Attention

1. Attention Everyone knows what attention is. It is the taking possession of the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of though. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others. William James (1890)

2. Attention Cognitive brain mechanism that facilitates processing

3. Taxonomy for Attention • Modality • Visual • Auditory • Control • Voluntary: intentional, endogenous, "top-down" • Reflexive: automatic, exogenous, "bottom-up" • Duration • Sustained • Momentary

4. Taxonomy for Attention • Modality • Control • Duration • Intensity • Focused • Selective • Divided

5. Attention Properties • Covert • Limited-capacity metaphors • Bottleneck • Early selection: prior to complete perceptual analysis of elementary features • Late selection: after to complete perceptual analysis of elementary features • Searchlight, spotlight, flashlight • Resources • One capacity or many?

6. Attention Theory • Cherry • Cocktail party effect • Auditory selective attention • Dichotic listening paradigm

7. Attention Theory • Broadbent's (1958) information-processing model • Limited-capacity • Early-selection • Top-down • But, can't explain intrusion of unattended input

8. Attention Theory • Late-selection theories • Deutsch & Deutsch • Treisman • Unattended sensory input attenuated at early stage, but not filtered out • High priority unattended input can reach semantic analysis stage

9. Cognitive Psychologyof Visual-spatial Selective Attention • Eriksen Flanker Task • Posner Cueing Task • Treisman Visual Search Task • Wolfe Visual Search Task

10. Eriksen Flanker Task Congruent AAA Incongruent EAE Neutral XAX

11. Eriksen Flanker Task Incongruent E A E E A E E A E

12. Eriksen Flanker Task • Searchlight of spatial attention about 1 degree of visual angle

13. Posner Cueing Task • Voluntary orienting of selective attention • Costs and benefits of intended covert attention shifts

14. Other Cueing Tasks • Reflexive orienting of selective attention • Abrupt onset visual stimulus at target location • Attentional "capture" • Time-dependent costs and benefits of unintended covert attention shift • Inhibition of return (>300 ms)

15. Treisman Visual Search Task • Preattentive • Pop-out search • Flat search function • Attentive • Conjunctive search • Serial search function • Moving spotlight • Guided • Conjunctive search of items that share a feature with the target

16. Wolfe Visual Search Task • Costs of voluntary control of attentional spotlight

17. Neurophysiology of Spatial Selective Attention Cortical or subcortical? • Need good temporal resolution to answer this question

18. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary auditory attention • Hillyard's N1 effect • Woldorff and Hillyard’s P20-50 and M20-50 effects

19. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary visual attention

20. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary visual attention • P1 effect for sustained covert attention

21. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary visual attention • P1 effect for cued covert attention

22. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Reflexive visual attention • P1 effect for cued automatic attention • Enhancement at short ISI • Inhibition at long ISI: Inhibition of return

23. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary visual attention • P1 effect for visual conjunction search

24. Neurophysiology of Spatial Selective Attention • ERP and MRF Evidence • Voluntary visual attention • N2pc (posterior contralateral) effect for visual conjunction search

25. Neurophysiology of Spatial Selective Attention • Summary of ERP and MRF Evidence • Supports early-selection models • Sensory information enhanced/attenuated by attention to spatial location • Selection occurs at least as early as secondary sensory cortex • Similar effects for both voluntary and reflexive attention

26. Neurophysiology of Spatial Selective Attention • Functional Neuroimaging Evidence • Summary of PET studies of visual selective attention

27. Neurophysiology of Spatial Selective Attention • Functional Neuroimaging Evidence • Attention control • Posner and Petersen's (1990) anterior and posterior attention systems • Anterior - executive control • Posterior - spatial attention

28. Neurophysiology of Spatial Selective Attention • Functional Neuroimaging Evidence • Jovicich et al. (2001) attentional load during motion tracking • Parametric fMRI • Additive factors type methodology that fits polynomial functions to the experimental manipulation levels (L) • Brain Activity = a0 + a1L1+ a2L2+ a3L3 + ...

29. Neurophysiology of Spatial Selective Attention • Functional Neuroimaging Evidence • Hopfinger et al. (2000) spatial cueing study • Event-related fMRI • Top-down attentional control

30. Neurophysiology of Spatial Selective Attention • Animal Single-Unit Evidence • Cortical activity and voluntary orienting • Moran and Desimone (1985) • V4 neurons • Wurtz et al. (1982) • Parietal neurons

31. Neurophysiology of Spatial Selective Attention • Animal Single-Unit Evidence • Subcortical activity and reflexive orienting • Wurtz et al. (1982) • Superior colliculus neurons

32. Hemineglect And Extinction

33. Neglect Failure to acknowledge objects in the field contralateral to the lesion, without perceptual deficit.

34. Extinction • Failure to respond to stimuli in the contralesional field when presented simultaneously with an ipsilesional stimulus.

35. Patients with neglect may: • fail to dress the left side of their body • disclaim “ownership” of left limbs • not recognize familiar people presented on the left side • scan only the right side of a dream • deny the illness

36. Some studies observed that: • Shifting visual field by 10o to the right eases the symptoms for some minutes • Between 38% and 69% of patients recover within 3 months • Extinction tends to persist longer • Neglect deficit can be improved by increasing activation of the sustained attention system

37. Explanatory Hypotheses • LOSS OF ABILITY TO ANALYSE SPATIAL PATTERNS • Neglect occurs only with lesion on the right hemisphere. • ATTENTIONAL DEFICIT • Single cell recordings in monkeys indicate firing in posterior parietal cortex during attention tasks.

38. Explanatory Hypotheses • Arousal • Each side of the brain has separate activation mechanisms. • Representational • Neglect results from inability to form a representation of the whole space.

39. Explanatory Hypotheses • Orienting • Each hemisphere operates attention shifting to the opposite direction in both hemispaces. Hemineglect results from damage in one hemisphere.

40. Posner et al. (1984) Interpretation: Attention happens in 3 stages:  disengagement shifting re-engagement

41. Posner et al. (1984) • Conclusions: • Temporal-parietal lobe is involved in contralesional disengagement • Engagement to the new target may rely on frontal sites

42. Raffal and Posner (1987) • Temporal-parietal junction e disengagement • Midbrain e shift • Thalamus e engagemant

44. Is there any processing in the neglected field?

45. Eglin et al. (1989) Neglect victims perform poorly at target detection on contralesional side, and performance worsens with presentation of stimuli to the ipsilesional side.

46. Volpe et al. (1979) Neglect patients can make ‘accurate’ same-different judgments between stimuli in the intact versus neglected visual field, even when they cannot identify the neglected item.

47. Grabowecky et al. (1993) Target detection in the neglected field is enhanced by increasing stimuli in the same field.

48. Neglect victims seem to process color, shape, and even meaning in the damaged hemifield, without ever being aware of the stimuli.

49. Does neglect affect visual memory?

50. Bisiach & Luzzatti (1978) Conclusion: Attention to material in visual-spatial memory is affected by damage in the parietal and posterior temporal lobes.