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  • 1
    Electronic Resource
    Electronic Resource
    An equivalent circuit for the quantitative description of inter-receptor coupling in the retina of the desert antCataglyphis bicolor (1980)
    Springer
    Journal of comparative physiology 139 (1980), S. 277-285 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. An ionic equivalent circuit model is developed for the purpose of quantifying the strengths of electrical coupling existing between certain receptor cells in the compound eye ofCataglyphis bicolor which show wavelength dependence in the slopes of their ‘V logI’ relations and orientations of maximum PS (Mote and Wehner, 1980). It combines the pure electrical equivalent of the plasma membrane, as proposed by Finkelstein and Mauro (1963), and a closed series circuit such that Kirchhoff's laws are applicable. 2. The model is applied to hypothetical pairs of cells with different sensitivities and different strengths of interaction. It predicts that cells are most strongly coupled when at rest and most weakly coupled when most active. When one is active and the second is not then “apparent rectification” can occur since the coupling strength is not symmetrical. This means that both “resting” and “dynamic” coupling coefficients must be considered. Transition between these modes causes irregularities in the ‘V logI’ relation of a weakly excited cell which is coupled to a strongly excited cell. 3. The model is then applied to data obtained from photoreceptors in the compound eye ofCataglyphis. It adequately simulates the wavelength dependence of both the ‘V logI’ relation (Fig. 6) and the orientation of maximum PS (Fig. 7) measured in these cells. In its simplest form the model permits an estimate of the coupling coefficients which are greater than 0.6 for strongly coupled cells and less than 0.4 for weakly coupled cells. 4. A hypothetical treatment of pairs of coupled cells under conditions approaching the natural situation in the animal's environment suggests that super-numerary analyzers of polarized light in the u.v. could arise through receptor coupling in certain ommatidial types found in the eye ofCataglyphis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00610459
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  • 2
    Electronic Resource
    Electronic Resource
    ‘On’ type interneurons in the optic lobe ofPeriplaneta americana (1981)
    Springer
    Journal of comparative physiology 141 (1981), S. 395-401 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Responses of ‘on’ type interneurons in the optic lobes of dark adaptedPeriplaneta americana to stationary spots of flashing monochromatic light have been recorded extracellularly. The majority of the recording sites were in the external chiasma and in the neuropil of the lamina. 2. Their spectral sensitivity, using threshold as a criterion, is similar to the class of retinal receptor which is most sensitive to green light. The pattern of discharge is more complex and is dependent on stimulus wavelength. At wavelengths shorter than 475 nm, there is a distinct ‘tonic’ component to the response which is not prominent with stimuli of longer wavelengths. 3. The wavelength dependence of the discharge pattern is best explained by the convergence of two classes of retinal photoreceptors which differ in their spectral sensitivity and time course. This results in a wavelength specific discharge pattern. 4. Selective adaptation experiments reveal that under normal conditions the input from the retinal UV receptors is suppressed or inhibited by activity in the green sensitive receptors. The potential significance of these relations is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609942
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  • 3
    Electronic Resource
    Electronic Resource
    Color receptors in marine crustaceans: A second spectral class of retinular cell in the compound eyes ofCallinectes andCarcinus (1982)
    Springer
    Journal of comparative physiology 145 (1982), S. 549-554 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Spectral and polarizational sensitivities of dark adapted retinular cells in the ventral regions of the compound eye of the crabsCallinectes andCarcinus have been measured with intracellular recording of responses to flashes of monochromatic light. The majority was maximally sensitive to green light (508 nm,n=108) and showed a mean sensitivity in the blue violet that was higher than expected from a rhodopsin like pigment (Fig. 1). 2. A small number of cells (n = 6) showed a maximum sensitivity to blue light (440 nm) and had a sensitivity function which was considerably wider than a nomogram pigment (Fig. 2). These cells were recorded in the ventral regions of the eye and ERG measurements under selective adaptation revealed statistically significant changes in the relative sensitivities to blue and red stimuli (Figs. 4 and 5). 3. PS values ranged from 1 to 13 when measured in green cells with 508 nm stimuli (n = 69) with the modal value being 3. When PS was tested at 410 nm, 508 nm, and 605 nm in the same cell there was a statistically significant (0.07 log,P 〈 0.01) elevation of PS in the orange region of the spectrum. 4. The results are discussed in relation to the possibility of color vision in marine crustaceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612820
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  • 4
    Electronic Resource
    Electronic Resource
    Electrophysiology and anatomy of medulla interneurons in the optic lobe of the cockroach, Periplaneta americana (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 745-756 
    Details
    ISSN: 1432-1351
    Keywords: Cockroach ; Optic lobe ; Medulla ; Broad-band ; Narrow band ; Color opponency ; Polarizational sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Medulla interneurons of the optic lobe of P. americana were studied to determine their spectral properties. These neurons exhibited tonic firing which changed with monochromatic broadfield illumination of the ipsilateral eye. The response patterns of these neurons were analyzed by inferring their relation to the ultraviolet (UV) and green (G) photoreceptor groups of the eye. Their anatomy was described after injection of Lucifer yellow. 2. Broadband neurons received either excitatory or inhibitory input from both UV and G receptors. These neurons were not strictly sensitive to luminosity levels and had large cell bodies in the central rind of the medulla and wide dendritic arbors in the medulla neuropil. 3. Narrow band neurons received input from predominantly one receptor type. Their spectral sensitivity curves were more finely tuned than those of the primary receptors presumably due to neural interactions within the optic lobe. 4. Color opponent neurons were inhibited by UV and excited by G inputs in their sustained response. Under certain conditions, some of these neurons also showed G inhibition. These neurons suggested the presence of a subsystem involved in color vision. 5. Broadband, narrow band and color opponent properties were seen in some single neurons when tested over a 5–6 log unit range of intensity. The responses of some of these neurons changed when stimulus duration was increased. These findings indicated that functional classification for these neurons was dependent on stimulus intensity and duration. 6. Polarizational sensitivity was tested in preliminary experiments. Two neurons responded to the movement and direction of polarized light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189765
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  • 5
    Electronic Resource
    Electronic Resource
    ‘On’ type interneurons in the optic lobe ofPeriplaneta americana (1981)
    Springer
    Journal of comparative physiology 141 (1981), S. 403-415 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Receptive fields and response latencies of dark adapted ‘on’ type interneurons in the optic lobe ofPeriplaneta americana were measured by determining threshold intensities of light flashes from stationary points. Markings of electrode position showed that recording sites were mainly in the medulla neuropil and external chiasma though some marks were found in the lamina neuropil and lobula. 2. Receptive fields of these cells depended strongly on the criterion used in their description. Sufficiently intense stimuli were effective in almost any part of the visual field. Considering only the most effective regions (within 0.5 log of maximum) it was found that most fields were less than 90° in their largest dimension (93%), were elliptical in shape (77%), and were in the anterior portion of the visual field (82%). Other characteristics are described and compared. 3. In about half of the cells tested appropriately it was found that fields measured with violet stimuli were generally larger and dorsally shifted (by at least 30°) than those measured with green stimuli (Fig. 3). 4. The mean minimum latency for 508 nm stimuli was 66 ms (S.D.=21ms) and the mean maximum latency was 135 ms (S.D.=40.5 ms). Two cells (not included in mean) had minimum latencies of 500 ms and maximum latencies of 600 ms and 650 ms, respectively. The mean latency to 410 nm stimuli at threshold was significantly longer than for 508 nm (mean of 431 ms, S.D.=93.3 ms) and was as long as 1,300 ms for one of the two cells with long minimum latencies. There appeared to be no strict relation between latency values and stimulus location or the cell's sensitivity to the stimulus. Comparison of latency vs. intensity functions and receptor potential rise times indicates that at least some of the wavelength dependence arises in the behavior of the retinal elements. 5. A particular cell's sensitivity to a given stimulus point occasionally increases when a portion of the receptor complement is shielded from that point and green stimuli are employed. Such increases are very rarely seen when violet stimuli are employed. It is hypothesized that the green receptors of the retina participate in a lateral inhibitory network while the UV receptors do not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609943
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  • 6
    Electronic Resource
    Electronic Resource
    Polarization sensitivity (1974)
    Springer
    Journal of comparative physiology 90 (1974), S. 389-403 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Polarization sensitivity of photoreceptors of the crabsCarcinus andCallinectes were measured with intracellular microelectrodes in the dark adapted condition with stimuli of very low intensity and under conditions of selective polarized adaptation. A mean polarization sensitivity ratio of 4.5 to one (n=25) was obtained. The values ranged from 3.2 to one to 9 to one. The value obtained in any given cell was independent of either (a) the intensity of the stimuli employed in its determination, or (b) any conditions of selective adaptation present during the experiment. The results of these experiments are discussed in reference to two hypothetical explanations for the discrepancy between microspectrophotometric measurements of rhabdomeric dichroism and electrophysiological determinations of polarization sensitivity in crustacean photoreceptors. They do not support the hypothesis of Muller (1971, 1973) that the high polarization sensitivity measured in such photoreceptors is due to a passive interaction between the retinular cells which serves to enhance polarization sensitivity imparted by the dichroism of the rhabdom. They do support the hypothesis of Shaw (1966, 1969) and Snyder (1973) which suggest that the dichroic ratio of the rhabdomere and the polarization sensitivity ratio of the cell are similarin situ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694178
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  • 7
    Electronic Resource
    Electronic Resource
    Spectral absorption and sensitivity measurements in single ommatidia of the green crab,Carcinus (1973)
    Springer
    Journal of comparative physiology 82 (1973), S. 151-163 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rhabdoms of the green crabCarcinus maenas were examined by microspectrophotometry and found to contain a visual pigment with λmax at 502–506 nm. Upon irradiation, a stable metarhodopsin formed with unchanged λmax and molar extinction coefficient. In the presence of 5% glutaraldehyde the rhabdoms were photobleached. Partial bleaching experiments indicate that in the rhabdoms studied, only one visual pigment was present, with an absorption spectrum appropriate for a hypothetical rhodopsin from Dartnall's (1953) nomogram. Retinular (photoreceptor) cells were studied with microelectrodes. They had negative resting potentials of 30–65 mV and responded to light with depolarizing receptor potentials. All cells had maximum sensitivity at ~493 nm, as did the ERG (electroretinogram). Selective adaptation failed to alter the spectral sensitivity functions of single cells or the ERG. If these spectral sensitivity data are pooled with Wald's (1968), the average sensitivity of the dark-adapted eye is accounted for adequately by the pigment of the rhabdom. The results of this work do not support the hypothesis of Horridge (1967) that each ommatidium ofCarcinus has two color receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696150
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  • 8
    Electronic Resource
    Electronic Resource
    Functional characteristics of photoreceptors in the compound eye and ocellus of the desert ant,Cataglyphis bicolor (1980)
    Springer
    Journal of comparative physiology 137 (1980), S. 63-71 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Intracellular recordings have been employed to measure the spectral and polarizational sensitivities of retinular cells in the compound eyes and ocelli ofCataglyphis bicolor. 2. In the central part of the compound eye the responses can be grouped into three classes. One type (VIS) has a sensitivity maximum at 506 nm and a mean sensitivity at 347 nm which is 0.7 log units lower. A second type (UV) is maximally sensitive at 347 nm and is weakly depolarized by long wavelength stimuli. The shape of the V log I relation in these cells is dependent on stimulus wavelength. The third type (UV-VIS) is maximally sensitive at 347 nm but shows a high sensitivity (〉50%) at 506 nm. The V log I relation measured in this class is not wavelength dependent. 3. 90% of the cells tested showed polarizational sensitivity (PS) ratios ranging from 1.5 to 6. In the VIS class PS in the u.v. was commonly lower than at the 506 nm peak, but when present the e-vector orientations of maximum and minimum PS were similar for the two spectral regions. In the UV-VIS class PS measured with 506 nm stimuli was commonly lower than in u.v., but in this case when PS was present in the response to green the orientations of maximum and minimum PS were different in the two spectral regions. In the UV class PS was present in the u.v. but not detected with green stimuli. 4. It is proposed that the UV-VIS class arises from strong electrical coupling between adjacent UV and VIS class cells. The long wavelength component of the UV cell's response is thought to arise from a similar but weaker interaction. 5. Photoreceptors in the ocelli are similar to the UV class found in the compound eye in terms of spectral and polarizational sensitivities. They differ, however, in that they do not show the depolarizations with intense green stimuli nor is there any mass response from the whole retina at wavelengths longer than 445 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656918
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