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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
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
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