Control of Human Voluntary Movement

1. Introduction. Plans, Strategies and Actions.- Categories of Muscles.- Problems of Moving.- A Legacy.- 2. Mechanical Properties of Muscles.- Review of Muscle Anatomy.- The Sliding Filament Hypothesis of Muscle Contraction.- Mechanical Properties of Muscle.- Studies on Tetanically Activated Isolated Muscle.- The Length-Tension Relationship.- Twitch Contractions at Different Muscle Lengths.- Force-Velocity Relationship.- The Effect of the Rate of Muscle Stimulation.- Behaviour of Isolated Muscle Stimulated at Subtetanic Rates.- Asynchronous Activation of Muscle.- Length-Tension Relationship at Different Levels of Muscle Activation.- Forced Lengthening of Partially Activated Muscle.- Muscle Mechanics in Intact Man.- Effects of Muscle Properties on Control of Movement.- Effects Arising from the Length-Tension Relationship.- Force Production at Different Muscle Lengths.- Stiffness of Muscle.- Effects Arising from the Force-Velocity Relationship.- Efficiency of Muscle Contraction.- Lengthening Contractions.- Intrinsic Feedback Control of Muscle Contraction.- A Theory of Movement Control which Makes Use of the Mechanical Properties of Muscle.- 3. The Motor Unit.- The Concept of the Motor Unit.- Twitch and Tonic Muscle Fibres.- Physiological Investigation of the Motor Unit.- Territory and Size of Motor Units.- Differences in the Contraction of Motor Units.- Speed of Contraction and Fatiguability.- Twitch Tension and Specific Twitch Tension.- Post-tetanic Potentiation.- Size and Conduction Velocity of Motor Axons.- Summary.- Histochemical and Biochemical Classification of Muscle Fibres.- Correlation between Histochemical and Physiological Classifications of Motor Units.- Some Electrophysiological Properties of Motoneurones.- Synaptic Inputs to Motoneurones.- Input Resistance of Motoneurones.- Firing Patterns of Motoneurones.- Control of Motor Units and their Recruitment Order.- Mechanisms Responsible for the Recruitment Order of Motoneurones.- Exceptions to the Normal Order of Recruitment.- Examples of Motoneurone Recruitment during Normal Movement.- The Study of Motor Units in Human Physiology.- Recording Motor Units in Man.- Histochemistry of Human Motor Units.- Mechanical Properties of Human Motor Units.- Recruitment Order of Motor Units in Man.- Changes in Recruitment Order.- Firing Frequency of Human Motor Units.- Gradation of Force in Human Muscle Contraction.- Muscle Fatigue.- Pathophysiology of the Motor Unit.- The Normal Electromyogram.- The Electromyogram in Neurogenic Diseases.- The Electromyogram in Myopathic Diseases.- Changes in Firing Rate and Recruitment Order of Motor Units.- 4. Proprioceptors in Muscle, Joint and Skin.- Muscle Receptors: I. The Muscle Spindle.- Anatomy.- Physiology of Spindle Afferent Responses.- The Effect of ? Activity on Spindle Afferent Responses.- Response of Spindle Endings to Very Small Displacements.- Muscle Receptors: II. Golgi Tendon Organs.- Anatomy.- Physiology of Golgi Tendon Organ Responses.- Muscle Receptors: III. Other Types of Ending.- Joint Receptors.- Anatomy.- Physiology.- Cutaneous Mechanoreceptors.- Recordings from Human Afferent Nerve Fibres.- Muscle Spindles.- Golgi Tendon Organs.- Cutaneous Mechanoreceptors.- Contribution of Muscle Afferents to Sensation.- 5. Reflex Pathways in the Spinal Cord.- Classification of Nerve Fibres.- Reflex Pathways from la Muscle Spindle Afferents.- Anatomy.- Electrophysiology.- Monosynaptic Excitation.- Disynaptic Inhibition.- Polysynaptic Actions.- Reflex Pathways from lb Tendon Organ Afferents.- Anatomy.- Electrophysiology.- Reflex Pathways from Group II Muscle Afferents and the 'Flexor Reflex Afferents'.- Anatomy.- Electrophysiology.- The Renshaw Cell.- Integration in Spinal Reflex Pathways.- Convergence onto the la Inhibitory Interneurone.- Convergence onto Ib Interneurones.- Comments on Convergence.- Presynaptic Inhibition.- 6. Functional Consequences of Activity in Spinal Reflex Pathways.- The Stretch Reflex in Animals.- Stretch Reflexes in Human Muscles.- The Tendon Jerk.- Long-latency Stretch Reflexes.- Vibration Reflexes.- The Servo Hypothesis and Alpha-Gamma Coactivation.- The Servo Theory.- Alpha-gamma Coactivation.- In Man.- In the Cat.- The Regulation of Stiffness Hypothesis and lb Effects.- Other Spinal Reflex Pathways.- Reciprocal Ia Inhibition.- Renshaw Inhibition.- Cutaneous Reflexes.- Nociceptive Cutaneous Reflexes in Man.- Low Threshold Cutaneous Reflexes in Man.- Pathophysiology of the Stretch Reflex: Disorders of Muscle Tone.- Hypotonus.- Hypertonus.- Spasticity v. Rigidity.- Reasons for the Increased Tendon Jerks in Spasticity.- Clasp-knife Phenomenon.- Changes in Muscle Tone Produced by Changes in the Mechanical Properties of Muscle.- Pathophysiology of Other Reflex Pathways.- Effects of Spinal Cord Transection.- Disynaptic Reciprocal Inhibitory Pathway.- Renshaw Cell Inhibition.- 7. Ascending and Descending Pathways of the Spinal Cord.- Ascending Pathways.- Afferent Input to the Spinal Cord.- Pathways to Thalamus and Cerebral Cortex.- Dorsal Column Pathway.- Spinocervical Pathway.- Spinothalamic Tract.- Thalamic Terminations of Somatic Afferents.- Pathways to the Cerebellum.- Dorsal Spinocerebellar and Cuneocerebellar Tracts.- Ventral and Rostral Spinocerebellar Tracts.- Spino-olivary-cerebellar Tracts.- Ascending Pathways to Other Structures.- Spinoreticular Tract.- Spinovestibular and Spinotectal Pathways.- Descending Motor Pathways.- Pyramidal Tract.- Rubrospinal Tract.- Vestibulospinal Tracts.- Reticulospinal Tracts.- Tectospinal and Interstitiospinal Tracts.- Summary of Descending Pathways.- 8. Cerebral Cortex.- Structure of Cerebral Cortex.- Sub-areas of Cerebral Cortex.- Which are the Motor Areas of Cortex?.- Cytoarchitecture and Connections of Cortical Motor Areas.- Cytoarchitecture.- Thalamic Inputs of Cortical Motor and Sensory Areas.- Cortico-cortical Inputs of the Motor Areas.- Outputs of Cortical Motor Areas.- Detailed Electrophysiology of Primary Motor (MI) Cortex.- Motor Cortex Mapping.- Corticospinal Localisation in MI.- Intracortical Microstimulation.- Stimulation of Motor Cortex in Man.- The Pyramidal Tract.- Motor Cortex Cell Activity During Voluntary Movements.- Timing of Discharge.- Relationship of Discharge to Movement Parameters.- Role of Small Pyramidal Tract Cells.- Sensory Input to Motor Cortex.- Controversy Over the Route by Which Afferent Input Reaches Motor Cortex.- Relation between Sensory Input and Motor Output.- Cutaneous Inputs.- Deep Inputs.- Transcortical Reflexes.- Other Motor Areas of Cortex.- Premotor Cortex.- Resume of Anatomical Connections.- Effects of Electrical Stimulation.- Electrical Recording and Lesion Studies.- Grasp Reflexes and Spasticity.- Supplementary Motor Area.- Resume of Anatomical Connections.- Effects of Electrical Stimulation.- Electrical Recording and Lesion Studies.- Electrical Recording.- Blood Flow.- Lesion Studies.- Motor Functions of Parietal Cortex.- Primary and Secondary Sensory Areas.- Parietal areas 5 and 7.- Lesion Studies.- Electrical Recording.- Pathophysiology of Motor Areas of Cerebral Cortex.- Epilepsy and Myoclonus.- Jacksonian Seizures.- Cortical Myoclonus.- Lesions of Descending Pathways.- Capsular Lesions.- The Effect of Pyramidal Tract Lesions.- Effects of Lesions of Other Descending Tracts.- Apraxia.- Premovement Potentials.- 9. The Cerebellum.- Cerebellar Anatomy.- Subdivisions of the Cerebellum.- Gross Anatomical Divisions.- Phylogenetic Divisions.- Divisions Based on Input and Output Arrangements.- Afferents.- Efferents.- Afferent Connections of the Cerebellum.- Direct Spinal Input.- Direct Vestibular Input.- Inputs from Precerebellar Reticular Nuclei.- Inputs from the Pontine Nuclei.- Inputs from the Inferior Olivary Nuclei.- Circuitry of the Cerebellar Cortex.- Anatomy.- Electrophysiology.- Efferent Pathways of the Cerebellum.- Projections to the Cerebellar Nuclei.- Projections to the Vestibular Nuclei.- Efferent Pathways of the Cerebellar Nuclei.- Electrophysiological Studies of the Cerebellum.- Background Levels of Discharge.- Afferent Input to the Cerebellar Cortex.- Afferent Input to the Cerebellar Nuclei.- Somatotopy.- Anaesthetised.- Awake.- Activity of Cerebellar Neurones during Active Movement.- Initiation and Control of Rapid Movements.- Relation of Discharge to Movement Parameters.- Relationship of Cerebellar Firing to Activity in Antagonist Muscles.- Activity of Cerebellar Neurones during Slow Movements.- Role of Cerebellum in Learning New Movements.- Limb Movements.- Vestibular-ocular Reflex.- Visually Triggered Movements.- Effects of Cerebellar Lesions.- Cerebellectomy in Cats and Dogs.- Cerebellectomy in Primates.- Reversible Cooling of Cerebellar Nuclei.- Electrical Stimulation of the Cerebellum.- Studies of Cerebellar Dysfunction in Man.- Clinical Symptoms.- Hypotonus.- Inco-ordination.- Physiological Investigations of Cerebellar Patients.- Stretch Reflexes.- Ballistic Limb Movements.- Slow Movements.- Complex Movements about More than One Joint.- Posture.- Theories of Cerebellar Function.- Cerebellum as a Timing Device.- Cerebellum as a Learning Device.- Cerebellum as Co-ordinator.- 10. The Basal Ganglia.- Anatomy.- Input-Output Connections of the Basal Ganglia.- Cortex-Basal Ganglia-Cortex Loop.- Motor Loop.- Complex Loop.- Other Outputs of the Basal Ganglia.- Strio-nigro-striatal and Strio-nigro-thalamic Loops.- GPi-Subthalamic Nucleus-GPe Loop.- Cytology and Pharmacology of Basal Ganglia Connections.- Electrophysiological Recordings from Behaving Animals.- Resting Discharge.- Relationship of Discharge to Movement.- Movement Related Cells: Somatotopy.- Movement Related Cells: Timing Relationships.- Movement Related Cells: Relationship to Movement Parameters.- Somatosensory Inputs to Basal Ganglia.- Context-dependent Cells.- Eye Movements and the SNpr.- Electrical Stimulation of the Basal Ganglia.- Effects of Lesions of the Basal Ganglia.- Globus Pallidus.- Substantia Nigra.- Subthalamic Nucleus.- Caudate and Putamen.- Summary.- Pathophysiology of Diseases of the Basal Ganglia in Man.- Parkinson's Disease.- Physiological Studies in Parkinson's Disease.- Rigidity.- Tremor.- Akinesia.- Postural Difficulties.- Chorea and Athetosis.- Torsion Dystonia.- Hemiballismus.