Disorders of Attention Orienting

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

2. Hemispatial Neglect • Unilateral lesion to Parietal or Temporo-Parietal are • Patients present with vision problems, but are not “blind” • Rather, they fail to apprehend (and interact appropriately with) stimuli in the contralesional field

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

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

5. 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

6. 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

7. 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

8. Investigation of Neglect with Cue-Target Paradigm • Interpretation: parietal lobe mediates a disengagement of attention in order to shift to another stimulus • Right parietal lesions tend to be more disruptive • Indicates that Rt. Parietal is disproportionately involved in spatial orienting in most people

9. Attention “Disorders” in Normal Subjects • A number of illusions/demonstrations exist that give us a hint of what it might be like to have a disorder of attention • Inattentional or “change” blindness can occur when something interferes with the normal attention orienting system • Object substitution demonstrates consequence of attending to only one of two objects at the same location