Neural Control of Movement

Presented with a choice of evils, most would prefer to be blinded rather than to be unable to move, immobilized in the late stages of Parkinson's disease. Yet in everyday life, as in Neuroscience, vision holds the centre of the stage. The conscious psyche watches a private TV show all day long, while the motor system is left to get on with it "out of sight and out of mind. " Motor skills are worshipped at all levels of society, whether in golf, tennis, soccer, athletics or in musical performance; meanwhile the subconscious machinery is ignored. But scientifically there is steady advance on a wide front, as we are reminded here, from the reversal of the reflexes of the stick insects to the site of motor learning in the human cerebral cortex. As in the rest of Physiology, evolution has preserved that which has already worked well; thus general principles can often be best discerned in lower animals. No one scientist can be personally involved at all levels of analysis, but especially for the motor system a narrow view is doomed from the outset. Interaction is all; the spinal cord has surrendered its autonomy to the brain, but the brain can only control the limbs by talking to the spinal cord in a language that it can understand, determined by its pre-existing circuitry; and both receive a continuous stream of feedback from the periphery.

Contenu
Afferent Mechanisms.- Isolated muscle spindles, their motor innervation and central control.- Recent developments in the physiology of the mammalian muscle spindles.- The human muscle spindle and its fusimotor control.- Mechanisms underlying the excitation of muscle afferents by suxamethonium.- Quantitative aspects of the use of succinylcholine in the classification of muscle spindle afferents.- Tendon organ discharges and their central effects during muscle contractions.- Proprioception.- Muscle, cutaneous and joint receptors in kinaesthesia.- Contribution of joint afferents to proprioception and motor control.- Assessing accuracy of positioning joints and limbs.- The behaviour of cutaneous and joint afferents in the human hand during finger movements.- Limitations in the neural control of human thumb and finger flexors.- Reflexes.- Fusimotor reflexes from joint and cutaneous afferents.- Reflex performance of the chronically isolated human spinal cord.- Enkephalinergic and monoaminergic control of segmental pathways from flexor reflex afferents (FRA).- Can the sympathetic nervous system activation contribute to context-related modulations of the stretch reflex?.- Classical conditioning of eyeblink in decerebrate cats and ferrets.- Locomotion.- Cellular bases of locomotor behaviour in lamprey: coordination and modulatory control of the spinal circuitry.- Reflex reversal in the walking systems of mammals and arthropods.- A locomotor-related autogenetic Ib excitation of hind-limb extensor muscles in thecat.- Modulation of stretch reflexes during behaviour.- A multiple-level approach to motor pattern generation.- The status of the premotor areas: evidence from PET scanning.- Development.- Organization of spinal locomotor networks and their afferent control inthe neonatal rat.- Dual control of central pattern generators: neonatal rat spinal cord in vitro.- Rhythmic activity patterns of motoneurones and interneurones in the embryonic chick spinal cord.- Postembryonic maturation of a spinal circuit controlling amphibian swimming behaviour.- Cerebellar Mechanisms.- The cerebellum as a predictive model of the motor system: a Smith predictor hypothesis.- Signalling properties of deep cerebellar nuclei neurones.- Visual input to the lateral cerebellum.- Inferior olive and the saccadic neural integrator.- Comparative Studies.- Presynaptic gain control in a locust proprioceptor.- Central and reflex recruitment of crayfish leg motoneurones.- Primitive role for GAB Aergic reticulospinal neurones in the control of locomotion.- Neuromodulation and motor pattern generation in the crustacean stomatogastric nervous system.- Mechanosensory signal processing: impact on and modulation by patterngenerating networks, exemplified in locust flight and walking.- Escape and swimming in goldfish: A model system for studying interactions between motor networks.