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  • 11
    Electronic Resource
    Electronic Resource
    On the fine structure of yaw torque in visual flight orientation ofDrosophila melanogaster (1979)
    Springer
    Journal of comparative physiology 130 (1979), S. 113-130 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Yaw torque fluctuations ofDrosophila in stationary flight at the torque meter in many cases represent meaningful behavior patterns (e.g., Figs. 4, 9a). In the closed loop situation for rotations around the fly's vertical axisDrosophila stabilizes any panorama by adjusting its “optomotor balance” (e.g., Figs. 2, 3, 8, 11) — a presumably integrative directionally movement sensitive flight control mechanism. In this state of “harmony” with the environmentDrosophila often performs active turns by means of body-saccades (Fig. 2). In this study these are recorded as “torque spikes” — an elementary motor pattern of typical size and time course (Fig. 3). Their polarity and frequency are dependent upon visual stimulation (Figs. 4, 5, 6). During a torque spike the fly does not respond to the visual stimulation caused by the relative displacement of the environment (Fig. 13); an artificial displacement in the opposite direction, however, causes a fast vigorous turning response. This is attributed to a directionally selectiveefference copy of the torque spike motor pattern which suppresses the reafferent visual input (Fig. 13a-f). The efference copy also relieves the visual system from certain inhibitory interactions which, in larger flies, have been shown to provide “figure-ground” discrimination (Fig. 13g-l). In addition the asymmetry in the fly's response to progressive and to regressive movement of small patterns is eliminated by the efference copy. Such information processing steps may be of minor importance during body-saccades. Optomotor balance inDrosophila is the basis of oriented flight. In closed loop experiments with one vertical black stripe the fly spends only part of its time keeping the stripe in its direction of flight (fixation). More often it stabilizes the stripe in other positions (non-fixation) (Fig. 8). Torque responses to the position of objects inDrosophila appear to be centrally controlled. Various situations in which the fly favors fixation (anti-fixation) or non-fixation are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611046
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  • 12
    Electronic Resource
    Electronic Resource
    On the fine structure of yaw torque in visual flight orientation ofDrosophila melanogaster (1980)
    Springer
    Journal of comparative physiology 140 (1980), S. 69-80 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Facing two or more moving objects in stationary flightDrosophila can restrict its torque response to one of them. Under such conditions it evaluates stimuli only in certain parts of the visual field. For the sake of brevity we call this ‘visual attention’. The fly is able to focus its ‘attention’ to any angular position (in the horizontal). In this process it follows the stimuli presented. In contrast, the optomotor control system, which adjusts the optomotor balance of the fly is mostly, if not always, sensitive at the same time to the movements of several objects in different parts of the visual field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613749
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  • 13
    Electronic Resource
    Electronic Resource
    Optomotor-blindH31—aDrosophila mutant of the lobula plate giant neurons (1978)
    Springer
    Journal of comparative physiology 124 (1978), S. 287-296 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In theDrosophila mutantoptomotorblind H31 (omb H31), previously isolated for its defects in the optomotor turning response, the visual giant neurons of the lobula plate are missing or significantly reduced. In particular, fibres homologous to the H-and V-cells ofCalliphora as well as two fibres (M-cells) in the middle plane of the plate are affected. Optomotor turning reactions in flight and in the walking mode are strongly reduced inomb H31. Also pattern induced orientation is disturbed. In flight this behavior is thought to be controlled by 3 parameters: the response to the position of the pattern, the response to the direction of motion of the pattern and the spontaneous torque fluctuations of the fly. All of these are reduced in the mutant. Two other visual reactions, the optomotor thrust response and the movement-stimulated landing response can readily be elicited. Althoughomb H31 and wild type differ in certain properties of these responses preliminary experiments indicate that in both cases the response strength is not significantly reduced by the mutation. These findings confirm the rôle of the H-cells in optomotor turning reactions but question the suggestions based on anatomical and electrophysiological results from big flies that the V-cells are mediating the optomotor thrust response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00661379
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  • 14
    Electronic Resource
    Electronic Resource
    Reafferent control of optomotor yaw torque inDrosophila melanogaster (1988)
    Springer
    Journal of comparative physiology 163 (1988), S. 373-388 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the flight simulator the optomotor response ofDrosophila melanogaster does not operate as a simple feedback loop. Reafferent and exafferent motion stimuli are processed differently. Under open-loop conditions responses to motion are weaker than under closed-loop conditions. It takes the fly less than 100 ms to distinguish reafferent from exafferent motion. In closed-loop conditions, flies constantly generate torque fluctuations leading to small-angle oscillations of the panorama. This reafferent motion stimulus facilitates the response to exafferent motion but does not itself elicit optomotor responses. Reafference control appears to be directionally selective: while a displacement of the patternm by as little as 0.1° against the ‘expected’ direction leads to a fast syndirectional torque response, displacements in the ‘expected’ direction have no comparable effect. Based on the behavior of the mutantrol sol, which under open-loop conditions is directionally motion-blind but in closed-loop conditions still performs optomotor balance, a model is proposed in which the fly's endogenous torque fluctuations are an essential part of the course control process. It is argued that the model may also account for wild type optomotor balance in the flight simulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00604013
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  • 15
    Electronic Resource
    Electronic Resource
    Visual control of straight flight in Drosophila melanogaster (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 269-283 
    Details
    ISSN: 1432-1351
    Keywords: Reafference ; Efference copy model ; Initiating activity ; Visual acceleration ; Pretorque
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The optomotor system of Drosophila is investigated in a flight simulator in which the fly's yaw torque controls the angular velocity of the panorama (striped drum, negative feedback). Flies in the flight simulator maintain a stable orientation even in a homogeneously textured panorama without landmarks. During ‘straight’ flight, torque is not zero. It consists of small pulses mostly alternating in polarity. The course is controlled by the duration (and possibly amplitude) of the pulses. The system operates under reafference control. By comparing the pulses with the visual input the system continuously measures and adjusts the efficacy of the torque output. The comparison, however, is not between angular velocity and yaw torque but, instead, between visual acceleration and pretorque, the first time derivative of torque. For comparison, the system first computes a cross-correlation. If the correlation coefficient is above a certain threshold the system calculates the external gain and adjusts its internal gain so as to keep the total gain constant. With the correlation coefficient below threshold, however, the system keeps the internal gain low despite the infinitely small external gain. We propose that for a reafferent optomotor system the coupling coefficient and the correlation coefficient of pretorque and visual acceleration are more relevant than the distinction between exafference and reafference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188119
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  • 16
    Electronic Resource
    Electronic Resource
    Flight control during ‘free yaw turns’ inDrosophila melanogaster (1988)
    Springer
    Journal of comparative physiology 163 (1988), S. 389-399 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. A new method for studying flight control in flies is introduced. In this set-up (thread paradigm) the fly is free to rotate around its vertical body axis but is otherwise kept stationary. The fly's orientation is continuously monitored optoelectronically. For statistical evaluation flight traces are divided into ‘turns’ (summed successive angular displacements until the direction of turning changes). 2. In the thread paradigm flies perform quick turning maneuvers corresponding to torque spikes at the torque compensator and to body saccades in free flight. In between, flies maintain a rather straight course. This obvious observation is reflected in bimodal velocity and turn histograms, both of which are composed approximately of a Gaussian and an exponential distribution. 3. The frequency of body saccades declines exponentially (decline constant 0.026/°), angular peak velocities increase linearly (12.5(°/s)/°=12.5/s), and the duration of saccades saturates (at about 250 ms) with increasing size of saccade. After a quick rising phase (40–60 ms) body saccades show, as a mean, an exponential drop of angular velocity with a time constant of about 40 ms. 4. The pattern dependency of the turning behavior resembles that measured using the torque compensator. The size of body saccades is influenced by the visual pattern wavelength. The direction of a body saccade may depend on that of the preceding one thus revealing its special status as part of a larger behavioral sequence. 5. Experiments with constant torque bias reveal an internal reference of zero torque. Corresponding measurements using the torque compensator suggest an efficacy model to be applicable in characterizing torque traces with constant rotatory bias. This new model allows simulation of constant-bias torque traces by applying a single efficacy factor to no-bias torque traces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00604014
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  • 17
    Electronic Resource
    Electronic Resource
    Coordination of legs during straight walking and turning in Drosophila melanogaster (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 403-412 
    Details
    ISSN: 1432-1351
    Keywords: Drosophila behavior ; Insect locomotion ; Leg coordination ; Turning behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Leg coordination of Drosophila melanogaster was studied using frame-by-frame film analysis. 1. For fastest walking alternating tripod coordination is observed which slightly deviates towards tetrapody as a function of step period. During acceleration or deceleration legs may transiently recover in diagonal pairs. 2. Mean step length increases with step frequency. 3. Mean recovery stroke duration increases with step period and plateaus beyond a period of about 110 ms. Middle legs recover significantly faster than others. 4. Ipsilateral footprints are transversally separated. 5. Walking is usually initiated in tripod coordination (frequently in combination with a turn), otherwise in an accelerating sequence which rapidly shifts towards tripod pattern. Flies can stop abruptly or decelerate over about one metachronal wave. 6. Short interruptions in walking are observed. Legs interrupted during swing phase stay lifted and finish recovery thereafter. 7. Slight changes in walking direction are obtained by altering step lengths only. Tight turns are composed of two or three phases with backward, zero and forward translatory components. In fast turning tripod coordination is maintained. Otherwise body sides can decouple widely. In all turns numbers of contralateral metachronal waves were equal. Results are compared to those for other walking insects and their relevance in screens for locomotor mutants is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192575
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  • 18
    Electronic Resource
    Electronic Resource
    Neuronal architecture of the central complex in Drosophila melanogaster (1989)
    Springer
    Cell & tissue research 257 (1989), S. 343-366 
    Details
    ISSN: 1432-0878
    Keywords: Central complex ; Golgi impregnation ; Neurotransmitters ; Protocerebrum, insect ; Immunocytochemistry ; Drosophila melanogaster (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary On the basis of 1200 Golgi-impregnated brains the structure of the central complex of Drosophila melanogaster was analyzed at the cellular level. The four substructures of the central complex — the ellipsoid body, the fanshaped body, the noduli, and the protocerebral bridge — are composed of (a) columnar small-field elements linking different substructures or regions in the same substructure and (b) tangential large-field neurons forming strata perpendicular to the columns. At least some small-field neurons belong to isomorphic sets, which follow various regular projection patterns. Assuming that the blebs of a neuron are presynaptic and the spines are postsynaptic, the Golgi preparations indicate that small-field neurons projecting to the ventral bodies (accessory area) are the main output from the central complex and that its main input is through the large-field neurons. These in turn are presumed to receive input in various neuropils of the brain including the ventral bodies. Transmitters can be attributed immunocytochemically to some neuron types. For example, GABA is confined to the R1–R4 neurons of the ellipsoid body, whereas these cells are devoid of choline acetyltransferase-like immunore-activity. It is proposed that the central complex is an elaboration of the interhemispheric commissure serving the fast exchange of data between the two brain hemispheres in the control of behavioral activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261838
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  • 19
    Electronic Resource
    Electronic Resource
    Vortrag in St. Petersburg, October, 1994. Pavlov's dog and Benzer's fly: The genetics of higher nervous activity (1997)
    Springer
    Neuroscience and behavioral physiology 27 (1997), S. 632-634 
    Details
    ISSN: 1573-899X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02463912
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  • 20
    Electronic Resource
    Electronic Resource
    Segregation of heterokaryons in the asexual cycle ofPhycomyces (1968)
    Springer
    Molecular genetics and genomics 102 (1968), S. 187-195 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Artificial heterokaryons between carotene mutants ofPhycomyces blakesleeanus Bgff. have been prepared by squeezing cytoplasm out of two different mutant sporangiophores and allowing the fused droplets to regenerate. These heterokaryons are used to study the distribution of nuclei at different stages of the asexual life cycle. It is proposed that the nuclear ratio is constant in all parts of the mycelium, sporangiophores and sporangia, and that random samples of nuclei are packaged into spores. This model permits quantitative predictions regarding the proportions of phenotypes in the asexual progeny and these predictions are corroborated by experiments. The nuclear ratio remains constant during repeated mycelial transfers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385973
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