the work of betty tuller and complex systems
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The Work of Betty Tuller and Complex Systems. John Cadwallader PSB 4065. Complex Systems. Composed of a large number of simple agents interacting with one another according to specified rules. Share universal patterns. Complex Systems. Examples: Molecules in a liquid Genes in a cell - PowerPoint PPT PresentationTRANSCRIPT
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The Work of Betty Tuller The Work of Betty Tuller and Complex Systemsand Complex Systems
John CadwalladerJohn Cadwallader
PSB 4065PSB 4065
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Complex SystemsComplex Systems
• Composed of a large number of simple agents interacting with one another according to specified rules.
• Share universal patterns.
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Complex SystemsComplex Systems
• Examples:– Molecules in a liquid– Genes in a cell– Organisms in an ecosystem– Buyers/sellers in an economy– ISPs on the internet– Neurons in a brain?!?!?
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Complex SystemsComplex Systems
• Share Common Properties:– Phase transitions– Order parameter(s)– Control parameter(s)– “Slaving”– Enhanced contrast– Hysteresis– Others…
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Phase TransitionsPhase Transitions
• Rayleigh-Bernard Instability
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Order and Control ParametersOrder and Control Parameters
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SlavingSlaving
• Analogy: state of an army can be described without reference to any individual soldier. The state of every soldier is a slave to the state of the army. In understanding the system we don’t have to worry about every single degree of freedom.
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HysteresisHysteresis
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How does all of this apply to How does all of this apply to behavior?behavior?
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Speech Categorization: Tuller et al. Speech Categorization: Tuller et al. 19941994
• How do we determine what a person’s utterance means?– Different people say the same word
differently.– The same word can sound different in
different environments.– Same-sounding words can have different
meanings.
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Speech Categorization: Tuller et al. Speech Categorization: Tuller et al. 19941994
• Used a “say” – “stay” continuum
• Varied the gap between the “s” and the rest of the word.
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Speech Categorization: Tuller et al. Speech Categorization: Tuller et al. 19941994
• Order parameter: interpretation of stimulus
• Control parameter: interval between s and rest of word
• Patterns:– Hysteresis– Enhanced contrast
• Indicative of complex systems-like behavior
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Speech Categorization: Tuller et al. Speech Categorization: Tuller et al. 19941994
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P. Kruse et al 1996P. Kruse et al 1996
• The perception of multistable visual objects• Different groups of lights flash alternately
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P. Kruse et al 1996P. Kruse et al 1996
• Percepts range from:– No apparent motion– Alternating motion– Unidirectional motion– Bidirectional motion– All lights appear on
simultaneously
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P. Kruse et al 1996P. Kruse et al 1996
• Order parameter: type of motion observed
• Control parameter: interval between lights
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P. Kruse et al 1996P. Kruse et al 1996
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Freeman 1997Freeman 1997
• Olfactory coding• How does olfactory bulb recognize
different odors?• No one-to-one correspondence between
odorant and cells in the olfactory bulb.• Even lesioning areas of the bulb that are
most activated by a particular odorant does not prevent the animal from recognizing the odorant.
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Freeman 1997Freeman 1997
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ConclusionsConclusions
• Complex systems approach offers powerful method for understanding macro-scale brain function
• Also offers direct path for simulating brain function on computers, something the cognitive approach and behavioristic approach do not allow (in any straightforward manner)