家鸽Herbst小体对振动的反应特征

鸟类的Herbst小体是一种形态特殊的感觉性神经末梢器官.本文利用电生理学方法,研究了家鸽腿部胫骨-腓骨之间的Herbst小体对振动刺激的反应特征.这种小体对振动刺激非常敏感,当振动频率在600—800赫时,它们有反应的最低阈值约为0.3微米.不同的Herbst小体的反应阈值与频率的关系曲线表明:这种小体具有明显的带通滤波的特征,对振动反应的最佳频率范围为400—1000赫.在适宜频率、超阈值强度的振动刺激下,Herbst小体能以1:1的方式作出反应,即相对于每次正弦波振动刺激都有一个锁相的神经脉冲产生.在背根脊神经节内的细胞外记录表明:对振动敏感的神经节细胞具有和Herbst小体完全相似的反应特征.     

Tactile sensitivity,tactile acuity,and affective touch: from childhood to early adolescence

The development of somatosensation and affective touch acquires a central role throughout our lives, for several reasons. In adults, these functions are driven by different, neuroanatomically and functionally segregated fibres. To date, very little is known about the basic features of these fibres in childhood and this lack of knowledge is mirrored in the affective touch domain, where there are no studies on the main physiological features of the tactile processes linked to the stimulation of the hairy skin, namely the preferential site of affective touch. Thus, our study aims to analyze (1) tactile sensitivity and tactile acuity of children’s hairy forearms; (2) a possible dissociation between somatosensation and the affective touch; and (3) the presence/absence of the perception of affective touch already in childhood. To these aims, participants (160 children, aged 6 to 14?years), were administered with the Von Frey (tactile sensitivity) and the 2 Point Discrimination (tactile acuity) tests. Affective touch was measured following the classic protocol and pleasantness ratings were recorded. Our findings showed a correlation between age and somatosensation, suggesting a progressive reduction of sensitivity and acuity as age grows. Further, there was no overlap between affective touch and somatosensation, suggesting a behavioural segregation. Lastly, we found higher pleasantness ratings for Affective versus Neutral stimulations at all ages and an enhanced preference for Affective as age grows. We concluded that both somatosensation and affective touch are already present as two separate components of touch in childhood and change as a function of age.     

Plexiform vascular structures in the human digital dermal layer: a SEM--corrosion casting morphological study

This study aimed to describe the impressive diversity of vascular plexiform structures of the hypodermal layer of human skin. We chose the human body site with the highest concentration of dermal corpuscles, the human digit, and processed it with the corrosion casting technique and scanning electron microscopy analysis (SEM). This approach proved to be the best tool to study these microvascular architectures, free from any interference by surrounding tissues. We took high-definition pictures of the vascular network of sweat glands, thermoreceptorial and tactile corpuscles, the vessels constituting the glomic bodies and those feeding the hair follicles. We observed that the three-dimensional disposition of these vessels strictly depends on the shape of the corpuscles supplied. We could see the tubular vascularization of the excretory duct of sweat glands and the ovoid one feeding their bodies, sometimes made up of two lobes. In some cases, knowledge of these morphological data regarding the normal disposition in space and intrinsic vascularization structure of the dermal corpuscles can help to explain many of the physiopathological changes occurring during chronic microangiopathic diseases.     

Facial bristle feather histology and morphology in New Zealand birds: Implications for function

Knowledge of structure in biology may help inform hypotheses about function. Little is known about the histological structure or the function of avian facial bristle feathers. Here we provide information on morphology and histology, with inferences for function, of bristles in five predominantly insectivorous birds from New Zealand. We chose species with differing ecologies, including: brown kiwi (Apteryx mantelli), morepork (Ninox novaezealandae), hihi (Notiomystis cincta), New Zealand robin (Petroica australis), and New Zealand fantail (Rhipidura fuliginosa). Average bristle length corrected for body size was similar across species. Bristles occurred in distinct groups on different parts of the head and upper rictal bristles were generally longest. The lower rictal bristles of the fantail were the longest possessed by that species and were long compared to bristles of other species. Kiwi were the only species with forehead bristles, similar in length to the upper rictal bristles of other species, and the lower rictal bristles of fantails. Herbst corpuscles (vibration and pressure sensitive mechanoreceptors) were found in association with bristle follicles in all species. Nocturnal and hole‐nesting birds had more heavily encapsulated corpuscles than diurnal open‐nesting species. Our results suggest that avian facial bristles generally have a tactile function in both nocturnal and diurnal species, perhaps playing a role in prey handling, gathering information during flight, navigating in nest cavities and on the ground at night and possibly in prey‐detection. These differing roles may help explain the observed differences in capsule thickness of the corpuscles. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Distribution of the intensity-characteristic parameters of cat rapidly adapting mechanoreceptive fibers

Modeling population responses of nerve fibers requires statistical characterization of fiber-response properties. The rate/intensity characteristics of cat rapidly adapting (RA) fibers were fitted by four-parameter, piece-wise linear functions using nonlinear regression (n = 14; R2 > 0.958). The parameters were tested against the null hypothesis that they are log normally distributed. The test fail to reject this hypothesis (Kolmogorov-Smirnov p>0.477). However, a significant statistical difference was found between the specific lognormal distributions obtained from monkey (Johnson, J Neurophysiol 37: 48-72, 1974) and cat for all four parameters (Kolmogorov-Smirnov, p<0.0075, p<0.05, p<0.0001, p<0.00007). Although the stimulus contactor size was not the same in monkey and cat studies, the differences between monkey and cat fibers are attributed to anatomical differences in the glabrous sin of both species. Modeling studies suggest that the absolute firing thresholds of RA fibers have a right-skewed distribution because of the anatomical constraints present in both species' skin. Meissner corpuscles, which are the sensory end-organs of RA fibers, are likely to be found deeper in the skin within dermal papilla, therefore, the thresholds can be elevated. However, the thresholds are bounded at lower end, probably due to the epidermal junction that acts as a superficial mechanical barrier for these corpuscles.     

Noninformative vision improves the spatial resolution of touch in humans

Research on sensory perception now often considers more than one sense at a time. This approach reflects real-world situations, such as when a visible object touches us. Indeed, vision and touch show great interdependence: the sight of a body part can reduce tactile target detection times [1], visual and tactile attentional systems are spatially linked [2], and the texture of surfaces that are actively touched with the fingertips is perceived using both vision and touch [3]. However, these previous findings might be mediated by spatial attention [1, 2] or by improved guidance of movement [3] via visually enhanced body position sense [4--6]. Here, we investigate the direct effects of viewing the body on passive touch. We measured tactile two-point discrimination thresholds [7] on the forearm while manipulating the visibility of the arm but holding gaze direction constant. The spatial resolution of touch was better when the arm was visible than when it was not. Tactile performance was further improved when the view of the arm was magnified. In contrast, performance was not improved by viewing a neutral object at the arm's location, ruling out improved spatial orienting as a possible account. Controls confirmed that no information about the tactile stimulation was provided by visibility of the arm. This visual enhancement of touch may point to online reorganization of tactile receptive fields.     

Differentiation of tactile corpuscles (Merkel's) in the beak of Coturnix coturnix quail during ontogeny

Succession of the Merkel's corpuscles appearance and the nervous fibers connected with them in the germ of the beak has been studied by means of light (silver nitrate impregnation) and electron microscopic techniques. Appearance of the Merkel's corpuscles in the subepithelial connective tissue is preceded by sprouting of nervous fibers into the area. From the very beginning of their differentiation the tactile corpuscles are in contact with nervous terminals. Sensory innervation is a necessary condition for differentiation of the Merkel's corpuscles and tactile bodies in the bird quail.     

Sensory neuroscience: from skin to object in the somatosensory cortex

Humans can perceive the shape of objects by touch alone, by extracting geometric features such as edges. Recently recorded responses of single neurons in the secondary somatosensory cortex of monkeys suggest how the brain integrates tactile shape information across different regions of skin and builds up a representation of tactile objects.     

Functional structure of the carpal and ventral vibrissae of the squirrel (Sciurus vulgaris)

A study is made of the histology, distribution and ultrastructure of nerve-organs in the carpal and ventral sinus hairs of the squirrel Sciurus vulgaris L. These sinus hairs were found to be typical tactile hairs. Their situation on the inner surfaces of the forelimbs, and on the ventral body wall is assumed to be useful during climbing. Five different types of nerve end-organs were found:
1. Ring-shaped end-organs, especially in the ring sinus, associated with certain cells in connectivetissue and in many cases also anchored to the hair follicle.
2. Merkelcells in the basal cell layer of the outer root sheath at the level of the ring sinus.
3. Lanceolate end-organs between the glassy membrane and the connective tissue of the ringwulst and betweenthese in the upper part of the ring sinus.
4. Encapsulated end-organs in the cavernous sinus.
5. Free thin nerveendings.     

Nerve supply and distribution of cholinesterase activity in the external nose of the mole

Summary Nerve supply and the distribution of cholinesterase activity were studied in the skin of the external nose of seven moles using a simplified Bielschowsky-Gross silver method and Koelle's histochemical technique.The sensory units of the mole's nose or the organs of Eimer are surrounded by blood sinuses which facilitate their movements during mechanical stimulation. All nerve fibres of the plexus deep to the basal cell layer of Eimer's organ ultimately become intra-epidermal endings. Contrary to the findings of earlier investigators, Merkel's discs, Pacinian corpuscles and Ruffini corpuscles have not been observed at the base of Eimer's organ. In the superficial layer of the plexus, the Schwann sheath cells increase in number, undergo modification and give a positive cholinesterase reaction.It is suggested that the organ of Eimer, the specialised nerve plexus deep to it and the surrounding blood sinus together constitute the touch receptor on a similar principle of transmission by leverage as in the tactile hair or the intermediate ridge of the papillary ridge.The role of the intra-epidermal nerve endings of the mole's nose as tactile receptors is disputed. A suggestion is made that tnese nerves may constitute pain and temperature receptors and that several modalities of sensation may be carried to the brain along one and the same medullated axon.We gratefully acknowledge the technical assistance of Miss Jill Hocknell. Our thanks are also due to Mr. C. J. Duncan and the staff of the Photography Department for their aid with the photographic work. We are particularly grateful to Mr. D. Burgess of the Ministry of Agriculture and Fisheries for kindly supplying us with live moles. One of the authors (N.C.) acknowledges an equipment grant from the Royal Society.     

The skin of primates. XLI. The skin of the silver marmoset—Callithrix (= Mico) Argentata

The skin of the silver marmoset, Callithrix (= Mico) argentata Linnaeus, has many outstanding characteristics. The unusually thin epidermis and dermis are generally devoid of melanotic melanocytes. The surface of the interramal gular region is peppered with small, elevated papillae; that of the corpus penis is characterized by keratinized, proximally directed hollow spines in whose cavities are organized nerve end-organs and capillary loops. Cholinesterase-reactive papillary nerve end-organs and Meissner corpuscles populate all volar friction surfaces. A highly vascular dermis and subcutaneous fat pad partially contribute to the characteristic rubicund color of the face, external ears, and anogenital region. Many body surface hairs are accompanied by the classic Haarscheibe of Pinkus. Sinus hairs are plentiful; a circumscribed vibrissa-bearing eminence is located on the ventral ulnar aspect of each wrist. Alkaline phosphatase-positive, stellate-shaped cells are found on the outer root sheath and epithelial sac of active and quiescent hairs in all cephalic regions; such cells are not argyrophilic, aurophilic, or osmiophilic. Hairs grow in linear perfect sets of 3 to 5 follicles; they do not grow singly on the cheek. Large sebaceous glands contain alkaline phosphatase in their peripheral acini; extensive fields of gigantic multilobular sebaceous glands contribute to the distinct, opaque-white color of the scrotal skin. Numbers of apocrine sweat glands are diminished in cephalic regions but one gland occurs with each hair follicle in the axilla, scrotum, suprapubic region, and ulnar eminence. Relatively avascular eccrine sweat glands are confined to the volar friction surfaces. Their secretory coils contain sporadically distributed glycogen and phosphorylase and surrounding nerves are much more reactive for acetyl- than butyrylcholinesterase.     

第二触觉系统:编码触觉情绪成分的C纤维

过去曾认为,人类触觉信息特异地由大直径有髓(Aβ)神经纤维传导。然而最近的研究表明,哺乳动物皮肤的机械感受器不仅有Aβ纤维分布,还有大量低阈值、低传导速度的小直径无髓(C)神经纤维分布,后者对轻微的非伤害性皮肤变形反应敏感,而对快速的皮肤运动反应微弱。初级传入C纤维投射至脊髓浅层,并与脊髓板层II内的次级感觉神经元形成突触联系,再通过脊髓丘脑束投射至岛叶。功能磁共振(fMRI)研究发现,缓慢移动的触觉刺激可以明显地激活岛叶并引起愉悦感,同时还可以激活眶额叶内与愉悦味觉和嗅觉激活区域邻近的部位。这些反应的性质和所激活的部位说明,C纤维触觉主要与边缘系统的功能有关,编码触觉的情绪成分。     

Rapid changes in weight and growth potential during childhood

The close resemblance between the skin of Goeldi's marmoset (Callimico goeldii) and that of the genus Saguinus (Hoffmannsegg) suggests that C. goeldii be placed in the family Callithricidae (Thomas, '03) as originally proposed by Pocock in 1920 and not in the family Cebidae (Swainson, 1835). Recent karyological evidence supports this point of view. The skin is characterized by (1) a melanin-laden epidermis and aggregates of melanocytes in the upper dermis; (2) nonglandular skin in the gular region distinguished by a sparsely haired, pebbly, granular surface; (3) cholinesterase-positive Meissner corpuscles and papillary nerve end-organs; (4) groups of 3 to 5 hair follicles in linear perfect sets; (5) sinus hairs on the ventral ulnar wrist; (6) manubrial, sternal, genitopubic, and circumanal sebaceous-apocrine glandular concentrations rich in phosphorylase and alkaline phosphatase; (7) eccrine glands, restricted to volar friction surfaces, whose clear and dark secretory cells contain phosphorylase but no glycogen; and (8) eccrine glomeruli surrounded by many acetyl- but few butyrylcholinesterase-reactive nerves.     

Ultrastructure of Merkel corpuscles in the tongue of the finch,Lonchura striata

Summary Merkel corpuscles in the lingual mucosa of the finch, Lonchura striata, were examined by means of the argyrophilic reaction and electron microscopy. These corpuscles are composed of 12 to 20 flattened Merkel cells and enclosed nerve terminals. The present study demonstrated for the first time argyrophilia in avian subepithelial Merkel cells with the use of Grimelius silver stain. Electron-microscopically, the Merkel cell was characterized by the presence of numerous densecore granules, approximately 80 to 140 nm in diameter, as well as specialized contacts with nerve terminals. The granules showed a tendency to accumulate in the cytoplasm in close association with both nerve terminals and basal lamina. This study also provided unequivocal evidence for exocytotic discharge of Merkel-cell granules at the plasma membrane facing not only the nerve terminals but also the basal lamina. The exocytotic figures toward the nerve terminals can be regarded as synaptic discharge of Merkel-cell granules, but the possibility also exists that the Merkel-cell granules may exert a trophic effect on the nerve terminals. The exocytotic release of Merkel-cell granules toward the basal lamina with no relation to nerve terminals may suggest an endocrine (paracrine) function for the Merkel cell. The avian subepithelial Merkel cells qualify as paraneurons, but their exact nature and function remain enigmatic as is the case of intraepithelial Merkel cells in other vertebrates.     

Journey to the skin

The peripheral axons of vertebrate tactile somatosensory neurons travel long distances from ganglia just outside the central nervous system to the skin. Once in the skin these axons form elaborate terminals whose organization must be regionally patterned to detect and accurately localize different kinds of touch stimuli. This review describes key studies that identified choice points for somatosensory axon growth cones and the extrinsic molecular cues that function at each of those steps. While much has been learned in the past 20 years about the guidance of these axons, there is still much to be learned about how the peripheral axons of different kinds of somatosensory neurons adopt different trajectories and form specific terminal structures.     

Light-evoked somatosensory perception of transgenic rats that express channelrhodopsin-2 in dorsal root ganglion cells

In vertebrate somatosensory systems, each mode of touch-pressure, temperature or pain is sensed by sensory endings of different dorsal root ganglion (DRG) neurons, which conducted to the specific cortical loci as nerve impulses. Therefore, direct electrical stimulation of the peripheral nerve endings causes an erroneous sensation to be conducted by the nerve. We have recently generated several transgenic lines of rat in which channelrhodopsin-2 (ChR2) transgene is driven by the Thy-1.2 promoter. In one of them, W-TChR2V4, some neurons were endowed with photosensitivity by the introduction of the ChR2 gene, coding an algal photoreceptor molecule. The DRG neurons expressing ChR2 were immunohistochemically identified using specific antibodies to the markers of mechanoreceptive or nociceptive neurons. Their peripheral nerve endings in the plantar skin as well as the central endings in the spinal cord were also examined. We identified that ChR2 is expressed in a certain population of large neurons in the DRG of W-TChR2V4. On the basis of their morphology and molecular markers, these neurons were classified as mechanoreceptive but not nociceptive. ChR2 was also distributed in their peripheral sensory nerve endings, some of which were closely associated with CK20-positive cells to form Merkel cell-neurite complexes or with S-100-positive cells to form structures like Meissner's corpuscles. These nerve endings are thus suggested to be involved in the sensing of touch. Each W-TChR2V4 rat showed a sensory-evoked behavior in response to blue LED flashes on the plantar skin. It is thus suggested that each rat acquired an unusual sensory modality of sensing blue light through the skin as touch-pressure. This light-evoked somatosensory perception should facilitate study of how the complex tactile sense emerges in the brain.     

Touch sense: Functional organization and molecular determinants of mechanosensitive receptors

Cutaneous mechanoreceptors are localized in the various layers of the skin where they detect a wide range of mechanical stimuli, including light brush, stretch, vibration and noxious pressure. This variety of stimuli is matched by a diverse array of specialized mechanoreceptors that respond to cutaneous deformation in a specific way and relay these stimuli to higher brain structures. Studies across mechanoreceptors and genetically tractable sensory nerve endings are beginning to uncover touch sensation mechanisms. Work in this field has provided researchers with a more thorough understanding of the circuit organization underlying the perception of touch. Novel ion channels have emerged as candidates for transduction molecules and properties of mechanically gated currents improved our understanding of the mechanisms of adaptation to tactile stimuli. This review highlights the progress made in characterizing functional properties of mechanoreceptors in hairy and glabrous skin and ion channels that detect mechanical inputs and shape mechanoreceptor adaptation.     

Touch sense

Cutaneous mechanoreceptors are localized in the various layers of the skin where they detect a wide range of mechanical stimuli, including light brush, stretch, vibration and noxious pressure. This variety of stimuli is matched by a diverse array of specialized mechanoreceptors that respond to cutaneous deformation in a specific way and relay these stimuli to higher brain structures. Studies across mechanoreceptors and genetically tractable sensory nerve endings are beginning to uncover touch sensation mechanisms. Work in this field has provided researchers with a more thorough understanding of the circuit organization underlying the perception of touch. Novel ion channels have emerged as candidates for transduction molecules and properties of mechanically gated currents improved our understanding of the mechanisms of adaptation to tactile stimuli. This review highlights the progress made in characterizing functional properties of mechanoreceptors in hairy and glabrous skin and ion channels that detect mechanical inputs and shape mechanoreceptor adaptation.     

Mesenteric and tactile Pacinian corpuscles are anatomically and physiologically comparable

Pacinian corpuscles (PCs) in cat mesentery have been studied extensively to help determine the structural and functional bases of tactile mechanotransduction. Although we, like many other investigators, have found that the mesenteric receptors are anatomically very similar to those found in mammalian skin, few physiological characteristics of the mesenteric PCs and those of the skin have been compared. Action-potential rate-amplitude and frequency characteristics (10 Hz-1 KHz), as well as interval (IH) and peri-stimulus-time (PSTH) histograms in response to sinusoidal displacements were obtained from nerve fibers innervating mesenteric PCs and from PC fibers innervating cat glabrous skin. The intensity characteristics obtained on both preparations showed similar response profiles, including equal slopes for low stimulus intensities (approximately 10, with impulse ratios/20 dB displacement) and one and two impulse/cycle entrainment. The frequency characteristics of both groups were U-shaped with similar low-frequency slopes (-12.5 dB/octave) and bandwidths (Q(3dB) = 1.4). The best frequency for both the tactile PCs' and mesenteric PCs was 250 Hz, which is in the expected range. The IHs showed entrainment and the PSTHs showed neither transient responses nor adaptation to steady-state sinusoidal stimuli. The functional similarity between mesenteric PCs' nerve responses and those of tactile PC afferents, as well as the receptors' anatomical similarity, lead us to suggest that the mesenteric PC can act as a model for those in the skin. Furthermore, since the frequency characteristics of the two PC types are similar, it is concluded that the skin, while attenuating stimulus intensity, does not impart temporal filtering of vibratory stimuli.     

Organization of Meissner corpuscles in the glabrous skin of monkey and cat

Reconstructing neural-population responses in the form of spatial event plots assumes that the receptors are organized in a dense linear array. We have found that this assumption is not valid by determining the spatial organization of Meissner corpuscles (MCs) in the glabrous skin of both cat and monkey. The tissue was excised from animals that had been cardiac perfused with 4% paraformaldehyde. One-micrometer plastic sections revealed that the morphology of these receptors is different in the two animal species. However, in both species, they reside in approximately the same place in the dermal pegs of the skin, between the epidermal ridges, and electrophysiologically they both respond to ramp-and-hold stimuli with a rapidly adapting firing pattern. Thus, in this study we will refer to the receptors of the cat as "Meissner-like". In monkey, MCs are located in the dermal papillae between the epidermal limiting and intermediate ridges, forming orderly rows, the contours of which follow the overlying fingerprint. Although the average density of MCs is 45/mm2, they are distributed along the dermal pegs in such a manner as to give rise to three significantly ( p < 0.017) different average distances between corpuscles. We note that "fingerprints" vary in topography across the hand and this is also reflected in the underlying MC arrays. In the cat, these "Meissner-like" receptors display no specific pattern and have a density much lower than in the monkey. Cat glabrous skin does not have "fingerprints". The results emphasize that the spatial organization of tactile receptors must be taken into account when interpreting reconstructed population responses.