Attention I

1. Attention I Attention Wolfe et al Ch 7

2. Dana said that most vision is agenda-driven. He introduced the slide where the people attended to the many weird surrounding objects before the test (including the upside-down cow). However, during the test, they only attended to the purple blocks (when they had an agenda), though there was still some attention given to other objects. Is it possible to completely ignore the other objects? Also, if the screen were blank until the absolute beginning of the test and the subject was told to only attend to "the purple blocks," would they be able to consciously ignore the other objects without first getting a survey of the entire image? We know that processing stimuli is limited; we simply cannot (or do not) see everything in a scene. However, is this something that can be trained (and the processing availability increased), in, for example, people that are private detectives or military jobs, etc.? Top-down and bottom-up signals of attention control are not totally separated, and my question is where are they integrated? A paper by Thompson et al. (2005) shows that FEF has a salience map that topologically integrate those signals as revealed by error signals. Do you know any other regions also have similar or different mechanisms that integrate bottom-up and top-down signals?

8. What is attention? • Arousal: a global state, ‘alertness’ Asleep Awake drowsy alert hyper • Attention: selective allocation of resources to certain stimuli, normally at the expense of other stimuli

9. Selective attention Asleep Awake drowsy alert hyper

10. What guides attention?

12. What guides attention?

13. What guides attention?

14. Why do we need attention? • Process behaviorally relevant stimuli • Filter out the irrelevant stimuli • Limited processing resources • Too much information

15. Why do we need attention? • Process behaviorally relevant stimuli • Filter out the irrelevant stimuli • Limited processing resources • Too much information

16. What guides attention? • Exogenous (from outside) • reflexive • automatic • naturally salient • ‘bottom up’ • Endogenous (from within) • voluntary • goal directed • prior knowledge • ‘top down’

17. Endogenous cues (Posner paradigm)

18. Endogenous cues (Posner paradigm) Faster reaction times for validly cued trials → benefit of attention being directed to target location

19. Another way of thinking about how attention is controlled • Virtual Humanoid has a small library of simple visual behaviors (modules): • Follow Sidewalk • Pick Up Blocks • Avoid Obstacles Modules use visual routines to update their state information Sprague, Ballard, & Robinson TAP (2007) Each behavior uses a limited,task-relevant selection of visual information from scene. Behaviors have different priority/ reward value.

20. Why do we need attention? • Too much information • Limited processing resources • Process behaviorally relevant stimuli • Filter out the irrelevant stimuli

21. Stroop Effect What color is the font? green blue yellow black brown pink

22. What color is the font?

23. The information that is processed is not entirely under the observer’s control. ie exogenous can trump endogenous in this case. But reading a work is clearly not “reflexive”. Need to re-think this simple classification.

24. Why do we need attention? • Too much information • Limited processing resources • Process behaviorally relevant stimuli • Filter out the irrelevant stimuli

25. Processing bottlenecks Attentional Blink (RSVP rapid serial visual presentation) Target 11 stimuli per second What is the likelihood of detecting a second target based on its distance from the first?

26. Processing bottlenecks Attentional Blink (RSVP) First Target Second 11 stimuli per second Processing of first target interferes with the ability to process the second

27. Is “limited processing resources” the right way to think about it? Fundamental sequential nature of processing perhaps results from the sequential nature of actions.

28. When does attention exert its influence? Broadbent model - gating early based on fundamental physical characteristics (e.g., color, frequency, location) determining what needs to be processed • Early selection - low level gating mechanism that filters (or attenuates) irrelevant information before completion of perceptual analyses

29. Auditory selective attention Dichotic listening At what stage of stimulus processing does attention come into play? ERPs a good index shadowing

30. When does attention exert its influence? • Early selection - low level gating mechanism that filters (or attenuates) irrelevant information before completion of perceptual analyses Triesman model - adaptive filter that attenuates irrelevant information in a flexible manner (some unattended information would make it through)

31. When does attention exert its influence? Hybrid model - filtering at various processing levels depending on the needs for the task where perceptual load influences how much is filtered • Late selection - all stimuli are processed through completion before attentional selection occurs

32. Attention and the brain 1 • Dynamic interaction between attentional control network and stimulus processing regions • Attention modifies the way you perceive the world and your behavior 2

33. Auditory ERPs to a tone Compare ERPs for attended vs. unattended ear at these different stages Early brainstem (10 ms): Auditory brainstem nuclei Early cortical (10-50 ms): Primary auditory cortex Late cortical (>100 ms): Auditory association areas

34. Early vs. late selection in audition * Deviant tone

35. Early vs. late selection in audition * Deviant tone Between Ears → Early Selection

36. Early vs. late selection in audition * Deviant tone Within Attended → Late Selection Between Ears → Early Selection

37. Early vs. late selection in audition No brainstem

38. Early vs. late selection in audition Early cortical

39. Effects on stimulus processing 1 • Enhancing the gain (increasing activity)? • Extending the duration of the processing? • Narrowing the tuning curves of relevant neurons?

40. Effect on V4 neurons Reduced activity even though an effective stimulus in receptive field

41. Effect on V4 neurons Tuning curve unaffected Spike rate increased → affect on gain

42. Attentional effects on features Attention to motion enhances MT+ signal Attend to moving or attend to stationary

43. Summary • Attention is the selective allocation of resources to certain stimuli and the ability to filter out distracting ones • Endogenous and exogenous factors influence attention • Attention modulates the activity of multiple brain regions (evidence for early and late effects) • Attention mainly affects the gain (the amplitude) of sensory regions (??)