• What is attention directed to?………………………………………….……28

   

  1. Space-based attention ……………………………………………….28

   

  1. Feature-based attention………………………………………………28

   

  1. Object-based attention…………………………………..…..….……29

 

• Sources and targets of attention in the brain…………………………….…31

 

• Attention modulates different response properties…………………..……..31

   

  1. Firing rate modulation………………….……………………………32

      

     1. Response enhancement.……………………….…………..…….32

      

     1. Response suppression…………………………………………33

 

 

• Baseline enhancement………………………………..………34

 

 

1. Reliability increase……………………………………….………….36

 

1. Response sensitivity increase……………………………….……….37

 

1. Response selectivity modulation…………………………….………38

 

1. Synchronization, oscillation and correlated responses across cell population…………………………………………………………….39

 

Objectives……………………………………………………………………..….42

 

Method……………………………………………………………………………43

 

 

1. Subjects………………………………………………………….…………43

 

1. Stereotactic MRI……………………………………………….…………..43

 

1. Head-post implantation surgery.……………………….…………………..44

 

1. Stimuli…………………………………………………….………………..46

 

1. Tasks…………………………………………………………………………47

    

   1. Passive task…………………………………………………………..47

    

   1. Active task (two-alternative forced-choice body/object categorization)……………………………………………………….47

 

1. Training…………………………………………………….………………50

 

1. Eye monitoring………………………………………………….………….52

 

1. Craniotomy surgery …………………………………………….………….52

 

1. Recording………………………………………………………….……….53

    

   1. Recoded area…………………………………………………….…..54

    

   1. Recording room…………………………………………….………..54

    

   1. Data acquisition setup…………………………………………….…54

    

   1. Noise reduction………………………………………………….…..55

    

   1. Electrode insertion ………………………………………………….56

    

   1. Signal amplification and frequency filtering ……………………….57

 

1. Data analysis……………………………………………………..…………59

    

   1. Category selectivity index…………………………………….……..60

    

   1. High and low baseline trials………………………………….………60

    

   1. RMI (rate modulation index)……………………………………..…61

    

   1. FF (fano factor)………………………………………………….…..61

    

2.  

   1. 

   2.  

      FFMI (fano factor modulation index)…………………………….…61

    

   1. CP (choice probability)………………………………………………62

    

   1. RMI onset……………………………………………………………65

    

   1. Neural/behavioral score……………………………………………..66

    

   1. Peristimulus time histograms (PSTH), normalizing and smoothing ……………………………………………………………………….67

 

 

 

Results…………………………………………………………………………….68

 

Conclusion………………………………………………………………………..88

 

Figures……………………………………………………………………………90

 

 

 

 

 

 

3. Stimulus set …………………………………….……………..….90

 

3. Figure 2. Different noise levels of an exemplar stimulus ……………….…91

 

3. Figure 3. Passive task……………………………………………………….92

 

3. Figure 4. Active task (two-alternative forced-choice body/object categorization…………………………………………………………….…93

 

3. Figure 5. Monkeys’ performance in body/object categorization task. …….95

 

3. Figure 6. The pattern of performance decline as a function of noise level was reverse for bodies and objects …………………………………………….. 96

 

3. Figure 7. Monkeys’ performance in body/object categorization task for subcategories …………………………………………………………..…..97

 

3. Figure 8 .Performance decline between adjacent signal levels in subcategories of bodies and objects ……………………………….………98

 

3. Figure 9. Behavioral d́ (d́ = Z “hit rate” – Z “false alarm”) in different visual signals ……………………………………………………………….…….. 99

 

3. Figure 10. Cumulative d́ in signal level of 90 ……………………….……100

 

3. Figure 11. Reaction time in different signal conditions in correct and wrong trials……………………………………………………………………….101

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12. Figure 12. Reaction time in subcategory level……………………………102

 

12. Figure 13. Relation between reaction time and performance in different signal levels…………………………………………………………….…103

 

12. Figure 14. Mean number of microsaccades in different noise levels……..104

 

12. Figure 15. Mean number of microsaccades in correct and wrong trials of different signal levels……………………………………………………..105

 

12. Figure 16. Reaction time in trials with and without microsaccades in different signal levels…………………………………………………..…106

 

12. Figure 17. Normalized mean firing rate of body cells across different visual signals and behavioral conditions…………………………………….…..107

 

12. Figure 18. Normalized mean firing rate of non-body cells across different visual signals and behavioral conditions…………………………………..109

 

12. Figure 19.Response modulation index (RMI) as a function of task difficulty……………………………………………………………….….111

 

12. Figure 20. Mean response modulation onset across body image signal levels in body cells’ correct trials…………………………………………….….112

 

12. Figure 21. Attentional enhancement of IT cells’ body-object discriminability (d’) was observed only in correct trials and degree of enhancement depended on task difficulty………………………………………………………..…114

 

12. Figure 22. Mean d’ modulation in correct (blue) and wrong (black) compared to passive condition in body cells…………………………………………116

 

12. Figure 23. Mean d’ modulation in correct (blue) and wrong (black) compared to passive condition in non-body cells……………………………………117

 

12. Figure 24. Temporal pattern of baseline firing rate modulation in active compared to passive condition…………………………………………….118

 

12. Figure 25. Temporal pattern of p-values of t-tests measuring significant increase of baseline rate in active compared to passive condition……..…119

 

12. Figure 26. Frequency distribution of proportion of HBTs in body (top) and non-body (bottom) cells during active task…………………………….…120

 

12. Figure 27. Baseline dependent enhancement of body and suppression of non-body cells’ responses to presentation of body images in correct condition……………………………………………………………….….121

 

12. Figure 28. Baseline dependent enhancement of body and suppression of non-body cells’ responses to presentation of body images in wrong condition………………………………………………………………..…122

 

12. Figure 29. Temporal dynamic of body and non-body cells’ RMI to presentation of body images in correct and wrong conditions for HBTs………………………………………………………………………123

 

12. Figure 30. Temporal dynamic of body and non-body cells’ RMI to presentation of body images in correct and wrong conditions for LBTs…124

 

12. Figure 31. P-values of t-tests measuring significant enhancement of body and suppression of non-body cells’ responses in HBTs as time window to define high baseline activity varied over time…………………………….125

 

12. Figure 32. P-values of t-tests measuring significantly larger RMI values of body and smaller RMI values of non-body cells’ in HBTs vs. LBTs as time window to define high vs. low baseline activity varied over time…….….126

 

12. Figure 33. Body cells’ RMI values of high and low baseline trials across body stimulus signal levels…………………………………………….…127

 

12. Figure 34. Baseline dependent modulation of body and non-body cells’ responses to presentation of object images…………………………….…129

 

12. Figure 35. Baseline dependent modulation of body and non-body cells’ responses to presentation of object images…………………………….…130

 

12. Figure 36. Temporal dynamics of body and non-body cells’ RMI to presentation of object images in correct and wrong conditions for HBTs………………………………………………………………………131

 

12. Figure 37. Temporal dynamics of body and non-body cells’ RMI to presentation of object images in correct and wrong conditions for LBTs………………………………………………………………………132

 

12. Figure 38. Frequency distribution of adjusted RMI values for body and non-body cells in HBTs and LBTs………………………………………….…133

 

12. Figure 39. Rate-matched fano factor modulation index (FFMI) of body and non-body cells to presentation of body images in correct condition for HBTs vs. LBTs………………………………………………………………..…134

 

12. Figure 40. Rate-matched fano factor modulation (FFMI) of body and non-body cells to presentation of object images in correct conditions for HBTs and LBTs. …………………………………………………………………135

 

12. Figure 41a. Frequency distribution of normalized d’ modulation difference in LBTs vs. HBTs for body and non-body cells…………………………..136

 

12. Figure 41b. The impact of task specific attentional modulation on firing rate depends on cells’ category selectivity……………………………………..137

 

12. Figure 42. The impact of task specific attentional modulation on firing rate depends on cells’ category selectivity………………………………….…138

 

12. Figure 43. Comparison of RMI values of correct vs. wrong trials of LBTs and HBTs……………………………………………………………….…139

 

12. Figure 44. Comparison of rate modulation in body and non-body cells population across trials of body images with different baseline spike counts……………………………………………………………………..140

 

12. Figure 45. Comparison of rate modulation in body and non-body cells population across trials of object images with different baseline spike counts………………………………………………………………….….142

 

12. Figure 46. Baseline dependent correlation of neural activity and behavioral choice…………………………………………………………………..…143

 

12. Figure 47. Correlation between CP and cells’ body/object discrimination power………………………………………………………………………144

 

12. Figure 48. CP values of body cells plotted against the HBTs proportion in active task………………………………………………………………….145

 

12. Figure 49. RMI values of body cells plotted against the HBTs proportion in active task…………………………………………………………………146

 

12. Figure 50. Attentional modulation of baseline and evoked response in 30 low baseline cells…………………………………………………………147

 

12. Figure 51. Attentional modulation of baseline and evoked response in 30 low baseline cells…………………………………………………………148

 

12. Figure 52. Percent of HBT in active is plotted vs. percent of HBT in passive for 14 body and 16 non-body cells………………………………………..149

 

12. Figure 53. RMI of low baseline body and non-body cells in different stimulus and choice conditions……………………………………………150