• 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
        1. 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

    1. Stimulus set …………………………………….……………..….90

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    2. مقالات و پایان نامه ارشد

    1. 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

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

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

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

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

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

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

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

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

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

    1. 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

    1. 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

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

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

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

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

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

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

    1. 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

    1. 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    1. Figure 54. RMI of low baseline body and non-body cells in different stimulus and choice conditions……………………………………………151

    1. Figure 55. Percent of HBT is active vs. percent of HBT in passive………152

    1. Figure 56. A combination of baseline firing rate and evoked response modulation in active compared with passive conditions affects monkeys’ performance…………………………………………………………….…153

    1. Figure 57. Polar plots of IT cells activity show that baseline dependent differential response of IT cell subpopulations determines monkey’s choice…………………………………………………………………..…155

Appendix1: Stimulus set……………………………………………….……….158

موضوعات: بدون موضوع  لینک ثابت


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