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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:

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:

The best technique to test the prediction is:

The experimental would work like this:


Attention Orienting System and Associated Disorders

Neglect, Extinction and Balint’s Syndrome


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

  • 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 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

  • 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 Neglect

  • E.g. line bisection task


Hemispatial Neglect

  • E.g. reproducing visual forms


Orienting Attention

  • Posner Cue - Target Paradigm:

Subject presses a button as soon as x appears


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:

X


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:

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


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:


Orienting Attention

  • Posner Cue - Target Paradigm:

X


Orienting Attention

  • Posner Cue - Target Paradigm:


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

  • 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

  • Visual search

  • auditory “Cocktail Party” problem

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


Attention as Information 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 models postulated that attention acted on later processing stages (not sensory)


Late vs. Early

  • Various hybrid models have been proposed

    • Early attenuation of non-attended input

    • Late enhancement of attended input


Electrophysiological Investigations of Attention


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 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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