The Timing of Sleep and Wakefulness: On the Substructure and Dynamics of the Circadian Pacemakers Underlying the Wake-Sleep Cycle

ISBN-13: 9783540096672 / Angielski / Miękka / 1980 / 263 str.

J. T. Enright

Opis

The brain functions like a computer composed of subsystems which in teract in a hierarchical manner. But it is not a single hierarchy, but a com plex system of hierarchies each of which has its very own and unique fea ture. One of these concerns the cyclic or rhythmic control of neuronal ac tivities which, among others, give rise to alternating states of wakefulness and sleep. The phenomenon of sleep still remains a mystery. The present monograph does not give us any new insights into its meaning and significance. Yet sleep research may not be the same after the appearance of this book be cause it gives us a comprehensive mathematical theory which opens our eyes to new insights into the mechanism of the rhythm generation that under lies the "wake-sleep" cycle. No one who has worked his way through this book can again look at ex perimental data without recognizing features which the "models" developed in its various chapters so strikingly reveal."

Spis treści

1 Introduction.- 2 A Description of Activity-rhythm Recordings and Their Implications.- 3 The Pacemaker and its Precision.- 4 A Class of Models for Mutual Entrainment of an Ensemble of Neurons.- 4.1 Structure and Dynamics of the Coupling.- 4.2 Intermittent Feedback.- 4.3 Discussion of the Coupling.- Appendix 4.A. Calculations Based on Conditional Probability.- Appendix 4.B. A FORTRAN Program for Computer Simulation.- 5 A “Type Model” and its Behavior: Partial and Loose-Knit Mutual Entrainment.- Appendix 5.A. Relative Coordination of Unentrained Pacers.- 6 Precision of Model Pacemakers.- 6.1 Precision, as Affected by Number of Pacers.- 6.2 Influence of Alpha and Beta on Precision.- 6.3 Precision as Affected by ?, x?b and ?.- 6.4 Threshold of the Discriminator.- 6.5 The Implications of Experimentally Observed Precision.- 6.6 Alternative Formulations of Parameters.- 6.7 The Relationship Between Pacer Input and Discriminator Output.- 6.8 Stochastic Variation in Threshold.- 6.9 Summary of Factors Influencing Precision.- Appendix 6.A. On the Influence of N upon Precision (by J. Thorson).- 7 Influences of Constant Light Intensity.- 7.1 Effects of Light upon Free-running Period.- 7.2 Effects of Light upon Duration and Intensity of Activity.- 7.3 Effects of Light Intensity upon Precision.- 7.4 Extremes of Constant Lighting Conditions.- 7.5 Ranges of Free-running Period Values.- 7.6 Summary.- Appendix 7.A. Aschoff’s Rule: Models with Other Parameter Values.- 8 A Brief Detour: Further Thoughts About the Discriminator of the Models.- 8.1 The Magnitude of Feedback.- 8.2 Stochastic Variation in Amount of Feedback.- 8.3 Can the Discriminator be Eliminated?.- 8.4 Threshold and Feedback: an Extreme Case.- 8.5 Inhibition vs Excitation.- Appendix 8.A. Pacemaker Ensembles with a Threshold of One: A Revolving Dictatorship.- 9 General Features of Entrainment: the Type Model.- 9.1 Entrainment of Nocturnal Animals: Inhibition by Light.- 9.2 Phasic vs Tonic Effects of Light.- 9.3 Entrainment of Diurnal Animals: Stimulation by Light.- 9.4 The “Anomalous” Effects of Threshold on Pacemaker Period.- 9.5 Entrainment with Gradual Transitions in Light Intensity.- 10 Responses to Single Light Pulses. Part I: Nocturnal Rodents.- 10.1 Phase Shifts of Coupled Stochastic Systems.- 10.2 Transients During Phase Advance: Their Origin and Significance.- 10.3 Interspecies Variations in Phase-response Curves.- 10.4 A Failure of the Elementary Class of Models.- Appendix 10.A. Transients Following Phase Shifts.- 11 Responses to Single Light Pulses. Part II: Diurnal Birds.- 11.1 Simulation Results: Several Deficiencies and Their Remedy.- 11.2 Phase-response Curves: a Review.- Appendix 11.A Constraints on Parameter Values.- 12 Plasticity in Pacemaker Period: a Dynamic Memory.- 12.1 After-effects of Initial Phase Conditions.- 12.2 After-effects of Entrainment.- 12.3 After-effects of Constant Light Intensity.- 12.4 After-effects of Phase Shifting and of Photo-period.- 12.5 Permanent vs Transitory Differences in Period.- 12.6 Bistability of a Pacemaker.- Appendix 12.A After-effects of Phase Shifting and of Photoperiod.- 12.A.1 Single Shifts of Phase.- 12.A.2 After-effects of Photoperiod.- Appendix 12.B Alternative Steady States in a Coupled Stochastic System.- 13 Predictions from Coupled Stochastic Systems.- 13.1 Introduction.- 13.2 Predictions Related to Aschoff’s Rule.- 13.3 Predictions Relating to Entrainment by Sinusoidal Light Cycles.- 13.4 Predictions About “Phasic” Effects of Light.- 13.5 Predictions About Transients.- 13.6 Predictions About After-effects.- 13.7 Predictions About Phase Shifting by “Dark Pulses”.- 13.8 Quantitative Predictions.- 14 Further Predictions: a Modest Success and Two Problem Cases.- 14.1 “Clamped” Free-run Experiments.- 14.2 Two Problem Cases.- 14.2.1 The Relationship Between the Discharge Coefficient and Excitation.- 14.2.2 Splitting of an Activity Rhythm.- Appendix 14.A Reconciling Phase Advance with Aftereffects.- 15 Morphology of the Models: Where is the Pacemaker?.- 15.1 The Pacers.- 15.2 The Discriminator.- 15.3 The Translation of Formalism into Concrete Morphology.- 16 A Reprise and Synopsis: On the Advantages of Apparent Redundancy.- References.- Author Index.