Barrel Cortex

Barrel Cortex

Cambridge University Press
9780521852173 - Barrel Cortex - by Kevin Fox and Thomas Woolsey
Table of Contents

	Foreword page xiii
	Preface xv
	Acknowledgements xvii
	Abbreviations xviii
1	Introduction to the barrel cortex 1
	1.1	Introduction 1
	1.2	System overview 2
		1.2.1	What animals have barrels? 2
		1.2.2	What are barrels? 6
		1.2.3	Why are barrels important? 11
2	Anatomical pathways 14
	2.1	Whisker follicle innervation 14
	2.2	Brainstem nuclei and their projections 17
		2.2.1	General organization of the trigeminal nuclei 17
		2.2.2	Projection patterns of the trigeminal nuclei 19
		2.2.3	Receptive field properties of trigeminal nuclei cells 20
	2.3	Thalamic circuits 23
		2.3.1	General organization of the somatosensory thalamus 23
		2.3.2	The ventroposterior medial thalamic nucleus 24
		2.3.3	The thalamic reticular nucleus 25
		2.3.4	The posterior medial thalamic nucleus 26
	2.4	Barrel cortex 29
		2.4.1	Thalamic inputs to barrels and septal areas 29
		2.4.2	Excitatory intracortical pathways 31
		2.4.3	Inhibitory intracortical pathways 40
		2.4.4	Non-specific innervation 43
	2.5	Cortical outputs 45
		2.5.1	Corticocortical connections 45
		2.5.2	Subcortical somatomotor projections 46
		2.5.3	Subcortical somatosensory projections 48
3	Cellular and synaptic organization of the barrel cortex 49
	3.1	Excitatory cells 49
		3.1.1	Spiny stellate cells 49
		3.1.2	Star pyramids 50
		3.1.3	Pyramidal cells 51
	3.2	Inhibitory cells 55
		3.2.1	Soma-targeting inhibitory cells (basket cells) 55
		3.2.2	Axon-targeting inhibitory cells 56
		3.2.3	Dendrite-targeting inhibitory cells 57
		3.2.4	Other categories of inhibitory interneuron 57
	3.3	Synaptic transmission 59
		3.3.1	Excitatory synaptic transmission 60
		3.3.2	Inhibitory synapses 62
	3.4	Short-term dynamics 64
		3.4.1	Regular spiking, fast spiking and low threshold spiking cells 65
		3.4.2	Short-term dynamics of excitatory connections on to excitatory cells 66
		3.4.3	Factors controlling short-term dynamics 67
		3.4.4	Thalamocortical and layer IV inputs on to inhibitory cells 68
		3.4.5	Layer IV and layers II/III input to layer II/III inhibitory cells 70
		3.4.6	Corticothalamic recurrent collateral to layer IV inhibitory cells 70
	3.5	Electrical synapses 71
	3.6	Organization of synaptic circuits 73
		3.6.1	Single layer cortex 73
		3.6.2	Multilayer cortex 75
4	Development of barrel cortex 79
	4.1	Premaps and clones 80
		4.1.1	Progenitor cells 80
		4.1.2	Columnar and layer development 83
		4.1.3	Tabla rasa concept 85
		4.1.4	Transplant studies 86
	4.2	Pattern formation 87
		4.2.1	Theories of pattern formation 87
		4.2.2	Thalamic afferents 91
		4.2.3	Influence of the periphery 93
		4.2.4	Activity dependence 94
	4.3	Barrel formation 97
		4.3.1	Organization of cellular domains 97
		4.3.2	Interaction of thalamic afferents with neurons 98
		4.3.3	Signaling pathways 99
	4.4	Synaptic development 101
		4.4.1	Thalamocortical synapses 101
		4.4.2	Intracortical synapses 106
		4.4.3	Inhibitory synapses 108
	4.5	Conclusions 109
5	Sensory physiology 111
	5.1	Topography 112
		5.1.1	The columnar hypothesis 112
		5.1.2	Labeled-line processing versus integration 113
	5.2	Intracortical transmission 117
		5.2.1	The thalamocortical response transformation 118
		5.2.2	Vertical transmission within the column 120
		5.2.3	Excitatory transmission between columns 122
		5.2.4	Feedforward and feedback inhibition 124
		5.2.5	Lateral inhibition 127
	5.3	Receptive field organization 129
		5.3.1	Receptive field size 129
		5.3.2	Dynamic receptive field analysis 131
		5.3.3	Cortical and subcortical receptive field components 131
		5.3.4	Velocity sensitivity 134
		5.3.5	Directional organization 135
		5.3.6	Multiwhisker integration 138
	5.4	Dynamic sensory processing 141
		5.4.1	Whisking and active touch 142
		5.4.2	Cortical feedback 145
	5.5	Conclusions 148
6	Synaptic plasticity of barrel cortex 150
	6.1	Long-term potentiation 151
		6.1.1	Historical context and significance 151
		6.1.2	Long-term potentiation at the thalamocortical synapse 154
		6.1.3	Long-term potentiation at the layer IV to layers II/III synapse 157
		6.1.4	Presynaptic long-term potentiation 157
		6.1.5	Mechanisms of long-term potentiation and relationship to experience-dependent plasticity 159
	6.2	Long-term depression 162
		6.2.1	Historical context and significance 162
		6.2.2	Properties and methods of induction 163
		6.2.3	Long-term depression at the thalamocortical synapse 165
		6.2.4	Long-term depression at the layer IV to II/III pathway 166
		6.2.5	Mechanisms of long-term depression and relationship to experience-dependent depression 168
	6.3	Conclusions 169
7	Experience-dependent plasticity 171
	7.1	Map plasticity in barrel cortex 172
		7.1.1	The effect of altered tactile experience 172
		7.1.2	The effect of local cortical interactions on plasticity 177
		7.1.3	Two components to depression of sensory responses 178
		7.1.4	Interactive and non-interactive potentiation of sensory responses 179
		7.1.5	Plasticity at different ages 180
	7.2	The locus of experience-dependent map plasticity 183
		7.2.1	Cortical versus subcortical locus 183
		7.2.2	Pathways for plasticity 188
		7.2.3	Traces of plasticity following deprivation 192
	7.3	Early-phase molecular mechanisms of map plasticity 193
		7.3.1	NMDA receptors 194
		7.3.2	Calcium-calmodulin-dependent kinase type II 195
		7.3.3	Protein kinase A 197
		7.3.4	Kinase substrates: glutamate receptor subunit 1 198
	7.4	Late-phase plasticity: gene expression and structural changes 199
		7.4.1	Structural plasticity 201
		7.4.2	Changes in gene expression 206
	7.5	Injury-induced plasticity 210
		7.5.1	Developmental plasticity 210
		7.5.2	Intracortical plasticity beyond the thalamocortical critical period 212
		7.5.3	Subcortical plasticity in adult animals 213
	7.6	Conclusions 215
8	New and emerging fields in barrel cortex research 217
	8.1	Cortical blood flow and stroke research 218
		8.1.1	Imaging cortical blood flow and oxygenation levels 219
		8.1.2	Dynamic blood flow in the barrel cortex 221
		8.1.3	Metabolic coupling of neuronal activity and blood flow 223
		8.1.4	Models of cortical ischemia 225
		8.1.5	Angiogenesis 226
	8.2	Understanding active touch 227
		8.2.1	Modeling whisker mechanics 228
		8.2.2	Studying natural whisking responses 231
	8.3	Studying synaptic physiology 234
		8.3.1	The thalamocortical slice preparation 234
		8.3.2	Intracortical pathways 235
	8.4	Modeling cortical function 237
		8.4.1	Modeling barrels 237
		8.4.2	Toward simulation of a cortical column 239
	8.5	Genetic analysis of barrel cortex 240
		8.5.1	Forward genetic approaches 241
		8.5.2	Reverse genetic approaches 242
	8.6	Conclusions 245
	References 247
	Index 287
	The Plates are between pages 48 and 49.

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Kevin Fox

Cardiff University

Foreword by Thomas Woolsey

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