Integration in Spinal Neuronal Systems

Abstract

The sections in this article are: 1 Methodological Considerations 1.1 Selective Stimulation of Primary Afferents 1.2 Stimulation of Central Motor Systems 1.3 Methods for Investigation of Convergence at Interneuronal Level 2 Spinal Neuronal Circuits Used in Common by Segmental Afferents and Supraspinal Motor Centers 2.1 Recurrent Inhibition 2.1.1 Convergence onto Renshaw Cells 2.1.2 Actions of Renshaw Cells on Spinal Neurons 2.1.3 Functional Considerations 2.2 Pathways From Ia-Afferents and Their Control by γ-Motoneurons 2.2.1 Reflex Pathways from Group Ia Muscle Spindle Afferents 2.2.2 Segmental and Supraspinal Control of γ-Motoneurons 2.2.3 Functional Consequences of α-γ-Linkage 2.3 Reflex Pathways From Group Ib Tendon Organ Afferents 2.3.1 Pattern of Ib Actions in α-Motoneurons 2.3.2 Convergence in Ib Pathways 2.3.3 Interneurons Interposed in Ib Pathways to α-Motoneurons (Ib-interneurons) 2.3.4 Functional Considerations 2.4 Reflex Pathways From Cutaneous and Joint Afferents and From Groups II and III Muscle Afferents 2.4.1 Cutaneous Afferents 2.4.2 Joint Afferents 2.4.3 Secondary Spindle Afferents 2.4.4 reflex Pathways from the “Flexor Reflex Afferents” 2.4.5 A Possible Role of FRA Activity 2.5 Propriospinal Neurons 2.5.1 Propriospinal Pathways Relaying Descending Motor Commands 2.5.2 propriospinal Neurons for Interlimb Coordination 2.5.3 Other Propriospinal Systems 2.6 Presynaptic Inhibition of Transmission From Primary Afferents 2.6.1 Effects from Primary Afferents to Primary Afferent Terminals 2.6.2 Segmental Control of Pathways to Primary Afferents 2.6.3 Effects from Supraspinal Centers to Primary Afferent Terminals 2.6.4 Primary Afferent Hyperpolarization 2.6.5 Functional Considerations 3 Reticulospinal Inhibition of Segmental Reflex Transmission 3.1 Dorsal Reticulospinal System 3.2 Ventral Reticulospinal Pathways 3.3 Monoaminergic Reticulospinal Pathways 3.4 Decerebrate Preparation 4 Direct Projections of Descending Pathways to α-Motoneurons 5 Ascending Pathways that Monitor Segmental Interneuronal Activity 5.1 Evidence That Ascending FRA Pathways Monitor Activity in Interneurons of Reflex Pathways 5.2 Information Via Ascending Collaterals of Interneurons 5.3 Ventral Flexor Reflex Tracts 5.4 Ventral Spinocerebellar Tract 6 General Summary and Epilogue 6.1 General Summary 6.2 Epilogue