A contribution to the nomenclature of peripheral sensory structures (sensory nerve endings)

The author has shown the variety in denominating peripheral sensory structures serving for mechanoreception, nociception, thermoreception and chemoreception. To term peripheral sensory structures as nerve endings is considered particularly unsuitable because this denomination is based only on morphogenesis of the ending. From the view of system approach, the peripheral sensory structures forms one unit formed by two or more structural subsystems. Even though the axon or its dendritic zone has the leading role in this unit, the function of the whole formation is influenced (modulated) by further non-nervous components. Although the causes of velocity of adaptation in some sensory structures have been already explained (e.g. in lamellar corpuscles with a thick capsule), different adaptation velocity of Merkel complexes in reptiles and birds on one side, and in mammals on the other, with the same structure has not been clear up to now. From the view of system approach as well as of the share of non-nervous components in the activity of the whole sensory structure, the author has suggested to introduce the term "sensory nerve formation" for peripheral sensory structures serving for mechanoreception, nociception, thermoreception and chemoreception. The term "complex sensory nerve formation" is suggested for more complex sensory structures in which either more sensory nerve formations of the same kind (Pinkus tactile dics) or different kinds of sensory formations (Eimer organ of a mole) are connected constantly or in which the connection of sensory nerve formations with other supporting structures (hairs, feathers) occurs.     

A fine structural localization of the non-specific cholinesterase activity in glomerular nerve formations (endings)

Snout glabrous skin (rhinarium) of the cat is innervated not only by typical simple lamellar corpuscles but also glomerular formations. In contrast to simple lamellar corpuscles, glomerular nerve formations are located away the dermal papillae. In cross sections, glomerular nerve formation consists of several axonal profiles enveloped by 1-2 cytoplasmic lamellae of Schwann cells. The space among them is filled by collagenous microfibrils and the basal lamina-like material. Capsule was composed from fibroblast-like cells without definite basal lamina. An electron-dense reaction product due to non-specific cholinesterase activity was associated with Schwann cells and their processes surrounding unmyelinated terminal portion of the sensory axons. Abundant reaction product was bound to the collagenous microfibrils and was deposited in extracellular matrix between Schwann cell processes. These results are further evidence for the presence of the non-specific cholinesterase molecules as integral component of the extracellular matrix in sensory corpuscles. On the basis of histochemical study two possible explanation are considered for functional involving of this enzyme in sensory nerve formations.     

Vocal-speech development of the child during the first year of life

The study aimed at investigation into the first step of language acquisition by Russian children and the imitation process as a possible mechanism of mastering the language through the sounds specific for their native language. On the basis of spectrographic, phonetic, and listener's analysis of the sounds infants, the beginning of shaping of the phonologic system in Russian language, was shown. It was shown that, during imitation of mother's voice, children acquire articulation skills and sound utterances approximating a phoneme category of the native language. The data obtained indicate that interaction between mother and child fulfills the function of learning transmitting a language data on the tongue trame.     

Formation of language-specific characteristics of speech sounds in early ontogeny

Heterochronic formation of basic and language-specific speech sounds in the first year of life in infants from different ethnic groups (Chechens, Russians, and Mongols) has been studied. Spectral analysis of the frequency, amplitude, and formant characteristics of speech sounds has shown a universal pattern of organization of the basic sound repertoire and “language-specific” sounds in the process of babbling and prattle of infants of different ethnic groups. Possible mechanisms of the formation of specific speech sounds in early ontogeny are discussed.     

Do newborn vocalizations affect the behavioral and hormonal responses of nonreproductive male common marmosets (Callithrix jacchus)?

Parental care in mammals is influenced by sensory stimuli from infants, such as sight and sound, and by changes in the hormone levels of caretakers. To determine the responsiveness of common marmoset (Callithrix jacchus) adult males with and without previous experience in caretaking to newborn sensory cues, we exposed twelve males to infant vocalization recordings and assessed their hormonal and behavioral responses. Males were placed in the testing cage for 10 min under two conditions: (a) control condition (exposure to adult conspecific vocalization recordings), and (b) experimental condition (exposure to infant vocalization recordings). We recorded the frequency of approach towards the sound source, the time spent near it and locomotion frequency of males in the cage under both conditions. Blood samples were collected after each test for cortisol, measured by the enzyme immunoassay method. Infant vocalization affects the behavioral and hormonal responses of non-reproductive male common marmosets. All males approached and spent more time near the sound source and showed an increase in locomotion during infant vocalization exposure compared to the control condition. Successive exposure to infant vocalization increased the responsiveness in inexperienced males. Cortisol levels were significantly higher following infant vocalization exposure compared to the control condition. These findings support the assumption that sound stimuli from the newborn are critical in initiating and maintaining caretaker responsiveness and that cortisol seems to be important for alertness to sensory stimuli, modulating their motivation to interact with infants.     

Functional morphology of the taste buds of Florida manatee,Trichechus manatus latirostris

The Florida manatee, Trichechus manatus latirostris, is a fully aquatic, threatened marine mammal for which increased understanding of their physiology, reproduction, and nutrition supports management decisions. Manatees may use taste to distinguish saltwater gradients, toxin detection, food assessment, and social interactions. This study sought to locate and characterize manatee taste buds comparing location, structure, number, and size to other species. Entire heads from manatees (6 males, 4 females) of various ages were obtained. The muzzle, tissue surrounding the nares, oral cavity, and epiglottis were examined grossly for pits and papillae. Tissues were examined using light and transmission electron microscopy. Within the predominant taste bud location, the tongue root, taste bud number was estimated using samples from four animals. The average number of taste buds within the tongue root was 11,534 (range 2,711–23,237) with sparse taste buds located on the soft palate and epiglottis. The location along the lateral surface of the tongue root and bordered by grooves, through which tastants could be easily transported, has functional significance. Large numbers of taste buds within the tongue root suggest that taste is an important component of manatee sensory systems and behavioral research would clarify this.     

Development of the tongue and taste disks in Pelobates fuscus

In the tadpole of Pelobates fuscus the process of tongue formation starts at the 32nd developmental stage. In more advanced stages (older than 38th) fast anterior and faucial growth of the tongue fold has been observed. This process is accompanied by the development of the gustatory organs. The dorsal surface of the tongue fold, smooth at the beginning, in older tadpoles (developmental stages 36-39th) forms protrusions in which gustatory organs of the taste disk type (TDs) develop. In the 41 st tadpole developmental stage anlages of TDs are formed by elongated cells, located more or less perpendicularly to the surface of the tongue. The diameter of the sensory area of a TD at the 45th developmental stage amounts to 94 microm, while in metamorphosed individuals it reaches 130-140 microm. At the base of a TD the presence of basal cell morphologically similar to that of Merkel cell was observed at the 42nd developmental stage of a tadpole. Fully developed afferent synaptic connections in the sensory epithelium of a TD were found starting from the 44th developmental stage. Single synaptic vesicles with an electron-dense core were observed in gustatory cells as early as at the 41 st developmental stage of the tadpole. From the observations reported here it can be inferred that in Pelobates fuscus development of both the tongue and TDs is similar to that already described in the representatives of the Rana genus.     

Category-Specific Processing of Scale-Invariant Sounds in Infancy

Increasing evidence suggests that the natural world has a special status for our sensory and cognitive functioning. The mammalian sensory system is hypothesized to have evolved to encode natural signals in an efficient manner. Exposure to natural stimuli, but not to artificial ones, improves learning and cognitive function. Scale-invariance, the property of exhibiting the same statistical structure at different spatial or temporal scales, is common to naturally occurring sounds. We recently developed a 3-parameter model to capture the essential characteristics of water sounds, and from this generated both scale-invariant and variable-scale sounds. In a previous study, we found that adults perceived a wide range of the artificial scale-invariant, but not the variable-scale, sounds as instances of natural sounds. Here, we explored the ontogenetic origins of these effects by investigating how young infants perceive and categorize scale-invariant acoustic stimuli. Even though they have several months of experience with natural water sounds, infants aged 5 months did not show a preference, in the first experiment, for the instances of the scale-invariant sounds rated as typical water-like sounds by adults over non-prototypical, but still scale-invariant instances. Scale-invariance might thus be a more relevant factor for the perception of natural signals than simple familiarity. In a second experiment, we thus directly compared infants'' perception of scale-invariant and variable-scale sounds. When habituated to scale-invariant sounds, infants looked significantly longer to a change in sound category from scale-invariant to variable-scale sounds, whereas infants habituated to variable-scale sounds showed no such difference. These results suggest that infants were able to form a perceptual category of the scale-invariant, but not variable-scale sounds. These findings advance the efficient coding hypothesis, and suggest that the advantage for perceiving and learning about the natural world is evident from the first months of life.     

Peripheral and central asymmetry in the swimmeret system of the hermit crab,Pagurus pollicarus

Summary The consequences of the degeneration of all pleopods on the right side in the adult hermit crab were examined by comparing the motor and sensory components of the first root on both sides of the abdomen. In the third segment, the populations of sensory receptors remain relatively unaffected, with the number of units recorded extracellularly, their position and mode of activation, and their conduction velocities similar on the two sides. In contrast, only 2 or 3 somata in the ganglion are back-filled with cobalt via the right first root, compared to approximately 20 filled through the left root. While no remnant of the pleopod musculature remains on the right side, extracellular action potentials propagating centrifugally could be elicited in the right first root. The central cytoarchitecture of the first root neurons, as revealed by cobalt staining, was also studied in 3 other macruran species. The apparent phylogenetic variability revealed in comparing the swimmeret systems of the 4 related decapods is discussed in terms of different probabilistic strategies for crustacean neuromuscular ontogeny.     

Modulation of prey capture kinematics and the role of lingual sensory feedback in the lizard Pogona vitticeps

Most organisms feed on a variety of prey that may differ dramatically in their physical and behavioural characteristics (e.g. mobility, mass, texture, etc.). Thus the ability to modulate prey capture behaviour in accordance with the characteristics of the food appears crucial. In animals that use rapid tongue movements to capture prey (frogs and chameleons), the coordination of jaws and tongue is based on visual cues gathered prior to the prey capture event. However, most iguanian lizards have much slower tongue-based prey capture systems suggesting that sensory feedback from the tongue may play an important role in coordinating jaw and tongue movements. We investigated the modulation of prey capture kinematics in the agamid lizard Pogona vitticeps when feeding on a range of food items differing in their physical characteristics. As the lizard is a dietary generalist, we expected it to be able to modulate its prey capture kinematics as a function of the (mechanical) demands imposed by the prey. Additionally, we investigated the role of lingual sensory feedback by transecting the trigeminal sensory afferents. Our findings demonstrated that P. vitticeps modulates its prey capture kinematics according to specific prey properties (e.g. size). In addition, transection of the trigeminal sensory nerves had a strong effect on prey capture kinematics. However, significant prey type effects and prey type by transection effects suggest that other sources of sensory information are also used to modulate the prey capture kinematics in P. vitticeps.     

Immunohistochemical study of sensory nerve formations in human glabrous skin.

The sensory nerve formations (or corpuscles) of normal human glabrous skin from hand and fingers, obtained by punch biopsies, were studied by the streptavidin-biotin method using monoclonal antibodies directed against neurofilament protein (NFP), S-100 protein, glial fibrillary acidic protein (GFAP), cytokeratins, and vimentin. NFP immunoreactivity (IR) was observed in the central axons of most sensory formations, while S-100 protein IR was restricted to non-neuronal cells forming the so-called inner cells core or lamellar cells. Furthermore, vimentin IR was found in the same cells of Meissner's and glomerular corpuscles. None of the sensory nerve formations were stained for GFAP or keratin. The present results suggest that the main nature of the intermediate filaments of the non-neuronal cells of sensory nerve formations from human glabrous skin is represented by vimentin and not by GFAP. Thus, our findings suggest that lamellar and inner core cells of SNF are modified and specialized Schwann cells and not epithelial or perineurial derived cells.     

Deglutitive movement of the tongue under local anesthesia

The purpose of the present study was to investigate whether or not sensory input from the tongue affects deglutitive tongue movement. Subjects were seven healthy volunteers with anesthetic applied to the surface of the tongue (surface group) and seven healthy volunteers with the lingual nerve blocked by anesthetic (blocked group). We established six stages in deglutition and analyzed deglutitive tongue movement and the time between the respective stages by cineradiography before and after anesthesia. After anesthesia in both surface and blocked groups, deglutitive tongue movement slowed and bolus movement was delayed. The deglutitive tongue tip retreated in the blocked group. These results suggest that delay of tongue movement by anesthesia causes weak bolus propulsion and that deglutitive tongue tip position is affected by sensory deprivation of the tongue or the region innervated by the inferior alveolar nerve.     

Generator locations of movement-related potentials with tongue protrusions and vocalizations: subdural recording in human

Movement-related potentials (MRPs) associated with tongue protrusions and vocalizations were recorded from chronically implanted subdural electrodes over the lower perirolandic area in 7 patients being evaluated for epilepsy surgery. In 3 patients, tongue protrusions elicited a clearly defined, well localized slow negative Bereitschaftspotential (BP) at the motor tongue area, and a positive BP at the sensory tongue area. At the motor tongue area the negative BP was followed by a negative slope (NS′) and a motor potential (MP), and at the sensory tongue area the positive BP and a positive reafferent potential (RAP) were seen but no NS′ and MP could be identified. In the other 4 patients, tongue protrusions elicited positive BP, NS′ and MP at the motor and sensory tongue area, and positive RAP at the sensory area. It was concluded that BPs, NS′ and MPs are mainly generated in the motor cortex involving the crown as well as the anterior bank of the central fissure. The sensory cortex (areas 3a and 3b) also participated in the generation of BPs but to a lesser degree. Different degree of involvement of these multiple generators most likely explains the interindividual variability of polarity and distribution of the MRPs. RAPS most likely arise from primary sensory areas 1 and 2. Brain potentials were also recorded at the motor (2 patients) and sensory (2 patients) language areas, but no specific language-related potentials could be identified.Evoked potentials to lip stimulation were investigated in 4 patients. In 3 patients, the responses at the sensory tongue area (P16, N21 and P30) had the same latency but opposite polarity to those at the motor tongue area. In the other patient, the responses (P16, N21 and P30) at the motor and sensory tongue areas were of the same polarity. The MRPs to tongue protrusions in those 4 patients revealed the same polarity relationship between the pre- and postcentral potentials. However, the maximal amplitude of evoked potentials and MRPs was seen at almost the same electrodes, suggesting that the main generators for these MRPs and evoked potentials must be located at contiguous areas in the anterior and posterior bank, respectively, of the central fissure.     

The role of hypoglossal sensory feedback during feeding in the marine toad, Bufo marinus.

Behavioral observations demonstrate that bilateral deafferentation of the hypoglossal nerves in the marine toad (Bufo marinus) prevents mouth opening during feeding. In the present study, we used high-speed videography, electromyography (EMG), deafferentation, muscle stimulation, and extracellular recordings from the trigeminal nerve to investigate the mechanism by which sensory feedback from the tongue controls the jaw muscles of toads. Our results show that sensory feedback from the tongue enters the brain through the hypoglossal nerve during normal feeding. This feedback appears to inhibit both tonic and phasic activity of the jaw levators. Hypoglossal feedback apparently functions to coordinate tongue protraction and mouth opening during feeding. Among anurans, the primitive condition is the absence of a highly protrusible tongue and the absence of a hypoglossal sensory feedback system. The hypoglossal feedback system evolved in parallel with the acquisition of a highly protrusible tongue in toads and their relatives.     

Light and scanning electron microscopic study of the structure of the ostrich (Strutio camelus) tongue

The ostrich's tongue is situated in the posterior part of the oropharyngeal cavity and its length is only about a quarter of the beak cavity. The triangular shortened tongue has retained the usual division into the apex, the body and the root. There are no conical papillae between the body and the root of the tongue, and the presence of the flat fold with lateral processes sliding over the tongue root in the posterior part of the lingual body is a unique morphological feature. All lingual mucosa covers non-keratinised stratified epithelium, and the lamina propria of the mucosa is filled with mucous glands whose round or semilunar openings are found on both the dorsal and ventral surface of the tongue. The complex glands found in the lingual body are composed of alveoli and/or tubules. Moreover, simple tubular glands seen in the posterior part of the tongue root are an exception. Numerous observations have shown that the ostrich's tongue is a modified structure, though not a rudimentary one, whose main function is to produce the secretion moisturising the beak cavity surface and the ingested semidry plant food in this savannah species.     

Mesencephalic root fibers of the trigeminal nerve in the cat

The trigeminal nerve has three motor roots and one sensory root in the cat. One of the motor roots can be divided into two bundles: the larger and the smaller. These motor roots form the common root with the sensory root at the exit from the pons, sometimes being separated partially by the subarachnoidal space between the medial and the ventral part of the common root. The mesencephalic root fibers are observed numerously in all the motor roots. Some degenerated fibers are observed in the sensory root. The transitional zone of the trigeminal nerve root between central and peripheral nervous system is occupied by interlocking processes of the fibrous astrocyte.     

Immunohistochemical study of the sensory formations in the glabrous skin of the rat

The presence of some cytoskeletal proteins related to the intermediate filaments glial fibrillary acidic protein -GFAP and vimentin) and S-100 protein has been investigated in sensory formations of the glabrous skin of the rat. A positive reaction both for S-100 protein and vimentin was found in the inner core and related cells of glomerular and simple sensory corpuscles; in contrast, no positive reaction was shown for GFAP. The authors discuss these results on the basis of the glial origin of the inner core and related cells in sensory formations.     

Acetylcholinesterase-containing nerve cells and their distribution in the pineal organ of the goldfish,Carassius auratus

Summary Histochemically, an intense acetylcholinesterase (AChE) reaction has been observed in the perikarya of the nerve cells and in the neuropil formations of the pineal organ in the goldfish, Carassius auratus. A group of AChE-rich nerve cells has also been observed between the caudal end of the pineal stalk and the habenular ganglion. No component of the complex revealed butyrylcholinesterase (BuChE) activity.Two different types of nerve cells were recognized on the basis of their size, AChE activity and distribution. Type I cells are characterized by large perikarya possessing a moderate AChE activity and by the presence of an extensive AChE-rich neuropil formation in their vicinity; they are restricted to the rostro-lateral regions of the pineal vesicle. Type II cells are situated in the medio-rostral area of the pineal vesicle and along the entire length of the stalk, and are smaller than Type I cells; they show an intense AChE activity in their perikarya.The neuropil formations in the medio-rostral area of the pineal vesicle are almost as large as those in the vicinity of the Type I cells; they exhibit a strong AChE activity. In the rostral half of the vesicle several sensory cells are associated with each nerve cell, while in the caudal portion only a few cells are apposed to each nerve cell. Thus, the ratio of the number of sensory cells to that of AChE-containing nerve cells in the anterior half of the pineal vesicle is high when compared with the remaining area. In the anterior half of the vesicle the outer segments of the sensory cells are more distinct and their inner segments possess a higher AChE activity than those in the posterior region and the stalk. A gradation in the degree of development of neuropil formations along the pineal axis is remarkable; their size and AChE activity gradually diminish in a caudal direction. In view of the structural specialization of the rostral region of the pineal organ, it has been argued that its terminal portion is more photosensitive.This work was supported by a fellowship from the Alexander von Humboldt Foundation, Federal Republic of Germany.     

The auditory sensory epithelium: the instrument of sound perception

The auditory sensory epithelium is the specialized region of the cochlear epithelium that transduces sound. It is composed of a highly ordered, repeated array of mechanosensory hair cells and nonsensory supporting cells that run along the length of the cochlea. On the apical surface of the hair cells is a specialized structure called the hair bundle that deflects in response to sound vibration, resulting in depolarization of the hair cell and neurotransmitter release. Formation of the auditory sensory epithelium during embryogenesis involves strict control of both cell proliferation and cell patterning. Misregulation of these events can lead to congenital hearing loss, and damage to the auditory sensory epithelium during adult life can lead to adult-onset deafness. This paper reviews recent data on the formation of the auditory sensory epithelium during embryogenesis, the identification of components of the sound transduction apparatus, and advances in the treatment of hearing impairment.     

Functional hemitongue reconstruction with the microvascular ulnar forearm flap.

Thirteen patients with squamous cell carcinoma of the tongue underwent full-thickness longitudinal resection of the hemitongue and immediate microvascular reconstruction using a large, contoured ulnar forearm flap. Six of the 13 patients had a composite resection for which an additional vascularized iliac crest graft was used to reconstruct the mandible and to provide support to the overlying contoured flap. To increase tongue mobility, the skin flap was designed for independent reconstruction of the hemitongue and the floor of mouth. Twelve patients were evaluated for swallowing and speech, including dietary assessment, cineradiography, and voice spectrographic analysis. Contrast cineradiography was performed to determine oral tongue mobility during the first phase of swallow. Nine patients with a narrow reconstructed tongue root and a large surface area in the floor of the mouth had good tongue mobility, allowing them to transfer food dynamically from the mouth into the pharynx for swallowing. The remaining three patients, who had a wide tongue root and an ill-defined floor of the mouth, had decreased tongue mobility and poor oral transport. The functional outcome of swallowing and speech strongly correlated with the shape of the root of the tongue, the proximity of the reconstructed tongue to the palate, and the surface area of the floor of the mouth.