Search Results

For the purpose of motor coordination, the nervous system faces a complex control problem, involving redundant degrees of freedom, nonlinear dynamics of limbs and actuators, noise, and perturbations. Models and architectures have been proposed to describe motor coordination in terms of computational processes, and to identify possible simplifying strategies that would alleviate the workload of the nervous system. This chapter reviews several strategies ranging from biomechanical to function levels. It concludes that none of the proposed strategies actually tackle the overall problem of motor coordination. It presents a principled approach that provides an overarching account of motor control.

When older as compared to younger adults perform motor tasks, their brain activation patterns are substantially different. Even though reduced activation may occur in certain brain areas, current evidence points to higher activation, either in some of those areas that are also activated in younger subjects or in additionally recruited areas. With respect to coordination of the ipsilateral hand and foot, increased activation is observed in brain regions involved in motor coordination, sensory processing/integration, visual imagery strategies, and cognitive monitoring. This increased neural recruitment points to a shift from automatic to controlled processing of movement in aging adults. Evidence suggests that the increased activation in some (but not all) brain areas is correlated with better performance. This indicates that altered brain function in the elderly can be compensatory, possibly reflecting neuroplastic changes. A better understanding of these age-related changes in the central nervous system is an important goal for future research and will require a detailed study of interactions between brain function, structure, and sensorimotor behavior.

This chapter introduces physical neuroergonomics as the emerging field of study focusing on the knowledge of human brain activities in relation to the control and design of physical tasks. It provides an introduction to this topic in separate sections on the human brain in control of muscular performance in the work environment and in motor control tasks. It discusses these issues in conditions of health, fatigue, and disease states.

This chapter discusses the specific clinical and neurophysiological principles that underlie the assessment of residual motor control caudal to a spinal cord injury (SCI) in humans. It describes clinical, laboratory, and neurophysiological criteria for recognizing subclinical neurocontrol of movement in chronic spinal cord injury. It also reviews published work that describes and supports the neurophysiologically differentiated “discomplete syndrome” that exists within the paralyzed, clinically motor-complete patient population. Finally, it covers the examination of motor control in gait and introduces the lumbosacral locomotor central pattern generator circuitry, its behavior, and modification after SCI.

Two main types of experiment have addressed the question of how neurons in motor cortex control movement. One type focuses on the descending pathways that map specific points in motor cortex to specific muscles. A second type of experiment focuses on the activity of single neurons in motor cortex while the animal, usually a monkey, performs a complex task. These two approaches have resulted in contrasting descriptions of motor cortex. This chapter reviews these two major approaches to motor cortex. The first part summarizes experiments on the direct pathways from motor cortex, through the spinal cord, to the muscles, and how those pathways might control movement. The second part summarizes experiments on correlations between the activity of neurons in motor cortex and a variety of control variables related to the arm.

This chapter discusses how established procedures using physiotherapy, neuromuscular and peripheral nerve stimulation, and spinal cord stimulation can be used as restorative procedures. It describes how the same restorative neurological procedures can be used to assess motor control. It also presents the intrathecal application of Baclofen and intramuscular injection of botulinum toxin (Botox) as examples of interventions that do not take advantage of residual motor control but rather suppress it. Briefly, it describes how clinical restorative neurological treatment can best be practiced in medical centers where multidiscipline programs exist.

The control of movement provides us with the ability to manipulate and move about within our environment, to satisfy our survival needs and to interact with each other. Motor control is also the process by which we express our sameness and uniqueness within our society. Changes in motor control brought about by damage to our central nervous system, therefore, alter who we are in quite profound ways. This chapter focuses on the results of damage to the spinal cord and how output from the brain and brain stem to the spinal neural circuits, the motor neurons, and muscle fibers that they activate is altered. It covers the essentials of measuring motor control using functional electromyography, the characteristics of non-injured motor control, the characteristic patterns of motor control in chronic spinal cord injury (SCI), and selective control of voluntary movement disrupted by SCI.

This chapter describes ways in which brain-computer interfaces (BCIs) might be used as therapeutic tools to restore more normal motor control and more normal cognitive and emotional function to people with disabilities. It reviews the present status, key problems, and future prospects of noninvasive BCIs with such therapeutic aims. It focuses on the use of electroencephalography and functional magnetic resonance imaging to abort or prevent seizures; to improve the chances against, and to abort or prevent seizures; to improve motor recovery after stroke; to improve attention, emotional reaction, and other cognitive processes; and to manage pain.

This chapter discusses recent notions on motor control and learning. It aims to give the reader an impression of modern psychological thinking on motor control and learning. The learning of motor control can be understood in terms of the acquisition of abstract plans or rules (or ways to link muscle-joint systems). Visual information, feedback, variability of practice, active movements, and ecologically valid context all play a role in this acquisition process. These requirements can be seen as instruments in the hands of a therapist, and can be employed in the development of a modern therapy.

This chapter discusses the Atkinson and Braddick neurobiological models of early visual development in typically developing infants. The first model is based on the idea developed by Atkinson from Bronson that newborn vision depends largely on subcortical networks which come under the control of the visual cortex, which starts to function in the first six months of life. This model is developed further, describing human development of the dorsal cortical stream responsible for spatial processing, visual motion, and visual control of action; and ventral stream, subserving recognition of objects and faces. In the fuller model, the development of cortical modules for discrimination of orientation (slant), colour, motion, and stereo disparity (3D vision) is linked to developing systems for visual attention. These attention systems determine the information delivered to dorsal stream visuo-motor modules controlling gaze, manual actions, and locomotion at different stages during the first year of life.

This chapter presents a study in which a monkey was trained for hand movement and vocalization, and cortical field potentials were recorded during the movement by a pair of electrodes implanted in the cerebral cortex in the monkey. The potentials were analyzed in connection with behavioral observations. The chapter argues that the specific response to information—i.e., to move or not to move, and to move willingly or reluctantly—is judged and decided on in the prefrontal cortex. It is also suggested that the limbic system is more significant in vocalization than in hand movements.

This chapter reviews functional imaging and electrophysiological studies addressing the cerebral organization of speech motor control. Functional imaging studies, based upon the production/repetition of lexical and non-lexical mono- or polysyllabic items, point at a ‘minimal brain network’ of motor aspects of speech production, encompassing the supplementary motor area (SMA) within the medial wall of the frontal lobe, opercular parts of the precentral gyrus and posterior components of the inferior frontal gyrus (Broca's area), the anterior insula at the floor of the lateral sulcus, the ‘mouth region’ of the primary sensorimotor cortex, the basal ganglia, thalamus, and the cerebellar hemispheres. Depending upon task demands and the selected activation contrasts, hemodynamic responses of other cerebral structures such as the superior temporal gyrus and lower parietal areas may emerge as well. Most noteworthy, functional imaging techniques now begin to provide new insights into the pathomechanisms of dysarthric deficits such as abnormalities of speaking rate in Parkinson's disease or in cerebellar ataxia.

Understanding the dynamics of agency and the sense of bodily ownership of action can be clarified by considering cases where these aspects of experience break down. In schizophrenic symptoms of delusions of control and thought insertion, for example, subjects lose a sense of agency for acting and thinking. Although models of motor control may be able to explain why this happens in the case of delusions of bodily movement, a different model is required to explain thought insertion. This chapter proposed that this alternative model, which is cast in terms of temporality, can be generalized to explain both delusions of control and thought insertion, and show a common structure to embodied action and cognition.

Variability in oral motor control has been an important topic in the literature for many years. The typical view is that motor output can be interpreted as a mixture of an invariant control signal (e.g., motor command) contaminated by a degree of random variation or neuromotor noise. This variation is supposed to originate somewhere along the pathway from the central nervous system where the command was generated to the peripheral structures responsible for its execution. This chapter explores different concepts on variability in speech production in more detail using examples of speech kinematic data from people who stutter and normal speaking individuals. The data indicate that popular indices of variability when applied to the same dataset are at odds with each other in terms of identifying specific trends for an individual or groups of individuals. Beyond these data examples, the chapter presents a new approach (for speech) to confront the challenging question if (and how) it is possible to identify the nature of movement variability and its potential relevance for speech motor control.