scholarly journals Spatiotemporal integration of light by the cat X-cell center under photopic and scotopic conditions

2005 ◽  
Vol 22 (4) ◽  
pp. 493-500
Author(s):  
J.B. TROY ◽  
D.L. BOHNSACK ◽  
J. CHEN ◽  
X. GUO ◽  
C.L. PASSAGLIA
Keyword(s):  
Temporal Frequency ◽  
Temporal Integration ◽  
Visual Responses ◽  
High Temporal Frequency ◽  
Light Levels ◽  
Retinal Circuitry ◽  
Lower Light ◽  
Spatial Window ◽  
Gain Adjustment ◽  
Spatiotemporal Integration

Visual responses to stimulation at high temporal frequency are generally considered to result from signals that avoid light adaptive gain adjustment, simply reflecting linear summation of luminance. Under conditions of high photopic illuminance, the center of the receptive field of the cat X-cell has been shown to expand in size when stimulated at high temporal frequency, raising the possibility that there is spatiotemporal interaction in luminance summation. Here we show that this expansion maintains constant the product of the center's luminance summing area and the temporal period of luminance modulation, implying that spatial and temporal integration of luminance can be traded for one another by the X-cell center. As such the X-cell has a spatiotemporal window for luminance integration that fuses the classical concepts of a spatial window of luminance integration (Ricco's Law) with a temporal window of luminance integration (Bloch's Law). We were interested to determine whether this tradeoff between spatial and temporal summation of luminance occurs also at lower light levels, where the temporal-frequency bandwidth of the X-cell is narrower. We found that it does not. Center radius does not expand with temporal frequency under either low photopic or scotopic conditions. These results are discussed within the context of the known retinal circuitry that underlies the X-cell center for photopic and scotopic conditions.

scholarly journals Pupillary reflex and behavioral masking responses to light as functional measures of retinal degeneration in mice

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0244702
Author(s):  
Ethan O. Contreras ◽  
Carley G. Dearing ◽  
Crystal A. Ashinhurst ◽  
Betty A. Fish ◽  
Sajila N. Hossain ◽  
...  
Keyword(s):  
Visual Responses ◽  
Pupillary Reflex ◽  
Rods And Cones ◽  
Light Levels ◽  
Retinal Circuitry ◽  
Retinal Pathology ◽  
Increased Sensitivity ◽  
Wheel Activity ◽  
Induced Changes ◽  
Photoreceptor Degenerations

Background Pre-clinical testing of retinal pathology and treatment efficacy depends on reliable and valid measures of retinal function. The electroretinogram (ERG) and tests of visual acuity are the ideal standard, but can be unmeasurable while useful vision remains. Non-image-forming responses to light such as the pupillary light reflex (PLR) are attractive surrogates. However, it is not clear how accurately such responses reflect changes in visual capability in specific disease models. The purpose of this study was to test whether measures of non-visual responses to light correlate with previously determined visual function in two photoreceptor degenerations. Methods The sensitivity of masking behavior (light induced changes in running wheel activity) and the PLR were measured in 3-month-old wild-type mice (WT) with intact inner retinal circuitry, Pde6b-rd1/rd1 mice (rd1) with early and rapid loss of rods and cones, and Prph2-Rd2/Rd2 mice (Rd2) with a slower progressive loss of rods and cones. Results In rd1 mice, negative masking had increased sensitivity, positive masking was absent, and the sensitivity of the PLR was severely reduced. In Rd2 mice, positive masking identified useful vision at higher light levels, but there was a limited decrease in the irradiance sensitivity of negative masking and the PLR, and the amplitude of change for both underestimated the reduction in irradiance sensitivity of image-forming vision. Conclusions Together these data show that in a given disease, two responses to light can be affected in opposite ways, and that for a given response to light, the change in the response does not accurately represent the degree of pathology. However, the extent of the deficit in the PLR means that even a limited rescue of rod/cone function might be measured by increased PLR amplitude. In addition, positive masking has the potential to measure effective treatment in both models by restoring responses or shifting thresholds to lower irradiances.

APB Selectively Reduces Visual Responses in Goldfish to High Spatiotemporal Frequencies

1989 ◽  
Vol 2 (1) ◽  
pp. 15-18 ◽  
Author(s):  
Paul J. DeMarco ◽  
Jonathan D. Nussdorf ◽  
Douglas A. Brockman ◽  
Maureen K. Powers
Keyword(s):  
Spatial Frequency ◽  
Optokinetic Nystagmus ◽  
Temporal Frequency ◽  
High Spatial Frequency ◽  
Visual Responses ◽  
High Temporal Frequency ◽  
Frequency Responses ◽  
Intraocular Injection ◽  
Before And After ◽  
High Doses

AbstractVisual responses of goldfish to rotating square-wave gratings were recorded before and after intraocular injection of 2-amino-4-phosphonobutyric acid (APB). High doses of APB reduced the rate of optokinetic nystagmus (OKN) to a relatively high spatial frequency grating moving at a high temporal frequency. Responses to a low spatial frequency grating were not altered, nor were responses to the higher spatial frequency when it rotated slowly. The effects of APB were transient and lasted no longer than 3 d. We conclude that APB reduces OKN to high spatiotemporal frequencies in goldfish.

Determination of spikelet number in wheat. II.* Effect of varying light level on ear development

1977 ◽  
Vol 28 (4) ◽  
pp. 575 ◽  
Author(s):  
MS Rahman ◽  
JH Wilson ◽  
Y Aitken
Keyword(s):  
Light Level ◽  
Floral Initiation ◽  
Wheat Cultivars ◽  
Spikelet Number ◽  
Rate Of Development ◽  
Light Levels ◽  
Two Factors ◽  
Lower Light ◽  
Ear Number

The effects of two light levels (0.98 and 4.90 cal cm-2 hr-1) on rate of development and spikelet number per ear were studied in eight wheat cultivars grown under a 16 hr photoperiod at 20°C. The objective was to ascertain how light affects spikelet number. At the lower light level the durations of the vegetative, spikelet and ear elongation phases were greater, but the number of spikelets per ear, number of phytomers present at floral initiation, final leaf number, number of phytomers that were converted into spikelets, apex length at floral initiation and rate of spikelet initiation were smaller than at the higher light level. Responses to varying light level for a11 these parameters were similar for different cultivars, but the sizes of the responses differed. Within a given cultivar, an increase in spikelet number was associated with longer apices at floral initiation and a higher rate of spikelet initiation. It was concluded that these two factors are important determinants of spikelet number. ___________________ *Part I, Aust. J. Agric, Res., 28: 565 (1977).

An evaluation of light-mediated vertical migration of fish based on hydroacoustic analysis of the diel vertical movements of rainbow smelt (Osmerus mordax)

1995 ◽  
Vol 52 (3) ◽  
pp. 504-511 ◽  
Author(s):  
A. R. Appenzeller ◽  
W. C. Leggett
Keyword(s):  
Vertical Migration ◽  
Strong Relationship ◽  
Fish Population ◽  
Osmerus Mordax ◽  
Ambient Light ◽  
Rainbow Smelt ◽  
Vertical Movements ◽  
Light Levels ◽  
Vertical Distributions ◽  
Lower Light

We used hydroacoustics to examine diel changes in the vertical distributions of rainbow smelt, Osmerus mordax, in Lake Memphremagog, Quebec/Vermont. Our objective was to evaluate hypotheses linking diel vertical movements of fish with light levels. Smelt distributions were also monitored from June through October (1988 and 1990) to evaluate seasonal changes in their behavior. A strong relationship (r2 = 0.83) between ambient light intensities and the upper fish layer in the water column was observed. Fish depth was also related to the depth of the thermocline during the night and when surface water temperatures were > 18 °C. The most characteristic feature was the strong avoidance of light levels > 0.1 μW/cm2. However, we found considerable variation in lower light levels experienced by the whole fish population. The results suggest that existing models of anti-predation behavior relating light and fish depth are consistent, with some limitations, with patterns of diel vertical migration in rainbow smelt.

Hazardous nature of high-temporal-frequency strobe light stimulation: neural mechanisms revealed by magnetoencephalography

Neuroscience ◽  
2010 ◽  
Vol 166 (2) ◽  
pp. 482-490 ◽  
Author(s):  
Y. Shigihara ◽  
M. Tanaka ◽  
N. Tsuyuguchi ◽  
H. Tanaka ◽  
Y. Watanabe
Keyword(s):  
Temporal Frequency ◽  
Neural Mechanisms ◽  
Light Stimulation ◽  
Strobe Light ◽  
High Temporal Frequency

A neural theory of circadian rhythms: Aschoff's rule in diurnal and nocturnal mammals

1984 ◽  
Vol 247 (6) ◽  
pp. R1067-R1082 ◽  
Author(s):  
G. A. Carpenter ◽  
S. Grossberg
Keyword(s):  
Neural Model ◽  
Light Level ◽  
Behavioral Activity ◽  
Circadian Period ◽  
Suprachiasmatic Nuclei ◽  
Light Levels ◽  
Lower Light ◽  
The Stability ◽  
Eye Closure ◽  
Nocturnal Mammals

A neural model of the suprachiasmatic nuclei suggests how behavioral activity, rest, and circadian period depend on light intensity in diurnal and nocturnal mammals. These properties are traced to the action of light input (external zeitgeber) and an activity-mediated fatigue signal (internal zeitgeber) on the circadian pacemaker. Light enhances activity of the diurnal model and suppresses activity of the nocturnal model. Fatigue suppresses activity in both diurnal and nocturnal models. The asymmetrical action of light and fatigue in diurnal vs. nocturnal models explains the more consistent adherence of nocturnal mammals to Aschoff's rule, the consistent adherence of both diurnal and nocturnal mammals to the circadian rule, and the tendency of nocturnal mammals to lose circadian rhythmicity at lower light levels than diurnal mammals. The fatigue signal is related to the sleep process S of Borbely (Hum. Neurobiol. 1: 195–204, 1982.) and contributes to the stability of circadian period. Two predictions follow: diurnal mammals obey Aschoff's rule less consistently during a self-selected light-dark cycle than in constant light, and if light level is increased enough during sleep in diurnal mammals to compensate for eye closure, then Aschoff's rule will hold more consistently. The results are compared with those of Enright's model.

Interspecific variation in the response of growth, crown morphology, and survivorship to light of six tree species in the conifer belt of the Bhutan Himalayas

2004 ◽  
Vol 34 (5) ◽  
pp. 1093-1107 ◽  
Author(s):  
Georg Gratzer ◽  
Andras Darabant ◽  
Purna B Chhetri ◽  
Prem Bahadur Rai ◽  
Otto Eckmüllner
Keyword(s):  
Tree Species ◽  
Radial Growth ◽  
Interspecific Variation ◽  
Low Light ◽  
Continuous Growth ◽  
Light Levels ◽  
Shade Tolerant Species ◽  
Lower Light ◽  
Crown Morphology ◽  
Changing Light

The responses of radial and height growth, plant architecture, and the probability of mortality of saplings to varying light levels were quantified for six tree species in temperate conifer forests of the Bhutan Himalayas. Increases in growth with increasing light were comparable with those of high latitude tree species but lower than those of tropical tree species and temperate species in North America. The shade-tolerant species Tsuga dumosa (D. Don.) Eichler showed the strongest increase in radial growth at low light and reached asymptotic growth early. It had the deepest crowns in low light and a low decrease of leader growth with decreasing light. It represents a continuous growth type, which invests in height rather than lateral growth under low light conditions. Betula utilis D. Don. showed greater increases in radial growth and a higher mortality at low light than the more shade-tolerant Abies densa Griff., in keeping with the trade-off between survivorship and growth at low light. Picea spinulosa Griff, Larix griffithiana Carriére, and Pinus wallichiana A.B. Jackson showed small increases in growth at low light levels. The latter two species showed no capacity to adapt their morphology in response to changing light levels, which resulted in higher probabilities of mortality at lower light levels. Differences in the probability of mortality at different light levels were more pronounced than differences in the light-growth response, underlining the importance of survivorship at low light for successional dynamics.

scholarly journals A Development Strategy for SHM Applications

2021 ◽  
pp. 1-17
Author(s):  
Peter Cawley
Keyword(s):  
Spatial Frequency ◽  
Development Strategy ◽  
Temporal Frequency ◽  
High Spatial Frequency ◽  
Operating Conditions ◽  
Damage Growth ◽  
Periodic Inspection ◽  
High Temporal Frequency ◽  
Industrial Use ◽  
Signal Changes

Abstract Permanently installed SHM systems are now a viable alternative to traditional periodic inspection (NDT). However, their industrial use is limited and this paper reviews the steps required in developing practical SHM systems. The transducers used in SHM are fixed in location, whereas in NDT they are generally scanned. The aim is to reach similar performance with high temporal frequency, low spatial frequency SHM data to that achievable with conventional high spatial frequency, low temporal frequency NDT inspections. It is shown that this can be done via change tracking algorithms such as the Generalized Likelihood Ratio (GLR) but this depends on the input data being normally distributed, which can only be achieved if signal changes due to variations in the operating conditions are satisfactorily compensated; there has been much recent progress on this topic and this is reviewed. Since SHM systems can generate large volumes of data, it is essential to convert the data to actionable information, and this step must be addressed in SHM system design. It is also essential to validate the performance of installed SHM systems, and a methodology analogous to the model assisted POD (MAPOD) scheme used in NDT has been proposed. This uses measurements obtained from the SHM system installed on a typical undamaged structure to capture signal changes due to environmental and other effects, and to superpose the signal due to damage growth obtained from finite element predictions. There is a substantial research agenda to support the wider adoption of SHM and this is discussed.

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