199,619 research outputs found
A preparation of the blowfly (*Calliphora erythrocephala*) brain for in vitro electrophysiological and pharmacological studies
No full textBrotz TM, Egelhaaf M, Borst A. A preparation of the blowfly (*Calliphora erythrocephala*) brain for in vitro electrophysiological and pharmacological studies. Journal of Neuroscience Methods. 1995;57(1):37-46
Mechanisms of dendritic integration underlying gain control in fly motion-sensitive interneurons
No full textBorst A, Egelhaaf M, Haag J. Mechanisms of dendritic integration underlying gain control in fly motion-sensitive interneurons. Journal of Computational Neuroscience. 1995;2(1):5-18
Motion computation and visual orientation in flies
No full textEgelhaaf M, Borst A. Motion computation and visual orientation in flies. Comparative Biochemistry and Physiology, A: Comparative Physiology. 1993;104(4):659-673.Visual orientation greatly relies on the evaluation of the motion patterns received by the eyes when the animal moves around. In a combination of behavioral, neurophysiological and pharmacological analysis and modelling, the mechanisms are established by which the visual system of the fly extracts three types of-basic retinal motion patterns. Coherent retinal large-field motion as is induced during deviations of the animal from its course, image expansion occurring when the animal approaches an obstacle, and relative motion which is induced when a nearby object is passed in front of its background. Separate neuronal networks are specifically tuned to each of these motion patterns and make use of them in three different orientation tasks: in compensatory course stabilization, the control of landing behaviour and the fixation of objects
Synapse distribution on VCH, an inhibitory, motion-sensitive interneuron in the fly visual system
No full textGauck V, Egelhaaf M, Borst A. Synapse distribution on VCH, an inhibitory, motion-sensitive interneuron in the fly visual system. JOURNAL OF COMPARATIVE NEUROLOGY. 1997;381(4):489-499
Beulah M. Borst
No full textOne photographic print mounted to Cabinet card of Beulah M. Borst (Zimmerman), a student at Buchtel College (now The University of Akron) in Akron, Ohio during the late 1890s (class of 1897). The print is slightly damaged and the card is yellowed and soiled on the back
Two-Dimensional Motion Perception in Flies
No full textBorst A, Egelhaaf M, Seung HS. Two-Dimensional Motion Perception in Flies. Neural Computation. 1993;5(6):856-868.We study two-dimensional motion perception in flies using a semicircular visual stimulus. Measurements of both the H1-neuron and the optomotor response are consistent with a simple model supposing spatial integration of the outputs of correlation-type motion detectors. In both experiment and model, there is substantial H1 and horizontal (yaw) optomotor response to purely vertical motion of the stimulus. We conclude that the fly's optomotor response to a two-dimensional pattern, depending on its structure, may deviate considerably from the direction of pattern motion
Transient and steady-state response properties of movement detectors
No full textEgelhaaf M, Borst A. Transient and steady-state response properties of movement detectors. Journal of the Optical Society of America, A: Optics, Image Science, and Vision. 1989;6(1):116-127.The transient and steady-state responses of movement detectors are studied at various pattern contrasts (i) by intracellularly recording from an identified movement-sensitive interneuron in the fly's brain and (ii) by comparing these results with computer simulations of an array of movement detectors of the correlation type. At the onset of stimulus motion, the membrane potential oscillates with a frequency corresponding to the temporal frequency of the stimulus pattern before it settles at its steady-state level. Both the transient and the steady-state response amplitudes show a characteristic contrast dependence. As is shown by computer modeling, the transient behavior that we found in the experiments reflects an intrinsic property of the general scheme of movement detectors of the correlation type. To account for the contrast dependence, however, this general scheme has to be elaborated by (i) a subtraction stage, which eliminates the background light intensity from the detector input signal, and (ii) saturation characteristics in both branches of each movement-detector subunit
Calcium accumulation in visual interneurons of the fly: stimulus dependence and relationship to membrane potential
No full textEgelhaaf M, Borst A. Calcium accumulation in visual interneurons of the fly: stimulus dependence and relationship to membrane potential. Journal of neurophysiology. 1995;73(6):2540-2552.1. The large motion-sensitive tangential neurons in the fly third visual neuropil spatially pool the postsynaptic signals of many local elements. The changes in membrane potential and calcium concentration induced in these cells by visual motion are analyzed in vivo by simultaneous optical and intracellular voltage recording techniques. 2. Visual motion in the preferred direction leads to depolarization of the cell and to calcium accumulation mainly in the axon terminal, the soma, and the dendritic tree. During motion in the null direction, the cell hyperpolarizes and virtually no changes in calcium concentration can be observed. 3. Dendritic calcium accumulation is first restricted to those dendritic branches that are close to the sites of direct synaptic input. In other parts of the dendrite the calcium concentration increases more slowly and usually reaches only lower levels. 4. Calcium starts accumulating at the onset of motion. However, the calcium concentration reaches its final steady-state level much later than the corresponding membrane potential changes. Even if these are completely transient at high temporal frequencies of pattern motion, the calcium signal stays high until the stimulus pattern stops moving. 5. The amplitute of the calcium signal depends on the temporal frequency of pattern motion in a similar way as do the corresponding membrane potential changes. However, there exist differences that can be attributed to the different time courses of both signals. 6. Depolarization of the dendritic tree by current injection through a microelectrode leads to similar changes in calcium accumulation as does activation by synaptic input, suggesting that calcium enters the cell via voltage-dependent channels. The possible function of calcium channels for dendritic integration of synaptic input is discussed
Are there separate ON and OFF channels in fly motion vision?
No full textEgelhaaf M, Borst A. Are there separate ON and OFF channels in fly motion vision? Visual Neuroscience. 1992;8:151-164
Temporal modulation of luminance adapts time constant of fly movement detectors
No full textBorst A, Egelhaaf M. Temporal modulation of luminance adapts time constant of fly movement detectors. Biological Cybernetics. 1987;56(4):209-215.The time constant of movement detectors in the fly visual system has been proposed to adapt in response to moving stimuli (de Ruyter van Steveninck et al. 1986). The objective of the present study is to analyse, whether this adaptation can be induced as well, if the luminance of a stationary uniform field is modulated in time. The experiments were done on motion-sensitive wide-field neurones of the lobula plate, the posterior part of the third visual ganglion of the blowfly, calliphora erythrocephala. These cells are assumed to receive input from large retinotopic arrays of movement detectors. In order to demonstrate that our results concern the properties of the movement detectors rather than those of a particular wide-field cell we recorded from two different types of them, the H1- and the HSE-cell. Both cell types respond to a brief movement stimulus in their preferred direction with a transient excitation. This response decays about exponentially. The time constant of this decay reflects, in a first approximation, the time constant of the presynaptic movement detectors. It was determined after prestimulation of the cell by the following stimuli: (a) periodic stationary grating; (b) uniform field, the intensity of which was modulated sinusoidally in time (flicker stimulation); (c) periodic grating moving front-to-back; (d) periodic grating moving back-to-front. The decay of the response is significantly faster not only after movement but also after flicker stimulation as compared with pre-stimulation with a stationary stimulus. This is interpreted as an adaptation of the movement detector's time constant. The finding that flicker stimulation also leads to an adaptation shows that movement is not necessary for this process. Instead the adaptation of the time constant appears to be governed mainly by the temporal modulation (i.e., contrast frequency) of the signal in each visual channel
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