Read this article for Wednesday:

1. Read this article for Wednesday: A Neural Basis for Visual Search in Inferior Temporal Cortex Leonardo Chelazzi et al. (1993) Nature

2. 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:

3. Attention Orienting System and Associated Disorders Neglect, Extinction and Balint’s Syndrome

4. What system orients attention through space • Corbetta et al. (1993) • Subjects oriented attention according to a light moving in the visual field

5. 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

6. 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)

7. 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

8. Hemispatial Neglect • E.g. line bisection task

9. Hemispatial Neglect • E.g. reproducing visual forms

10. Orienting Attention • Posner Cue - Target Paradigm: Subject presses a button as soon as x appears

11. Orienting Attention • Posner Cue - Target Paradigm:

12. Orienting Attention • Posner Cue - Target Paradigm:

13. Orienting Attention • Posner Cue - Target Paradigm:

14. Orienting Attention • Posner Cue - Target Paradigm: X

15. Orienting Attention • Posner Cue - Target Paradigm:

16. Orienting Attention • Posner Cue - Target Paradigm: That was a validly cued trial because the x appeared in the box that flashed

17. Orienting Attention • Posner Cue - Target Paradigm:

18. Orienting Attention • Posner Cue - Target Paradigm:

19. Orienting Attention • Posner Cue - Target Paradigm: X

20. Orienting Attention • Posner Cue - Target Paradigm:

21. Orienting Attention • Posner Cue - Target Paradigm: That was an invalidly cued trial because the x appeared in the box that didn’t flash

22. 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

23. Attention as Information Selection • Visual search • auditory “Cocktail Party” problem • somatosensory “I don’t feel my socks” problem

24. Attention as Information Selection

25. 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

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

27. Late vs. Early • Various hybrid models have been proposed • Early attenuation of non-attended input • Late enhancement of attended input

28. Electrophysiological Investigations of Attention

29. 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

30. 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