that the “meaning of an object” is secondary to the meaning of the interactions which the object makes possible .

…a symbol is constructed much later than the sensorimotor strategy which grounds it…In summary, symbols are merely shorthand notation for elements of behavioral control strategies…

Let’s consider communication from the evolutionary perspective which has been used throughout.

  • In order to survive, an organism must exert control over its situation, and this control can only be achieved if there exist reliable relationships between actions and their results
  • While laws of chemistry create opportunity for biochemical homeostasis, laws of geometry, optics, etc. create opportunity for behavioral interaction
  • A behavioral control loop can be constructed wherever consistencies exist in the environment. And of course, such consistencies also exist in the behavior of other animals
  • Animals respond in complex but predictable ways to various stimuli.

Communications
Thus, like physiology and behavior, communication is also an extension of control: one which encompasses other creatures in the environment.  To describe communication merely as “transmission of information” is incomplete…As the system for communication grows in complexity and acquires syntax, the meaning of its elements derives from the behavioral control goals of the speaker.

Making the change in perspective from viewing the brain as an input-output device to viewing it as a control system also leads to a number of important conceptual shifts.

  • A major one is a shift from an emphasis on representations to an emphasis on behaviors
  • from the analysis of serial stages of processing to an analysis of parallel control streamsSecond, motivated action is also not a mystery – when an animal’s physiological state no longer meets its internal demands (like a growing hunger), action is generated so as to bring it to a more satisfying state
  • Third, once one no longer assumes the presence of a complete internal representation of the external world, many forms of the “binding problem” are no longer difficult. When environmental regularities are allowed to take part in behavior, they can give it coherence without need of explicit internal mechanisms for binding perceptual entities together
  • Finally, the shift away from serial representations leads one to reconsider some classic notions concerning consciousness.

 

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