Title: Studying interactions between frontal area FEF and parietal area LIP using electrophysiology and functional imaging in the awake macaque monkey
Other Titles: Onderzoek van interacties tussen het frontale hersengebied FEF en het parietale hersengebied LIP door middel van elektrofysiologie en functionele beeldvorming in de wakkere makaak-aap
Authors: Premereur, Elsie
Issue Date: 3-May-2012
Abstract: The objective of our research was to gain more insights in the lateral intraparietal area (LIP) and frontal area frontal eye fields (FEF), two higher order cortical areas involved in saccade planning and spatial attention; and the functional interactions between both areas. To expand our knowledge of parietal area LIP, we extensively tested the neurons under different task constraints. Firstly, we recorded spike rate activity during saccade tasks, and found that area LIP displays a strong heterogeneity with regard to anticipatory activity and memory delay activity. Furthermore, non-anticipatory neurons, which are most prominently present in our population of LIP neurons, were strongly influenced by salient visual stimuli appearing in their receptive field, but less so by the direction of the impending saccade. These results are highly important for the interpretation of previous LIP-studies, which often selected neurons based on certain properties. Because spike rate activity represents however only the output of the neuron, we next recorded local field potential (LFP) activity, which represents both the input and local processing. We found that gamma band activity largely mimics spike rate activity and differentiates between targets and distractors, while frequencies below 25 Hz have a relatively aspecific nature as they do not distinguish between presence or absence of a stimulus in the receptive field (RF). Low gamma power seems to occupy a unique position, in that its activity is only modulated by the presence of a highly salient saccade target, while no further distinction is made between the absence of stimuli and the presence of distractors in the RF. Finally, we showed that the LFP is tightly coupled to the temporal expectation of task-relevant cues, as power builds up in expectancy of the go-cue (in frequencies < 25 Hz), and power increases precisely locked to the time the monkey expects a stimulus to appear. In a third experiment, we investigated the effect of subthreshold FEF-microstimulation on LIP spike rate- and LFP-activity. Using weak subthreshold stimulation parameters (compared to previous research) FEF-microstimulation does not affect LIP spike rate activity or behavior. Surprisingly, stimulating FEF does modulate low-gamma power, but only when the saccade target remains present in the LIP RF, which has to be aligned with the FEF movement field (MF). Furthermore, FEF-stimulation causes increased alpha power when the monkey makes a saccade away from the LIP RF (and the FEF MF). Since the allocation and disengagement of spatial attention in visual cortex have been associated with increases in gamma and alpha power, respectively, the effects of FEF-microstimulation on LIP are consistent with the known effects of spatial attention. Furthermore, besides spike rate- and LFP-activity, we also measured functional magnetic resonance imaging (fMRI) activations during FEF-stimulation, and found that the effect of FEF-stimulation on activations in visual cortex is task-dependent, as it is larger during saccades compared to fixation. Furthermore, the effect of FEF-stimulation is mostly pronounced in voxels which were not highly activated during stimulus-presentation. In a final experiment, we compared the fMRI activity in attention-related areas during a saccade-task and an arm-movement task. Although the attentional conditions remained similar in both tasks, we found two distinct, non-overlapping networks, showing opposite response patterns. Taken together, our results support the role of areas FEF and LIP in spatial attention and saccade planning, and the functional connection between both areas.
Table of Contents: Table of Contents
Acknowledgements i
Abbreviations vii
Chapter 1. Introduction 1
1.1. Spatial Attention 1
1.1.1. Behavioral effects of spatial attention. 2
1.1.2. Neural effects of spatial attention. 2
1.1.3. Sources of spatial attention 5
1.2. Frontal Eye Fields 9
1.3. The lateral intraparietal area 13
1.4. LIP-FEF relationship 16
1.5. Local Field Potentials 17
1.5.1. Gamma band 19
1.5.2. Beta band 20
1.5.3. Alpha band 21
1.6. functional Magnetic Resonance Imaging 22
1.7. Microstimulation 23
1.8. Objectives 24
Chapter 2. Functional heterogeneity of macaque Lateral Intraparietal neurons. 27
2.1. Introduction 28
2.2. Materials and Methods 29
2.2.1. Subjects and surgery 29
2.2.2. Stimuli and tests 30
Visually-Guided Saccade Task with Multiple Distractors 30
Visually Guided Saccade Task with Single Distractor 31
Memory Guided Saccade Task 31
Passive Fixation Task 32
Recording procedure 32
2.2.3. Data analysis 33
2.3. Results 35
2.3.1. Multiple-distractor task 35
2.3.2. Single-distractor task 44
2.3.3. Memory Guided Saccades 45
2.3.4. Passive Fixation Task 47
2.4. Discussion 48
Chapter 3. Local Field Potential activity associated with temporal expectations in the macaque Lateral Intraparietal area 53
3.1. Introduction. 54
3.2. Materials and Methods 55
3.2.1. Subjects and surgery 55
3.2.2. Stimuli and tests 56
3.2.3. Recording procedure 58
3.2.4. Data analysis 59
3.3. Results 61
3.3.1. Visually-guided saccade task with multiple distractors 61
3.3.2. Single-distractor task 66
3.3.3. Suppressive LIP responses 68
3.3.4. Memory-Guided Saccade Task 70
3.3.5. Passive Fixation Task 72
3.3.6. Summary of results 76
3.4. Discussion 77
Chapter 4. Frontal Eye Field microstimulation induces task-dependent gamma oscillations in the Lateral Intraparietal area 83
4.1. Introduction 84
4.2. Materials and Methods 85
4.2.1. Subjects and surgery 85
4.2.2. Stimuli and tests 86
4.2.3. Recording and stimulation techniques 88
4.2.4. Stimulation artifact removal 89
4.2.5. Data analysis 90
4.2.6. Spike rate analyses 91
4.2.7. Reaction Time 91
4.3. Results 91
4.4. Discussion 99
Chapter 5. FEF-microstimulation causes task-dependent modulation of occipital fMRI activity. 103
5.1. Introduction 103
5.2. Methods 104
5.2.1. Surgery 104
5.2.2. Training 105
5.2.3. Stimulation 105
5.2.4. Tasks 106
5.3. Results 110
5.3.1. Behavior 111
5.3.2. fMRI Activations 113
5.4. Discussion 120
Chapter 6. Segregated frontoparietal networks in the macaque brain for saccades and arm movements. 123
6.1. Introduction 123
6.2. Methods 124
6.2.1. Surgery 124
6.2.2. Training 124
6.2.3. Tasks 124
6.2.4. Scanning 127
6.2.5. Image preprocessing 128
6.2.6. Event-Related analysis 128
6.2.7. Volume-based data analysis 128
6.2.8. Region of interest-based analysis 129
6.2.9. ROIS 129
6.3. Results 130
6.3.1. fMRI Activations 131
6.3.2. Percent Signal Change 134
6.4. Discussion 138
Chapter 7. General Discussion and future perspectives. 141
7.1. Summary of results. 141
7.2. Final remarks. 142
7.3. Drawbacks and limitations of the studies presented in this thesis. 143
7.3.1. Limitations with respect to the task. 143
7.3.2. Limitations with respect to single cell recordings. 143
7.3.3. Limitations with respect to electrical microstimulation. 144
7.3.4. Limitations inherent to fMRI. 144
7.4. Future perspectives 145
Summary 147
Samenvatting 149
Professional Career 151
References 153
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Research Group Neurophysiology

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