Sensory expectations and anti-Hebbian synaptic plasticity in cerebellum-like structures

Cerebellum-like sensory structures in different groups of fish have been shown to generate a negative image of predictable features of the sensory input. We show here that anti-Hebbian plasticity is present at the synapse between parallel fibers and Purkinje-like cells which could mediate the generation of these negative images. We also show that this synapse is capable of bidirectional changes in synaptic efficacy with the direction of change depending on the precise temporal relation of presynaptic input and postsynaptic spike during pairing. Parallel fiber-evoked EPSPs are depressed after pairings in which the EPSP begins between 0 and 60 ms before the postsynaptic spike but are enhanced at other delays, including those in which the postsysnaptic spike occurs just before the EPSP.     

Reversible associative depression and nonassociative potentiation at a parallel fiber synapse

The electrosensory lobe (ELL) of mormyrid electric fish is one of several cerebellum-like sensory structures in fish that remove predictable features of the sensory inflow. This adaptive process obeys anti-Hebbian rules and appears to be mediated by associative depression at the synapses between parallel fibers and Purkinje-like cells of ELL. We show here that there is also a nonassociative potentiation at this synapse that depends only on the repeated occurrence of the EPSP. The depression can be reversed by the potentiation and vice versa. Finally, we show that the associative depression requires NMDA receptor activation, changes in postsynaptic calcium, and the occurrence of a postsynaptic dendritic spike within a few milliseconds following EPSP onset.     

Design principles of sensory processing in cerebellum-like structures

Cerebellum-like structures are compared for two sensory systems: electrosensory and auditory. The electrosensory lateral line lobe of mormyrid electric fish is reviewed and the neural representation of electrosensory objects in this structure is modeled and discussed. The dorsal cochlear nucleus in the auditory brainstem of mammals is reviewed and new data are presented that characterize the responses of neurons in this structure in the mouse. Similarities between the electrosensory and auditory cerebellum-like structures are shown, in particular adaptive processes that may reduce responses to predictable stimuli. We suggest that the differences in the types of sensory objects may drive the differences in the anatomical and physiological characteristics of these two cerebellum-like structures.     

Glass Capillary Chromatographic Profiles of Soy Sauce Aroma Correlated with Sensory Assessment

The relationship between soy sauce gas chromatographic (GC) patterns precisely analyzed on a glass capillary column and ranked order in sensory analysis was investigated by stepwise multiple regression analysis. The most negative and positive correlation between the GC peaks and sensory data were shown by trans-2-hexen-l-ol contributing to preferable aroma and iso-butyric acid concerning to unpleasant smell, respectively. Highly predictable multiple regression models were calculated in the analysis. The variety of volatile components selected for the equations indicated that these constituents represented not only different groups of chemical structures in aroma compounds but also growth of various microorganisms during the soy sauce making process.     

Adaptive processing in electrosensory systems: Links to cerebellar plasticity and learning

The first central stage of electrosensory processing in fish takes place in structures with local circuitry that resembles the cerebellum. Cerebellum-like structures and the cerebellum itself share common patterns of gene expression and may also share developmental and evolutionary origins. Given these similarities it is natural to ask whether insights gleaned from the study of cerebellum-like structures might be useful for understanding aspects of cerebellar function and vice versa. Work from electrosensory systems has shown that cerebellum-like circuitry acts to generate learned predictions about the sensory consequences of the animals’ own behavior through a process of associative plasticity at parallel fiber synapses. Subtraction of these predictions from the actual sensory input serves to highlight unexpected and hence behaviorally relevant features. Learning and prediction are also central to many current ideas regarding the function of the cerebellum itself. The present review draws comparisons between cerebellum-like structures and the cerebellum focusing on the properties and sites of synaptic plasticity in these structures and on connections between plasticity and learning. Examples are drawn mainly from the electrosensory lobe (ELL) of mormyrid fish and from extensive work characterizing the role of the cerebellum in Pavlovian eyelid conditioning and vestibulo-ocular reflex (VOR) modification. Parallels with other cerebellum-like structures, including the gymnotid ELL, the elasmobranch dorsal octavolateral nucleus (DON), and the mammalian dorsal cochlear nucleus (DCN) are also discussed.     

Relative LWS cone opsin expression determines optomotor thresholds in Malawi cichlid fish

Associating quantitative genetic traits with quantitative behaviors is a relatively unexplored region of sensory neurobiology. The visual system is an ideal place to test models associating these levels of sensory perception. In this study, we reared cichlid fish from Lake Malawi in different ambient light environments. We then tested the visual sensitivities of these fish using the optomotor response (OMR) behavioral paradigm and measured the relative expression of cone opsin genes. We found that the light environment experienced by fish during development can alter gene expression, particularly as it applies to the long wavelength-sensitive (LWS) opsin gene. Also, fish from different rearing conditions exhibited different behavioral sensitivities. We combined these data with predictions of opsin pigment absorption by the different OMR stimuli to determine which cone types are most likely to influence the OMR behavior. While we hypothesized that this behavior would be controlled by a random-wiring model reflecting the expression of both medium wavelength-sensitive (MWS) and LWS opsins, our models suggest that only the LWS pigment is required to predict behavior. Furthermore, analyses show that LWS expression variation accounts for ~20% of the observed behavioral variance. This work confirms that sensory gene expression influences behavior in a predictable fashion. It also suggests that the neural wiring of basal visual pathways in cichlid fish may differ from that observed in mammals and zebrafish, but is similar to that described in goldfish. This finding has important implications for the evolution of the magnocellular neural pathway in teleosts.     

Predicting Cortical Dark/Bright Asymmetries from Natural Image Statistics and Early Visual Transforms

The nervous system has evolved in an environment with structure and predictability. One of the ubiquitous principles of sensory systems is the creation of circuits that capitalize on this predictability. Previous work has identified predictable non-uniformities in the distributions of basic visual features in natural images that are relevant to the encoding tasks of the visual system. Here, we report that the well-established statistical distributions of visual features -- such as visual contrast, spatial scale, and depth -- differ between bright and dark image components. Following this analysis, we go on to trace how these differences in natural images translate into different patterns of cortical input that arise from the separate bright (ON) and dark (OFF) pathways originating in the retina. We use models of these early visual pathways to transform natural images into statistical patterns of cortical input. The models include the receptive fields and non-linear response properties of the magnocellular (M) and parvocellular (P) pathways, with their ON and OFF pathway divisions. The results indicate that there are regularities in visual cortical input beyond those that have previously been appreciated from the direct analysis of natural images. In particular, several dark/bright asymmetries provide a potential account for recently discovered asymmetries in how the brain processes visual features, such as violations of classic energy-type models. On the basis of our analysis, we expect that the dark/bright dichotomy in natural images plays a key role in the generation of both cortical and perceptual asymmetries.     

网蝽科十一属昆虫体表感觉结构的电镜观察

对在扫描电子显微镜下观察到的网蝽科(半翅目：异翅亚目)11个属18种网蝽的成虫及2种的若虫体表感觉结构的特征进行了比较,并根据体表感觉器官的主要特征将所观察的11个属大致划分为6个类群;进一步证实了体表感觉结构的差异性在属水平上的分类学意义,认为在属的鉴别上是一类可靠而适用的新型特征依据,在属内某些种的区分上也具有一定的参考价值;对网蝽科昆虫体表感觉器官的发生发展、系统演化作了探讨性分析并提出了见解。     

Environmental influences on fish assemblages in irrigation ponds

Ponds are common features of the landscape and are considered important for freshwater biodiversity conservation. Although fish have a significant impact on the lentic ecosystems, the environmental factors that regulate fish assemblages in human-created water bodies, such as irrigation ponds, remain unclear. We evaluated the relationship between environmental factors and the fish assemblage structure in 31 ponds located in northern Japan. Species richness (range: 1–9) was positively correlated with the size of the inflow channel. Multivariate analyses revealed that the size of the inflow channel was a better predictor for species richness than lake morphology (surface area and maximum depth), vegetation coverage, water quality (turbidity, pH, DO, and EC), distance to the main channel, and distance to an adjacent pond. Species richness was significantly different between ponds with and without an inflow channel. Furthermore, three of the four most commonly observed species are thought to be relatively tolerant to low oxygen. Given that ponds have a relatively high local extinction rate resulting from exposure to stressful conditions, such as low oxygen and/or small population sizes, our results suggest that immigration from surrounding water bodies plays an important role in maintaining species richness of pond-dwelling fish.     

Using deep neural networks to model similarity between visual patterns: Application to fish sexual signals

The evolution of visual patterns is a frontier in the theory of sexual selection as we seek to understand the function of complex visual patterning in courtship. Recently, the sensory drive and sensory bias models of sexual selection have been applied to higher-level visual processing. One prediction of this application is that animals' sexual signals will mimic the visual statistics of their habitats. An enduring difficulty of testing predictions of visual pattern evolution is in developing quantitative methods for comparing patterns. Advances in artificial neural networks address this challenge by allowing for the direct comparison of images using both simple and complex features. Here, we use VGG19, an industry‑leading image classification network to test predictions of sensory drive, by comparing visual patterns in darter fish (Etheostoma spp.) to images of their habitats. We find that images of female darters are significantly more similar to images of their habitat than are images of males, supporting a role of camouflage in female patterning. We do not find direct evidence for sensory drive shaping the design of male patterns; however, this work demonstrates the utility of network methods for pattern analysis and suggests future directions for visual pattern research.     

Are mushroom bodies cerebellum-like structures?

The mushroom bodies are distinctive neuropils in the protocerebral brain segments of many protostomes. A defining feature of mushroom bodies is their intrinsic neurons, masses of cytoplasm-poor globuli cells that form a system of lobes with their densely-packed, parallel-projecting axon-like processes. In insects, the role of the mushroom bodies in olfactory processing and associative learning and memory has been studied in depth, but several lines of evidence suggest that the function of these higher brain centers cannot be restricted to these roles. The present account considers whether insight into an underlying function of mushroom bodies may be provided by cerebellum-like structures in vertebrates, which are similarly defined by the presence of masses of tiny granule cells that emit thin parallel fibers forming a dense molecular layer. In vertebrates, the shared neuroarchitecture of cerebellum-like structures has been suggested to underlie a common functional role as adaptive filters for the removal of predictable sensory elements, such as those arising from reafference, from the total sensory input. Cerebellum-like structures include the vertebrate cerebellum, the electrosensory lateral line lobe, dorsal and medial octavolateral nuclei of fish, and the dorsal cochlear nucleus of mammals. The many architectural and physiological features that the insect mushroom bodies share with cerebellum-like structures suggest that it might be fruitful to consider mushroom body function in light of a possible role as adaptive sensory filters. The present account thus presents a detailed comparison of the insect mushroom bodies with vertebrate cerebellum-like structures.     

Functional specifics of cortical associative regions participating in learning to differentiate visual information in monkeys

In 3 groups of monkeys: intact, those with their 7th field bilaterally removed, and those with bilateral removal of the sulcus principalis, functional specifics of the cortex' associative areas were studied. Removal of the 7th field practically does not affect processes of training for images with such features as spatial frequency, colour, and images of animals, but considerably impairs the learning characteristics in visual differentiation of objects' size and spatial interrelationships among objects. Removal of the sulcus principalis considerably impairs the characteristics of differentiation of objects' size and spatial interrelationships among them, as well as differently coloured stimuli. In both these groups, the stable motor response term and the probability of refusal increase. The data obtained suggest that the sensory processing results in forming a few (at least three) functional visual informational flows with which different cortical areas operate.     

The effect of forelimb deafferentation in early postnatal ontogeny on the development of synaptic transmission in the hippocampus]

Hippocampal slices from 15-20-day-old Wistar rats were used to study the development of some features of synaptic transmission in hippocampus and the influence of partial limitation of the sensory inflow in the early ontogeny of this transmission. The dynamics of population spike changes was observed in the CA1 hippocampal field in response to stimulation of Schaffer collaterals. The early ontogenetic limitation of the sensory inflow was accomplished by cutting n. medianus on the 13th day. Between the 15th and 20th days, the dynamics of the population spike amplitude increase in the control and experimental animals was similar, however, the response amplitude of the control rats remained higher than in the experimental animals throughout the whole period of observation. It is suggested that the partial limitation of sensory inflow from a forelimb at the early stages of the ontogeny alters the formation of synaptic transmission in hippocampus.     

Contributions of electric fish to the understanding of sensory processing by reafferent systems.

Sensory systems must solve the inverse problem of determining environmental events based on patterns of neural activity in the central nervous system that are affected by those environmental events. Different environmental events can give rise to indistinguishable patterns of neural activity, so that there will often, perhaps even always, be multiple solutions to a sensory inverse problem. Imaging strategies and brain organization confine these multiple solutions within a bounded set. Three different active strategies may be employed by animals to constrain the number of solutions to the sensory inverse problem: active generation of the energy (carrier) that stimulates receptors; reorientation of the point of view; and control of signal conditioning before transduction (pre-receptor mechanisms). This paper describes how these strategies are used in sensory-motor systems, using electric fish as a paradigmatic example. Carrier generation and receptor tuning to the carrier improve signal to noise ratio. Receptor tuning to different frequency bands of the carrier spectrum allows a sensory system to evaluate different kinds of carrier modulations and to extract the different features of objects in the environment. Pre-receptor mechanisms condition the signals, optimizing their detection at a foveal region where the sensory resolution is maximum. Active orientation of the sensory surface redirects the fovea to explore in detail the source of interesting signals. Sensory input generated by these active exploration mechanisms ('reafference') has two components: one, necessary, derived from the self-generated actions and another, contingent, consisting of the information obtained from the external world. Extracting environmental information ('exafference') requires that the self generated afference be subtracted from the sensory inflow. Such subtraction is often associated with the generation and storage of expectations about sensory inputs. It can be concluded that an animal's perceptual world and its ability to transform the world are inextricably linked. Understanding sensory systems must, therefore, always require understanding the organization of motor behavior.     

Studying Visual Cues in Fish Behavior: A Review of Ethological Techniques

This paper reviews the variety of approaches available to fish ethologists to study the role of visual cues in fish behavior. Examples of studies that have used live fish, mirror images, dummies (i.e. models), or video playback as stimuli to investigate fish behavior are described and discussed. These examples represent a diversity of functional categories of behavior exhibited by fishes, including aggression, courtship, aggregation, or schooling behavior, parent–offspring, predator–prey, and cleaner–host interactions. The specific techniques that fish biologists have used to control or manipulate body shape, size, posture, morphological structures, color, marking patterns, or movement are systematically discussed, and the importance of each of these visual features to fish behavior is documented through examples. Studies that have used these techniques to investigate the interaction between visual and nonvisual cues are also considered. Each section encompassing a general experimental approach ends with a discussion of the advantages and disadvantages of that approach for studying fish behavior.     

Electric Imaging through Evolution,a Modeling Study of Commonalities and Differences

Modeling the electric field and images in electric fish contributes to a better understanding of the pre-receptor conditioning of electric images. Although the boundary element method has been very successful for calculating images and fields, complex electric organ discharges pose a challenge for active electroreception modeling. We have previously developed a direct method for calculating electric images which takes into account the structure and physiology of the electric organ as well as the geometry and resistivity of fish tissues. The present article reports a general application of our simulator for studying electric images in electric fish with heterogeneous, extended electric organs. We studied three species of Gymnotiformes, including both wave-type (Apteronotus albifrons) and pulse-type (Gymnotus obscurus and Gymnotus coropinae) fish, with electric organs of different complexity. The results are compared with the African (Gnathonemus petersii) and American (Gymnotus omarorum) electric fish studied previously. We address the following issues: 1) how to calculate equivalent source distributions based on experimental measurements, 2) how the complexity of the electric organ discharge determines the features of the electric field and 3) how the basal field determines the characteristics of electric images. Our findings allow us to generalize the hypothesis (previously posed for G. omarorum) in which the perioral region and the rest of the body play different sensory roles. While the “electrosensory fovea” appears suitable for exploring objects in detail, the rest of the body is likened to a “peripheral retina” for detecting the presence and movement of surrounding objects. We discuss the commonalities and differences between species. Compared to African species, American electric fish show a weaker field. This feature, derived from the complexity of distributed electric organs, may endow Gymnotiformes with the ability to emit site-specific signals to be detected in the short range by a conspecific and the possibility to evolve predator avoidance strategies.     

Shared and unique features of morphological differentiation between predator regimes in Gambusia caymanensis

When multiple groups of organisms experience similar environmental gradients, their patterns of differentiation might exhibit both shared and unique features. Here, we investigated the relative importance of three factors in generating body shape variation in a livebearing fish, Gambusia caymanensis, inhabiting the Cayman Islands: (i) shared patterns of divergent selection between predator regimes (presence/absence of piscivorous fish) driving replicated morphological differentiation, (ii) historical island effects yielding different morphologies across the three islands and (iii) unique effects of predation on morphological differentiation within each island. Shared effects of predation proved much more important than historical or unique effects. Populations coexisting with piscivorous fish exhibited larger caudal regions and smaller heads than conspecifics found in the absence of predatory fish. These results match a priori predictions, and mirror recent findings in a number of fish species, suggesting predation might often drive predictable morphological trends in disparate fishes. However, interestingly, the sexes achieved this morphological pattern through different means: head depth, caudal peduncle length and depth in males; head length, caudal peduncle depth in females. In G. caymanensis, we quantitatively confirmed that predation intensity represents a primary driver of body shape differentiation.     

Time scales and mechanisms of estuarine variability,a synthesis from studies of San Francisco Bay

This review of the preceding papers suggests that temporal variability in San Francisco Bay can be characterized by four time scales (hours, days-weeks, months, years) and associated with at least four mechanisms (variations in freshwater inflow, tides, wind, and exchange with coastal waters). The best understood component of temporal variability is the annual cycle, which is most obviously influenced by seasonal variations in freshwater inflow. The winter season of high river discharge is characterized by: large-scale redistribution of the salinity field (e.g. the upper estuary becomes a riverine system); enhanced density stratification and gravitational circulation with shortened residence times in the bay; decreased tissue concentrations of some contaminants (e.g. copper) in resident bivalves; increased estuarine inputs of river-borne materials such as dissolved inorganic nutrients (N, P, Si), suspended sediments, and humic materials; radical redistributions of pelagic organisms such as copepods and fish; low phutoplankton biomass and primary productivity in the upper estuary; and elimination of freshwater-intolerant species of macroalgae and benthic infauna from the upper estuary. Other mechanisms modulate this river-driven annual cycle: (1) wind speed is highly seasonal (strongest in summer) and causes seasonal variations in atmosphere-water column exchange of dissolved gases, resuspension, and the texture of surficial sediments; (2) seasonal variations in the coastal ocean (e.g. the spring-summer upwelling season) influence species composition of plankton and nutrient concentrations that are advected into the bay; and (3) the annual temperature cycle influences a few selected features (e.g. production and hatching of copepod resting eggs). Much of the interannual variability in San Francisco Bay is also correlated with freshwater inflow: wet years with persistently high river discharge are characterized by persistent winter-type conditions.Mechanisms of short-term variability are not as well understood, although some responses to storm events (pulses in residual currents from wind forcing, erosion of surficial sediments by wind waves, redistribution of fish populations) and the neap-spring tidal cycle (enhanced salinity stratification, gravitational circulation, and phytoplankton biomass during neap tides) have been quantified. In addition to these somewhat predictable features of variability are (1) largely unexplained episodic events (e.g. anomalous blooms of drift macroalgae), and (2) long-term trends directly attributable to human activities (e.g. introduction of exotic species that become permanent members of the biota).     

Electric imaging through active electrolocation: implication for the analysis of complex scenes

The electric sense of mormyrids is often regarded as an adaptation to conditions unfavourable for vision and in these fish it has become the dominant sense for active orientation and communication tasks. With this sense, fish can detect and distinguish the electrical properties of the close environment, measure distance, perceive the 3-D shape of objects and discriminate objects according to distance or size and shape, irrespective of conductivity, thus showing a degree of abstraction regarding the interpretation of sensory stimuli. The physical properties of images projected on the sensory surface by the fish's own discharge reveal a "Mexican hat" opposing centre-surround profile. It is likely that computation of the image amplitude to slope ratio is used to measure distance, while peak width and slope give measures of shape and contrast. Modelling has been used to explore how the images of multiple objects superimpose in a complex manner. While electric images are by nature distributed, or 'blurred', behavioural strategies orienting sensory surfaces and the neural architecture of sensory processing networks both contribute to resolving potential ambiguities. Rostral amplification is produced by current funnelling in the head and chin appendage regions, where high density electroreceptor distributions constitute foveal regions. Central magnification of electroreceptive pathways from these regions particularly favours the detection of capacitive properties intrinsic to potential living prey. Swimming movements alter the amplitude and contrast of pre-receptor object-images but image modulation is normalised by central gain-control mechanisms that maintain excitatory and inhibitory balance, removing the contrast-ambiguity introduced by self-motion in much the same way that contrast gain-control is achieved in vision.     

Development and application of methods for investigating the ratio of rheoreaction types of fish in a circular tank

Methods for evaluating the motivational component of the fish rheoreaction (ratio of rheoreaction types) are developed and tested in a circular hydrodynamic tank for three fish species (Danio rerio, Poecilia reticulata, and Inpaichthys kerri). Three rheoreaction types of fish were distinguished: a positive type (fish movements against water current), a negative type (fish movements along with water current), and a compensatory type (fish maintaining their position in relation to immobile reference points). The main distinguishing features of these new methods are unrestricted distance for fish movements, continuous monitoring of individual fish movements (video recording), and evaluation of ratio between the types of rheoreaction in terms of duration of demonstration of these types by each. The minimum required observation time and water current velocities are determined. It is shown that these methods can be used for investigating the types of rheoreaction in different fish species. Every single individual repeatedly demonstrated all these three rheoreaction types during the test.