Changes in the intensity-response function of an insect's photoreceptors due to light adaptation

1981 ◽  
Vol 145 (2) ◽  
pp. 169-177 ◽  
Author(s):  
T. Matić ◽  
S. B. Laughlin
Keyword(s):  
Response Function ◽  
Light Adaptation ◽  
Intensity Response

Peripheral neural correlates of magnitude of cutaneous pain and hyperalgesia: simultaneous recordings in humans of sensory judgments of pain and evoked responses in nociceptors with C-fibers

1984 ◽  
Vol 51 (2) ◽  
pp. 325-339 ◽  
Author(s):  
H. E. Torebjork ◽  
R. H. LaMotte ◽  
C. J. Robinson
Keyword(s):  
Response Function ◽  
Scaling Function ◽  
Normal Skin ◽  
Heat Pain ◽  
Evoked Responses ◽  
Pain Thresholds ◽  
Heat Injury ◽  
Magnitude Scaling ◽  
Intensity Response ◽  
Stimulus Temperature

The peripheral neuronal correlates of heat pain elicited from normal skin and from skin made hyperalgesic following a mild heat injury were studied by simultaneously recording, in humans, evoked responses in C mechanoheat (CMH) nociceptors and the magnitude estimations of pain obtained from the same subjects. Subjects made continuous magnitude ratings of pain elicited by short-duration stimuli of 39-51 degrees C delivered to the hairy skin of the calf or foot before and at varying intervals of time after a heat injury induced by a conditioning stimulus (CS) of 50 degrees C, 100 s or 48 degrees C, 360 s. The stimuli were applied with a thermode pressed against the nociceptor's receptive field. For heat stimulations of normal skin, that is, uninjured skin, pain thresholds in 14 experiments with nine subjects ranged from 41 to 49 degrees C, whereas response thresholds for most of the 14 CMH nociceptors were 41 degrees C (in two cases, 43 degrees C). The latter suggested that spatial summation of input from many nociceptors was necessary at pain threshold. An intensity-response function was obtained for each CMH by relating the total number of nerve impulses evoked per stimulus to stimulus temperature. A corresponding magnitude scaling function for pain was obtained by relating the maximum rating of pain elicited by each stimulus to stimulus temperature. The relation between the subject's scaling function and the intensity-response function of his CMH nociceptor varied somewhat from one experiment to the next, regardless of whether the results were obtained from the same or from different subjects. However, when averages were computed for all 14 tests, there was a near linear relationship between the mean number of impulses elicited in the CMHs and the median ratings of pain, over the range of 45-51 degrees C. It was concluded that the magnitude of heat pain sensation was more closely related to the magnitude of response in a population of CMH nociceptors than in any individual nociceptor. At 0.5 min after the CS, the pain thresholds of most subjects were elevated, and the magnitude ratings of pain elicited by supra-threshold stimuli were lower than pre-CS values (hypoalgesia). Corresponding changes were seen in the increased thresholds and decreased responses (fatigue) of most CMHs. By 5-10 min after the CS, the pain thresholds of most subjects were lower, and their magnitude ratings of suprathreshold stimuli were greater than pre-CS values (hyperalgesia).(ABSTRACT TRUNCATED AT 400 WORDS)

Light adaptation in cells of macaque lateral geniculate nucleus and its relation to human light adaptation

1983 ◽  
Vol 50 (4) ◽  
pp. 864-878 ◽  
Author(s):  
V. Virsu ◽  
B. B. Lee
Keyword(s):  
Receptive Field ◽  
Lateral Geniculate Nucleus ◽  
Light Adaptation ◽  
Single Cells ◽  
Activity Level ◽  
Field Size ◽  
Adaptation Level ◽  
Response Functions ◽  
Lateral Geniculate ◽  
Intensity Response

Responses of macaque lateral geniculate nucleus (LGN) cells to stimuli of different incremental intensities and wavelength compositions were studied at different levels of light adaptation from scotopic to low photopic levels. Stimuli were large in comparison with receptive-field size. Human increment thresholds were measured for comparison. The strength of responses grew in many cells from threshold up to a saturation level as a logarithmic function of incremental intensity. More complex intensity-response functions were also obtained, particularly from parvocellular layer (PCL) cells, but the shape and slope of the intensity-response function changed as a function of adaptation level only with chromatic backgrounds. As a function of adaptation level, the intensity-response functions shifted along the logarithmic abscissa but not sufficiently for a complete contrast constancy. Thus responses to any constant contrast became smaller when adaptation level decreased. The change from cone to rod responses, when possible, took place without noticeable change in shape of intensity-response functions, and much of the adaptive shift of the functions could be attributed to the change-over between rods and cones. Differences between different cells in light adaptation and dark-adapted sensitivity were large, mostly because of variation in the strength of rod input. The strongest excitatory rod inputs were found in PCL cells activated by short-wavelength light, so that the highest sensitivity at low levels of illumination occurred in blue- and blue-green-sensitive cells. The lowest increment thresholds based on cones matched the thresholds of macaque cone late receptor potentials recorded by Boynton and Whitten (3). They were also similar to human cone thresholds measured psychophysically but only for small stimulus sizes that may approximate the size of the receptive-field centers. Human sensitivity was much higher when measured with large stimulus sizes, indicating integration at post-geniculate neural levels. Light adaptation, as evaluated with respect to contrast constancy and Weber law behavior, was similarly incomplete in monkey single cells and human perception. A few cat LGN cells were studied in a control experiment; results agreed with previous findings. The light adaptation of cat cels was more complete and sensitivity higher than those observed under comparable conditions in macaque single cells and human. The maintained activity level of cells was little affected by the intensity of steady backgrounds. Thus, the steady-state hyper-polarisation of receptors was not transmitted to LGN cells.

scholarly journals Light-induced reduction in excitation efficiency in the trp mutant of Drosophila.

1982 ◽  
Vol 79 (3) ◽  
pp. 361-385 ◽  
Author(s):  
B Minke
Keyword(s):  
Rise Time ◽  
Transient Receptor Potential ◽  
Light Adaptation ◽  
Receptor Potential ◽  
Background Light ◽  
Excitation Efficiency ◽  
Early Receptor Potential ◽  
Intensity Response ◽  
Trp Mutant ◽  
Transient Receptor

In the transient receptor potential (trp) mutant of Drosophila, the receptor potential appears almost normal in response to a flash but quickly decays to baseline during prolonged illumination. Photometric and early receptor potential measurements of the pigment suggest that the pigment is normal and that the decay of the trp response during illumination does not arise from a reduction in the available photopigment molecules. However, there is reduction in pigment concentration with age. Light adaptation cannot account for the decay of the trp response during illumination: in normal Drosophila a dim background light shortens the latency and rise time of the response and also shifts the intensity response function (V-log I curve) to higher levels of light intensity with relatively little reduction in the maximal amplitude (Vmax) of response. In the trp mutant, a dim background light or short, strong adapting light paradoxically lengthens the latency and rise time of the response and substantially reduces Vmax without a pronounced shift of the V-log I curve along the I axis. The effect of adapting light on the latency and V-log I curve seen in trp are associated with a reduction in effective stimulus intensity (reduction in excitation efficiency) rather than with light adaptation. Removing extracellular Ca+2 reduces light adaptation in normal Drosophila, as evidenced by the appearance of "square" responses to strong illumination. In the trp mutant, removing extracellular Ca+2 does not prevent the decay of the response during illumination.

Light adaptation and the luminance-response function of the cone electroretinogram

1992 ◽  
Vol 79 (4) ◽  
pp. 363-369 ◽  
Author(s):  
Neal S. Peachey ◽  
Kenneth R. Alexander ◽  
Deborah J. Derlacki ◽  
Gerald A. Fishman
Keyword(s):  
Response Function ◽  
Light Adaptation ◽  
Cone Electroretinogram

scholarly journals Visual pigment and photoreceptor sensitivity in the isolated skate retina.

1978 ◽  
Vol 71 (4) ◽  
pp. 369-396 ◽  
Author(s):  
D R Pepperberg ◽  
P K Brown ◽  
M Lurie ◽  
J E Dowling
Keyword(s):  
Dark Adaptation ◽  
Visual Pigment ◽  
Response Curve ◽  
Time Course ◽  
Light Adaptation ◽  
Receptor Sensitivity ◽  
Strong Light ◽  
Receptor Response ◽  
Intensity Response ◽  
Isolated Retina

Photoreceptor potentials were recorded extracellularly from the aspartate-treated, isolated retina of the skate (Raja oscellata and R. erinacea), and the effects of externally applied retinal were studied both electrophysiologically and spectrophotometrically. In the absence of applied retinal, strong light adaptation leads to an irreversible depletion of rhodopsin and a sustained elevation of receptor threshold. For example, after the bleaching of 60% of the rhodopsin initially present in dark-adapted receptors, the threshold of the receptor response stabilizes at a level about 3 log units above the dark-adapted value. The application of 11-cis retinal to strongly light-adapted photoreceptors induces both a rapid, substantial lowering of receptor threshold and a shift of the entire intensity-response curve toward greater sensitivity. Exogenous 11-cis retinal also promotes the formation of rhodopsin in bleached photoreceptors with a time-course similar to that of the sensitization measured electrophysiologically. All-trans and 13-cis retinal, when applied to strongly light-adapted receptors, fail to promote either an increase in receptor sensitivity or the formation of significant amounts of light-sensitive pigment within the receptors. However, 9-cis retinal isin. These findings provide strong evidence that the regeneration of visual pigment in the photoreceptors directly regulates the process of photochemical dark adaptation.

Teaching insect retinal physiology with newly designed, inexpensive micromanipulators

2006 ◽  
Vol 30 (4) ◽  
pp. 254-261
Author(s):  
Jacob Krans ◽  
Cole Gilbert ◽  
Ron Hoy
Keyword(s):  
Response Function ◽  
High Precision ◽  
Undergraduate Teaching ◽  
Visual Transduction ◽  
House Flies ◽  
Temporal Characteristics ◽  
Intensity Response ◽  
Flesh Flies

In this article, we detail how to produce two inexpensive micromanipulators that offer high precision (∼25 μm) along a single axis of movement. The more expensive of the designs provides improved versatility along multiple axes. Both manipulators offer substantial savings over commercially available micromanipulators with comparable capabilities. Plans and instructions are given such that a novice can produce the manipulators with simple tools. The manipulators are designed to serve undergraduate teaching exercises in physiology. An electroretinogram exercise is suggested in adult house flies ( Musca) or flesh flies ( Neobellieria). Measuring the intensity-response function and temporal characteristics of visual transduction are discussed. A brief introduction to the field of visual transduction and the physiology of the laboratory exercises is provided as well.

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