Section_3_Notes

Section_3_Notes - Cognitive Neuroscience Lecture 3 The...

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Cognitive Neuroscience Lecture 3 The underlying premises of this book are that: 1) All cognitive functions, e.g. perception, memory, attention, share the same representational substrate of neurons and their connections. 2) Different functions differ in the portion of that substrate used at any given time. No cognitive function has a fully dedicated cortical area or network. 3) A representational cortical network (cognit) may be used by any and all cognitive functions. This chapter concerns the morphological features of cognits.
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Structure of knowledge in connectionist models Connectionist models of cognition explain the distributed nature of knowledge. Common features of connectionist models: 1) they assume the distribution of knowledge in assemblies of units, neurons, or nodes that represent the component elements of knowledge. 2) the nodes are interconnected in networks by synapses. 3) the networks are layered. 4) some connections between layers are reciprocal, supporting reentrant processing . 5) layers are connected by parallel, convergent, and divergent connections. 6) networks learn by modification of synaptic weights 7) in unsupervised learning , synapses are strengthened by temporal coincidence of pre- and post-synaptic activity
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Categories of knowledge 1) Cognitive function is based on the categorization of knowledge. Knowledge can be categorized according to an astronomical number of criteria. Perceptual categories are organized in cognitive hierarchies of progressive generality and abstraction. Sensory percepts are at the low levels and symbolic percepts at the higher levels. E.g. a picture of a terrier can be categorized as “dog”, “mammal”, “animal”, or “living thing”. It can also be categorized as “Rover”. The picture can be categorized according to its elemental sensory properties, such as size, shape, color, texture, etc. Since the lowest levels of sensory categories appear to be hard-wired at birth, they may be considered to be a part of the phyletic memory of the species. At any hierarchical level, an item can belong to more than one category. E.g. “dog” belongs to the category of “mammal” and the category of “four-legged animals”.
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2) Perception is seen to consist in the classification of sensory items by the binding of features according to Gestalt grouping principles. Examples of grouping principles: a) common motion Motion examples: http://www.ontariosciencecentre.ca/scizone/games/camouflage/default.asp http://www.biomotionlab.ca/Demos/BMLwalker.html b) spatial contiguity (proximity)
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c) temporal contiguity (proximity) Temporal contiguity occurs when two or more stimuli are experienced close together in time and, as a result an association is formed. Tone sequences, or “streams”
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This note was uploaded on 10/21/2011 for the course ISC 5465 taught by Professor Bressler during the Fall '11 term at FAU.

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Section_3_Notes - Cognitive Neuroscience Lecture 3 The...

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