Imaging the Brain with Optical Methods (eBook)

Preface 5
Contents 6
Contributors 8
Chapter 1 13
Casting Light on Neural Function: A Subjective History 13
1.1 Imaging of Neural Function 19
1.1.1 Endogenous Chromophores 19
1.1.2 Optical Reporters 20
1.1.3 Functional Imaging 20
1.1.4 Calcium Imaging 21
1.1.5 Fast Intrinsic Signals 23
1.1.6 Neural Investigation 31
1.1.7 Technical Progress 31
1.1.8 Future Directions 33
References 35
Chapter 2 38
Fluorescent Sensors of Membrane Potential that Are Genetically Encoded 38
2.1 Introduction 38
2.2 First Generation FP Voltage Sensors 40
2.3 Second Generation FP Voltage Sensors 44
2.4 Next Generation FP Voltage Sensors 47
2.4.1 Linker Optimized Variants 47
2.4.2 Alternative FP Colors 47
2.4.3 Alternative Designs 48
2.5 Genetic Targeting of Neurons 48
2.6 Genetically Encoded Sensors of Membrane Potential Compared to Alternative Targeting Approaches 49
2.7 Signal-to-Noise Considerations 50
2.8 Capacitative Load and Other Possible Caveats 51
2.9 Future Directions 51
References 52
Chapter 3 55
The Influence of Astrocyte Activation on Hemodynamic Signals for Functional Brain Imaging 55
3.1 Brief Review of Hemodynamic Signals 55
3.1.1 The BOLD Signal and Its Components 56
3.1.2 Intrinsic Signal Imaging Relies on Similar Signals as BOLD 56
3.1.3 Origin and Complexity of Hemodynamic Signal Components 57
3.2 Astrocytes and Their Link with Neurons and the Vasculature 58
3.2.1 Synaptic Inputs to Astrocytes 59
3.2.2 Activation of Calcium Signaling in Astrocytes 59
3.3 Role of Astrocytes in Hemodynamic Signaling 60
3.3.1 Astrocytes and Hemodynamic Responses 60
3.3.2 Response Specificity of Astrocytes 61
3.3.3 Role of Astrocytes in Hemodynamic Signaling 63
3.4 Conclusions and Outstanding Issues 69
3.4.1 Astrocytes and Neurovascular Coupling 69
3.4.2 Neural Activity, Astrocyte Activity, and Hemodynamic Response Parameters 70
3.4.3 Effects of Anesthesia on Astrocyte Responses 70
References 71
Chapter 4 75
Somatosensory: Imaging Tactile Perception 75
4.1 Introduction 76
4.2 Methodology of Optical Imaging of Primary Somatosensory Cortex in New World Monkeys 77
4.2.1 The Somatosensory Optical Imaging Signal 77
4.2.2 Relationship of Tactile Stimulation with the Optical Signal 78
4.3 Somatotopic Representation in Primary Somatosensory Cortex 79
4.3.1 Topography in Somatosensory Cortex 79
4.3.2 Optical Imaging of Cortical Topography in Anesthetized Monkeys 79
4.3.3 Optical Imaging of Cortical Topography in Alert Monkeys 80
4.3.4 Correlations of Optical Imaging and fMRI Maps 83
4.4 Representation of Perception in Primary Somatosensory Cortex 85
4.4.1 The Funneling Illusion 85
4.4.2 Two-Point Stimulation Produces Cortical Merging in Area 3b 85
4.4.3 Intensity of Funneling Percept 87
4.4.4 Tactile Funneling Illusion Revealed by High-Resolution fMRI 89
4.5 Modality Representation in SI 90
4.5.1 “Labeled Lines” in Touch 90
4.5.2 Presence of Interdigitated Multiple Maps 91
4.5.3 Relationship of Vibrotactile Domains with Somatotopy 93
4.6 A New Model of Functional SI Organization 94
References 96
Chapter 5 103
How Images of Objects Are Represented in Macaque Inferotemporal Cortex 103
5.1 Introduction 103
5.2 Optical Intrinsic Signal Imaging (OISI) in IT Cortex 105
5.3 Evidence for the Columnar Organization with Respect to the Critical Features in Area TE 107
5.4 Object Representation by Combinations of Activity Spots in Area TE 109
5.5 Representation of Configurational Information Appeared in Object Images 113
5.6 Face Neurons in Area TE as Ones that Represent Facial Configuration 117
5.7 Object Representation at Different Levels: Columns and Single Cells Within a Column 120
5.8 Summary and Discussion 124
References 126
Chapter 6 128
Optical Imaging of Short–Term Working Memory in Prefrontal Cortex of the Macaque Monkey 128
6.1 Introduction 128
6.2 Prefrontal Delay Period Activity Encodes Short–Term Working Memory 129
6.3 Does Prefrontal Cortex Contain Clustered Functional Organization? 131
6.4 Topographic Organization of Prefrontal Cortex 132
6.5 Is There Spatial Organization for Memory Location? 133
6.6 Is There a Signal for Suppression in Prefrontal Cortex? 138
6.7 Summary 140
References 140
Chapter 7 143
Intraoperative Optical Imaging of Human Cortex 143
7.1 The Intrinsic Optical Signal 144
7.1.1 Neurovascular Coupling 145
7.2 The History of Human IOS 145
7.3 Imaging Normal Cortical Architecture 146
7.3.1 Somatosensory Cortex 146
7.3.2 Language Cortex 149
7.4 Imaging Pathologic Cortical Activity 152
7.4.1 Cortical Stimulation 152
7.4.2 Triggered Afterdischarges 154
7.4.3 Spontaneous Seizures 155
7.4.4 Spontaneous Interictal Spikes 156
7.5 Noise Reduction 158
7.5.1 Periodic Motion 158
7.6 Aperiodic Motion 160
7.7 Transient Linear Motion 162
7.8 Future Directions 163
7.9 Summary 164
References 164
Chapter 8 166
Using Optical Imaging to Investigate Functional Cortical Activity in Human Infants 166
8.1 How Does NIRS on Infants Work? 167
8.2 Review of the Existing Studies Using NIRS on Infants 168
8.3 Preliminary Studies on Motor and Visual Responses 170
8.4 Methodological Advances 177
8.5 Preliminary Studies on Auditory Activation 178
8.6 Speculations About the Future 181
8.7 Probe Design 181
8.8 Analysis Methods 181
References 182
Chapter 9 184
In Vivo Dynamics of the Visual Cortex Measured with Voltage Sensitive Dyes 184
9.1 The Method 185
9.1.1 Noises and Noise Reduction 187
9.1.1.1 Dark Noise 187
9.1.1.2 Shot Noise 189
9.1.2 Signal-to-Noise Ratio and Spatial–Temporal Resolution 189
9.1.2.1 Pulsation Artifact 190
9.1.3 Methods for Achieving High Signal-to-Noise Ratio 190
9.1.3.1 High Numerical Aperture Optics 190
9.1.3.2 Staining 191
9.1.3.3 Dye Bleaching, Washout, and Phototoxicity 192
9.1.4 A Concrete Example from the Barrel Cortex 194
9.1.5 Limitations of the Current Method 195
9.1.6 Interpretation of the Voltage Sensitive Dye Signal 196
9.2 How Has Voltage Sensitive Dye Imaging Changed Our View on How the Brain Works? 197
9.2.1 Spontaneous Activity, Up-States, Down-States 197
9.2.2 Propagating Waves in Cortex 199
9.2.3 Columns or No Columns, That Depends 203
9.3 The Visual Cortex 206
9.3.1 Dynamics in V1/area 17 Evoked by Natural Visual Stimulation 206
9.3.1.1 Flash 207
9.3.1.2 Stationary Objects, Bars, Gabor Patches 208
9.3.1.3 Moving Stimuli 209
Drifting Gratings 209
Drifting Lines and Moving Objects 211
9.3.1.4 Visual Illusions: The Line Illusion, Apparent Motion 214
9.3.2 Communications Between Visual Areas 216
9.4 Conclusions 222
References 223
Chapter 10 229
Fast Optical Neurophysiology 229
10.1 Where Science Meets Science Fiction 229
10.2 History 231
10.3 Electromagnetic Phenomena 232
10.3.1 Elastic Scattering 232
10.3.2 Inelastic Scattering 233
10.3.3 Polarization 234
10.3.4 Dichroism 234
10.3.5 Birefringence 235
10.4 Temporal Signal Components 235
10.5 Physiological Mechanisms for Polarization and Scattering Changes 237
10.6 Technological Issues 238
10.6.1 Light Sources 238
10.6.2 Noise Sources In Vitro 238
10.6.3 Noise Sources In Vivo 239
10.7 Reflection Mode Imaging 240
10.8 Spatial Signal Components 240
10.9 Action Potential Movie 241
10.10 Irregular Cell Orientation 241
10.11 In Vivo Applications and Fast Optical Responses 244
10.11.1 Hippocampus 244
10.11.2 Barrel Cortex 244
10.11.3 Noninvasive Measurements 246
10.12 Future Approaches 247
References 248
Chapter 11 250
Two-Photon Laser Scanning Microscopy as a Tool to Study Cortical Vasodynamics Under Normal and Ischemic Conditions 250
11.1 Macroscopic Imaging of Blood Oxygenation and Flow 250
11.2 Microscopic In Vivo Imaging of Vascular Reactivity on the Level of Single Blood Vessels 252
11.3 Measurements of Diameter and RBC Speed Describe Blood Flow in Individual Vessels 253
11.4 Simultaneous Measurements of Neuronal and Vascular Activity 258
11.5 TPLSM Guided Plasma Mediated Ablation as an Intervention Tool 260
11.6 Conclusion 262
References 262
Index 267