We characterize manic-depression in terms of symbolic logic and dynamical systems, and describe a computer simulation used to develop our theory. A formal theory of cognitive deficit has four parts. (1) For a normal representation we use the concept of sound and complete “self-axioms.” (2) Normal processing occurs when changes in our personal environment trigger a search for a new set of sound and complete self-axioms. (3) Deficits can lead to unsound judgement in mania and incomplete judgement in depression. (4) Adaptation may consist of attempts to suppress or use the changes in reasoning style. Since manic-depression involves changes in the temporal organization of mood and judgement, it can be classified as a dynamical disease. Nonlinear dynamical systems exhibit transitions between steady state, periodic, and chaotic behavior. We illustrate our approach with a computer simulation that searches through a small set of “self-axioms” while exhibiting periodic and chaotic behavior. In conclusion we conjecture that manic-depression may represent a bifurcation from the chaotic dynamics of normal emotional lability to the pathological periodicity of affective illness.
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