1,277 research outputs found

    Spatial vision in insects is facilitated by shaping the dynamics of visual input through behavioral action

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    Egelhaaf M, Boeddeker N, Kern R, Kurtz R, Lindemann JP. Spatial vision in insects is facilitated by shaping the dynamics of visual input through behavioral action. Frontiers in Neural Circuits. 2012;6:108.Insects such as flies or bees, with their miniature brains, are able to control highly aerobatic flight maneuvres and to solve spatial vision tasks, such as avoiding collisions with obstacles, landing on objects, or even localizing a previously learnt inconspicuous goal on the basis of environmental cues. With regard to solving such spatial tasks, these insects still outperform man-made autonomous flying systems. To accomplish their extraordinary performance, flies and bees have been shown by their characteristic behavioral actions to actively shape the dynamics of the image flow on their eyes ("optic flow"). The neural processing of information about the spatial layout of the environment is greatly facilitated by segregating the rotational from the translational optic flow component through a saccadic flight and gaze strategy. This active vision strategy thus enables the nervous system to solve apparently complex spatial vision tasks in a particularly efficient and parsimonious way. The key idea of this review is that biological agents, such as flies or bees, acquire at least part of their strength as autonomous systems through active interactions with their environment and not by simply processing passively gained information about the world. These agent-environment interactions lead to adaptive behavior in surroundings of a wide range of complexity. Animals with even tiny brains, such as insects, are capable of performing extraordinarily well in their behavioral contexts by making optimal use of the closed action-perception loop. Model simulations and robotic implementations show that the smart biological mechanisms of motion computation and visually-guided flight control might be helpful to find technical solutions, for example, when designing micro air vehicles carrying a miniaturized, low-weight on-board processor

    Neural processing of imminent collision in humans

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    Detecting a looming object and its imminent collision is imperative to survival. For most humans, it is a fundamental aspect of daily activities such as driving, road crossing and participating in sport, yet little is known about how the brain both detects and responds to such stimuli. Here we use functional magnetic resonance imaging to assess neural response to looming stimuli in comparison with receding stimuli and motion-controlled static stimuli. We demonstrate for the first time that, in the human, the superior colliculus and the pulvinar nucleus of the thalamus respond to looming in addition to cortical regions associated with motor preparation. We also implicate the anterior insula in making timing computations for collision events

    Depth information in natural environments derived from optic flow by insect motion detection system: a model analysis

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    Knowing the depth structure of the environment is crucial for moving animals in many behavioral contexts, such as collision avoidance, targeting objects, or spatial navigation. An important source of depth information is motion parallax. This powerful cue is generated on the eyes during translatory self-motion with the retinal images of nearby objects moving faster than those of distant ones. To investigate how the visual motion pathway represents motion-based depth information we analyzed its responses to image sequences recorded in natural cluttered environments with a wide range of depth structures. The analysis was done on the basis of an experimentally validated model of the visual motion pathway of insects, with its core elements being correlation-type elementary motion detectors (EMDs). It is the key result of our analysis that the absolute EMD responses, i.e. the motion energy profile, represent the contrast-weighted nearness of environmental structures during translatory self-motion at a roughly constant velocity. In other words, the output of the EMD array highlights contours of nearby objects. This conclusion is largely independent of the scale over which EMDs are spatially pooled and was corroborated by scrutinizing the motion energy profile after eliminating the depth structure from the natural image sequences. Hence, the well-established dependence of correlation-type EMDs on both velocity and textural properties of motion stimuli appears to be advantageous for representing behaviorally relevant information about the environment in a computationally parsimonious way

    Collision-sensitive neurons in the optic tectum of the bullfrog, Rana catesbeiana

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    In this study, we examined the neuronal correlates of frog collision avoidance behavior. Single unit recordings in the optic tectum showed that 11 neurons gave selective responses to objects approaching on a direct collision course. The collision-sensitive neurons exhibited extremely tight tuning for collision bound trajectories with mean half-width at half height values of 0.8 and 0.9° (n = 4) for horizontal and vertical deviations, respectively. The response of frog collision-sensitive neurons can be fitted by a function that simply multiplies the size dependence of its response, e(-αθ(t)), by the image\u27s instantaneous angular velocity θ\u27(t). Using fitting analysis, we showed that the peak firing rate always occurred after the approaching object had reached a constant visual angle of 24.2 ± 2.6° (mean ± SD; n = 8), regardless of the approaching velocity. Moreover, a linear relationship was demonstrated between parameters l/v (l: object\u27s half-size, v: approach velocity) and time-to-collision (time difference between peak neuronal activity and the predicted collision) in the 11 collision-sensitive neurons. In addition, linear regression analysis was used to show that peak firing rate always occurred after the object had reached a constant angular size of 21.1° on the retina. The angular thresholds revealed by both theoretical analyses were comparable and showed a good agreement with that revealed by our previous behavioral experiments. This strongly suggests that the collision-sensitive neurons of the frog comprise a threshold detector, which triggers collision avoidance behavior

    Neuronal processing of translational optic flow in the visual system of the shore crab Carcinus maenas

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    This paper describes a search for neurones sensitive to optic flow in the visual system of the shore crab Carcinus maenas using a procedure developed from that of Krapp and Hengstenberg. This involved determining local motion sensitivity and its directional selectivity at many points within the neurone's receptive field and plotting the results on a map. Our results showed that local preferred directions of motion are independent of velocity, stimulus shape and type of motion (circular or linear). Global response maps thus clearly represent real properties of the neurones' receptive fields. Using this method, we have discovered two families of interneurones sensitive to translational optic flow. The first family has its terminal arborisations in the lobula of the optic lobe, the second family in the medulla. The response maps of the lobula neurones (which appear to be monostratified lobular giant neurones) show a clear focus of expansion centred on or just above the horizon, but at significantly different azimuth angles. Response maps such as these, consisting of patterns of movement vectors radiating from a pole, would be expected of neurones responding to self-motion in a particular direction. They would be stimulated when the crab moves towards the pole of the neurone's receptive field. The response maps of the medulla neurones show a focus of contraction, approximately centred on the horizon, but at significantly different azimuth angles. Such neurones would be stimulated when the crab walked away from the pole of the neurone's receptive field. We hypothesise that both the lobula and the medulla interneurones are representatives of arrays of cells, each of which would be optimally activated by self-motion in a different direction. The lobula neurones would be stimulated by the approaching scene and the medulla neurones by the receding scene. Neurones tuned to translational optic flow provide information on the three-dimensional layout of the environment and are thought to play a role in the judgment of heading

    Engineering data compendium. Human perception and performance. User's guide

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    The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

    Localized direction selective responses in the dendrites of visual interneurons of the fly

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    <p>Abstract</p> <p>Background</p> <p>The various tasks of visual systems, including course control, collision avoidance and the detection of small objects, require at the neuronal level the dendritic integration and subsequent processing of many spatially distributed visual motion inputs. While much is known about the pooled output in these systems, as in the medial superior temporal cortex of monkeys or in the lobula plate of the insect visual system, the motion tuning of the elements that provide the input has yet received little attention. In order to visualize the motion tuning of these inputs we examined the dendritic activation patterns of neurons that are selective for the characteristic patterns of wide-field motion, the lobula-plate tangential cells (LPTCs) of the blowfly. These neurons are known to sample direction-selective motion information from large parts of the visual field and combine these signals into axonal and dendro-dendritic outputs.</p> <p>Results</p> <p>Fluorescence imaging of intracellular calcium concentration allowed us to take a direct look at the local dendritic activity and the resulting local preferred directions in LPTC dendrites during activation by wide-field motion in different directions. These 'calcium response fields' resembled a retinotopic dendritic map of local preferred directions in the receptive field, the layout of which is a distinguishing feature of different LPTCs.</p> <p>Conclusions</p> <p>Our study reveals how neurons acquire selectivity for distinct visual motion patterns by dendritic integration of the local inputs with different preferred directions. With their spatial layout of directional responses, the dendrites of the LPTCs we investigated thus served as matched filters for wide-field motion patterns.</p

    Functional and developmental characterization of local motion sensing neurons in the fly visual system

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    Sighted animals use visual motion information to navigate in their environment, to search for food sources or mating partners and to avoid potentials predators. However, directional motion information is not explicitly represented in the photoreceptor signals, but rather needs to be extracted by postsynaptic circuits. For such a motion computation, different algorithmic models were proposed. The most prominent model multiplies the signal of two neighboring photoreceptors after one of them was temporally delayed. Fruit flies are well suited as a model organism to study the neuronal mechanisms underlying motion perception. With a low spatial but high temporal visual resolution, fruit flies are able to detect many different kinds of motion stimuli and perform a wide range of visually evoked behaviors. Thanks to the multitude of genetic tools optimized for Drosophila melanogaster, detailed manipulation of neuronal function can be performed on a molecular as well as on a cellular level. These tools allow to dissect the components of a neuronal circuit and investigate their respective function. In the visual system of flies exist neurons sensitive to wide field motion, which are important for the course control of flies. An open question remains the computation of upstream neurons detecting local motion. During my doctoral work I studied various aspects of the local motion sensing cells in the fly visual system: their functional properties, their importance for different behavioral tasks as well as their differentiation during development. In the first manuscript included in this thesis, we demonstrated that T4 and T5 cells are the elementary local motion sensing neurons of the fly. Calcium activity imaging of T4 and T5 cells revealed that four subtypes exist, each sensitive to motion along one of the four cardinal directions. Moreover, T4 cells responded specifically to light increments and T5 cells to light decrements. Blocking T4 neurons abolished the ON motion responses of postsynaptic lobula plate tangential cells. Accordingly, inactivating T5 cells inhibited the reaction of lobula plate tangential cells to OFF motion. We confirmed this effect by examining the turning behavior of walking flies with either T4 or T5 cells blocked. Flies without T4 output responded only to OFF edge motion, while flies with blocked T5 cells responded exclusively to ON edge motion. To investigate the functional role of the local motion sensing T4 and T5 cells, we studied the consequences of blocking these neurons and tested visual behavior. In the second manuscript, we described that inactivating T4 and T5 cells abolished the optomotor turning response of the flies. However, the motion blind flies were still able to orient towards a dark, vertical bar. Wedemonstrated that flies respond to the position of a bar independent of a motion cue. Therefore, we concluded that flies use positional as well as motion information to orient towards an attractive object. In the third manuscript, we further investigated the role of T4 and T5 cells in flight behavior and found these cells involved in the detection of expansion motion. Flight avoidance turns as well as landing responses of flies depend on functional T4 and T5 cells. These behaviors are evoked by expansion motion like a looming stimulus, which mimics an approaching predator or object. The importance of T4 and T5 cells for looming evoked behavior suggests, that these cells are not only connected to lobula plate tangential cells, which respond to rotatory wide-field motion, but are also presynaptic to looming sensitive neurons in the lobula plate. The last manuscript describes transcription factors important for the differentiation of T4 and T5 neurons. The morphology of all T4 and T5 subtypes is comparable; their dendrites are oriented opposite to the preferred direction of the cell and the axon terminals target one of the four lobula plate layers. Both the dendrites and the axon terminals are limited to only one layer of their respective neuropil. We found two postmitotic transcription factors expressed in the young T4 and T5 cells, SoxN and Sox102F, which regulate the common features of all subtypes. These transcription factors are crucial for the proper morphology of the T4 and T5 cells, as well as the function of the adult neurons

    Functional and developmental characterization of local motion sensing neurons in the fly visual system

    Get PDF
    Sighted animals use visual motion information to navigate in their environment, to search for food sources or mating partners and to avoid potentials predators. However, directional motion information is not explicitly represented in the photoreceptor signals, but rather needs to be extracted by postsynaptic circuits. For such a motion computation, different algorithmic models were proposed. The most prominent model multiplies the signal of two neighboring photoreceptors after one of them was temporally delayed. Fruit flies are well suited as a model organism to study the neuronal mechanisms underlying motion perception. With a low spatial but high temporal visual resolution, fruit flies are able to detect many different kinds of motion stimuli and perform a wide range of visually evoked behaviors. Thanks to the multitude of genetic tools optimized for Drosophila melanogaster, detailed manipulation of neuronal function can be performed on a molecular as well as on a cellular level. These tools allow to dissect the components of a neuronal circuit and investigate their respective function. In the visual system of flies exist neurons sensitive to wide field motion, which are important for the course control of flies. An open question remains the computation of upstream neurons detecting local motion. During my doctoral work I studied various aspects of the local motion sensing cells in the fly visual system: their functional properties, their importance for different behavioral tasks as well as their differentiation during development. In the first manuscript included in this thesis, we demonstrated that T4 and T5 cells are the elementary local motion sensing neurons of the fly. Calcium activity imaging of T4 and T5 cells revealed that four subtypes exist, each sensitive to motion along one of the four cardinal directions. Moreover, T4 cells responded specifically to light increments and T5 cells to light decrements. Blocking T4 neurons abolished the ON motion responses of postsynaptic lobula plate tangential cells. Accordingly, inactivating T5 cells inhibited the reaction of lobula plate tangential cells to OFF motion. We confirmed this effect by examining the turning behavior of walking flies with either T4 or T5 cells blocked. Flies without T4 output responded only to OFF edge motion, while flies with blocked T5 cells responded exclusively to ON edge motion. To investigate the functional role of the local motion sensing T4 and T5 cells, we studied the consequences of blocking these neurons and tested visual behavior. In the second manuscript, we described that inactivating T4 and T5 cells abolished the optomotor turning response of the flies. However, the motion blind flies were still able to orient towards a dark, vertical bar. Wedemonstrated that flies respond to the position of a bar independent of a motion cue. Therefore, we concluded that flies use positional as well as motion information to orient towards an attractive object. In the third manuscript, we further investigated the role of T4 and T5 cells in flight behavior and found these cells involved in the detection of expansion motion. Flight avoidance turns as well as landing responses of flies depend on functional T4 and T5 cells. These behaviors are evoked by expansion motion like a looming stimulus, which mimics an approaching predator or object. The importance of T4 and T5 cells for looming evoked behavior suggests, that these cells are not only connected to lobula plate tangential cells, which respond to rotatory wide-field motion, but are also presynaptic to looming sensitive neurons in the lobula plate. The last manuscript describes transcription factors important for the differentiation of T4 and T5 neurons. The morphology of all T4 and T5 subtypes is comparable; their dendrites are oriented opposite to the preferred direction of the cell and the axon terminals target one of the four lobula plate layers. Both the dendrites and the axon terminals are limited to only one layer of their respective neuropil. We found two postmitotic transcription factors expressed in the young T4 and T5 cells, SoxN and Sox102F, which regulate the common features of all subtypes. These transcription factors are crucial for the proper morphology of the T4 and T5 cells, as well as the function of the adult neurons
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