scholarly journals Increment Threshold Functions in Retinopathy of Prematurity

2016 ◽  
Vol 57 (6) ◽  
pp. 2421 ◽  
Author(s):  
Ronald M. Hansen ◽  
Anne Moskowitz ◽  
Jennifer N. Bush ◽  
Anne B. Fulton
Keyword(s):  
Retinopathy Of Prematurity ◽  
Threshold Functions ◽  
Increment Threshold

Depletion of retinal dopamine does not affect the ERG b-wave increment threshold function in goldfish in vivo

1994 ◽  
Vol 11 (4) ◽  
pp. 695-702 ◽  
Author(s):  
Zheng-Shi Lin ◽  
Stephen Yazulla
Keyword(s):  
Horizontal Cell ◽  
Threshold Function ◽  
Photopic Vision ◽  
Threshold Functions ◽  
Increment Threshold ◽  
Intensity Response ◽  
Purkinje Shift ◽  
6 Hydroxydopamine ◽  
Fish Retina

AbstractIncrement threshold functions of the electroretinogram (ERG) b–wave were obtained from goldfish using an in vivo preparation to study intraretinal mechanisms underlying the increase in perceived brightness induced by depletion of retinal dopamine by 6–hydroxydopamine (6–OHDA). Goldfish received unilateral intraocular injections of 6–OHDA plus pargyline on successive days. Depletion of retinal dopamine was confirmed by the absence of tyrosine-hydroxylase immunoreactivity at 2 to 3 weeks postinjection as compared to sham-injected eyes from the same fish. There was no difference among normal, sham-injected or 6–OHDA-injected eyes with regard to ERG waveform, intensity-response functions or increment threshold functions. Dopamine-depleted eyes showed a Purkinje shift, that is, a transition from rod-to-cone dominated vision with increasing levels of adaptation. We conclude (1) dopamine-depleted eyes are capable of photopic vision; and (2) the ERG b–wave is not diagnostic for luminosity coding at photopic backgrounds. We also predict that (1) dopamine is not required for the transition from scotopic to photopic vision in goldfish; (2) the ERG b–wave in goldfish is influenced by chromatic interactions; (3) horizontal cell spinules, though correlated with photopic mechanisms in the fish retina, are not necessary for the transition from scotopic to photopic vision; and (4) the OFF pathway, not the ON pathway, is involved in the action of dopamine on luminosity coding in the retina.

Temporal-Contrast Discrimination and its Neural Correlates

Perception ◽  
1996 ◽  
Vol 25 (5) ◽  
pp. 505-522 ◽  
Author(s):  
Yue Chen ◽  
Harold E Bedell ◽  
Laura J Frishman
Keyword(s):  
Temporal Frequency ◽  
Neural Mechanism ◽  
Normal Subjects ◽  
Threshold Function ◽  
Uniform Field ◽  
Power Functions ◽  
Threshold Functions ◽  
Increment Threshold ◽  
Parvocellular Neurons ◽  
Contrast Discrimination

Reported differences in neuronal contrast processing between the parallel magnocellular (M) and parvocellular (P) visual pathways invite the hypothesis that contrast discrimination in the human visual system is more sensitive at low contrasts and less sensitive at high contrasts, for stimuli modulated at high compared with low temporal frequencies. In the present study, an edgeless temporally modulated uniform field was selected as the stimulus for psychophysical contrast discrimination, and contrast-increment thresholds for pedestal contrasts ranging from 5.5% to 78.2% were determined with a temporal two-alternative forced-choice staircase procedure. The increment thresholds for five normal subjects were adequately fit by power functions with exponents that shifted continuously from about 0.5 (square-root-law behavior) to about 1.0 (Weber's-law behavior) as stimulus temporal frequency increased from 1 to 30 Hz. A neural simulation, with the use of published contrast-response functions of magnocellular and parvocellular neurons, adjusted with an estimate of response variance, produced two distinct ‘neural increment-threshold functions’ that were similar to the psychophysical results obtained at the highest and the lowest temporal frequencies, respectively. A shift from a relatively more noise-limited neural mechanism to one whose response is predominantly determined by gain is suggested to account for the change of the contrast-increment-threshold function with increasing temporal frequency.

Increment-threshold functions for different rodent species

1975 ◽  
Vol 15 (3) ◽  
pp. 375-378 ◽  
Author(s):  
Gerald H. Jacobs ◽  
David Birch
Keyword(s):  
Rodent Species ◽  
Threshold Functions ◽  
Increment Threshold

scholarly journals Desensitization of skate photoreceptors by bleaching and background light.

1982 ◽  
Vol 80 (6) ◽  
pp. 863-883 ◽  
Author(s):  
J W Clack ◽  
D R Pepperberg
Keyword(s):  
Background Intensity ◽  
Receptor Sensitivity ◽  
Transient Effect ◽  
Full Field ◽  
Background Light ◽  
Photochemical Processes ◽  
Threshold Functions ◽  
Increment Threshold ◽  
Isolated Retina ◽  
Relationship Of

Through extracellular measurements of photoreceptor responses to flashed stimuli, we examined how the bleaching of rhodopsin affects increment receptor threshold in the isolated retina of the skate (Raja oscellata and R. erinacea). Both initially unbleached and previously bleached photoreceptors, when exposed to full-field luminous backgrounds of fixed intensity, attain approximately stable levels of increment threshold that vary with the intensity of the background light. Values of stabilized increment thresholds measured after various extents of bleaching (less than approximately 50%), when plotted against background intensity in log-log coordinates, tend to converge with increasing intensity of the background; this relationship of the increment threshold functions resembles that which Blakemore and Rushton (1965b) found to describe the transient effect of bleaching on psychophysical increment threshold for the human rod mechanism. Our data are consistent with the possibility that related photochemical processes govern the stabilized levels of receptor sensitivity exhibited by the isolated retina (a) during steady illumination and (b) long after substantial bleaching.

Retinopathy of Prematurity Challenges

2007 ◽  
Vol 2007 ◽  
pp. 179-182
Author(s):  
Kammi B. Gunton
Keyword(s):  
Retinopathy Of Prematurity

RISK PREDICTORS FOR THE DEVELOPMENT OF RETINOPATHY OF PREMATURITY IN VERY LOW BIRTH WEIGHT NEONATES

2017 ◽  
Vol 04 (01) ◽  
pp. 22-26
Author(s):  
Sheena Shreetal ◽  
S Sobhakumar ◽  
Reshmi Rhiju ◽  
Shreetal Rajan Nair
Keyword(s):  
Birth Weight ◽  
Low Birth Weight ◽  
Retinopathy Of Prematurity ◽  
Very Low Birth Weight ◽  
Risk Predictors
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