Table of Contents
Preface vii
Acknowledgments xv
The Effort of Movement 1
1.1 Choosing, Moving, Then Harvesting 1
1.2 A Measure of Effort 3
1.3 Utility of a Movement 13
1.4 Additive versus Multiplicative Interaction of Reward and Effort 20
1.5 Temporal Discounting of Effort 21
1.6 Alternative Representations of Effort 24
1.7 Cognitive Effort versus Movement Effort 27
2 Movements and Decisions in a Normative Framework 33
2.1 Optimal Foraging Theory 35
2.2 Marginal Value Theorem 43
2.3 Optimizing Movement Vigor 51
2.4 Example: Walking Speed 56
2.5 Walking Speed at Various Cities 60
2.6 Foraging with Our Eyes 62
2.7 Salience versus Utility 69
3 Reaction Time and Deliberation 77
3.1 Latency to Start a Movement: The LATER Model 80
3.2 The Variable Threshold Model 83
3.3 Linking Latency and Utility 84
3.4 Reward Modulates Vigor 88
3.5 Effort Modulates Vigor 95
3.6 Rate of Reward Modulates Vigor 98
3.7 Deliberation and Decision-Making 101
3.8 Modulation of Saccade Vigor during Decision-Making 107
3.9 Decision Uncertainty and Vigor of Movements 112
3.10 Between-Subject Differences in Vigor 114
3.11 Decision-Making and Movement Traits of Individuals 119
4 Neural Prelude to a Movement 129
4.1 Superior Colliculus 130
4.2 Bursting to Move 134
4.3 Bursting to Hold Still 138
4.4 Movement Latency and the Activity in the Fovea-Related Cells 144
4.5 Movement Latency and the Rate of Rise in the Buildup Cells 148
4.6 Reaction Time as an Interaction between Utility of Holding versus Utility of Moving 152
4.7 Salience versus Utility 156
4.8 Effect of Reward on the Colliculus 157
4.9 Reacting Much Earlier 162
4.10 Influencing Decisions with Manipulation of the Colliculus 169
5 Cortical Computation of Utility 175
5.1 Moving without Computation of Utility 177
5.2 Attention and the Effort Cost of Movement 179
5.3 Inhibiting Reflexive Behavior 184
5.4 Activity in the FEF during the Reaction Time Period 188
5.5 FEF and Deciding Where to Direct Gaze 193
5.6 Setting a Threshold to Move: Omnipause Neurons 202
5.7 The Premotor Cortex and the Decision to Reach 206
5.8 Encoding Utility and Salience in the Parietal Cortex 212
5.9 Good-Based versus Action-Based Models of Decision-Making 220
5.10 Deciding When to Leave 224
6 Basal Ganglia and the Motivation to Move 231
6.1 Anatomy of the Basal Ganglia 233
6.2 Substantia Nigra Reticulata 234
6.3 Caudate 244
6.4 Dopamine and the Pleasure of Moving 256
6.5 Dopamine and the Willingness to Exert Effort 278
7 Serotonin and the Promotion of Sloth 289
7.1 Anatomy of the Serotonergic System 290
7.2 Serotonin and the Average Reward Rate 292
7.3 Serotonin and the Willingness to Wait 295
7.4 Serotonin and Movement Vigor 306
7.5 Serotonin, Dopamine, and the Willingness to Work 312
7.6 Serotonin and Motoneuron Activity 316
Conclusions 323
Appendix A Effective Mass of the Human Arm 329
Appendix B Alternate Forms of Utility 331
Appendix C Afgebra of Random Variables 333
References 337
Index 349
