1 Correlations Between Spike Trains of Supraspinal Neurones.- 1.1 Correlations Between Discharge Patterns of Cortical Neurones.- 1.2 The Basic Method of Cross-Correlating Spike Trains.- 1.3 Correlations Between Discharge Patterns of Cortical Neurones and Their Role in Some Recent Models of Brain function.- 1.4 Brainstem.- 2 Correlations Between Spinal Neurones.- 2.1 Correlations Between ?-Motoneurone Discharges.- 2.2 Correlations Between ?-Motoneurone Discharges.- 2.3 Correlations Between ?-Motoneurone Discharges.- 2.4 Summary.- 2.5 Correlations Between Muscle Afferent Discharges.- 2.6 The Effect of Fusimotor Input on Spindle Afferent Correlations.- 2.7 Summary.- 2.8 Effects of Correlations Between Presynaptic Fibres on Spinal Neurones.- 2.9 Interneuronal Circuits.- 3 Tremor States.- 3.1 Frequency-Displacement Amplitude Relations for Normal Hand Tremor.- 3.2 Muscle Contraction as a Stochastic Process.- 3.3 Localised Stretch Reflexes Acting as a Tremor-Suppressive Mechanism?.- 3.4 Further Feedback Systems.- 3.5 Plasticity in the Spinal Cord.- 3.6 Summary.- 4 Recurrent Inhibition and Proprioceptive Feedback.- 4.1 Fundamental Functions of the Spinal Cord.- 4.2 Specific Functions of Recurrent Inhibition and the Stretch Reflex.- 4.3 Structural and Functional Analogies Between Spinal Recurrent Inhibition and Proprioceptive Feedback.- 4.4 The Reafference Principle.- 4.5 The Renshaw Cell System as an Efference Copy?.- 4.6 Model-Reference Control Systems.- 4.7 Adaptive Control Systems.- 4.8 An Integrated Model Including Proprioceptive Feedback and Recurrent Inhibition.- 4.9 Remarks on the Function of the Integrated System.- 4.10 Are the Inputs to ?-Motoneurones and Renshaw Cells Matched to Each Other?.- 4.11 Relation of Fusi- and Skeletomotor Activation Patterns: TaskDependence.- 4.12 ?-Motoneurones and Renshaw Cells as Integrative Centres.- 4.13 Suggestions for Further Research.- 4.14 Summary.- 5 Problems in Motor Control.- 5.1 On the Modules of Motor Control.- 5.2 The Problem of the Variable(s) Controlled in Motor Acts.- 5.3 Which Are the Measured Variables?.- 5.4 Spatial Transformations.- 5.5 Temporal Aspects.- 5.6 Multimodal Organisation of Spinal Neural Assemblies.- 5.7 Summary.- 5.8 Concluding Remarks.- Appendix A Auto- and Cross-Correlations.- Appendix B Cross-Correlations Between Three Spike Trains.- Appendix C Event-Related Cross-Correlations.- Appendix D Statistical Analysis of Nonlinear Physiological Systems.- Appendix E On Spurious Synchronisation of Two Semiregularly Firing Neurones.- Appendix F Spectral Analysis.- Appendix G A Remark on Correlation Patterns.- References.