The sense of vibration is a perceptual quality of the sense of touch, which is realized by the Meissner and Vater Pacini corpuscles. The sense of vibration in humans plays a role not only for stimuli from the environment, but also for those from our own bodies. Peripheral nerve damage can interfere with the sense of vibration.
What is the sense of vibration?
The Vater-Pacini and Meissner corpuscles are primarily responsible for the human sense of vibration. The corpuscles are located particularly in the subcutis and respond to changes in pressure and vibration. The human sense of touch has various perceptual qualities. In addition to pressure perception, it is capable of perceiving vibrations. Thus, the human sense of vibration is a subcategory of the tactile qualities and is also called pallesthesia. The first place for tactile perceptions are the so-called mechanoreceptors. Humans possess various types of these sensory cells. For the human sense of vibration, the Vater-Pacini and the Meissner corpuscles are primarily responsible. These sensory cells pick up high-frequency and low-frequency vibratory stimuli from the environment, convert them into proportional excitation, and send the vibratory information to the central nervous system, where it reaches consciousness. The adequate stimulus for the vibration sense is the mechanical vibration energy in a periodic time course. Humans therefore register, for example, thanks to their vibration sense on the fingertip, mainly vibrations with a frequency around 200 Hz. To trigger a sensation, humans require much higher vibration amplitudes than, for example, insects, which have special organs for vibration perception.
Function and task
The Vater-Pacini corpuscles of the vibration sense are rapidly adapting mechanoreceptors with an oval-shaped base and a longitudinal diameter of about one millimeter. Their lamellae are arranged in an onion–skin fashion and lie around the uninsulated medullary end of insulated medullary nerve fibers. The lamellae of the corpuscles are composed of Schwann cells separated by layers of interstitial fluid and contain collagen fibers with glycoproteins. The interior is fluid-filled and contains a free neuron. The corpuscles are located particularly in the subcutis and respond to changes in pressure and vibration. They are not capable of registering constant sustained pressure. Deformation of the receptors by a vibration or pressure stimulus changes the conformation of their sodium channels. Sodium thus flows in from the cell membrane, triggering an action potential that travels along afferent nerve pathways to the brain. Vater-Pacini corpuscles respond only to high-frequency vibration. Together with Meissner’s tactile corpuscles for low-frequency vibration, they form the entirety of the human sense of vibration. The Meissner corpuscles are located within the inguinal skin in the dermal stratum papillare. The receptors are up to 150 µm long and are cone-shaped. Inside their connective tissue capsules lie isolated myelin-containing nerve fibers, whose uninsulated terminals generate the action potentials upon vibration and pressure. Meissner’s corpuscles are fast-adapting differential receptors, so-called D receptors, with an action potential frequency proportional to the speed of the stimulus change. Each receptive field of a Meissner corpuscle has only a small size, but a higher resolving power. This allows the corpuscles to discriminate even closely spaced vibrations. Like the Vater-Pacini corpuscles, the Meissner corpuscles send information about detected vibrations via the spinal cord to the central nervous system and the brain for transmission to consciousness. Pallesthesia or the sense of vibration is relevant not only for the detection of extroceptive stimuli from the environment, but also for the registration of introceptive vibratory stimuli from within the self. In this context, the sensory quality of touch plays a role especially for depth sensitivity.
Diseases and ailments
Disorders or complaints of the sense of vibration and touch are nerve disorders and thus a field of neurology. Pallesthesia is studied in neurology primarily to assess depth sensitivity because of its relevance to depth sensitivity.A graduated 128-Hz tuning fork according to Rydel-Seiffer is used to quantify vibration sensations in scale ranges between 0 and eight. The neurologist strikes the tuning fork and places it on superficial parts of the bone, starting distally. If perceptual deficits related to vibration are apparent in the distal area, the neurologist continues the examination in a proximal direction. On the lower extremities, for example, he places the tuning fork on the big toe or the spina iliaca anterior superior. On the upper extremities, he places it on the ulnar styloid process or the olecranon, and in the region of the trunk he checks the vibration sensation on the sternum. For the entire duration of the examination, the patient must keep his eyes closed and, following instructions, indicate to the neurologist the times when he no longer perceives vibrations. The value for vibration sensation is thus read on the scale. Disturbances of the sense of vibration can correspond either to a reduced perception of vibration with values below 6/8 or to a complete loss of the sense of vibration. In the former case, pallhypesthesia is present. Complete failure is also referred to as pallanesthesia. In both disorders, a nerve disorder in the peripheral nervous system is suspected, such as a polyneuropathy. Polyneuropathies can be related to poisoning or previous infections, for example. Impaired vibratory sensation as a result of a lesion in the central nervous system is rather rare. In some circumstances, however, spinal cord lesions or injuries to the lemniscus medialis may be associated with vibration disorders. Particularly rare, but possible, vibration sense disorder is a consequence from injury to the sensory cortex. If a lesion in the central nervous system actually underlies the vibration sense disorder, this lesion may be, for example, tumors or inflammatory injury to nerve tissue, in addition to traumatic injury.
