The position sense or position sense is one of three perceptual qualities of interoceptive depth sensitivity. This sense provides permanent information about joint positions and the current body position in space. In cerebellar lesions and spinal cord lesions, the position sense may be impaired, causing ataxia.
What the the sense of position?
The position sense is also called the position sense or position sense and gives people a sense of their own body position. The sense provides comprehensive information about the body’s current position in space. Humans perceive stimuli from their environment as well as from their own body. The perception of stimuli from the environment is summarized as exteroception. Perception of stimuli from one’s own body is called interoception and corresponds to self-perception. Depth sensitivity is one of the most important types of perception from the field of self-perception. Proprioceptors receive stimuli from one’s own movement and holding apparatus and transmit them to the central nervous system. The depth sensibility can be divided into three different qualities of perception. The sense of force and resistance together with the sense of movement and the sense of position form the so-called kinesthetic system. The sense of position is also known as the position sense and gives people a sense of their own body position. The sense provides comprehensive information about the current position of the body in space. Included in this positional information are the positions of individual joints and the head. The interoceptors of depth sensibility are the muscle spindles, the tendon spindles and the sensitive receptors of the joint capsules, ligaments and periosteum. Through these receptors, the position sense makes a comprehensive picture of the body position and permanently projects it further to consciousness.
Function and task
The senses of the kinesthetic system play closely together and are irreplaceable for other senses of the human being. Together with the gravitational sense of the inner ear, for example, they form an important basis for the sense of balance. Only the sense of position allows humans to develop an awareness of the current inclination when the head is tilted. The sense of position is therefore indispensable for adopting a stable posture or adapting the body position to changing environmental conditions. Most proprioceptive afferents do not enter consciousness. Minor adjustments of posture, for example, tend to occur subconsciously. From all proprioceptive afferents the nervous system develops a sum and supplies in this way an information product from the spatial body relationship, the position of individual limbs to each other and the position change with movements to the central nervous system. Influences on the organism must be permanently recognized for this. The sensory information is selected there according to relevance and integrated with vestibular and optical information. During the sensory-motor integration of the stimuli, the elaboration of purposeful motor and cognitive functions takes place. The receptors of the position sense are mechanoreceptors in the joints, muscles and tendons. These sensory cells detect pressure and calculate the joint position and body position from these effects, which is transmitted to the spinal cord as a bioelectrical impulse. The static position sense detects the joint position in a body posture. The dynamic part of the position sense, on the other hand, detects changes in body posture during movement. Without the position sense, no appropriate interaction of sensory and motor stimulus processing would be possible. Purposeful and exact movements would thus be subject to disturbances. Exteroception and interoception thus play together in kinesthetics. The brain is capable of kinesthetic learning and thus stores, for example, targeted body postures, environmental information, and motor responses to adjust body postures with each other in order to be able to immediately initiate a suitable postural correction to specific environmental conditions the next time.
Diseases and ailments
One of the best-known complaints related to the sense of posture is hereditary motor-sensory neuropathy. This is a classic primary axonal HMSN disorder. Distally, patients show symmetric muscle atrophy and hollow feet. They suffer from reduced vibratory sensation and positional sense. The disease is caused by mutations of the MED25 gene and is inherited in an autosomal recessive manner.The gene MED25 corresponds to a subunit of ARC, which is known as a family of coactivators for transcription. The mutation has now been localized to chromosome 19q13.3. All disorders affecting position sense are included in the group of depth sensitivity disorders. In addition to position sense disorders, these include disorders of the sense of vibration and stereognosia. Such phenomena, apart from hereditary and genetic disorders, occur mainly after damage to the posterior horns or white matter. Such damage occurs, for example, in the course of traumatic injuries of the spinal column. Tumors in the spinal cord can also cause the lesions. The same applies to funicular spinal disorders. Just as often, the disorders described are preceded by a neurological disease such as multiple sclerosis. In this autoimmune disease, the immune system causes destructive inflammation in central nervous tissue. The consequence of a depth sensitivity disorder with cause in the spinal cord is spinal ataxia, which worsens especially in darkness. Spinal ataxias may also be triggered by vitamin B deficiency or poisoning and infectious diseases such as syphilis. Alcohol intoxication also triggers such ataxia, which is associated with an inability to coordinate movements and control posture. Depth sensitivity disorders may just as well be caused by lesions in the cerebellum or disturbances of specific receptors in the Golgi tendon organs, muscle spindles, and joint receptors. In all cases, patients no longer correctly estimate their own position in space. The result is an idiosyncratic posture, a disturbed gait pattern, and often an inability to make rapid agonist-antagonist movements. Treatment of such ataxias relies on occupational therapy and physical therapy and is primarily intended to improve patients’ body awareness.
