The acronym sensorimotor is composed of the two terms sensory and motor and describes a motor function of the muscles, which are controlled largely unconsciously by sensory impressions. As a rule, this involves learned complex movement sequences such as walking upright, riding a bicycle, playing with balls, steering a car and much more. During the learning process, connections (synapses) are formed in certain centers of the brain, which are stored in the multisensory movement memory.
What is sensorimotor function?
The acronym sensorimotor is composed of the two terms sensory and motor. It usually refers to learned complex movements such as walking upright, riding a bicycle, or steering a car. The term sensorimotor is an acronym and is composed of the terms ‘sensory’ and ‘motor’. Sensory includes all sensory services that can be consciously experienced, such as vision, hearing, vestibular and proprioceptive sensations, and many others. A key feature of sensorimotor activity is that the complex movement processes are based on multi-sensory messages, some of which may be received unconsciously. The complex sensorimotor movement sequences themselves can also proceed largely unconsciously after they have been trained sufficiently intensively. This has the advantage that motor instructions to the muscles come about much more quickly, almost reflexively. Corrective motor activity, based on inputs from specific sensors, can thus begin and proceed much more fluidly, elegantly and delicately in fine motor activity. Typical is the learning of the upright gait in a toddler, which needs a lot of time and intensive practice to be able to walk upright fluently and unconsciously. The field of sensorimotor science concerns both neuroscience, which deals with stimulus processing in the brain and its translation into motor stimuli in addition to stimulus transmission, and sports science, which deals with the optimization of the musculoskeletal system.
Function and task
Complex movement sequences rely on inputs from our senses for control in gross and fine motor functions. The processing of the “input signals” provided by the eyes, the sense of balance, the ears, and proprioception occupies the largest space. A systematic interconnection between the sensory and motor systems therefore forms the prerequisite not only for very complex movement sequences, but also for movement sequences that make normal life possible in the first place. Complex interconnections between the individual sensors even make it possible to continue the movement sequence even in the event of the temporary failure of a sensor. For example, the upright gait is possible even in the dark, because the control of the upright gait is only possible via the vestibular system (organ of equilibrium) in connection with the proprioception. The feedback from the proprioceptors in the feet is sufficient to walk upright. In contrast, riding a bicycle in complete darkness is not possible because the proprioceptors in the feet cannot provide feedback on the position of the bicycle and the vestibular system can only report accelerations. On the other hand, the eye also relies on vestibular messages because vestibular stimuli are faster than the complex image processing in the brain. This is noticeable, for example, in a flight simulator without a motion system. Many pilots find it difficult to cope with a fixed flight simulator without a motion platform because the fast, vestibular stimuli for sensitive and timely control corrections are missing. The multisensory motion sequence then becomes a one-dimensional motion sequence that relies solely on the eye. Most protective reflexes, such as the eyelid closure reflex or the patellar tendon reflex, are also based on a sensorimotor process, which in some cases is only switched via a single ganglion, in favor of a reduction in the reaction time between stimulus and execution of the reflex. In the eyelid closure reflex, which is intended to prevent an approaching insect from striking the unprotected eye, for example, a few milliseconds can determine the success or failure of the reflex.
Diseases and complaints
The compound term sensorimotor already suggests that problems can occur on either the sensory or motor side.Due to the neuronal complexity of the overall sensory system and neuronal circuitry, it is not surprising that problems and diseases are more common on the sensory side than on the motor, muscular side. Sensory-motor dysfunction is often caused by primary neuronal diseases such as stroke, Parkinson’s disease, cerebral hemorrhage, dementia, or by impairments of the neuronal afferent sensory transmission pathways or the efferent motor nerves. In strokes, occlusion of an artery causes a lack of oxygen to the area of the brain that was supplied by the affected artery. This can have a serious impact on sensorimotor performance if the relevant centers are affected by the infarction. Polyneuropathy disease affects peripheral nerves, including sensitive nerves, so that sensorimotor performance may be seriously impaired. Increased risks for the occurrence of neuropathy exist in diabetics, in chronic alcohol abuse and in nicotine addiction. Polyneuropathy is an example of a loss of sensorimotor function due to disease of the peripheral nerves or the transmission lines of sensory messages. The central nervous system is not affected in neuropathy. Parkinson’s disease is a non-contagious neuronal disease that manifests itself very early in its course in an impairment of sensorimotor performance due to a marked slowing of movements. An impairment of the sensorimotor system can also have genetic causes, which in weakly developed cases only become noticeable in the adolescent. Frequently, the tactile sensors of the skin are affected, leading to certain malfunctions and deficits in sensorimotor function. On the muscular side, various muscle diseases can cause impaired motor function. Typical diseases include muscle inflammations (myopathies) and muscular dystrophies, as well as various metabolic diseases.
