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Kurtz R, Hayward V. Multiple-goal kinematic optimization of a parallel spherical mechanism with actuator redundancy. ACTA ACUST UNITED AC 1992. [DOI: 10.1109/70.163788] [Citation(s) in RCA: 146] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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146 |
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Egelhaaf M, Kern R, Krapp HG, Kretzberg J, Kurtz R, Warzecha AK. Neural encoding of behaviourally relevant visual-motion information in the fly. Trends Neurosci 2002; 25:96-102. [PMID: 11814562 DOI: 10.1016/s0166-2236(02)02063-5] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Information processing in visual systems is constrained by the spatial and temporal characteristics of the sensory input and by the biophysical properties of the neuronal circuits. Hence, to understand how visual systems encode behaviourally relevant information, we need to know about both the computational capabilities of the nervous system and the natural conditions under which animals normally operate. By combining behavioural, neurophysiological and computational approaches, it is now possible in the fly to assess adaptations that process visual-motion information under the constraints of its natural input. It is concluded that neuronal operating ranges and coding strategies appear to be closely matched to the inputs the animal encounters under behaviourally relevant conditions.
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Review |
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133 |
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Wong C, Malang S, Sawan M, Dagher M, Smolentsev S, Merrill B, Youssef M, Reyes S, Sze D, Morley N, Sharafat S, Calderoni P, Sviatoslavsky G, Kurtz R, Fogarty P, Zinkle S, Abdou M. An overview of dual coolant Pb–17Li breeder first wall and blanket concept development for the US ITER-TBM design. FUSION ENGINEERING AND DESIGN 2006. [DOI: 10.1016/j.fusengdes.2005.05.012] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19 |
98 |
4
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13 |
83 |
5
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Abstract
Small-cell carcinoma of the esophagus is a rare tumor. In most reported cases, surgery has been the major mode of therapy. Most patients have relapsed rapidly with disseminated disease. We treated a patient with small-cell carcinoma of the esophagus with a multi-drug regimen being used in small cell-carcinoma of the lung. Within two months of beginning therapy, the primary lesion, as evaluated by barium esophogram, had completely resolved. Residual disease was seen on panendoscopy. The patient was considered to be in partial remission. She relapsed nine months after starting therapy and died with widespread metastases. Small-cell carcinoma of the esophagus should not be treated surgically but rather in the same fashion as is small-cell carcinoma of the lung, i.e., with multi-drug chemotherapy and radiation therapy.
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Case Reports |
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80 |
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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. Front Neural Circuits 2012; 6:108. [PMID: 23269913 PMCID: PMC3526811 DOI: 10.3389/fncir.2012.00108] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 12/03/2012] [Indexed: 11/30/2022] Open
Abstract
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.
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review-article |
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71 |
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Kurtz R, Fricke M, Kalb J, Tinnefeld P, Sauer M. Application of multiline two-photon microscopy to functional in vivo imaging. J Neurosci Methods 2006; 151:276-86. [PMID: 16442636 DOI: 10.1016/j.jneumeth.2005.12.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 11/28/2005] [Accepted: 12/04/2005] [Indexed: 10/25/2022]
Abstract
High spatial resolution and low risks of photodamage make two-photon laser-scanning microscopy (TPLSM) the method of choice for biological imaging. However, the study of functional dynamics such as neuronal calcium regulation often also requires a high temporal resolution. Hitherto, acquisition speed is usually increased by line scanning, which restricts spatial resolution to structures along a single axis. To overcome this gap between high spatial and high temporal resolution we performed TPLSM with a beam multiplexer to generate multiple laser foci inside the sample. By detecting the fluorescence emitted from these laser foci with an electron-multiplying camera, it was possible to perform multiple simultaneous linescans. In addition to multiline scanning, the array of up to 64 laser beams could also be used in x-y scan mode to collect entire images at high frame rates. To evaluate the applicability of multiline TPLSM to functional in vivo imaging, calcium signals were monitored in visual motion-sensitive neurons in the brain of flies. The capacity of our method to simultaneously acquire signals at different cellular locations is exemplified by measurements at branched neurites and 'spine'-like structures. Calcium dynamics depended on branch size, but 'spines' did not systematically differ from their 'parent neurites'. The spatial resolution of our setup was critically evaluated by comparing it to confocal microscopy and the negative effect of scattering of emission light during image detection was assessed directly by running the setup in both imaging and point-scanning mode.
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Journal Article |
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41 |
8
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48 |
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Kurtz R, Dürr V, Egelhaaf M. Dendritic calcium accumulation associated with direction-selective adaptation in visual motion-sensitive neurons in vivo. J Neurophysiol 2000; 84:1914-23. [PMID: 11024084 DOI: 10.1152/jn.2000.84.4.1914] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Motion adaptation in directionally selective tangential cells (TC) of the fly visual system has previously been explained as a presynaptic mechanism. Based on the observation that adaptation is in part direction selective, which is not accounted for by the former models of motion adaptation, we investigated whether physiological changes located in the TC dendrite can contribute to motion adaptation. Visual motion in the neuron's preferred direction (PD) induced stronger adaptation than motion in the opposite direction and was followed by an afterhyperpolarization (AHP). The AHP subsides in the same time as adaptation recovers. By combining in vivo calcium fluorescence imaging with intracellular recording, we show that dendritic calcium accumulation following motion in the PD is correlated with the AHP. These results are consistent with a calcium-dependent physiological change in TCs underlying adaptation during continuous stimulation with PD motion, expressing itself as an AHP after the stimulus stops. However, direction selectivity of adaptation is probably not solely related to a calcium-dependent mechanism because direction-selective effects can also be observed for fast moving stimuli, which do not induce sizeable calcium accumulation. In addition, a comparison of two classes of TCs revealed differences in the relationship of calcium accumulation and AHP when the stimulus velocity was varied. Thus the potential role of calcium in motion adaptation depends on stimulation parameters and cell class.
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25 |
35 |
10
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Duffy A, Capanu M, Allen P, Kurtz R, Olson SH, Ludwig E, Klimstra DS, O'Reilly EM. Pancreatic adenocarcinoma in a young patient population--12-year experience at Memorial Sloan Kettering Cancer Center. J Surg Oncol 2009; 100:8-12. [PMID: 19384918 DOI: 10.1002/jso.21292] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND There is a dearth of data in a younger population of patients with pancreatic ductal adenocarcinoma (PAC) regarding epidemiology, genetics, prognosis, and outcome. This report examines a large cohort of patients with PAC <or=45 years of age evaluated at MSKCC over a 12-year period. METHODS A retrospective analysis of patients referred to MSKCC with PAC identified from the institutional tumor registry, who were <or=45 years on the date of the diagnostic biopsy, between January 1995 and February 2008, was performed. Information reviewed included demographics, clinical and pathological staging, surgical management, therapy, date of relapse, death or last follow-up. Survival curves were estimated using the Kaplan-Meier method and compared using the log-rank test. RESULTS One hundred thirty-six cases of PAC, age <or=45 years at diagnosis, were identified. Seventy-four (54%) females, 62 (46%) males. Age range: 24-45; 4, 38, and 94 patients in age groups 20-29, 30-39, 40-45 years, respectively. Fifty (37%) had a smoking history. Fourteen (10.3%) had a positive family history of PAC. Thirty-five (25.7%) underwent a curative resection for localized disease. Twenty-eight (20.1%) presented with locally advanced, inoperable disease. Sixty-eight (50%) presented as AJCC Stage IV. Twenty-three (37%) of those resected underwent adjuvant chemoradiation. Thirteen received adjuvant gemcitabine. The median overall survival for the entire cohort was 12.3 months (95% CI 10.2-14.0 months). The median overall survival for the patients with locally resectable disease was 41.8 months (95% CI 20.3-47 months). The median overall survival for the patients who presented with locally advanced, unresectable disease was 15.3 months (95% CI 12-19.3 months). The median overall survival for those who presented with metastatic disease was 7.2 months (95% CI 5.2-9.5 months). CONCLUSIONS This is the largest reported cohort of young patients with PAC <or=45 years of age. The data suggest that patients with stages I-II disease may have an improved prognosis, however the prognosis for stages III-IV patients appears to be similar to the typical (older) patient population with PAC.
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Journal Article |
16 |
28 |
11
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Warzecha AK, Kurtz R, Egelhaaf M. Synaptic transfer of dynamic motion information between identified neurons in the visual system of the blowfly. Neuroscience 2003; 119:1103-12. [PMID: 12831867 DOI: 10.1016/s0306-4522(03)00204-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Synaptic transmission is usually studied in vitro with electrical stimulation replacing the natural input of the system. In contrast, we analyzed in vivo transfer of visual motion information from graded-potential presynaptic to spiking postsynaptic neurons in the fly. Motion in the null direction leads to hyperpolarization of the presynaptic neuron but does not much influence the postsynaptic cell, because its firing rate is already low during rest, giving only little scope for further reductions. In contrast, preferred-direction motion leads to presynaptic depolarizations and increases the postsynaptic spike rate. Signal transfer to the postsynaptic cell is linear and reliable for presynaptic graded membrane potential fluctuations of up to approximately 10 Hz. This frequency range covers the dynamic range of velocities that is encoded with a high gain by visual motion-sensitive neurons. Hence, information about preferred-direction motion is transmitted largely undistorted ensuring a consistent dependency of neuronal signals on stimulus parameters, such as motion velocity. Postsynaptic spikes are often elicited by rapid presynaptic spike-like depolarizations which superimpose the graded membrane potential. Although the timing of most of these spike-like depolarizations is set by noise and not by the motion stimulus, it is preserved at the synapse with millisecond precision.
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22 |
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12
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Liang P, Heitwerth J, Kern R, Kurtz R, Egelhaaf M. Object representation and distance encoding in three-dimensional environments by a neural circuit in the visual system of the blowfly. J Neurophysiol 2012; 107:3446-57. [PMID: 22423002 DOI: 10.1152/jn.00530.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Three motion-sensitive key elements of a neural circuit, presumably involved in processing object and distance information, were analyzed with optic flow sequences as experienced by blowflies in a three-dimensional environment. This optic flow is largely shaped by the blowfly's saccadic flight and gaze strategy, which separates translational flight segments from fast saccadic rotations. By modifying this naturalistic optic flow, all three analyzed neurons could be shown to respond during the intersaccadic intervals not only to nearby objects but also to changes in the distance to background structures. In the presence of strong background motion, the three types of neuron differ in their sensitivity for object motion. Object-induced response increments are largest in FD1, a neuron long known to respond better to moving objects than to spatially extended motion patterns, but weakest in VCH, a neuron that integrates wide-field motion from both eyes and, by inhibiting the FD1 cell, is responsible for its object preference. Small but significant object-induced response increments are present in HS cells, which serve both as a major input neuron of VCH and as output neurons of the visual system. In both HS and FD1, intersaccadic background responses decrease with increasing distance to the animal, although much more prominently in FD1. This strong dependence of FD1 on background distance is concluded to be the consequence of the activity of VCH that dramatically increases its activity and, thus, its inhibitory strength with increasing distance.
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Research Support, Non-U.S. Gov't |
13 |
26 |
13
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Kurtz R, Egelhaaf M, Meyer HG, Kern R. Adaptation accentuates responses of fly motion-sensitive visual neurons to sudden stimulus changes. Proc Biol Sci 2009; 276:3711-9. [PMID: 19656791 DOI: 10.1098/rspb.2009.0596] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Adaptation in sensory and neuronal systems usually leads to reduced responses to persistent or frequently presented stimuli. In contrast to simple fatigue, adapted neurons often retain their ability to encode changes in stimulus intensity and to respond when novel stimuli appear. We investigated how the level of adaptation of a fly visual motion-sensitive neuron affects its responses to discontinuities in the stimulus, i.e. sudden brief changes in one of the stimulus parameters (velocity, contrast, grating orientation and spatial frequency). Although the neuron's overall response decreased gradually during ongoing motion stimulation, the response transients elicited by stimulus discontinuities were preserved or even enhanced with adaptation. Moreover, the enhanced sensitivity to velocity changes by adaptation was not restricted to a certain velocity range, but was present regardless of whether the neuron was adapted to a baseline velocity below or above its steady-state velocity optimum. Our results suggest that motion adaptation helps motion-sensitive neurons to preserve their sensitivity to novel stimuli even in the presence of strong tonic stimulation, for example during self-motion.
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Research Support, Non-U.S. Gov't |
16 |
24 |
14
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El-Guebaly L, Kurtz R, Rieth M, Kurishita H, Robinson A. W-Based Alloys for Advanced Divertor Designs: Options and Environmental Impact of State-of-the-Art Alloys. FUSION SCIENCE AND TECHNOLOGY 2017. [DOI: 10.13182/fst11-a12349] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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8 |
24 |
15
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Qureshi N, Takayama K, Seydel U, Wang R, Cotter R, Agrawal P, Bush C, Kurtz R, Berman D. Structural analysis of the lipid A derived from the lipopolysaccharide of Brucella abortus. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/096805199400100303] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Lipopolysaccharide (LPS) of Brucella abortus strain 45/20 was purified using a novel method. Monophosphoryl lipid A (MPLA) was prepared from this LPS, methylated, and purified by high performance liquid chromatography. Chemical, mass spectral, and nuclear magnetic resonance analyses showed that MPLA consists of heptaacyl lipid As with molecular weights of 2095, 2123, 2151 and 2179. They contained the β-1,6-linked 2,3-diamino-2,3,-dideoxy-glucose disaccharide backbone and a phosphate group at the 4' position. Bisphosphoryl lipid A was also prepared and completely O-deacylated. It contained an additional phosphate group, and either 2 hydroxyhexadecanoic, 1 hydroxytetradecanoic, 1 hydroxydodecanoic acids or 2 hydroxyhexadecanoic and 2 hydroxydodecanoic acids, all in amide linkage. The predominant ester-linked fatty acyl group in acyloxyacyl linkage was hexadecanoate. The purified LPS, bisphosphoryl lipid A, and MPLA from B. abortus showed about 14%, 3% and 1%, respectively, of the B cell mitogen activity of ReLPS from Escherichia coli at 1.0 μg/ml.
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Kalb J, Egelhaaf M, Kurtz R. Robust integration of motion information in the fly visual system revealed by single cell photoablation. J Neurosci 2006; 26:7898-906. [PMID: 16870735 PMCID: PMC6674221 DOI: 10.1523/jneurosci.1327-06.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the brain, sensory information needs often to be read out from the ensemble activity of presynaptic neurons. In the most basic case, this may be accomplished by an individual postsynaptic neuron. In the visual system of the blowfly, an identified motion-sensitive spiking neuron is known to be postsynaptic to an ensemble of graded-potential presynaptic input elements. Both the presynaptic and postsynaptic neurons were shown previously to be capable of representing the velocity of preferred-direction motion reliably and linearly over a large frequency range of velocity fluctuations. Accordingly, the synaptic transfer properties of the connecting excitatory synapses between individual input elements and the postsynaptic neuron were shown to be linear over a similar range of presynaptic membrane potential fluctuations. It was not known, however, how the postsynaptic neuron integrates and reads out the presynaptic ensemble activity. We were able to compare the response properties of the integrating cell before and after eliminating individual presynaptic elements by a laser ablation technique. For most of the input elements, we found that their elimination strongly affected the activity of the postsynaptic neuron but did not degrade its performance to encode motion with constant and time-varying velocity. Our results suggest that the integration of individual synaptic inputs within the neural circuit operates with some redundancy. This feature might help the postsynaptic neuron to encode in a highly robust way the direction and the velocity of self-motion of the animal.
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Research Support, Non-U.S. Gov't |
19 |
19 |
17
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Rien D, Kern R, Kurtz R. Octopaminergic modulation of contrast gain adaptation in fly visual motion-sensitive neurons. Eur J Neurosci 2012; 36:3030-9. [PMID: 22775326 DOI: 10.1111/j.1460-9568.2012.08216.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Locomotor activity like walking or flying has recently been shown to alter visual processing in several species. In insects, the neuromodulator octopamine is thought to play an important role in mediating state changes during locomotion of the animal [K.D. Longden & H.G. Krapp (2009) J. Neurophysiol., 102, 3606-3618; (2010) Front. Syst. Neurosci., 4, 153; S.N. Jung et al. (2011)J. Neurosci., 31, 9231-9237]. Here, we used the octopamine agonist chlordimeform (CDM) to mimic effects of behavioural state changes on visual motion processing. We recorded from identified motion-sensitive visual interneurons in the lobula plate of the blowfly Calliphora vicina. In these neurons, which are thought to be involved in visual guidance of locomotion, motion adaptation leads to a prominent attenuation of contrast sensitivity. Following CDM application, the neurons maintained high contrast sensitivity in the adapted state. This modulation of contrast gain adaptation was independent of the activity of the recorded neurons, because it was also present after stimulation with visual motion that did not result in deviations from the neurons' resting activity. We conclude that CDM affects presynaptic inputs of the recorded neurons. Accordingly, the effect of CDM was weak when adapting and test stimuli were presented in different parts of the receptive field, stimulating separate populations of local presynaptic neurons. In the peripheral visual system adaptation depends on the temporal frequency of the stimulus pattern and is therefore related to pattern velocity. Contrast gain adaptation could therefore be the basis for a shift in the velocity tuning that was previously suggested to contribute to state-dependent processing of visual motion information in the lobula plate interneurons.
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Journal Article |
13 |
18 |
18
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Kurtz R. Direction-selective adaptation in fly visual motion-sensitive neurons is generated by an intrinsic conductance-based mechanism. Neuroscience 2007; 146:573-83. [PMID: 17367948 DOI: 10.1016/j.neuroscience.2007.01.058] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Revised: 01/28/2007] [Accepted: 01/29/2007] [Indexed: 11/18/2022]
Abstract
Motion-sensitive neurons in the blowfly brain present an ideal model system to study the cellular mechanisms and functional significance of adaptation to visual motion. Various adaptation processes have been described, but it is still largely unknown which of these processes are generated in the motion-sensitive neurons themselves and which originate at more peripheral processing stages. By input resistance measurements I demonstrate that direction-selective adaptation is generated by an activity-dependent conductance increase in the motion-sensitive neurons. Based on correlations between dendritic Ca(2+) accumulation and slow hyperpolarizing after-potentials following excitatory stimulation, a regulation of direction-selective adaptation by Ca(2+) has previously been suggested. In the present study, however, adaptation phenomena are not evoked when the cytosolic Ca(2+) concentration is elevated by ultraviolet photolysis of caged Ca(2+) in single neurons rather than by motion stimulation. This result renders it unlikely, that adaptation in fly motion-sensitive neurons is regulated by bulk cytosolic Ca(2+).
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Research Support, Non-U.S. Gov't |
18 |
17 |
19
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55 |
15 |
20
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Liang P, Kern R, Kurtz R, Egelhaaf M. Impact of visual motion adaptation on neural responses to objects and its dependence on the temporal characteristics of optic flow. J Neurophysiol 2011; 105:1825-34. [PMID: 21307322 DOI: 10.1152/jn.00359.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is still unclear how sensory systems efficiently encode signals with statistics as experienced by animals in the real world and what role adaptation plays during normal behavior. Therefore, we studied the performance of visual motion-sensitive neurons of blowflies, the horizontal system neurons, with optic flow that was reconstructed from the head trajectories of semi-free-flying flies. To test how motion adaptation is affected by optic flow dynamics, we manipulated the seminatural optic flow by targeted modifications of the flight trajectories and assessed to what extent neuronal responses to an object located close to the flight trajectory depend on adaptation dynamics. For all types of adapting optic flow object-induced response increments were stronger in the adapted compared with the nonadapted state. Adaptation with optic flow characterized by the typical alternation between translational and rotational segments produced this effect but also adaptation with optic flow that lacked these distinguishing features and even pure rotation at a constant angular velocity. The enhancement of object-induced response increments had a direction-selective component because preferred-direction rotation and natural optic flow were more efficient adaptors than null-direction rotation. These results indicate that natural dynamics of optic flow is not a basic requirement to adapt neurons in a specific, presumably functionally beneficial way. Our findings are discussed in the light of adaptation mechanisms proposed on the basis of experiments previously done with conventional experimenter-defined stimuli.
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Research Support, Non-U.S. Gov't |
14 |
13 |
21
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Hirt M, Kurtz R, Ross WD. The relationship between dysmenorrhea and selected personality variables. PSYCHOSOMATICS 1967; 8:350-3. [PMID: 6078042 DOI: 10.1016/s0033-3182(67)71923-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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58 |
13 |
22
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Safai B, Grant JM, Kurtz R, Lightdale CJ, Good RA. Cutaneous manifestation of internal malignancies (I). Acanthosis nigricans. Int J Dermatol 1978; 17:312-5. [PMID: 659033 DOI: 10.1111/j.1365-4362.1978.tb06084.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Skin changes may be the first clue to a neoplastic process at a stage when it still is treatable (Such as the development of Acanthosis Nigrican (AN) in an otherwise healthy adult). Ninety percent of the neoplasm responsible for the development of AN originate in the abdomen. The tumor, even in a subclinical state, seems to possess unidentified properties that activate the dermatosis.
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Case Reports |
47 |
12 |
23
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Maier SF, Ryan SM, Kurtz R. The formalin test and the opioid nature of stress-induced analgesia. BEHAVIORAL AND NEURAL BIOLOGY 1984; 41:54-62. [PMID: 6087789 DOI: 10.1016/s0163-1047(84)90719-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Exposure to electric shock produces an analgesic reaction (SIA) that is reversed by opiate antagonists ("opioid" SIA) under some conditions but not under other conditions ("nonopioid" SIA). A number of studies using tail-flick to radiant heat as the measure of pain sensitivity have found that a small number of shocks lead to nonopioid SIA, while a large number of shocks produce opioid SIA. In contrast, a small number of shocks have been reported to produce opioid SIA when the Formalin test was used to measure pain reactivity. However, the Formalin test involves administering a chronic pain stimulus (injection of Formalin into the paw) for an extended period before the shocks. Here it is reported that this "preexperimental" stress is sufficient to convert the SIA after a small number of shocks measured by tail-flick to the opioid form.
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41 |
11 |
24
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Spalthoff C, Egelhaaf M, Tinnefeld P, Kurtz R. Localized direction selective responses in the dendrites of visual interneurons of the fly. BMC Biol 2010; 8:36. [PMID: 20384983 PMCID: PMC2876097 DOI: 10.1186/1741-7007-8-36] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 04/12/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND 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. RESULTS 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. CONCLUSIONS 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.
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Research Support, Non-U.S. Gov't |
15 |
10 |
25
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Beckers U, Egelhaaf M, Kurtz R. Synapses in the fly motion-vision pathway: evidence for a broad range of signal amplitudes and dynamics. J Neurophysiol 2007; 97:2032-41. [PMID: 17215505 DOI: 10.1152/jn.01116.2006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synapses are generally considered to operate efficiently only when their signaling range matches the spectrum of prevailing presynaptic signals in terms of both amplitudes and dynamics. However, the prerequisites for optimally matching the signaling ranges may differ between spike-mediated and graded synaptic transmission. This poses a problem for synapses that convey both graded and spike signals at the same time. We addressed this issue by tracing transmission systematically in vivo in the blowfly's visual-motion pathway by recording from single neurons that receive mixed potential signals consisting of rather slow graded fluctuations superimposed with highly variable spikes from a small number of presynaptic elements. Both pre- and postsynaptic neurons were previously shown to represent preferred-direction motion velocity reliably and linearly at low fluctuation frequencies. To selectively assess the performance of individual synapses and to precisely control presynaptic signals, we voltage clamped one of the presynaptic neurons. Results showed that synapses can effectively convey signals over a much larger amplitude and frequency range than is normally used during graded transmission of visual signals. An explanation for this unexpected finding might lie in the transmission of the spike component that reaches larger amplitudes and contains higher frequencies than graded signals.
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