scholarly journals Increment threshold functions for radial frequency motion trajectories exhibit a dipper function above threshold

2012 ◽  
Vol 12 (9) ◽  
pp. 644-644 ◽  
Author(s):  
M. Daar ◽  
C. C.-F. Or ◽  
H. Wilson
Keyword(s):  
Motion Trajectories ◽  
Threshold Functions ◽  
Increment Threshold ◽  
Radial Frequency

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.

scholarly journals Detection of radial frequency motion trajectories

2010 ◽  
Vol 10 (7) ◽  
pp. 825-825
Author(s):  
C. C.- F. Or ◽  
M. Thabet ◽  
H. R. Wilson ◽  
F. Wilkinson
Keyword(s):  
Motion Trajectories ◽  
Radial Frequency

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 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

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.

A Study on Polymer Particle Flow in a Disk Zone of a Screw-Disk Extruder

2014 ◽  
Vol 35 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Tomasz Rydzkowski ◽  
Iwona Michalska-Pożoga
Keyword(s):  
Mechanical Properties ◽  
Computer Simulations ◽  
Particle Motion ◽  
Polymer Melt ◽  
Experimental Tests ◽  
Polymer Particle ◽  
Particle Flow ◽  
Material Particle ◽  
Motion Trajectories ◽  
Stretching Effect

Abstract The paper presents the summary of research on polymer melt particle motion trajectories in a disc zone of a screw-disk extruder. We analysed two models of its structure, different in levels of taken simplifications. The analysis includes computer simulations of material particle flow and results of experimental tests to determine the properties of the resultant extrudate. Analysis of the results shows that the motion of melt in the disk zone of a screw-disk extruder is a superposition of pressure and dragged streams. The observed trajectories of polymer particles and relations of mechanical properties and elongation of the molecular chain proved the presence of a stretching effect on polymer molecular chains.

scholarly journals THÖR: Human-Robot Navigation Data Collection and Accurate Motion Trajectories Dataset

2020 ◽  
Vol 5 (2) ◽  
pp. 676-682
Author(s):  
Andrey Rudenko ◽  
Tomasz P. Kucner ◽  
Chittaranjan S. Swaminathan ◽  
Ravi T. Chadalavada ◽  
Kai O. Arras ◽  
...  
Keyword(s):  
Data Collection ◽  
Robot Navigation ◽  
Motion Trajectories ◽  
Navigation Data
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