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

2. Orienting Spatial Attention Corbetta et al. (1993) – Subjects oriented attention according to a light moving in the visual field

3. Orienting Spatial Attention Results: – Parietal and Pre-motor areas were activated by attention tracking task – Hemisphere of activation depended on which visual field attention was being shifted in

4. Orienting Spatial Attention Corbetta et al (1993) confounded stimulus w/ orienting Hopfinger et al. (2000) used event-related fMRI to identify top-down orienting processes (distinct from stimulus-driven processes) – Cue-target paradigm using arrows – What is the brain activity caused by the cue?

5. 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)

6. Orienting Spatial Attention Result: – Directly contrasting cue vs. target reveals an attention orienting network distinct from a target processing network Cue activity > Target activityTarget activity > Cue activity

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. 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 attended to the ipsilesional (good) side

11. Extinction Extinction is a more complicated aspect of neglect Patients fail to apprehend objects in the contralesional field when stimuli are present in the ipsilesional field

12. Balint’s Syndrome Bilateral parietal lesions Patients fail to apprehend all but one of simultaneously presented objects at the same location Condition is object-based, not location-based – Multi-colored dots are properly seen if they are connected by lines

13. Balint’s Syndrome