Movement control

Motion control (English: motor control ) is a term from movement science .

Movement control is an internal process in which humans and animals coordinate their movement system in such a way that planned and unplanned movements take place in such a way that their intended goal is safely reached. No physical movement is performed without movement control. It guarantees the performer the physiological safety of the process and plays an important role in the execution and learning of motion sequences. As a rule, the person performing the work is not aware of it. It can be described as monitoring of the motion sequences. Information from both the environment and the body itself is included in the movement control , which is then processed in a targeted manner through cooperative interaction between the peripheral and central nervous system (CNS) and the muscle system .

In the past ten years, ideas about movement control have changed significantly due to new knowledge about brain structures . For a long time it was assumed that commands for movements come from the brain and that a correction is only made when something disturbs or hinders the process. Today we know that these commands that trigger a movement activate an entire network of movement control at the same time . This means that the constantly arriving information about the environment and the internal state of the organism is geared towards the successful execution of this sequence of movements. This means that a movement sequence is under constant online control during its execution .

Numerous disciplines work together in the study of motion control: from biomechanics , mechanics , physics and engineering to psychology , behavioral and neurosciences .

Concept history

In Germany, movement control has long been understood to mean that the teacher controls the execution of the learner in the sense that errors, undesired components or qualities of a movement execution are recognized and named, which should be avoided in the following explanations or should be additionally considered. That is, a control was seen as given from outside.

Movement control in movement science today means the internal control of the process carried out by the organism itself. It corresponds to the method used in technology to regulate a process - in the human organism, however, this is not a technical, but a biological process. The term is directly related to the feedback or feedback of a (partial) result of the process, because the feedback can determine a difference between the completed and the intended implementation, which then needs to be reduced.

The control process

Simple control loop with target specification, controlled system, result evaluation and feedback

In the case of regulation (control process), a goal is specified for a process (input). This goal should be worked out on the so-called controlled system by means of specified or constructed processes. Once the processes have been completed, the result (output) is assessed (measured). If the goal is achieved, the process is over. If it is not achieved, an attempt can be made to achieve the goal in a new process by means of correction specifications and a new input to the controlled system (changed processes). This cycle can be repeated until the goal is achieved. The earlier a deviation from the planned process is discovered in your process, the greater the chance of achieving the goal safely and in the planned time through targeted corrective measures. For all these processes, it is important that the necessary information - about the goal, current status, partial results - is provided and available at the right time in the right places. In this respect, movement control has a lot to do with information intake and information processing in the human organism. These tasks are performed by the nervous system .

With movement regulation in the human organism - as it was understood for a long time - the goal is determined by the person carrying out the task or by a teacher (trainer, therapist). The controlled system is the human movement system. The processes are the execution of motor (partial) actions. The assessment of whether the goal has been achieved or not is made for the consciously perceptible part of the performer, teacher or trainer; for the internal control mechanisms, this is also done internally by the organism (current knowledge).

Why is movement control necessary?

With the first assumptions about the execution of movement sequences - until about the middle of the 20th century - it was found that the commands issued by the cerebrum were passed directly to the motor neurons in the spinal cord and from there to the corresponding muscles ( pyramidal system ) and were taken indicates that they and there are executed exactly as planned - as with an earlier (as was customary at the time: rigid) computer program . This was also based on the observation that a movement sequence, if it is mastered, conveys the optical perception of a stereotypical, invariant sequence (automated movement sequence that supposedly runs without control ). Opposite the pyramidal system was the extrapyramidal system, to which all neuronal connections were assigned that did not belong to the pyramidal system. They work "automatically". That means without conscious control. However, it was clear that they contribute to ensuring that the entire system of movement functions safely. Today, many of the control loops that exist in the so-called extrapyramidal system have been researched and we know what part they play in controlling the movement of vertebrates (including humans). They are mainly neural networks for basic movements that have evolved over the years. They are referred to as Central Pattern Generators (CPGs). They play an important role in controlling movement. Their functions and their interaction with voluntary motor skills are the subject of intensive research.

However, if you consider that the transmission of signals or information in the organism, not to mention the occurrence and recognition of signals from the environment, is also subject to inaccuracies, even errors, it becomes clear that for a correct, but above all a safe one Execute corrective actions are necessary. The purpose of motion control is to recognize such errors - perhaps even only possibly occurring inaccuracies and errors - in good time, to initiate their correction and to monitor them.

Balance control

The sense of balance and above all a disturbance of the balance belonged to very early interests not only in neurophysiology , but in medicine in general. It is a problem in medicine because it affects the health and thus the quality of life (physical safety) of a person. It was therefore not considered and examined from the point of view of a technical / biological control, but because of the health risk.

The problem of balance control is very complex. For a long time, investigations into this complex have not been carried out in the sense of movement research, but from the medical aspect of finding out why people have balance disorders and how one can help them to avoid the consequences as far as possible (e.g. falls) and to deal with the consequences. However, the findings from this research are now of central importance when considering movement control as a whole, because its mechanisms are also fundamental for the control of other movement sequences.

Why is movement control necessary?

The first assumptions about the execution of movements - until about the mid-20th century - was imagined that the cerebrum orders given directly to the motor neurons in the spinal cord, routed to the appropriate muscles and there exactly as planned are carried - as with an earlier (as was common then: rigid) computer program. This was also based on the observation that a movement sequence, if it is mastered, conveys the optical perception of a stereotypical, invariant sequence (automated movement sequence that supposedly runs without control). However, if you consider that the transmission of signals or information in the organism, not to mention the occurrence and recognition of signals from the environment, is also subject to inaccuracies, even errors, it becomes clear that for a correct, but above all a safe one Execution of corrective actions are necessary. The purpose of motion control is to recognize such errors - perhaps even only possibly occurring inaccuracies and errors - in good time, to initiate their correction and to monitor them.

The research disciplines involved

Neurophysiology, Neuroscience

Neurophysiology deals with the anatomy and physiology of the central and peripheral nervous systems . The interaction of nerve activity (electricity) and movement was discovered by Luigi Galvani as early as the 18th century . A controlled investigation of these phenomena did not take place at that time. It was not until the beginning of the 19th century that experiments on targeted electrical stimulation and reflex responses to stimuli from individual sensory organs began.

New knowledge, for example about the coloration of certain nerve fibers, made it possible to trace the course of nerves at the beginning of the 20th century. With this, Charles Scott Sherrington was able to trace individual nerve fibers and in this way to recognize and describe the spinal reflexes and their importance for regulating movements on the spinal level. Today technology provides numerous methods with the help of which not only the course of individual nerve fibers can be followed, but also the course of a current action.

Behavioral sciences

In behavioral research , the behavior of animals is researched in order to draw conclusions about the behavior of humans from the findings in animals. It was carried out in Germany and the USA from different parent disciplines and with different methods.

In Germany, behavioral science is a sub-area of animal physiology , scientists are biologists (zoologists) or physicians (physiologists). Konrad Lorenz is considered to be the founder . This worked primarily with the method of pure observation of animals - similar to behaviorism . Other researchers such as Erich von Holst and Bernard Hassenstein examined the nervous systems of animals, for example to find out how they coordinate their movements.

The term motion control was not in use in the first half of the 20th century. One spoke of movement coordination or movement regulation.

In the US, psychologists studied behavioral science. They developed the methods of behaviorism . This means that only the objectively observable behavior was used to form theories. In this way one tried to understand learning processes and transferred the knowledge to the behavior and learning of people. One was not interested in the physiology that took place within the animals and led to the creation of the movements, even rejected this as unscientific because too little was known about it. It was only when movement science ( Psycho Motor Behavior ) established itself as a separate discipline that neurophysiology was included in the explanation of behavior.

Engineering

In the engineering sciences - with the exception of prosthesis design after the First World War - at the beginning of the 20th century, no one was concerned with human movement. The regulation of technical processes was known, but did not become a routine procedure until the 1930s. Today, the engineering sciences, with many of their sub-disciplines (e.g. biomechanics, measurement technology and control engineering), play an important role in research into motion control.

Motion science

Energy processing

Information processing

Functional anatomy

Work physiology

Biomechanics

Movement control

Psychomotor behavior

Sociology of movement

bone

breathing

ergonomics

Movement learning

genetic specifications

Group influence

Joints

Cycle

Orthopedics

Information processing

Experience

Traditions

Tapes

Muscle work

rehabilitation

Control mechanisms

Knowledge

Opinions

Tendons

fitness

Tissue mechanics

Neurological structures

Muscles

Work in water / heat

Sports

Structure and function of the motor neuron

Dentistry

Structure of the nervous system from a motor point of view

Forensic Biomechanics

Control task of the individual brain sections

Movement science with its sub-disciplines

From separate beginnings to collaboration

At the beginning of the 20th century, the above-mentioned disciplines with regard to movement control developed separately from one another. The first collaborations between researchers in these disciplines took place around the middle of the last century. Around this time, the awareness of the need for cooperation between engineers and physiologists arose when control engineering began to play an increasingly important role in technology and engineers and biologists discovered that the processes involved in both areas were comparable. This collaboration between engineers, biologists, physiologists and psychologists is also evident in the integrative disciplines that emerged at the time, such as cybernetics , synergetics, and finally neural networks .

In the USA, studies on pilots for their use in World War II made a major contribution to this development . In Germany, the professor of electrical engineering Karl Küpfmüller should be mentioned here as a representative , who supported the physiologists in understanding the technical elements.

Behavioral scientist Erich von Holst (physiologist) played a major role in the development of movement control . In contrast to Konrad Lorenz, who worked with observations and partly behavioral methods, von Holst concentrated on the (physiological) processes in the nervous system during the movements of animals in order to examine the functions of the central nervous system . He did his doctorate on the functions of the central nervous system in earthworms. His investigations on the principle of reactivity were pioneering . He did not use the language of engineers, although it was clearly a matter of control processes that he described. This is also one reason why the importance of this work for movement control was only recognized in the 1980s. Another reason is that his work was not or only incompletely translated into English and was therefore not known for a long time where more intensive efforts were made to understand movement control.

The processes of movement control were examined and described above all in the USA. However, due to the long dominance of behavioral research on learning and behavior in psychology, her studies only began to play a role in motor skills research after 1960. In Germany, awareness of the importance of movement control is still low and occasionally leads to misunderstandings. In the USA, too, initially there was apparently only a general interest in knowing how exercise works - general exercise and sport traditionally play a major role in the USA. Richard A. Schmidt's work is behaviorist . He developed the schematic theory , through which the necessary memory requirement in the brain is less than in program theory. In which a single program must be saved for each learned movement. The memory requirement is lower because there is, so to speak, an execution scheme for a movement family that, in the current situation, can be adapted not only to the required size and execution speed, but also to execution with different limbs. So you can write a word, if you can write it, with your non-preferred hand, with your foot or with a stylus in your mouth ( generalized scheme ).

Then more and more attempts were made to set up the experiments in such a way that conclusions could be drawn about how the movements might come about in the organism - first in the muscle system, but then also in the nervous system, as this triggers and determines the muscle work. The neurophysiology began to play a role in the movement research. With the introduction of information processing into psychological thinking by Lindsay and Norman and the corresponding expansion to sport by Ronald Marteniuk, considerations about how the information in the organism is transmitted during movement played an increasingly important role. For the first time, internal feedback appeared, which is a prerequisite for controlling a movement. What is new about these approaches is that one does not start from the movement as a reaction to a signal, as in behaviorism , but that a movement can be triggered willingly by an acting person and carried out in a targeted manner.

The 1980s can be described as the years in which the Motor Control Theory established itself as an independent movement theory that organized and summarized previously used terms and concepts. The researchers from the disciplines involved entered into a direct exchange with one another. International congresses took place in which the theories were discussed and future directions worked out. Since then, the term motor control has also been used more uniformly for this research area, which has given other often unclear (such as movement regulation ) or ambiguous terms (such as movement coordination ) a clear meaning.

One of the new directions in movement theory - with its own approaches to movement control was z. B. the so-called ecological theory (or action theory ), which was advocated by James Gibson and Edward Reed, and which went back in part to considerations and publications by Nikolai Bernstein (see below). This theory says that it is not the living being, including humans, that initiates and executes a movement, but that the environment in which it is located contains challenges (affordances) that stimulate or force it to carry out certain actions the environment determines our movements.

There were various international congresses at which these approaches and considerations were discussed. One of these congresses - or workshops - took place in Münster in 1986 . It was subtitled The Motor-Action Controversy . Mainly the old movement researchers who were trained in the time of behaviorism and who carefully dealt with information-theoretical and feedback approaches as well as with the new action theory reported here (for example Richard A. Schmidt). The congress held in Varna / Bulgaria in 1985, which already had Motor Control as its name, was more scientifically oriented (neurophysiology and model approaches from control engineering) .

In addition to the above-mentioned action theory, the discussion about the work on movement research by the Russian physiologist Nikolai Bernstein, which took place around the same time, was important for the further development in the English-speaking countries . They went back to his book: The Coordination and Regulation of Movements , which was published in England in 1967. Since all American movement scientists refer to this book after this time - until today - but it was out of print at some point and was not reprinted, his work was discussed and commented on by selected movement researchers and reassessed in a new volume Human Motor Actions, Bernstein by HTA Whiting summarized and edited.

In contrast to the American movement researchers, like almost all Russian movement researchers, Bernstein was a physiologist and mathematician / engineer by training . He wanted to “further his understanding of the brain through the study of movement”. He wrote more than 140 publications, some of which have been translated into German or English. His most important contributions to movement control to this day are his statements about the redundancy of the movement possibilities given by the anatomy of the body, which on the one hand allows a high variability of the possible movements, but on the other hand force the organism to reduce the high number of degrees of freedom of a movement and to control that a coordinated movement is possible. In line with his training, his expression was strongly mathematical, so that engineers in the USA and England also became interested in the control of human movement and tried to show and deepen their views and findings through special experiments. Gradually, the focus of research shifted, in addition to neurophysiology , in which one tried above all to find the fast information paths in the organism necessary for control, to the research area of ​​engineers. These try to represent the findings using mathematical models .

Research into movement control is increasing because its importance is playing an ever greater role, for example for the construction and control of artificial limbs ( rehabilitation ), but above all for the construction of adaptive robots . The robotics designers are interested in how the movement control of living beings is organized because nature, with its millions of years of evolution , has organized the movements of living organisms in such a way that they are optimally and thus adaptable and adaptable in an exemplary manner and are characterized by high efficiency and Distinguish elegance.

Movement Control Theories

The psychologists (especially in the USA), who did not deal with neurophysiological issues at the beginning of the 20th century, assumed that movement control was mainly based on so-called open loop control . In this presentation, a sequence of movements is planned, the necessary commands for their execution are issued from a center (the primary motor cortex, MI) and the movement is carried out. Classically, there is no control whatsoever during the entire process - open loop . However, there is always the possibility of evaluating these after the execution - and, depending on the success or failure of the process, to propose or plan corrections for a subsequent execution - by the executor himself or by an outsider. In the real sense, this then closes the control loop.

For a long time it was believed that this type of control, especially in the case of fast (for example so-called ballistic movements), was the only possible one, because it was assumed that the entire execution is too fast to be influenced by internal control mechanisms.

The advantage of open loop control is that in the course of the learning process a kind of (perceptible) optimization of the process can take place and that the result, if its process is not disrupted, can be predicted exactly - as long as no disruptions occur. Their disadvantage, however, is that the process is rigid and not variable and therefore cannot adapt to changed environmental or internal conditions.

The open loop control is opposed to the closed loop control (closed control loop ). As already mentioned, a correction after the execution of the movement could also be viewed as closing the control loop during movements. However, the closed loop control is understood as the internal control of the organism that takes place during a movement. In order to understand how there can be such a control, it is necessary that the organism looks inside and the physiological structures that can afford it, examines and describes. It turns out that knowledge of movement control depends on knowledge of the central (CNS) and peripheral nervous systems (PNS). The search for the paths of the signals that determine the running time and thus the speed of a feedback and correction of a movement sequence is an important subject of research.

In the closed loop control , the advantage is that all disorders that may occur in the course of the movement execution, as delays of information lines of noise ( noise ) in the area, in the sense organs or the pipes, they can be compensated quickly. Due to the high variability of the execution options, an adaptation to current requirements of the environment or the condition of the executing organism is given.

The main problem of movement control

The main problem of movement control is therefore - in some cases still - its time requirement. This is because the control processes require a certain period of time to take effect. The feedback loops actually have to be run through , as it was believed, and a certain amount of time elapses which, as one believes (e), is not sufficient - especially with fast movements - to be able to intervene in the process. The information paths in the organism known before 1980 did not provide the necessary rapid information flows.

This time problem still plays a major role in the discussion of the possibilities and forms of movement control. For example, it is still used today as a justification for the fact that at the beginning of learning a new movement the execution should take place slowly, because then the control loops first have to be established so that they can take place quickly and smoothly later.

In order to solve this time problem, the structures in the central and peripheral nervous system are sought in the organism that guarantee an information transfer that is fast enough to guarantee online control , because this corresponds to the observations and needs.

Structure of the control system

Brain structures involved in movement control

The central nervous system reveals a hierarchical structure that has different levels on which one can examine and describe the movement control. It has been known for a long time. Erich von Holst gave a description of the movement control within this hierarchical system in his essay on the principle of reactivity . (According to his observations and his imagination, the motor commands issued by the cortex are stored in the nervous system in a file (efference copy) in the CNS. The motor commands (efferents) that then follow are carried out and the resulting (feedback) messages (reafferences) on the The lowest central level is compared with the efferent copy. If these messages are identical to the expectations from the efferent copy, the efferent copy is deleted and the sequence of movements is completed. If there are any remains of the efferent copy, an attempt is made to resolve and resolve them by taking measures at the next higher central level This is continued until the efferent copy is completely deleted and can lead to a conscious control (change) of the commands). The concept of control was not yet familiar in von Holst's time. He gained his knowledge through careful observations of the behavior and the nervous system of numerous simple (worms, fish, flies) living things. Reading the article will provide a basic understanding of motion control.

overview

The network of motion control consists of equal - also nested - networks (elements), which nevertheless have a hierarchical structure.

The highest level of neural control of this hierarchical structure within the cerebrum , ( central nervous system ), is the cortex, the cerebral cortex, the gray matter. The management of all functions resides in the cortex. There is, for example, decided there about which products (movements, thinking, etc.) and how it made you want to. Furthermore, the entire (creation and implementation) production process is monitored. It is the supreme authority for all actions (conscious and unconscious) of the organism, from planning to execution and monitoring (control). After all, it is responsible for assessing the result and adding it to the wealth of experience.

The subcortical centers can be represented as the middle level. The most important ones for movement control are the basal ganglia for the selection of and as initiator and starter of movement sequences, the cerebellum as the computing unit of the brain and the brain stem as a kind of toolbox of the neural networks - other subcortical centers are also involved, for example the thalamus , the hypothalamus and the hippocampus . However, they are not primarily responsible for controlling movement.

The lowest level of movement control is the spinal cord as a kind of workshop, in which the resulting information, which is available in electrical form (energy), is passed on for mechanical conversion in the muscles to the movements (energy). Here it is ensured that the product (the sequence of movements) corresponds precisely to the intention and the planning. To do this, the development of the product must be constantly monitored and controlled and, in the event of even minor deviations, corrected and adjusted immediately. For this purpose, there are smaller networks that can trigger and carry out simple sequences quickly and in a variable manner.

Structure and function of the individual control elements

The cerebrum

→ Main article : cerebrum

Layout and function

The cerebrum consists of the outer cerebral cortex (cortex, gray matter), and the subcortical structures underneath, which contain the nerve cells, as well as of the conduction pathways (white matter), which all these structures both with each other and with the downstream brain structures and ultimately also connect to the muscles. It is the central processing and integration organ for information from the body and the environment.

The cerebrum consists of two hemispheres (halves) of the same structure, which are connected to one another by a bar (duct). The surface of the cortex is strongly structured with many furrows (Latin: sulci , singular: sulcus ) and crevices (fissures, fissura ). This increases it considerably. Larger areas are as lobes ( lobuli hereinafter), which are referred to according to their location (frontal, parietal, occipital).

The cortex is divided into different regions (areas). They are numbered based on the work of Korbinian Brodman according to the functions he has assigned to them. They have different tasks to perform, but work together intensively through recursive information flows. In this way, you can also modulate current actions (e.g. movements). For this purpose, they form networks with the subordinate structures such as the thalamus , basal ganglia but also with the cerebellum and the brain stem , from which they constantly receive information about current events. In this respect, the cortex represents the higher-level control authority that controls all processes. We are not aware of most of these information flows.

These regions and their tasks can be roughly divided into sensory , motor and associative areas. As we know today, most areas are not homogeneous, but rather divided into smaller areas, each of which has different tasks, for example by controlling the movements of different parts of the body. However, all areas of the cerebrum are organized as networks in themselves and with all other areas - even across regions that are far apart.

Sensory perceptions are recorded in the sensory areas. They are processed at different levels of depth (primary areas, secondary areas, etc.). The different sensory stimuli in the primary areas (see, hear, feel ( proprioception , skin afferents)) each have their own areas. In the higher areas they are more and more integrated into one another.

The primary areas ( primary areas ) get their information via the thalamus. They are built up topographically. This means that information from neighboring fields of perception (of the signal recording) is also sent to neighboring locations and stored there ( maps , maps). This gives the primary motor cortex the shape of a small person ( homunculus ). The relative size of the representation zones shows the density of innervation in the associated fields of perception, for example a high density for the fingertips. The two hemispheres generally receive the sensory perception from the contralateral side of the body, i.e. the right motor cortex from the left side of the body.

In the motor areas, the movements are prepared and their execution initiated. Classically, this motor area (Brodmann Area 6) is divided into 3 sub-areas. Here, too, there is a much finer breakdown today. The individual areas differ in their neuron types , but also in their more differentiated tasks.

For a long time it took that the motion-inducing commands only from the primary motor cortex ( primary motor cortex , M1), located in the front (anterior) of para central lobe at the middle, internal surface, going out. However, these commands are supplemented, updated in the subcortical structures, finally passed into the spinal cord and implemented there in motion. But the other motor areas also play an important role in triggering movements. Direct connections from the primary motor cortex to motor neurons in the spinal cord with rapid conversion into motion do not exist for all muscles, but for finely coordinated movements of the hands and fingers. The latter is the prerequisite for quick and precise control of hand and finger movements.

The signals from the primary motor cortex mainly contain commands for the kinetic parameters of the movements, which are adjusted accordingly when the ambient conditions change. Research into the complex tasks and capabilities of neurons in the primary motor cortex continues to provide new insights.

Movements of higher complexity seem to be controlled more by the premotor area, which is located in front of the primary motor cortex, for example for direct control of the proximal trunk muscles. This is also where preparations for movements are made, such as spatial guidance for reaching and showing. Corresponding information is required for this, which is obtained from the sensory reports in the parietal cortex.

The supplement motor complex (SMC), formerly known as the supplement motor area (SMA), lies in front of the primary motor area, roughly on the midline of the cortex. It has many supporting functions, including the internal planning of movement sequences, especially movement sequences, as well as the coordination of movements on both sides of the body, especially the bimanual coordination as well as the control and adjustment of posture to a movement.

Parts of the posterior parietal cortex , which belongs to the association areas , but which is also mainly responsible for planning and transforming multisensory information into motor commands , also play an important role in movement planning and execution . The primary somatosensory cortex is also involved in the development of movements because it is close to the primary motor cortex and can cooperate closely with it.

Many other areas - distributed over large parts of the cortex - are known as association areas. The association areas take up most of the surface of the cortex. They are responsible for the complex processing of information between the primary sensory areas and the development of behavior (motor and cognitive). You are responsible for a meaningful interpretation of the perceptions and enable us to interact successfully with the world. They are located in the parietal , temporal, and occipital lobes, all of which are located in the posterior ( posterior ) part of the cortex. Like the whole brain, they are organized as an active network. This means that they communicate internally in all their functions with each other and with all other parts of the entire brain, including the basal ganglia , the cerebellum and the pons in the midbrain .

Arbitrary movements are primarily initiated by the motor cortex ( M1 ) after preliminary work on numerous, if not all, brain structures (because of the constantly updated analysis of the external (environment) and internal (organism) situation ). The pre-frontal cortex also plays an important role in their development and control, as it has a kind of filter function and can thus promote targeted actions and block irrelevant ones. Most movement sequences, especially those of daily life such as breathing, chewing, swallowing, but also eye movements, balance control and locomotion can be initiated and controlled without the cortex and parts of the cerebrum.

Visual information, which has very fast connections to the cortex, plays an important role in controlling movement . The precise control of arm, hand and finger muscles for the finely coordinated manipulation of processes is of particular importance. This is an evolutionary advancement of motor skills in primates and humans. The control loops for these processes have arisen from the phylogenetically existing networks for the tasks of the upper extremities and are closely linked to these archetypes for locomotion.

The movement control of the cortex also differs from that of the other control bodies in that, on the one hand, the cortex also selects, compiles and initiates the voluntary movements so that they can be changed or terminated via recurrent connections during the process ("point of no return"). The same sensory inputs can also trigger different actions in the cortex, depending on the intention or necessity developed in the cortex.

Research into the complex tasks and capabilities of neurons in the primary motor cortex continues to provide new insights.

The investigation of the times for the feedback about movements in progress is of great scientific interest. Information about executed movements ( reafferences ) first reaches the parietal cortex (after 25 ms) ( parietal lobe ), a little later (between 40 ms and 60 ms) several parts of the somatosensory and premotor cortex.

The cooperation of all brain structures involved in a movement or action can be improved through repetition. This is called learning.

The basal ganglia

→ Main article : Basal ganglia

Course of information in the basal ganglia

construction

The basal ganglia play an important role in the selection of movement sequences and their initiation. They are located inside the cerebrum (subcortical) and consist of several parts: the caudate nucleus (curly nucleus) and the lentiform nucleus (lens-shaped nucleus) which in turn consists of the putamen and the globus pallidus (internal and external). The caudate nucleus and putamen are only separated from one another in the later embryonic phase, but remain loosely connected to one another and are then referred to together as the striatum . In a broader sense (functional), the basal ganglia also include the subthalamic nucleus and the substantia nigra (black substance). The latter forms a core area in the midbrain. It consists of a pars compacta and a pars reticulata .

All of these parts are interconnected in a network. They receive their most important information from all parts of the cerebrum, to which they also send signals back, also from other parts of the brain, for example the thalamus and the reticular formation that runs through the brain stem .

function

The main functions of the basal ganglia are triggering and selection of movements and according to recent theories and models (see below) the empowering learning (reinforcement learning). There are different models of how the movements are selected.

The movements are triggered by the information from the pallidum (globus pallidus internus), the output formation of the basal ganglia . Under rest conditions, these trigger commands are prevented by strong inhibitory (tonic inhibition) control commands. In order to trigger the sequence of movements, this inhibition (through disinhibition) must be lifted. This occurs through neurons in the entrance formation of the basal ganglia, the striatum .

The striatum receives its information from different areas of the cerebrum and directly from the thalamus , through which the sensory perceptions reach the cerebrum. The information from these sources is processed in the networks of the striatum and - if the movements are to be triggered - the inhibitions there are lifted by the excitatory connections to the pallidum . The globus pallidus internus and the substantia nigra (pars reticulata) both send feedback about their actions to the thalamus and the cortex (thalamocortical loop). Through the dopamine , which is sent from the pars compacta of the substantia nigra to all areas of the basal ganglia as well as the nucleus subthalamicus , the processes that lead to the initiation of movement can be modulated.

It is believed that the loops between the basal ganglia , thalamus and cortex are involved in planning and controlling voluntary movements, while those between the basal ganglia and the brain stem are responsible for the correct and safe execution of involuntary movements such as swallowing or coughing but also, for example, the implementation of locomotion (walking) are responsible. The activities of both loops work together intensively. For example, the thalamocortical loops are responsible for the planned start or end of a walking process, or if an unevenness in the floor makes (conscious) adjustment of the process necessary. On the other hand, the connections to the brain stem ensure that the pure walking movement is safe. These two control processes must be integrated into one another.

The basal ganglia therefore represent the crucial place from which the movement sequences are activated and then coordinated in the brain stem ,

The cerebellum

→ Main article : cerebellum

construction

The cerebellum is located at the base of the skull under the occipital lobe, behind the brain stem . Like the cortex, it consists of an outer covering of neurons ( gray matter ) which, in order to increase its surface area, is structured much more strongly by furrows than the cortex. The conduction pathways, the white matter ( medullary bed ) lie within this covering . They contain groups (nuclei) of gray matter ( neurons ), the deep cerebellar nuclei: the nucleus fastigius , the nucleus globosus, the nucleus emboliformis and the largest, the nucleus dentatus . Three parts of the cerebellum (pedunculi) connect the cerebellum to the other parts of the nervous system .

Visibly, the surface of the cerebellum is divided horizontally into the two hemispheres with the outer parts of the cerebrocerebellum and the more inner part of the spinocerebellum, the middle part of which is also known as vermis (worm). In addition, at the bottom front, on the side facing the brain stem , starting from the worm, there is a ridge, the flocculus , which, together with the adjacent worm part, the nodulus , is combined to form the flocculonodular lobe (also vestibulocerebellum ). These individual areas have different functions and are connected to the parts of the brain that correspond to their functions . They receive their information from other parts of the brain, process it - with information from the other cerebellar areas as well - and pass the results on again via the deep nuclei directly or indirectly to different motor (and other, non-motor) subsystems.

The inflows to the cerebellum ( afferents ) come from almost all parts of the nervous system : from many parts of the cortex, from nuclei in the brain stem (switching stations) and from the spinal cord . They reach the cerebellum via the deep nuclei of the cerebellum and from there to the cerebellar envelope via two types of afferent fibers.

function

The shell of the cerebellum (cerebellum) contains almost half of all neurons , although it only takes up 10% of the brain's volume. Each section of its parts consists of the same units of neural elements with a very stereotypical geometry. These structures can be divided into numerous separate modules, also known as microcircuits.

These microcircuits with their neurons and their connections are located in the three layers of gray matter. In the outer, the molecular layer, are the basket and the (outer) star cells. In the underlying Purkinje cell layer and the Purkinje cells in the lowest, the grain layer, the grains cells and the Golgi or (inner) stellate cells.

There are two types of afferent fibers, the moss and the climbing fibers , which lead to the neurons . The moss fibers come from different nuclei outside the cerebellum, the climbing fibers only from the lower olive nucleus on the contralateral side in the brain stem . The only efferents lead from the Purkinje cells to the deep cerebellar nuclei, the output structure of the cerebellum.

The climbing fibers form stimulating synapses with the dendrites of the Purkinje cells . The moss fibers initially form stimulating synapses in the granular layer with many granular cells, the axons of which extend to the molecular layer and there run parallel to the cerebellar cortex. There they make numerous contacts with the dendrites of the Purkinje cells. Collaterals of the moss and climbing fibers also pull to the deep cerebellar nuclei. From the cerebellar nuclei, for example, inhibitory connections to the olive complex and stimulating connections to various other nerve nuclei, to the thalamus and to the brain stem, run.

For a long time it was assumed that the main processing power of the cerebellum takes place within these microcircuits, that incoming and outgoing as well as excitatory and inhibitory signals are compared and offset with one another. It is also assumed that they serve to coordinate movements and their parts. It is now known, however, that this processing power mainly takes place in the cerebellar nuclei. The processing steps in these deep cerebellar nuclei have not yet been well researched.

The functions of the individual cerebellar areas can be described as follows:

The vestibulocerebellum (Lobus flocculonodularis) is the evolutionarily oldest part of the cerebellum (hence also called Archizerebellum ). It is responsible for the equilibrium and balance of the body. It therefore receives its information ( afferents ) from the semicircular canals and the otholite organ in the inner ear (these report, for example, the position of the head in relation to gravity ). In addition, it receives visual information from the 1st and 2nd visual cortex via pontine and pretectal nuclei . This shows the importance of visual information - especially unconscious information - for balance and equilibrium. The efferents of the vestibulocerebellum go to the vestibular nuclei . They control the eye muscles and the coordination of the eye muscles and head.

The spinocerebellum can be divided into the more centrally located vermis and a more outer area. The Vermis controls the support motor skills. It therefore receives its information (afferents) from the somatosensory receptors of the trunk muscles and the external eye muscles as well as from the vestibular nuclei. All of this information is important for balance and balance. Its efferents via the deep nuclei (especially the nucleus fastigius ) to other nuclei in the brainstem and from there via the reticular and vestibulospinal wings to inter- and motor neurons in the spinal cord .

The outer part of the spinocerebellum receives its information from the somatosensory receptors of the limbs (touch, pressure, position of the limbs). He receives it both directly and indirectly. The indirect route runs through various brain stem nuclei, mostly those of the reticular formation . Two lines of transmission can be distinguished. On the dorsal line, muscle and joint information from movements that have been carried out, which are included in the planning, are transmitted. They form the efference (feedforward). The information about a current movement is provided via the ventral line. The information from these two lines is compared with one another (feedback), whereby the necessary modulations of the movement sequence can be triggered and carried out.

The cerebrocerebellum is connected to the association cortex . It receives information from the premotor and supplement motor cortex via the pontine nuclei and the middle cerebellar stalk. After processing, it releases the efferent information about the upper cerebellar stem and the dentate nucleus . From there, part of the information reaches the motor cortices via the thalamus , a second part forms a loop over the red nucleus ( nucleus ruber ) and the olive nucleus back to the cerebellum. It is assumed that the loop over the red nucleus (nucleus ruber) and the premotor cortex supports the practice ( training ) of movement sequences and therefore movement learning.

The task of the cerebrocerebellum is to plan movements and regulate the motor programs emanating from the cortex. But it is also involved in the planning and regulation of pure cognitive functions.

Tasks and properties of the cerebellum can be described as follows:

The cerebellum ensures at all levels of planning and implementation that voluntary and involuntary movements can be carried out safely and successfully. For this purpose, it compares expected signals based on the planning with incoming ( afferent as well as reafferent) signals , which represent the current state of both the organism and the environment, but also with stored data from previous implementation of the same or similar processes. In this way, movement experiences are incorporated and adapted to new situations. This allows the muscle contractions to be coordinated so that the movements are harmonious. All of these cerebellar actions occur online .

The following specific mechanisms can serve as special aids:

1. The Purkinje cells and the deep cerebellar nuclei fire violently almost simultaneously with voluntary movements. The result is closely related to the direction and speed of movement. The somatotopic structure of the primary motor cortex can also be found within these nuclei. This indicates the recurrent loops between these two structures.
2. The muscle contractions and thus the timing (= timing) are regulated by feedforward structures . These also ensure that the force curve is not jerky, as with feedback structures, but is guided gently to the end point.
3. It is now assumed that the cerebellum has internal dynamic and kinematic models (especially for the arms and eyes) that ensure that, for example, when grasping movements, the end point occurs through a sequence of timed commands for the muscle contractions. At the same time, precise kinematic models describe the relationship between the joint angles and the position of the fingers, the necessary position of the desired end point.

The brain stem

→ Main article : brain stem

In contrast to the cerebrum, the brain stem is responsible for the unconscious states, for the preparation of actions and the communication with other individuals. It takes care of the background states such as wakefulness and conscious attention as well as sleep . He has far-reaching controlling tasks in the areas of motor skills , vegetative states but also cognitive functions. Together with the spinal cord , the brainstem can be seen as a kind of toolbox for the neural networks , because it contains the basic repertoire for the concrete preparation, execution and control of all motor actions: You can think of it like a kind of assembly line (in English meets the word assembly line ) pretty good idea this feature: When the basal ganglia arrives the requirement for a particular sequence of movements in the brain stem are all for this process needed information from the places where they from their sources delivered were and are processed on the Assembly line sent, compiled and appropriately integrated for the task - under constant control and updating - so that the current product can be transferred to the spinal cord for execution. He takes care of the processes that are necessary for survival such as breathing , swallowing , gestures and facial expressions , but also for other necessary ones such as eye movements, posture and locomotion as well as for voluntary movements. For example, after receiving the selection of the action by the striatum in the basal ganglia, he triggers the central pattern generators (CPGs), which are carried out from the spinal cord.

This is possible because all strands of information - descending (efferent) and ascending (afferent) - run through the brain stem between the cerebrum and the spinal cord, and other important information is added. This is where the messages coming from the cerebrum and those fed back from the spinal cord, those coordinated by the cerebellum and the information from the cranial nerves from the sensory organs of the head and the vital processes in the organism meet and are integrated into one another. The numerous nerve nuclei serve for this integration work (these are clusters of numerous neurons that work together to fulfill certain tasks and are connected to one another by far-reaching and reciprocal branches and connections).

Structure and functions

The brain stem connects the functionally different structures of the cerebrum and the spinal cord . It lies behind and below ( caudal ) the cerebrum and above ( rostral ) the spinal cord. It consists of the midbrain ( mesencephalon ), the bridge ( pons ) and the elongated medulla ( medulla oblongata ) and mainly contains nerve connections and nerve cords (tracts) for example the corticospinal tract ( motor system ), the medial lemniscus tract ( sensor system ) or the spinothalamic tract (for pain, touch and temperature sensation) and nerve nuclei.

In the area of ​​the midbrain, in the uppermost part, the roof of the midbrain, there is the four- hill plate with the superior colliculus (upper hill), which, like the lateral knee cusp (geniculate lateralis), with which it is connected, is involved in processes of vision . The inferior colliculus (lower hill), also located there, is the most important core of the midbrain for the auditory tract . He receives information from the auditory cortex and several other brain stem nuclei. In the tegmentum , the part below the tectum, there are, in addition to a series of nuclei of the cranial nerves, further nerve nuclei and nerve tracts, the formatio reticularis , a network of nerve cells that extends over the entire tegmentum and through the entire spinal cord . This is where the kernels for regulating vital functions such as circulation , breathing and the ascending reticular activation system (ARAS), which regulates attention and alertness, but also drowsiness and mental absence, are located.

The midbrain also contains the nuclei of some cranial nerves , the nucleus ruber (red nucleus), a switching nucleus of the motor pathways between the cerebrum and the cerebellum, and the substantia nigra , the nucleus of the dopaminergic system that controls the intensity of actions, positive due to reward , negative due to disappointment. Towards the apex (cranial) the midbrain is joined by the diencephalon .

The pons (bridge) is an area through which mainly connecting fibers run between the front and rear areas of the brain. The cerebellar stalks, which contain the nerve pathways between the cerebellum and the cerebrum , are also located here.

The medulla oblongata is the cranial (towards the head) continuation of the spinal cord . It extends from the sacral section of the spinal cord to the thalamus and consists of diffusely arranged neurons .

As mentioned, movements are prepared in the brain stem, which are then carried out by networks of the central pattern generators (CPGs) in the spinal cord.

Two examples are briefly described here for a better understanding.

1. For the organization (activation - via the reticulospinal connection) of locomotion (walking) and its control, there are two centers in the brain stem, the mesencephalic motor region (MLR) and the diencephalic motor region (DLR) . (Evolutionary in all vertebrates - including humans - intensively studied in animals up to monkeys ). If these areas are mildly irritated, the animals begin to walk. If you increase the stimulus, they accelerate their locomotion up to a gallop - birds begin to fly. The brain controls the entire motor pattern with the numerous different muscles required for this with the help of a simple, graduated signal. - The muscular details of the movement are then adapted to the acute external situation by the pattern generators in the spinal cord and by sensory control.

2. The network that organizes the saccades of the eyes and the accompanying slow head movements is located in the upper (superior) colliculus. There is a quick central command (which determines direction and amplitude) that brings the eyes (the fovea centralis ) quickly to the point of visual interest, then a slower counter-movement of the eyes when they reach the object with the slow head movement. This process is accompanied by the vestibulo-ocular reflex. This process is controlled by the visual signals from the front field of view of the eyes.

An important interaction of both systems takes place when the locomotion takes place over an unsafe surface, i.e. when precise positioning of the feet is required. In these conditions, the visuomotor control is superimposed on the locomotion pattern created in the spinal cord . This is done via the projection from the visual areas of the cerebral cortex to the motor areas via the dorsal current for movement perception.

The spinal cord

→ Main article : spinal cord

construction

The spinal cord runs through the entire spine . It has a segmental (spinal segments) structure and consists of gray and white matter. The gray matter of the nerve cells lies inside and is roughly the shape of a butterfly. The nerve cells is interneurons that numerous information merge, process and forward while networks organize, as well as motor neurons , of which the muscles of the corresponding segment are innervated. Topographically, the motor neurons are precisely arranged according to the position of the muscles they innervate. They are each grouped together in so-called pools (large groups that innervate the same muscle).

The white matter contains the nerve cords that carry the information from the higher-level brain structures to the nerve cells of the segments (descending, efferent pathways) and, conversely, the information from the individual segments to the higher-order structures (afferent pathways). The nerve cords have a fixed arrangement. The afferent tracts are more on the outer circumference of the spinal cord, the efferents more towards the center. Further afferent tracts are located in the posterior ( dorsal ) gap between the butterfly wings . Efferent tracts, for example parts of the pyramidal tract, are located in the front ( ventral ) part. The neural connections necessary for the respective segment emerge or enter between the vertebrae.

function

The information from the higher centers ( efferent ) as well as from the muscles , tendons , joints and skin ( afferent ) is integrated in the spinal cord and converted into the mechanical system of the muscles that triggers the movements.

The spinal reflexes emanating from the spinal cord are the longest known and also most carefully examined and described . They form a very quick response (contraction) e.g. B. on the stretching of a muscle - for example the hamstring reflex. These reflexes were described by the physiologist Charles Sherington at the beginning of the 20th century. For a long time it was assumed that they represent rigid behavior patterns and cannot be modified. In this respect, they were only rarely included in the considerations on movement control. For a long time it was assumed that these “reflexes” represent rigid behavior patterns and cannot be modified. In this respect, they were not included in the considerations for movement control.

They were later discovered as control loops that work at the spinal cord level. They are fast enough (approx. 20–45 ms) to be able to take effect there during a movement sequence. Their loops run from the motor neurons in the spinal cord to the muscles associated with them. In the muscles or tendons concerned, there are sensors (the muscle spindles or Golgi tendon receptors ) that report the success of the innervation back to the motor neurons. The muscle spindles, which lie within the muscle, measure the length and the speed of the change in length of the muscle fibers . The Golgi tendon receptors, which are located in the tendons, measure the tension in the muscles. The measurement results of these sensors are reported back to various neurons in the spinal cord segment from which the innervation of the muscle fibers came - the muscle spindles report directly (monosynaptically) stimulating signals back to the triggering motor neuron , the tendon receptors their inhibitory signals to interneurons . These interconnections are modified according to the current requirements. In this respect one can speak of regulation or control loops. In addition to these feedback messages from the muscles, signals from other receptors (for example skin afferents and joint information) also reach the motor neurons. This enables a quick reaction to a complex environmental situation and they offer a quick first response to the disturbance of a movement sequence.

Today we know that these control loops are parts of larger networks that organize and control entire motion sequences. These networks, also known as central pattern generators (CPG), have evolved over the course of evolution.

The pattern generators are arranged across segments so that they also organize and control movements of muscle groups across segments (legs for walking, arms for manipulation). These networks belong to the equipment of living beings from birth for elementary movement sequences (e.g. walking, grasping, but also swallowing, coughing). They have evolved from the simplest forms of movement to the higher forms of life and are modified and expanded in the course of life through adaptation and learning processes.

These patterns are assembled into ordered networks by local interneurons in the spinal cord . They coordinate the commands to the muscles and control their actions. During the execution, sensitive feedback mechanisms (afferents) ensure a refinement of the execution and an adaptation to the current environmental situation . This means that these networks are extremely flexible

The triggering, coordination and control of these networks takes place in the brain stem , because this is where the signals (information) from the cerebrum , the cranial nerves ( sensory organs , vegetative and emotional influences) and the information about the state of the skeletal muscles and the current state of the body are brought together and then forwarded to the executive systems ( muscles ).

The complexity that arises from the interaction of this control circle with the higher centers is currently being intensively researched.

Investigation method and results

The classic paradigm in research in the field of motor control is to perturb a prescribed posture or movement (perturbation) and to observe and measure whether and how the intended movement or posture is restored (compensated). For this purpose, the test person is given the task of either maintaining a certain position or performing a prescribed movement. The execution of this task is then disturbed, usually by a mechanical effect on the posture or the performing limbs. Both the type and the onset and duration of the response to this disorder are then measured. The measured values ​​are the kinematic values ​​for location, angle , speed and acceleration , the kinetic values of acting forces and the actions of the muscles that occur during the motion sequences.

Currently, the main focus is on the control of arm / hand positions and their movements. These are important for the control of artificial limbs, for example after the loss of a natural part of the body (for example a hand), but also for the construction of adaptive robots that are required in industry. For this reason, it is important to convert the research results into mathematical models , that is, to set up the associated equations .

Since the complexity of the mathematical equations for the models increases with the number of moving limbs involved, one is currently limited mainly to the investigation of arm movements, because these are with few controllable body parts (hand, forearm, upper arm) and few joints (wrist, elbow - and shoulder joint - usually only one or a maximum of two joints are considered at a time) and only a small number of muscles are involved.

In some of the investigations, the procedure is that the test person is asked to hold the arm or hand in a certain position in a defined environment, even if a sudden force (defined in terms of strength and direction) tries to break the arm (Hand) to move from this position. The following are then measured: the reaction time of the test subject, the direction , speed and acceleration of the movement triggered, as well as the intensity and time course of the activity of the muscles involved (electromyographic recordings - electromyography ). Finally, the duration of the entire action - until the arm (hand) comes to rest again, until the disturbance is compensated for - is measured. From the duration of the compensatory movement, an attempt is made to draw conclusions about the possible ways of signal processing in the organism from the perception of the disturbance to its compensation.

In another part of the investigation, it is the test person's task to perform a prescribed, targeted movement from a defined position, which is then disturbed by the forces acting on it (or by manipulating the perception of the environment). The same measured values ​​are recorded as described in the previous paragraph.

When evaluating the results of these examinations, values ​​such as the time it takes for the organism to show a regulating reaction (reaction time) and the termination of the compensatory movement also play a role. The compensatory movement consists in transferring the arm from the deflected position back into the intended movement. Joint angles and muscle actions are measured and recorded. The differences in the reactions to different but always controlled disorders are then evaluated. It is hoped to be able to draw conclusions about the control paths from the time courses of the muscle actions and their assignment to the various disorders.

The results confirm long-standing assumptions about a possible control structure. For the arm movements there are 3 to 4 different time periods (epochs) of the reaction. They are: short-latency response (20–45 ms), long-latency response (50–105 ms) and volitional response (120–180 ms). Occasionally, a period of preparation time ( baseline epoch (−100–0 ms)) is calculated for this. This means: after less than 40 ms of the disturbance, an increased activity can be detected in the EMG ( electromyography ). This part is called the 1st epoch. It is a consequence of the short circle of control over the spinal cord. After that, the electrical activity increases. The "long latency response" begins, which changes into the arbitrary phase (100–180 ms) of movement control. This results in the previously assumed correction time (with visual inspection) for an open loop control. of approx. 200 ms.

The information about the transit times - also for the 1st epoch - are so different because there are different ways of the signals . In the 1st epoch of the reaction, the shortest connection is the monosynaptic (only the synapses on the motor neuron ) connection from the muscle spindle to the motor neuron of the homonymous muscle (it innervates the muscle fibers that have been contracted). The signals from the muscle spindles can also reach interneurons via collaterals and thus to other motor neurons - that means longer switching paths. However, collaterals are also sent to ascending nerve tracts, which trigger the higher-level control circuits and possibly other activations of the muscles.

It can also be observed that in the first very short reaction time no major variations in muscle activity can be observed - due to the limitation of the feedback to the motor neuron pool, only a few muscles in the direct area of ​​action of the spinal cord. These neurons can react very quickly. The variability of muscle activity then increases with the duration of the reaction, because more and more system parts can be included.

In the time range of the short latency and the 1st part of the long latency response , very fast responses to the disturbance of a movement sequence can be made, which are often referred to as automated responses. But they are also specific for each movement sequence and are learned together with it.

In contrast to the short-latency response on the causes and sources of which there are hardly any different views in movement science, there are divergent views on the sources and the composition of the long-latency response that have been discussed for over 60 years.

Some researchers still see a proportion as a kind of automatic - i.e. independent of the specific task or movement - response that only comes from higher centers of movement control, i.e. parts in the brainstem . Another part is assigned to the specific task. How large these respective proportions are and whether they can be temporally separated from one another or overlap is the subject of current investigations.

literature

• JA Adams: A closed loop theory of motor learning. In: Journal of Motor Behavior. 3, pp. 111-150 (1971).
• Tyler Cluff, Fréderic Crevecoeur, Stephen H Scott: A perspective on multisensory integration an rapid perturbation. In: Vision Research. 2014, doi: 10.1016 / j.visres.2014.06.011
• F. Crevecoeur, I. Kurtzer, SH Scott: Fast corrective responses are evoked by perturbations approaching the natural variability of posture and movement tasks. In: Journal of Neurophysiology. 107 (2012), pp. 2821-2832.
• F. Crevecoeur, I. Kurtzer, T. Bourke, SH Scott: Feedback responses rapidly scale with the urgency to correct for external perturbations. In: Journal of Neurophysiology. 110 (2013) pp. 1323-1332.
• James Gibson: Perception and Environment. Urban and Schwarzenberg, Munich 1982.
• Sten Grillner : Biological Pattern generation: The Cellular and Computational Logic of Networks in Motion in: Neuron 52 (2006). Pp. 751-766.
• Sten Grillner, Thomas Jessel; Measured Motion: Searching for Simplicity in Spinal Locomotor Networks . In: Current Opinion in Neurobiology. 19 (2009) pp. 572-586. doi. 10.1016 / jconb.2009.10.011.
• Sten Grillner, Peter Wallén: Innate versus learned movements - a false dichotomy? in: Progress in Brain Research. 143 (2004). doi : 10.1016 / S0079-6123j43001-X
• Sten Grillner, Jeannette Hellgren, Ariane Ménard, Kazuya Saitoh, Martin A. Wikström: Mechanisms for selection of basic motor programs - Roles for the striatum and Pallidum . In: Trends in Neuroscience 28 (2005). Pp. 363-370.
• Joachim Haase, Hans Dieter Henatsch, Richard Jung, Piergiorgio Brescia, Uwe Toden; Sensorimotor in OHGauer / K.Kramer / R. Jung (ed.); Human physiology . Urban and Schwarzenberg Munich 1976. Vol. 14.
• Erich von Holst : Investigations into the functions of the central nervous system in earthworms . Dissertation 1932. Printed in: International Journal of Zoological Sciences. 51 (1932), pp. 547-588.
• Erich von Holst: On behavioral physiology in animals and humans. Collected papers Volume I and II. Piper & Co Verlag, Munich 1969.
• Erich von Holst, Horst Mittelstaedt: The Reafferenzprinzip . In: Natural Sciences. 37 (1950) pp. 464-476.
• Jim C. Houk, and SP Wise (1995). "Distributed modular architectures linking basal ganglia, cerebellum, and cerebral cortex: Their role in planning and controlling action." Cerebral Cortex 5: 95-110.
• Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science McGraw Hill, New York. 5th edition 2013, ISBN 978-0-07-139011-8
• Karl Küpfmüller: Fundamentals of information theory and cybernetics. In: OH Gauer, K. Kramer, R. Jung: Physiology of humans. Volume 10, Urban & Schwarzenberg, Munich 1974, pp. 209-248.
• Mark Latash: Progress in Motor Control. Volume I, Movement Kinetics Publishers. Champaign, Illinois 1996.
• Peter H. Lindsay, Donald A. Norman: Human Information Processing. 2nd Edition. Academic Press, New York 1977.
• Ronald G. Marteniuk: Information Processing in Motor Skills . Holt Rinehart & Winston, New York 1976.
• J. Andrew Pruszinski, Isaac Kurtzer, Stephen H. Scott: The long latency reflex is composed of at least two functionally independent processes. In: Journal of Neurophysiology. 106 (2011), p. 451.
• Edward S. Reed: An Outline of the Theory of Action Systems. In: Journal of Motor Behavior. 14, 1982, pp. 98-134.
• Richard A. Schmidt : Motor control and learning. Human Kinetics Publishers, Champaign, Illinois 1982, ISBN 0-931250-21-8 .
• Stephen Scott: Optimal feedback control and the neural basis of volitional motor control . in: Nature Reviews Neuroscience 5 (2004) pp. 532-546. doi: 10.1038 / nrn1427
• Charles C. Sherington: Flexion-reflex of the limb, crossed extension-reflex, and reflex stepping and standing. In: Journal of Physiology. 40 (1910), pp. 28-121.
• Lior Shmuelof, John W. Krakauer, Pietro Mazzoni: How is a motor skill learned? Change and invariance at the levels of task success and trajectory control. In: Journal of Neurophysiology. 108 (2012) pp. 578-594.
• Paul SG Stein, Sten Grillner, Allen I. Selverston, Douglas G. Stuart; Neurons, 'Networks, and Motor Behavior . MIT Press, Cambridge Massachusetts. 1997, ISBN 0-262-19390-6
• K. Takakusaki, K.Saitoh, H. Harada, M.Kashiwayanagi: Role of basal ganglia - brainstem pathways in the control of motor behavior . Neurosci. Res. 50 (2) (2004). Pp. 137-51. doi : 10.1016 / j.neures.2004.06.015
• Emanuel Todorov: Optimality principles in sensorimotor control. In: Nature Neuroscience. 7 (2004), pp. 907-715.
• Norbert Wiener : Man and man machine. Cybernetics and Society . Alfred Metzner Verlag, Frankfurt am Main 1952.
• Howard N. Zelaznik (Ed.): Advances in Motor Learning and Control. Human Kinetics Publishers, Champaign, Ill. 1996, ISBN 0-87322-947-9 .

Individual evidence

1. ↑ Mark Latash: Progress in Motor Control I. Movement. Kinetics Publishers, Champaign, Illinois 1996. Introduction
2. ↑ For example: Paul SG Stein, Sten Grillner, Allen I. Selverston, Douglas G. Stuart; Neurons, `` Networks, and Motor Behavior ''. MIT Press, Cambridge Massachusetts. 1997, ISBN 0-262-19390-6 )
3. ^ Joachim Haase, Hans Dieter Henatsch, Richard Jung, Piergiorgio Brescia, Uwe Toden; Sensorimotor in OHGauer / K.Kramer / R. Jung (ed.); Human physiology . Urban and Schwarzenberg, Munich 1976. Vol. 14, p. 292 f.
4. ^ Joachim Haase, Hans Dieter Henatsch, Richard Jung, Piergeorgio Brescia, Uwe Toden; Sensorimotor in OHGauer / K.Kramer / R. Jung (ed.); Human physiology . Urban and Schwarzenberg Munich 1976. Vol. 14, p. 318 f.
5. ↑ see for example: Sten Grillner. Biological Pattern generation: The Cellular and Computational Logic of Networks in Motion in: Neuron 52 (2006) pp. 751-766.
6. ↑ for example: Tyler Cluff, Fréderic Crevecoeur, Stephen H Scott: A perspective on multisensory integration an rapid perturbation. In: Vision Research. (2014), doi: 10.1016 / j.visres.2014.06.011
7. ^ Luigi Galvani: De viribus electricitatis in motu musculari. Verlag Deutsch, Frankfurt am Main 1996, ISBN 3-8171-3052-X .
8. ↑ Richard Jung: Introduction to Movement Physiology. In: J. Haase, H.-D. Henatsch, R. Jung, P. Strata, U. Thoden: Sensomotorik. In: OH Gauer, K. Kramer, R. Jung: Physiology of humans. Volume 14. Urban and Schwarzenberg, Munich 197. p. 2.
9. ↑ see for example: Edwin A. Fleischmann, Walter Hempel: Factorial Analysis of Complex Psychomotor Performance and Related Skills. In: The Journal of Applied Psychology. 40 (1956) pp. 96-104.
10. ^ Karl Küpfmüller: Fundamentals of information theory and cybernetics. In: OH Gauer, K. Kramer, R. Jung: Physiology of humans. Volume 10, Urban & Schwarzenberg, Munich 1974, pp. 209-248.
11. ↑ Erich von Holst: Investigations into the functions of the central nervous system in earthworms. Dissertation . 1932. Reprinted in: International Journal of Zoological Sciences. 51 (1932) pp. 547-588.
12. ↑ Erich von Holst, Horst Mittelstaedt: The Reafferenzprinzip. In: Natural Sciences. 37 (1950) pp. 464-476.
13. ^ Richard A. Schmidt: Motor control and learning. Human Kinetics Publishers, Champaign, Illinois 1982.
14. ^ Lindsay / Norman
15. ↑ Ron Marteniuk
16. ↑ for example: perception and environment. Urban and Schwarzenberg, Munich 1982.
17. ^ Edward S. Reed: An Outline of the Theory of Action Systems. In: Journal of Motor Behavior. 14, 1982, pp. 98-134.
18. ^ OG Meijer, K. Roth (ed.): Complex Motor Behavior, The Motor-Action Controversy. North Holland Publishers, Amsterdam.
19. ↑ GN Ganchev, B. Dimitrov, P. Gatev (ed.): Motor Control, proceedings of the Fifth International Symposium on Motor Control 1985 in Varna, Bulgaria. Plenum Press, New York 1987.
20. ^ Nicolas Bernstein: The Coordination and Regulation of Movements. Pergamon Press, Oxford 1967.
21. ↑ HTA Whiting (Ed.): Human Motor Actions, Bernstein reassessed. 2nd Edition. North Holland. 1986.
22. ↑ Rob Bongaard, Onno Meijer G: Bernstein's Theory of Movement Behavior: Historical Development and Contemporary Relevance. In: Journal of Motor Behavior. 2000, p. 59.
23. ↑ see: Richard A. Schmidt: Motor control and learning. Human Kinetics Publishers, Champaign, Illinois 1982, pp. 190f.
24. ↑ Emanuel Todorov: Optimality principles in sensorimotor control. In: Nature Neuroscience. 7 (2004), pp. 907/908.
25. ^ JA Adams: A closed loop theory of motor learning. In: Journal of Motor Behavior. 3, pp. 111-150 (1971).
26. ↑ Emanuel Todorov: Optimality principles in sensorimotor control. In: Nature Neuroscience. 7 (2004), p. 908.
27. ↑ for example: Lior Shmuelof, John W. Krakauer, Pietro Mazzoni: How is a motor skill learned? Change and invariance at the levels of task success and trajectory control. In: Journal of Neurophysiology. 108 (2012), pp. 578-594.
28. ↑ Erich von Holst, Horst Mittelstaedt: Das Reafferenzprinzip In: Naturwissenschaften. 37 (1950) pp. 464-476
29. ↑ Sten Grillner, Jeannette Hellgren, Ariane Ménard, Kazuya Saitoh, Martin A. Wikström; Mechanisms for selection of basic motor programs - Roles for the striatum and Pallidum. In Trends in Neuroscience 28 2005. pp. 363-370.
30. ↑ Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science McGraw Hill, New York. 5th edition 2013, ISBN 978-0-07-139011-8
31. ↑ ^{a b} Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science . McGraw Hill, New York. 5th edition 2013, ISBN p. 843
32. ↑ Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science . McGraw Hill, New York. 5th edition 2013, ISBN p. 841
33. ↑ Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science. McGraw Hill, New York. 5th edition 2013. p. 845, ISBN 978-0-07-139011-8
34. ↑ Sten Grillner, Peter Wallén: Innate versus learned movements - a false dichotomy? in: Progress in Brain Research. 143 (2004). doi : 10.1016 / S0079-6123j43001-X
35. ↑ among others: Mohsen Omrani, Chantelle D. Murnaghan, J. Andrew Pruszynski, Stephen H. Scott; Distributed task-specific processing of somatosensory feedback for voluntary motor control. In: eLive 2016; 5: e13141. doi : 10.7554 / eLive.13141
36. ^ Houk, JC and SP Wise (1995). "Distributed modular architectures linking basal ganglia, cerebellum, and cerebral cortex: Their role in planning and controlling action." Cerebral Cortex 5: 95-110.
37. ^ Jim Houk, Models of the basal ganglia. in. Scholarpedia (2007) 2 (10): 1633. doi : 10.4249 / scholarpedia.1633
38. ^ Jim Houk, Models of the basal ganglia. in. Scholarpedia (2007) 2 (10): 1633. doi : 10.4249 / scholarpedia.1633 . P. 2
39. ↑ K. Takakusaki, K. Saitoh et al. a .: Role of basal ganglia - brainstem pathways in the control of motor behaviors. In: Neuroscience Research. 50, 2004, p. 137, doi : 10.1016 / j.neures.2004.06.015 .
40. ↑ Sten Grillner; Biological pattern generation: The cellular and computational logic of networks in motion. In: Neuron 52 (2006). Pp. 751-766.
41. ↑ Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science McGraw Hill, New York. 5th edition 2013, ISBN 978-0-07-139011-8 , pp. 960 ff.
42. ↑ M Uusisaari, E. De Schutter: The mysterious microcircuitry of the cerebellar nuclei. In: Journal of Physiology 15 (2011). Pp. 3441-3457. doi : 10.1113 / jphysiol.2010.201582
43. ↑ Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, Steven A. Siegelbaum, AJ Hudson; Principles of Neural Science . McGraw Hill, New York. 5th edition 2013, p. 973
44. ↑ Sten Grillner, Peter Wallén; Innate versus learned movements - a false dichotomy? In: Progress in Brain Research 143 (2004). doi : 10.1016 / S0079-6123 (03) 43001-X . P. 4
45. ↑ Sten Grillner, Peter Wallén; Innate versus learned movements - a false dichotomy? In: Progress in Brain Research 143 (2004). doi : 10.1016 / S0079-6123 (03) 43001-X . P. 7
46. ↑ CS Sherrington: Flexion-reflex of the limb, crossed extension-reflex, and reflex stepping and standing. In: Journal of Physiology. 40 (1910), pp. 28-121
47. ↑ for example: F. Crevecoeur, I. Kurtzer, SH Scott: Fast corrective responses are evoked by perturbations approaching the natural variability of posture and movement tasks. In: Journal of Neurophysiology. 107 (2012), p. 2823.
48. ↑ Sten Grillner, Peter Wallén: Innate versus learned movements - a false dichotomy? in: Progress in Brain Research. 143 (2004). doi : 10.1016 / S0079-6123j43001-X .
49. ↑ Sten Grillner, Thomas Jessel; Measured Motion: Searching for Simplicity in Spinal Locomotor Networks . In: Current Opinion in Neurobiology. 19 (2009) pp. 572-586. doi. 10.1016 / jconb.2009.10.011.
50. ↑ ^{a b} J. Andrew Pruszinski, Isaac Kurtzer, Stephen H. Scott: The long latency reflex is composed of at least two functionally independent processes. In: Journal of Neurophysiology. 106 (2011), p. 451.
51. ^ F. Crevecoeur, I. Kurtzer, T. Bourke, SH Scott: Feedback responses rapidly scale with the urgency to correct for external perturbations. In: Journal of Neurophysiology. 110 (2013), pp. 1323-1332.