明视人听词分类任务时的视皮层激活——跨感觉通道的新证据

近期的脑成像研究在盲人等感官缺陷被试者身上发现了感觉替换现象,即传统上认为仅对单一感觉通道刺激反应的皮层区域也参与其他感觉通道的信息加工．类似的效应在感觉剥夺(蒙住眼睛)的明视人被试中也被观察到,提示脑内可能预存着多感觉交互作用的神经通路．通常认为,上述神经通路在常态的人脑中是以潜伏形式存在的,只有当感觉剥夺时才显露出来或得到加强．但是,感觉剥夺是否是该类神经通路发挥作用的必要条件,已有的研究尚缺乏确切的证据．采用统计力度较强的实验设计,给未蒙眼明视人被试听觉呈现一组名词,要求其对听到的每一个词语做出是人工物体还是自然物体的语义判断．对同步采集的功能磁共振信号进行统计分析,观察到视皮层脑区有显著激活．这些结果表明,跨感觉通道的神经通路在未实施感觉剥夺的条件下依然能够显示出来,因而在常态人脑中也不是完全以潜伏形式存在的．上述研究为建立多感觉交互作用神经机制的具体理论模型提供了一个约束条件．     

Statocysts of hydromedusae

The statocysts of Leptomedusae are formed as a depression in the velum. They are lined on the inside towards the distal part of the velum by thin epithelium and towards the proximal part by ciliated sensory cells. Lithocytes are present in the centre. The concretion contains calcium sulphate and in some cases, calcium phosphate is also present in addition to some membranous material. The statocysts of Narcomedusae arise from the exumbrellar nerve ring as free sensory clubs. They have a proximal basal cushion of sensory cells from the centre of which arises a sensory club (Aegina) or a sensory papilla carrying a sensory club (Solmissus). The sensory club has an axial strand of endodermal cells covered by ciliated sensory cells. Some of the endodermal cells have a concretion. While the statocysts of Leptomedusae are totally ectodermal, those of Narcomedusae are ecto-endodermal in origin. The sensory cilia of Leptomedusae, especially those present on the sensory cells adjacent to the lithocyte, run close and parallel to the lithocyte membrane. In Narcomedusae the sensory cilia of the basal cusion and sensory papilla are tall and strong. Ciliary rootlets are missing in the sensory cilia of Leptomedusae and in the sensory club of Narcomedusae but they are strongly developed in the cilia of basal cusion and sensory papilla. The cilia have 9+2 filament content. A ring of stereocilia surrounds the kinocilium of the sensory club cells. Mechanism of statocyst function is discussed.     

Tissue preparation and immunostaining of mouse sensory nerve fibers innervating skin and limb bones

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in animals and humans. These peripheral sensory nerve fibers express a plethora of receptors and ion channel proteins which detect and initiate specific sensory stimuli. Methods are available to characterize the electrical properties of peripheral sensory nerve fibers innervating the skin, which can also be utilized to identify the functional expression of specific ion channel proteins in these fibers. However, similar electrophysiological methods are not available (and are also difficult to develop) for the detection of the functional expression of receptors and ion channel proteins in peripheral sensory nerve fibers innervating other visceral organs, including the most challenging tissues such as bone. Moreover, such electrophysiological methods cannot be utilized to determine the expression of non-excitable proteins in peripheral sensory nerve fibers. Therefore, immunostaining of peripheral/visceral tissue samples for sensory nerve fivers provides the best possible way to determine the expression of specific proteins of interest in these nerve fibers. So far, most of the protein expression studies in sensory neurons have utilized immunostaining procedures in sensory ganglia, where the information is limited to the expression of specific proteins in the cell body of specific types or subsets of sensory neurons. Here we report detailed methods/protocols for the preparation of peripheral/visceral tissue samples for immunostaining of peripheral sensory nerve fibers. We specifically detail methods for the preparation of skin or plantar punch biopsy and bone (femur) sections from mice for immunostaining of peripheral sensory nerve fibers. These methods are not only key to the qualitative determination of protein expression in peripheral sensory neurons, but also provide a quantitative assay method for determining changes in protein expression levels in specific types or subsets of sensory fibers, as well as for determining the morphological and/or anatomical changes in the number and density of sensory fibers during various pathological states. Further, these methods are not confined to the staining of only sensory nerve fibers, but can also be used for staining any types of nerve fibers in the skin, bones and other visceral tissue.     

Evolution of sensory systems

Sensory systems evolve and enable organisms to perceive their sensory Umwelt, the unique set of cues relevant for their survival. The multiple components that comprise sensory systems — the receptors, cells, organs, and dedicated high-order circuits — can vary greatly across species. Sensory receptor gene families can expand and contract across lineages, resulting in enormous sensory diversity. Comparative studies of sensory receptor function have uncovered the molecular basis of receptor properties and identified novel sensory receptor classes and noncanonical sensory strategies. Phylogenetically informed comparisons of sensory systems across multiple species can pinpoint when sensory changes evolve and highlight the role of contingency in sensory system evolution.     

Pollution going multimodal: the complex impact of the human-altered sensory environment on animal perception and performance

Anthropogenic sensory pollution is affecting ecosystems worldwide. Human actions generate acoustic noise, emanate artificial light and emit chemical substances. All of these pollutants are known to affect animals. Most studies on anthropogenic pollution address the impact of pollutants in unimodal sensory domains. High levels of anthropogenic noise, for example, have been shown to interfere with acoustic signals and cues. However, animals rely on multiple senses, and pollutants often co-occur. Thus, a full ecological assessment of the impact of anthropogenic activities requires a multimodal approach. We describe how sensory pollutants can co-occur and how covariance among pollutants may differ from natural situations. We review how animals combine information that arrives at their sensory systems through different modalities and outline how sensory conditions can interfere with multimodal perception. Finally, we describe how sensory pollutants can affect the perception, behaviour and endocrinology of animals within and across sensory modalities. We conclude that sensory pollution can affect animals in complex ways due to interactions among sensory stimuli, neural processing and behavioural and endocrinal feedback. We call for more empirical data on covariance among sensory conditions, for instance, data on correlated levels in noise and light pollution. Furthermore, we encourage researchers to test animal responses to a full-factorial set of sensory pollutants in the presence or the absence of ecologically important signals and cues. We realize that such approach is often time and energy consuming, but we think this is the only way to fully understand the multimodal impact of sensory pollution on animal performance and perception.     

Transformation of sensory organs by mutations of the cut locus of D. melanogaster

The identities of two types of sensory organs in the body wall of Drosophila, namely the external sensory organs and the chordotonal organs, are under genetic control. Embryonic lethal mutations in the cut gene complex transform the external sensory organs into chordotonal organs. The neurons, as well as the support cells forming the external sensory structures, change their morphological and antigenic characteristics to those of chordotonal organs, providing genetic evidence that these two types of sensory organs are homologous. Similar transformations of external sensory organs are observed in adult mosaic flies. Analysis of mosaic larvae and flies suggests that the cut gene function is required either in or near external sensory organs in order for them to acquire their correct identity.     

Identification and Pattern of Primary Sensory Cells in the Body Wall Epithelium of the Tubificid Worm, Limnodrilus hoffmeisteri

This study compares the effectiveness of two examination methods suitable for morphological observations, scanning electron microscopy (SEM) and light microscopic NADH-diaphorase (NADP-d) histochemistry, to identify location and distribution pattern of primary sensory cells situated in the body wall epithelium of Limnodrilus hofmeisteri. SEM observations revealed that grouped sensory cells forming two distinct types of sensillas (or sense organs) are scattered over the body surface. The easily identifiable first type (ciliated sensilla) contains numerous penetrative ciliate sensory cells while no ciliate sensory cells were seen in the second type (sensory bud). NADH-d staining proved to be a suitable method to identify both structures further staining solitary sensory cells, and certain sensory fibres that could not be visualised by SEM preparations. Our results show that NADH-d staining, as a histochemical marker of primary sensory cells, is a suitable and effective method to reveal their morphology and distribution pattern in whole mount preparations in the smallest detail, suggesting that the application of this relatively simple and cheap method may contribute to understand the basic organisation and evolution of the peripheral sensory structures of oligochaetes.     

Learning from sensory and reward prediction errors during motor adaptation

Voluntary motor commands produce two kinds of consequences. Initially, a sensory consequence is observed in terms of activity in our primary sensory organs (e.g., vision, proprioception). Subsequently, the brain evaluates the sensory feedback and produces a subjective measure of utility or usefulness of the motor commands (e.g., reward). As a result, comparisons between predicted and observed consequences of motor commands produce two forms of prediction error. How do these errors contribute to changes in motor commands? Here, we considered a reach adaptation protocol and found that when high quality sensory feedback was available, adaptation of motor commands was driven almost exclusively by sensory prediction errors. This form of learning had a distinct signature: as motor commands adapted, the subjects altered their predictions regarding sensory consequences of motor commands, and generalized this learning broadly to neighboring motor commands. In contrast, as the quality of the sensory feedback degraded, adaptation of motor commands became more dependent on reward prediction errors. Reward prediction errors produced comparable changes in the motor commands, but produced no change in the predicted sensory consequences of motor commands, and generalized only locally. Because we found that there was a within subject correlation between generalization patterns and sensory remapping, it is plausible that during adaptation an individual''s relative reliance on sensory vs. reward prediction errors could be inferred. We suggest that while motor commands change because of sensory and reward prediction errors, only sensory prediction errors produce a change in the neural system that predicts sensory consequences of motor commands.     

Absence of rapid sensory adaptation in neocortex during information processing states

One prominent feature of sensory responses in neocortex is that they rapidly adapt to increases in frequency, a process called "sensory adaptation." Here we show that sensory adaptation mainly occurs during quiescent states such as anesthesia, slow-wave sleep, and awake immobility. In contrast, during behavior-ally activated states, sensory responses are already adapted. For instance, during learning of a behavioral task, when an animal is very alert and expectant, sensory adaptation is mostly absent. After learning occurs, and the task becomes routine, the level of alertness lessens and sensory adaptation becomes robust. The primary sensory thalamocortical pathway of alert and expectant animals is in the adapted state, which may be required for adequate sensory information processing.     

Independent development of sensory and motor innervation patterns in embryonic chick hindlimbs

Previous studies suggest that sensory axon outgrowth is guided by motoneurons, which are specified to innervate particular target muscles. Here we present evidence that questions this conclusion. We have used a new approach to assess the pathfinding abilities of bona fide sensory neurons, first by eliminating motoneurons after neural crest cells have coalesced into dorsal root ganglia (DRG) and second by challenging sensory neurons to innervate muscles in a novel environment created by shifting a limb bud rostrally. The resulting sensory innervation patterns mapped with the lipophilic dyes DiI and DiA showed that sensory axons projected robustly to muscles in the absence of motoneurons, if motoneurons were eliminated after DRG formation. Moreover, sensory neurons projected appropriately to their usual target muscles under these conditions. In contrast, following limb shifts, muscle sensory innervation was often derived from inappropriate segments. In this novel environment, sensory neurons tended to make more "mistakes" than motoneurons. Whereas motoneurons tended to innervate their embryologically correct muscles, sensory innervation was more widespread and was generally from more rostral segments than normal. Similar results were obtained when motoneurons were eliminated in embryos with limb shifts. These findings show that sensory neurons are capable of navigating through their usual terrain without guidance from motor axons. However, unlike motor axons, sensory axons do not appear to actively seek out appropriate target muscles when confronted with a novel terrain. These findings suggest that sensory neuron identity with regard to pathway and target choice may be unspecified or quite plastic at the time of initial axon outgrowth.     

A matter of focus: monoaminergic modulation of stimulus coding in mammalian sensory networks

Although the presence of neuromodulators in mammalian sensory systems has been noted for some time, a groundswell of evidence has now begun to document the scope of these regulatory mechanisms in several sensory systems, highlighting the importance of neuromodulation in shaping feature extraction at all levels of neural processing. The emergence of more sophisticated models of sensory encoding and of the interaction between sensory and regulatory regions of the brain will challenge sensory neurobiologists to further incorporate a concept of sensory network function that is contingent on neuromodulatory and behavioral state.     

Ultrastructure of sensory cells on the mantle tentacles of the gastropod Notoacmea scutum

Previous studies have indicated that the mantle margin of the gastropod mollusc Notoacmea scutum is sensitive to chemical, photic, and mechanical stimulation. Here, the ultrastructure of sensory cells on the mantle tentacles of N. scutum is examined by transmission electron microscopy to determine if morphological types of sensory cells can be correlated with known sensory capabilities. The sensory cells of the mantle tentacles are found to be ciliated, primary receptors with subepithelial nuclei. The ciliated sensory endings are concentrated at the tip of the tentacles, but also occur in smaller numbers along the shaft. Ultrastructural differences between cilia form the basis of distinguishing two types of sensory ending. Type 1 sensory endings, which are over 90% of the endings, bar unusual cilia that typically are filled with an electron-dense material. Type 2 sensory endings bear cilia that have a 9 + 2 arrangement of longitudinal elements and thus more closely resemble previously reported sensory cilia of molluscs.     

Sensory bias as an explanation for the evolution of mate preferences

The sensory bias model of sexual selection posits that female mating preferences are by-products of natural selection on sensory systems. Although sensory bias was proposed 20 years ago, its critical assumptions remain untested. This paradox arises because sensory bias has been used to explain two different phenomena. First, it has been used as a hypothesis about signal design, that is, that males evolve traits that stimulate female sensory systems. Second, sensory bias has been used as a hypothesis for the evolution of female preference itself, that is, to explain why females exhibit particular preferences. We focus on this second facet. First, we clarify the unique features of sensory bias relative to the alternative models by considering each in the same quantitative genetic framework. The key assumptions of sensory bias are that natural selection is the predominant evolutionary mechanism that affects preference and that sexual selection on preferences is quantitatively negligible. We describe four studies that would test these assumptions and review what we can and cannot infer about sensory bias from existing studies. We suggest that the importance of sensory bias as an explanation for the evolution of female preferences remains to be determined.     

Response Properties of a Sensory Hair Excised from Venus''s Flytrap

Multicellular sensory hairs were excised from the leaf of Venus's flytrap, and the sensory cells were identified by a destructive dissection technique. The sensory layer includes a radially symmetrical rosette of 20–30 apparently identical cells, and the sensory cells are organized in a plane normal to the long axis of the sensory hair. The sensory cells were probed with intracellular glass electrodes. The resting membrane potential was about -80 mv, and the response to a mechanical stimulus consisted of a graded response and an "action potential." The action potential appears to be similar to the action potential which propagates over the surface of the leaf. In the absence of stimulation, the upper and lower membranes of a single sensory cell behave in an electrically symmetrical fashion. Upon stimulation, however, the upper and lower membranes become electrically asymmetrical. Limiting values for the response asymmetry were calculated on the hypothesis of an electrical model consistent with the histology of the sensory cells.     

An unusual mechanosensitive cell in a crustacean exteroceptor

The ultrastructure and mechanosensitivity of a sensory organ in a terrestrial isopod are investigated. The mechanosensitivity of this sensory organ is demonstrated. Seven sensory cells are observed; one of them displays unusual ultrastructural features, a lamellar ciliary root and a tubular body-like structure. The six other sensory cells are similar to usual chemosensitive cells. No sensory cell presents the characteristic cytological features of crustacean mechanosensitive exteroceptors.     

Fine structure of the sensory pore present in the eyestalk of crustacea natantia

Summary Ultrastructural observation of the sensory pore of several species of Natantia reveals a twofold organ. A main sensory pore (M.S.P.) comprises a layer of supporting cells which encapsulate the terminal region of sensory cell bodies. These sensory cells include two ciliary processes dividing into a flat sub-cuticular cavity. The cuticle opposite is thin and perforated with crater-like paired micropores. Next to the main sensory pore, a second organ, the lateral sensory pore (L.S.P.), is smaller and more difficult to observe. A complex-shaped cavity underlies a contorted epicuticular invagination. Ciliary outer segments, belonging to a bundle of sensory cells, branch out in this cavity.M.S.P. and L.S.P. appear to be chemoreceptors.I thank Mme Colette Besse for her technical assistance and Mr. A. Martin, photographer.     

Ultrastructural investigation of the nuchal organs ofPygospio elegans (Polychaeta). I. Larval nuchal organs

The structural differentiation of the nuchal organs during the post-embryonic development ofPygospio elegans is described. The sensory organs are composed of two cell types: ciliated cells and bipolar primary sensory cells, constituting the nuchal ganglion, which is associated with both the sensory epithelium and the brain. Since the sensory neurons are largely integrated into posterolateral parts of the cerebral ganglion, the nuchal organs are primary presegmental structures. The microvilli of the ciliated cells form a cover over the cuticle with a presumed protective function. An extracellular space extends between cuticle and sensory epithelium. The distal dendrites of the sensory cells terminate in sensory bulbs, bearing one modified sensory cilium each that projects into the olfactory chamber, embedded within the secretion of the ciliated cells. During development, the nuchal organs increase in size. This is accompanied by a shift in position, an expansion of the sensory area, and secretory activity of the ciliated cells. The nuchal ganglion differentiates into three nuchal centres forming three distinct sensory areas around the ciliated region. Each nuchal complex reveals two short nuchal nerves comprising the sensory axons, which enter the posterior circumesophageal connective. The sensory cells lying in the brain exhibit neurosecretory activity; the sensory cilia enlarge their surface area by dilating and branching. Nuchal organs accomplish the basic structural adaptions of chemoreceptors and show structural analogies to arthropod olfactory sensilla; thus, there is every reason to suppose chemoreceptor function.     

Combination of non-specific cholinesterase histochemistry and immunofluorescence staining for the study of the sensory innervation of skin and muscle

Summary In the present study we describe the application of the non-specific cholinesterase (nChE) histochemical method for the detection of encapsulated sensory nerve endings prior to immunofluorescence staining of the sensory nerve fibres. The nChE staining of Schwann-derived structures surrounding sensory terminals allowed us to identify unequivocally the sensory corpuscles in the skin and the muscle proprioceptors (muscle spindles and Golgi tendon organs) in longitudinal sections of muscle tissue. The nChE staining of sensory nerve endings and immunofluorescence-labelled nerve fibres and their terminals could be viewed and photographed in the same section using appropriate filters. Since nChE activity persists in terminal Schwann cells for a long time after loss of the sensory axons, this combined enzyme- and immunohistochemical approach is also useful for experimental studies involving denervation and re-innervation of sensory nerve endings.