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Read this article for Wednesday:. A Neural Basis for Visual Search in Inferior Temporal Cortex Leonardo Chelazzi et al. (1993) Nature. How are you doing on your projects?. By now you should have sorted out: The theory is that: The prediction is that:

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Read this article for wednesday

Read this article for Wednesday:

A Neural Basis for Visual Search in Inferior Temporal Cortex

Leonardo Chelazzi et al. (1993) Nature


How are you doing on your projects

How are you doing on your projects?

By now you should have sorted out:

The theory is that:

The prediction is that:

The best technique to test the prediction is:

The experimental would work like this:


Attention orienting system and associated disorders

Attention Orienting System and Associated Disorders

Neglect, Extinction and Balint’s Syndrome


What system orients attention through space

What system orients attention through space

  • Corbetta et al. (1993)

    • Subjects oriented attention according to a light moving in the visual field


Orienting spatial attention

Orienting Spatial Attention

  • Results:

    • Parietal and Pre-motor areas were activated by attention tracking task

    • Hemisphere of activation depended somewhat on which visual field attention was being shifted in


Orienting spatial attention1

Orienting Spatial Attention

  • Result:

    • Cue-related activations indicate a distributed network that mediates voluntary orienting

    • Network includes mainly frontal and parietal structures, mainly on the left side (keep this in mind for discussing neglect)


Hemispatial neglect

Hemispatial Neglect

  • Unilateral lesion to Parietal or Temporo-Parietal Junction

  • Patients present with vision problems, but are not “blind”

    • Rather, they fail to apprehend (and interact appropriately with) stimuli in the contralesional field


Hemispatial neglect1

Hemispatial Neglect

  • E.g. line bisection task


Hemispatial neglect2

Hemispatial Neglect

  • E.g. reproducing visual forms


Orienting attention

Orienting Attention

  • Posner Cue - Target Paradigm:

Subject presses a button as soon as x appears


Orienting attention1

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention2

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention3

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention4

Orienting Attention

  • Posner Cue - Target Paradigm:

X


Orienting attention5

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention6

Orienting Attention

  • Posner Cue - Target Paradigm:

That was a validly cued trial because the x appeared in the box that flashed


Orienting attention7

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention8

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention9

Orienting Attention

  • Posner Cue - Target Paradigm:

X


Orienting attention10

Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting attention11

Orienting Attention

  • Posner Cue - Target Paradigm:

That was an invalidly cued trial because the x appeared in the box that didn’t flash


Investigation of neglect with cue target paradigm

Investigation of Neglect with Cue-Target Paradigm

  • Posner et al. (late 1970s) used a cue-target paradigm

  • Parietal Lobe patients are profoundly impaired only when invalidly cued to attend to the ipsilesional (good) side


Attention as information selection

Attention as Information Selection

  • Visual search

  • auditory “Cocktail Party” problem

  • somatosensory “I don’t feel my socks” problem


Attention as information selection1

Attention as Information Selection


Early selection

Early Selection

  • Early Selection model postulated that attention acted as a strict gate at the lowest levels of sensory processing

  • Based on concept of a limited capacity bottleneck


Late selection

Late Selection

  • Late Selection models postulated that attention acted on later processing stages (not sensory)


Late vs early

Late vs. Early

  • Various hybrid models have been proposed

    • Early attenuation of non-attended input

    • Late enhancement of attended input


Electrophysiological investigations of attention

Electrophysiological Investigations of Attention


Modulation of auditory pathways

Modulation of Auditory Pathways

attending LEFT

Ignoring RIGHT

  • Hillyard et al. (1960s) showed attention effects in human auditory pathway using ERP

  • Selective listening task using headphones

    • Every few minutes the attended side was reversed

    • Thus they could measure the brain response to identical stimuli when attended or unattended

beep beep beep beep boop beep

beep beep beep boop beep beep


Modulation of auditory pathways1

Modulation of Auditory Pathways

  • Result: ERP elicited by attended and unattended stimuli diverges by about 90ms post stimulus

    • Long before response is made

    • Probably in primary or nearby auditory cortex


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