The sense of motion is part of the interoceptive and kinesthetic depth sensitivity that provides permanent feedback to the brain about the extent of movement. Proprioceptors in muscles, tendons, bones, and joints are responsible for motion perception. Neurological diseases can disrupt the sense of movement.
What the depth sensitivity?
The sense of motion is part of the interoceptive and kinesthetic depth sensibility, which provides permanent feedback to the brain about the extent of movement. Human perception consists of exteroception and interoception. Exteroception corresponds to the perception of stimuli from the environment and determines the impressions a person gains of situations and the world. Interoception, on the other hand, means the perception of stimuli from one’s own body and is a considerable part of self-perception. Surface sensitivity, for example, as a perceptual quality of the skin, is an instance of exteroception. Depth sensitivity or proprioception, on the other hand, summarizes human abilities to detect one’s own body position in space and corresponds to an interoceptive perceptual quality. Through depth sensitivity, humans are endowed with kinesthesia, i.e., sensation of movement. He can unconsciously control and steer the movement of his body parts. In the 19th century, the British neurologist Henry Charlton Bastian defined the sense of movement and a brain area for processing movement as kinesthesia. The sense of movement is one of three qualities of depth sensitivity and, together with the sense of position and the sense of force or resistance, forms the totality of the depth-sensitive perceptual faculty. The position sense gives the person information about the current body position. The sense of force and resistance mediates the dosage between push and pull, and the sense of movement provides continuous feedback to the brain about the extent of movement. Thus, the sense of motion unconsciously regulates one’s body position during movements. The sensory cells of the sense of motion are depth-sensitive muscle spindle, tendon spindle, and receptors in the joint capsules, ligaments, and periosteum.
Function and task
Thanks to the sense of motion, a person can, for example, bring his index finger to the tip of his nose with his eyes closed. He can walk, jump and run in the dark and does not have to rely on the sense of sight for his movements. The qualities of depth-sensitive perception are closely interconnected. The direction and speed of movements are measured by the sense of motion. The sense of perception continuously transmits movement and position information to the brain. Meanwhile, the force for movement execution is measured by the sense of force and the current position of the body is determined by the sense of position. The depth sensibility not only plays a close role in itself, but is also closely interconnected with the sense of balance. The receptors of depth sensitivity, and thus also of the sense of movement, are called proprioceptors. They bind to stimulus molecules and in this way register information about the tension and length of the muscles. Each skeletal muscle contains centrally located muscle spindles. Individual muscle fibers are arranged in a spindle shape around the muscle spindle. The muscle ends with the tendon and the Golgi tendon organ. The tendon organ is also a sensory cell and is located at the boundary between the muscle fibers and the tendon. Muscle spindle and Golgi tendon organ provide important information about body position and body movement. Muscle spindles are each surrounded by a nerve fiber that picks up muscle tension. When a muscle contracts or starts moving, a rotational movement takes place on the muscle fibers. The twisting motion triggers the monosynaptic twisting reflex. The nerve fibers at the muscle spindles detect the impulse and transmit it to the brain. The nerves transmit the information as an afferent reflex component to motoneurons. These movement-specialized nerve cells transmit the impulse via the tractus spinocerebellaris to the cerebellum and via the hindbrain to the cerebrum. Thus, together with the joint receptors, they feed detailed information about the position of the body to the cortex. The conscious perception of this information corresponds to kinesthesia. The sense of balance provides important additional information to balance the position of the body. Its receptor cells are the hair cells and are often included among the motion receptors.
Diseases and disorders
Depth sensitivity, with the sense of motion as its main component, is not expressed to the same degree in all people.Although every human being with the corresponding anatomical structures has at least the ability to perceive movement, the sense of movement is only formed through movement experiences. For this reason, people with a lack of movement sometimes have a less pronounced sense of movement. This phenomenon plays a role especially in the 21st century, as the modern lifestyle of the western world is often accompanied by a lack of movement. A below-average sense of movement can manifest itself, for example, in the inability to perform movements without visual control. Apart from the individual expression of the sense of movement, complaints in the area of body sensation can also be due to neurological diseases. Polyneuropathy, for example, is a disease of the peripheral nervous system that can occur in the context of poisoning, malnutrition, infection, and diabetes or alcoholism. Various nerves suffer damage. In addition to surface-sensitive sensory disturbances, the disease can also cause depth-sensitive sensory disturbances. The result is paralysis or other movement deficits. Familiar movements are sometimes perceived as difficult when there is damage to the depth-sensitive structures and nerve pathways. Often, the movement deficits are also associated with sensitivity disorders of the skin, especially in the case of a peripheral nervous disorder. Even more frequently, disorders of deep sensitivity and sense of movement are associated with central nervous disorders. In the autoimmune disease multiple sclerosis, for example, the patient’s immune system attacks nerve tissue of the central nervous system and can thus cause damage to the sense of movement. However, complaints with the sense of movement do not necessarily have to be due to diseases, but can also be caused by medication or alcohol and drugs. Unlike neurological diseases or trauma, medications and alcohol or drugs only turn off depth-sensing perception for a period of time.
