Read this article for Wednesday: A Neural Basis for Visual Search in Inferior Temporal Cortex...
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Transcript of Read this article for Wednesday: A Neural Basis for Visual Search in Inferior Temporal Cortex...
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:
oThe experimental would work like this:
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
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:
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• 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
attending LEFTIgnoring RIGHT