December 1, 2009Introduction to Cognitive Science Lecture 22: Neural Models of Mental Processes 1...

December 1, 2009 Introduction to Cognitive Science Lecture 22: Neural Models of Mental Processes

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Some YouTube movies:Some YouTube movies:

The Neocognitron Part I:The Neocognitron Part I:http://www.youtube.com/watch?v=Qil4kmvm2Sw

The Neocognitron Part II:The Neocognitron Part II:http://www.youtube.com/watch?v=oVYCjL54qoY

Automatic license plate recognition:Automatic license plate recognition:http://www.youtube.com/watch?v=3GJWvsUIiyk

Evolution of neural network robotic controllers:Evolution of neural network robotic controllers:http://www.youtube.com/watch?v=lmPJeKRs8gE

http://www.youtube.com/watch?v=Qil4kmvm2Sw

http://www.youtube.com/watch?v=oVYCjL54qoY

http://www.youtube.com/watch?v=3GJWvsUIiyk

http://www.youtube.com/watch?v=lmPJeKRs8gE


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Review of Neural Network FactsReview of Neural Network Facts• In biological systems, neurons of similar In biological systems, neurons of similar

functionality are usually organized in separate functionality are usually organized in separate areasareas (or (or layerslayers).).

• Often, there is a Often, there is a hierarchyhierarchy of interconnected layers of interconnected layers with the lowest layer receiving sensory input and with the lowest layer receiving sensory input and neurons in higher layers computing more complex neurons in higher layers computing more complex functions.functions.

• For example, neurons in macaque visual cortex For example, neurons in macaque visual cortex have been identified that are activated only when have been identified that are activated only when there is a there is a face face (monkey, human, or drawing) in the (monkey, human, or drawing) in the macaque’s visual field.macaque’s visual field.


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“Data Flow Diagram”of Visual Areas inMacaque Brain

Blue:motion perception pathway

Green:object recognition pathway


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Receptive Fields in Hierarchical Neural NetworksReceptive Fields in Hierarchical Neural Networks

neuron A

receptive field of A


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Receptive Fields in Hierarchical Neural NetworksReceptive Fields in Hierarchical Neural Networks

receptive field of A in input layer

neuron Ain top layer


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Visual AttentionVisual AttentionThe attentional cueing task introduced by Michael Posner The attentional cueing task introduced by Michael Posner gives insight into the dynamics of visual attention.gives insight into the dynamics of visual attention.

Subjects are instructed to fixate on the central cross.Subjects are instructed to fixate on the central cross.

One of the two boxes flashes to capture the subject’s One of the two boxes flashes to capture the subject’s attention (an automatic, involuntary response).attention (an automatic, involuntary response).

After some a short delay (stimulus onset asynchrony - After some a short delay (stimulus onset asynchrony - SOA) an asterisk appears in one of the boxes.SOA) an asterisk appears in one of the boxes.

The subject has to report as quickly as possible in which The subject has to report as quickly as possible in which box the asterisk appeared.box the asterisk appeared.


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The Posner Attention TaskThe Posner Attention Task

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For short SOAs (< 200 ms), subjects respond For short SOAs (< 200 ms), subjects respond fasterfaster if if flash and asterisk appear on the same side.flash and asterisk appear on the same side.

Cueing of attention to relevant location allowsCueing of attention to relevant location allows faster response. faster response.

For longer SOAs, subjects respond For longer SOAs, subjects respond more slowly more slowly if if flash and asterisk appear on the same side.flash and asterisk appear on the same side.

Inhibition-of-Return mechanism makes attention Inhibition-of-Return mechanism makes attention less likely to remain on the side of the flash until the less likely to remain on the side of the flash until the asterisk appears.asterisk appears.


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The FrThe Frööhlich Effecthlich Effect

The Fröhlich effect is a localization error that occurs The Fröhlich effect is a localization error that occurs when observers are asked to indicate the initial when observers are asked to indicate the initial position of a fast moving stimulus. position of a fast moving stimulus.

Compared to the actual starting location, the Compared to the actual starting location, the perceived starting location is shifted in the direction of perceived starting location is shifted in the direction of motion.motion.

This perceptual illusion was named after Friedrich This perceptual illusion was named after Friedrich Fröhlich, a German physiologist who discovered the Fröhlich, a German physiologist who discovered the phenomenon more than 80 years agophenomenon more than 80 years ago..


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The FrThe Frööhlich Effecthlich Effect

Today the most widely accepted explanation of this Today the most widely accepted explanation of this effect is given by the “effect is given by the “Asynchronous Updating ModelAsynchronous Updating Model”” (Scharlau & Neumann, 2003)(Scharlau & Neumann, 2003)..

This model This model states that the stimulus onset triggers an states that the stimulus onset triggers an attention shift towards its location. attention shift towards its location.

During the shift the stimulus changes its location, and During the shift the stimulus changes its location, and because the conscious perception depends on the because the conscious perception depends on the stimulus being attended, a later position is consciously stimulus being attended, a later position is consciously perceived as being the first position.perceived as being the first position.


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The FrThe Frööhlich Effecthlich EffectWe tried to build a quantitative, neural model of the We tried to build a quantitative, neural model of the relevant parts of the visual system to explain this effect.relevant parts of the visual system to explain this effect.

This model includes a vision hierarchy (simple features This model includes a vision hierarchy (simple features and small receptive fields in lower layers, complex and small receptive fields in lower layers, complex features and large receptive fields in higher layers).features and large receptive fields in higher layers).

In this hierarchy, processing of visual input is done in In this hierarchy, processing of visual input is done in bottom-up direction, and attentional modulation (selective bottom-up direction, and attentional modulation (selective enhancement of processing) works in a top-down enhancement of processing) works in a top-down fashion.fashion.


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The FrThe Frööhlich Effect Modelhlich Effect Model


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The FrThe Frööhlich Effect - Resultshlich Effect - Results


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December 1, 2009Introduction to Cognitive Science Lecture 22: Neural Models of Mental Processes 1...

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