Temporal Contrast Sensitivity Function Research Articles

Psychophysics of neon color spreading: Chromatic and temporal factors are not limiting

Neon color spreading (NCS) is an illusory color phenomenon that provides a dramatic example of surface completion and filling-in. Numerous studies have varied both spatial and temporal aspects of the neon-generating stimulus to explore variations in the strength of the effect. Here, we take a novel, parametric, low-level psychophysical approach to studying NCS in two experiments. In Experiment 1, we test the ability of both cone-isolating and equiluminant stimuli to generate neon color spreading for both increments and decrements in cone modulations. As expected, sensitivity was low to S(hort-wavelength) cone stimuli due to their poor spatial resolution, but sensitivity was similar for the other color directions. We show that when these differences in detection sensitivity are accounted for, the particular cone type, and the polarity (increment or decrement), make little difference in generating neon color spreading, with NCS visible at about twice detection threshold level in all cases. In Experiment 2, we use L-cone flicker modulations (reddish and greenish excursions around grey) to study sensitivity to NCS as a function of temporal frequency from 0.5 to 8 Hz. After accounting for detectability, the temporal contrast sensitivity functions for NCS are approximately constant or even increase over the studied frequency range. Therefore there is no evidence in this study that the processes underlying NCS are slower than the low-level processes of simple flicker detection. These results point to relatively fast mechanisms, not slow diffusion processes, as the substrate for NCS.

Estimates of Temporal Edge Detection Filters in Human Vision

Edge detection is an important process in human visual processing. However, as far as we know, few attempts have been made to map the temporal edge detection filters in human vision. To that end, we devised a user study and collected data from which we derived estimates of human temporal edge detection filters based on three different models, including the derivative of the infinite symmetric exponential function and temporal contrast sensitivity function. We analyze our findings using several different methods, including extending the filter to higher frequencies than were shown during the experiment. In addition, we show a proof of concept that our filter may be used in spatiotemporal image quality metrics by incorporating it into a flicker detection pipeline.

Contributed Session I: The perceptual experience of optogenetic vision.

Optogenetic therapy for retinal degenerative diseases aims to elicit light response in remaining retinal cells (bipolar and/or ganglion cells). Animal models suggest that these proteins have lower sensitivity, and slower kinetics compared to neurotypical vision. Here we describe a framework for simulating 'virtual patients' to quantify the predicted perceptual experience of optogenetic vision. We simulated the neural responses of rd1 mouse retina expressing 4xBGAG12,460:SNAP-mGluR2 (Holt et al., 2022) and used this simulation to generate virtual patients: sighted participants viewing the visual stimulus filtered through our simulations. We measured the visual performance of these virtual patients (n=6) using temporal contrast sensitivity functions. Virtual patients had a 10x fold loss of sensitivity, which was exacerbated at higher temporal frequencies, corresponding to a loss of Snellen acuity from ~20/40 at low temporal frequencies to ~20/100-20/200 at high temporal frequencies. We predict that the ability to process fast-moving objects may be impaired in optogenetic vision, and patients with uncontrollable nystagmus may be poor candidates for optogenetic treatments with sluggish kinetics. Our virtual patient framework can easily be extended to simulate any optogenetic protein, and thereby provides a way to quantify and compare the expected perceptual performance of different opto-proteins based on in vitro retinal data.

Resilience of temporal processing to early and extended visual deprivation

Early visual deprivation is known to have profound consequences on the subsequent development of spatial visual processing. However, its impact on temporal processing is not well characterized. We have examined spatial and temporal contrast sensitivity functions following treatment for early and extended bilateral visual deprivation in fifteen children born with congenital cataracts in rural India. The results reveal a marked difference in post-treatment spatial and temporal sensitivities. Whereas spatial processing in newly sighted children is significantly impaired relative to age-matched controls, temporal processing exhibits remarkable resilience and is comparable to that in the control group. This difference in spatial and temporal outcomes is especially surprising given our computational analyses of video sequences which indicate a strong linkage between the spatial and temporal spectral content of natural visual inputs. We consider possible explanations for this discrepancy.

Temporal filtering of luminance and chromaticity in macaque visual cortex

SummaryContrast sensitivity peaks near 10 Hz for luminance modulations and at lower frequencies for modulations between equiluminant lights. This difference is rooted in retinal filtering, but additional filtering occurs in the cerebral cortex. To measure the cortical contributions to luminance and chromatic temporal contrast sensitivity, signals in the lateral geniculate nucleus (LGN) were compared to the behavioral contrast sensitivity of macaque monkeys. Long wavelength-sensitive (L) and medium wavelength-sensitive (M) cones were modulated in phase to produce a luminance modulation (L + M) or in counterphase to produce a chromatic modulation (L − M). The sensitivity of LGN neurons was well matched to behavioral sensitivity at low temporal frequencies but was approximately 7 times greater at high temporal frequencies. Similar results were obtained for L + M and L − M modulations. These results show that differences in the shapes of the luminance and chromatic temporal contrast sensitivity functions are due almost entirely to pre-cortical mechanisms.

Hue shifts produced by temporal asymmetries in chromatic signals depend on the alignment of the first and second harmonics.

When M- or L-cone-isolating sawtooth waveforms flicker at frequencies between 4 and 13.3 Hz, there is a mean hue shift in the direction of the shallower sawtooth slope. Here, we investigate how this shift depends on the alignment of the first and second harmonics of sawtooth-like waveforms. Below 4 Hz, observers can follow hue variations caused by both harmonics, and reliably match reddish and greenish excursions. At higher frequencies, however, the hue variations appear as chromatic flicker superimposed on a steady light, the mean hue of which varies with second-harmonic alignment. Observers can match this mean hue against a variable-duty-cycle rectangular waveform and, separately, set the alignment at which the mean hue flips between reddish and greenish. The maximum hue shifts were approximately frequency independent and occurred when the peaks or troughs of the first and second harmonics roughly aligned at the visual input-consistent with the hue shift's being caused by an early instantaneous nonlinearity that saturates larger hue excursions. These predictions, however, ignore phase delays introduced within the chromatic pathway between its input and the nonlinearity that produces the hue shifts. If the nonlinearity follows the substantial filtering implied by the chromatic temporal contrast-sensitivity function, phase delays will alter the alignment of the first and second harmonics such that at the nonlinearity, the waveforms that produce the maximum hue shifts might well be those with the largest differences in rising and falling slopes-consistent with the hue shift's being caused by a central nonlinearity that limits the rate of hue change.

Perifoveal S-cone and rod-driven temporal contrast sensitivities at different retinal illuminances.

We evaluated a technique for measuring temporal contrast sensitivities to sine-wave modulation driven by S-cones and rods in the perifovea using triple silent substitution. Isolating stimuli for S-cones and rods were created using an eight-channel, four-primary LED stimulator that has been validated before. Sensitivities were measured at 10 different temporal frequencies between 1 and 28 Hz in three normal observers at 14 different retinal illuminances between 0.07 and 587 photopic troland (phot Td) and at three different retinal illuminances over the same range in one S-cone monochromat. The technique was further validated by measuring bleaching adaptation in two normal subjects, demonstrating sufficient isolation in rods. Good isolation was apparent from the differences in the temporal contrast sensitivity functions and the sensitivity-versus-retinal illuminance functions between S-cones and rods, and also from the results in the S-cone monochromats and the delayed recovery of rod sensitivities after bleaching. The results will help to determine optimal stimulus conditions in future studies. The results in the S-cone monochromat demonstrate the potential clinical value of our protocol.

Perifoveal L- and M-cone-driven temporal contrast sensitivities at different retinal illuminances.

We established a protocol using a well-established LED stimulator to measure temporal contrast sensitivities driven by sine-wave modulation of L- and M-cones in the perifovea using triple silent substitution. The stimulus was presented in an annular field (2° inner diameter, 13° outer diameter). We validated this technique by studying the contrast sensitivity of three color normal observers at 10 different temporal frequencies (between 1 and 28 Hz) over a large range of retinal illuminances (between 0.07 and 587 phot Td), spanning the complete mesopic range. In one subject, sensitivities to counterphase modulation of L- and M-cones and in-phase modulation of L, M, and S-cones were additionally measured, which putatively reflected the parvo- and magnocellular retinogeniculate pathways, respectively. Furthermore, we performed measurements of temporal contrast sensitivities as a function of frequency at 294 phot Td in two protanopes, in two deuteranopes, and in one subject with S-cone monochromacy. Quality of isolation was satisfactory and we were able to reproduce known physiological patterns of temporal vision, such as the typical temporal contrast sensitivity functions of the L- and M-cone, the parvo- and magnocellular retinogeniculate pathways, as well as the light adaptation curves. These results will help determine optimal stimulus conditions in future studies. Results from the dichromats and the S-cone monochromat also support the quality of isolation of our protocol and underpin its potential clinical value.

A five-primary photostimulator suitable for studying intrinsically photosensitive retinal ganglion cell functions in humans.

Intrinsically photosensitive retinal ganglion cells (ipRGCs) can respond to light directly through self-contained photopigment, melanopsin. IpRGCs also receive synaptic inputs from rods and cones. Thus, studying ipRGC functions requires a novel photostimulating method that can account for all of the photoreceptor inputs. Here, we introduced an inexpensive LED-based five-primary photostimulator that can control the excitations of rods, S-, M-, L-cones, and melanopsin-containing ipRGCs in humans at constant background photoreceptor excitation levels, a critical requirement for studying the adaptation behavior of ipRGCs with rod, cone, or melanopsin input. We described the theory and technical aspects (including optics, electronics, software, and calibration) of the five-primary photostimulator. Then we presented two preliminary studies using the photostimulator we have implemented to measure melanopsin-mediated pupil responses and temporal contrast sensitivity function (TCSF). The results showed that the S-cone input to pupil responses was antagonistic to the L-, M- or melanopsin inputs, consistent with an S-OFF and (L + M)-ON response property of primate ipRGCs (Dacey et al., 2005). In addition, the melanopsin-mediated TCSF had a distinctive pattern compared with L + M or S-cone mediated TCSF. Other than controlling individual photoreceptor excitation independently, the five-primary photostimulator has the flexibility in presenting stimuli modulating any combination of photoreceptor excitations, which allows researchers to study the mechanisms by which ipRGCs combine various photoreceptor inputs.

A randomized placebo-controlled study on the effects of lutein and zeaxanthin on visual processing speed in young healthy subjects

Speed of processing is a particularly important characteristic of the visual system. Often a behavioral reaction to a visual stimulus must be faster than the conscious perception of that stimulus, as is the case with many sports (e.g., baseball). Visual psychophysics provides a relatively simple and precise means of measuring visual processing speed called the temporal contrast sensitivity function (tCSF). Past study has shown that macular pigment (a collection of xanthophylls, lutein (L), meso-zeaxanthin (MZ) and zeaxanthin (Z), found in the retina) optical density (MPOD) is positively correlated with the tCSF. In this study, we found similar correlations when testing 102 young healthy subjects. As a follow-up, we randomized 69 subjects to receive a placebo (n=15) or one of two L and Z supplements (n=54). MPOD and tCSF were measured psychophysically at baseline and 4months. Neither MPOD nor tCSF changed for the placebo condition, but both improved significantly as a result of supplementation. These results show that an intervention with L and Z can increase processing speed even in young healthy subjects.

Temporal contrast sensitivity function based on cones and melanopsin photoreceptors

Temporal contrast sensitivity function based on cones and melanopsin photoreceptors

Cone Dystrophy With “Supernormal” Rod ERG: Psychophysical Testing Shows Comparable Rod and Cone Temporal Sensitivity Losses With No Gain in Rod Function

We report a psychophysical investigation of 5 observers with the retinal disorder "cone dystrophy with supernormal rod ERG," caused by mutations in the gene KCNV2 that encodes a voltage-gated potassium channel found in rod and cone photoreceptors. We compared losses for rod- and for cone-mediated vision to further investigate the disorder and to assess whether the supernormal ERG is associated with any visual benefit. L-cone, S-cone, and rod temporal acuity (critical flicker fusion frequency) were measured as a function of target irradiance; L-cone temporal contrast sensitivity was measured as a function of temporal frequency. Temporal acuity measures revealed that losses for vision mediated by rods, S-cones, and L-cones are roughly equivalent. Further, the gain in rod function implied by the supernormal ERG provides no apparent benefit to near-threshold rod-mediated visual performance. The L-cone temporal contrast sensitivity function in affected observers was similar in shape to the mean normal function but only after the mean function was compressed by halving the logarithmic sensitivities. The name of this disorder is potentially misleading because the comparable losses found across rod and cone vision suggest that the disorder is a generalized cone-rod dystrophy. Temporal acuity and temporal contrast sensitivity measures are broadly consistent with the defect in the voltage-gated potassium channel producing a nonlinear distortion of the photoreceptor response but after otherwise normal transduction processes.

Measuring the Temporal Contrast Sensitivity Function and Macular Pigment Optical Density in Older Adults with and Without Cognitive Impairment

Measuring the Temporal Contrast Sensitivity Function and Macular Pigment Optical Density in Older Adults with and Without Cognitive Impairment

Human vision with a lesion of the parvocellular pathway: an optic neuritis model for selective contrast sensitivity deficits with severe loss of midget ganglion cell function

Achromatic visual function in primates is distributed between two pathways from retina to cortex, the parvocellular and the magnocellular. The relative contribution of these to human achromatic vision is controversial and largely unknown. Here, we use an optic neuritis (ON) model to investigate the effects of a severe loss of parvocellular function on human contrast sensitivity. In our first experiment, we use Gabor stimuli (0.5 cpd, 2 Hz) to show that, compared to normal control eyes, ON causes selective deficits in the two chromatic, cone opponent pathways, with L/M cone opponency affected more than S cone opponency, and a relative sparing of achromatic function. Since L/M cone opponency is carried exclusively by the midget ganglion cells of the parvocellular pathway, this demonstrates a selective deficit of parvocellular function. In a second experiment, we report on two subjects who have lost all L/M cone opponent response in both eyes, indicating a severe loss of parvocellular function. We measure the spatial and temporal contrast sensitivity functions of their remaining achromatic vision, compared with a normal control group, to determine the selectivity of the visual deficit caused by the differential parvocellular loss, and assess the relative contributions of the parvocellular and magnocellular pathways to achromatic contrast sensitivity. We find that parvocellular function contributes selectively at mid- to high spatial frequencies (at low temporal frequencies), whereas magnocellular function determines contrast sensitivity over a very broad temporal frequency range (at low spatial frequencies). Our data bear a striking resemblance to results obtained from primate parvocellular lesions.

Attentional Modulation of Temporal Contrast Sensitivity in Human Vision

Recent psychophysical studies have shown that attention can alter contrast sensitivities for temporally broadband stimuli such as flashed gratings. The present study examined the effect of attention on the contrast sensitivity for temporally narrowband stimuli with various temporal frequencies. Observers were asked to detect a drifting grating of 0–40 Hz presented gradually in the peripheral visual field with or without a concurrent letter identification task in the fovea. We found that removal of attention by the concurrent task reduced the contrast sensitivity for gratings with low temporal frequencies much more profoundly than for gratings with high temporal frequencies and for flashed gratings. The analysis revealed that the temporal contrast sensitivity function had a more band-pass shape with poor attention. Additional experiments showed that this was also true when the target was presented in various levels of luminance noise. These results suggest that regardless of the presence of external noise, attention extensively modulates visual sensitivity for sustained retinal inputs.

Combination of rod and cone inputs in parasol ganglion cells of the magnocellular pathway

This study investigates how rod and cone inputs are combined in the magnocellular (MC) pathway in the mesopic luminance range, when both rods and cones are active. Responses of parafoveal MC ganglion cells from macaque retina were measured as a function of temporal frequency (0.62-20 Hz) or contrast (0.05-0.55) at mesopic light levels (0.2, 2, 20, and 200 td). Stimuli were of three modulation types: (1) isolated rod stimuli (only rod signals were modulated), (2) isolated cone stimuli (only cone luminance signals from long- and middle-wavelength sensitive cones were modulated), and (3) combined rod and cone stimuli (both rod and cone luminance signals were modulated in phase, as with conventional stimuli). The results showed that under mesopic conditions, the relative rod and cone inputs to the MC cells varied with light level and they are combined linearly prior to saturation. Further, rod contrast gain is relatively stable over the mesopic range while cone contrast gain increased with light level. Finally, the measured rod and cone inputs are consistent with the measured human temporal contrast sensitivity functions under comparable stimulation conditions.

A practical method of measuring the human temporal contrast sensitivity function

One of the more significant indicators of neural age-related loss and disease is reduced temporal processing speed. It would, therefore, be useful to have an accurate and practical device that measures the full range of an individual's temporal processing abilities (characterized as the temporal contrast sensitivity function, TCSF). 70 subjects (15-84 yrs) were tested. A small tabletop device utilizing electronic control of light-emitting diodes (LEDs) was constructed that delivered a 1-degree, 660 nm test (the modulation depth of which could be adjusted directly by the subject) centered within a 10-degree 660 nm surround. The method provided a TCSF that had a shape consistent with past studies (peaking around 8 Hz). Also consistent with past work, the largest age-decline was found at the highest frequencies and for the central fovea (r = 0.47, p<0.0001, ~2 Hz per decade). Psychophysical assessment of temporal vision offers an easy and dynamic measure of central visual function.

The relation between the macular carotenoids, lutein and zeaxanthin, and temporal vision

Lutein (L) and zeaxanthin (Z) are the dominant carotenoids within the central retina (there, termed macular pigment, MP) and brain (approximately 70% of total carotenoid concentration). Past studies have shown that MP is related to many static indicators of visual performance, such as visibility and disability glare. It has also been shown that MP is related to a dynamic measure of visual performance, the critical flicker fusion threshold (CFF). In this study, we examine whether MP is related to CFF in a larger sample. We also test the relation between MP and the more complete temporal contrast sensitivity function (TCSF). A total of 70 participants were assessed for a comparison of MP and the full temporal function. A separate pool of 354 participants was assessed for a MP and CFF comparison. Peak MP density was measured psychophysically (via heterochromatic flicker photometry) using a 1-degree diameter test. CFF was measured using a 1-degree 570 nm test varied at 100% modulation. The full TCSF was measured centrally using a 1-degree, 660 nm test (the modulation depth of which could be adjusted directly by the subject) centered within a 5.5-degree, 660 nm surround. A small fixation point was used to test a 7-degree parafoveal site. MP density was positively related to temporal function as assessed by the full TCSF in the center (n = 70, r = -0.29, p < 0.01) but not at the parafoveal location (p < 0.07). MP was also positively related to critical flicker fusion thresholds (n = 354, r = 0.21, p < 0.0001).

Flicker is a primitive visual attribute in visual search.

At the earliest processing stages, visual stimuli are decomposed by a set of filters tuned to specific values of such attributes as colour, orientation, and motion. These filters have been characterised both neurophysiologically and behaviourally. The single exception is the attribute of flicker that has been characterised neurophysiologically but not behaviourally. Using a visual search paradigm, the authors provide the first behavioural demonstration that flicker is indeed a primitive attribute used by the visual system in stimulus encoding. Consistent with the temporal contrast-sensitivity function, sensitivity to flicker was highest at about 10 Hz and decreased as the flicker rate was either increased or decreased.

Spatio-Temporal Just Noticeable Distortion Profile for Grey Scale Image/Video in DCT Domain

In image and video processing field, an effective compression algorithm should remove not only the statistical redundancy information but also the perceptually insignificant component from the pictures. Just-noticeable distortion (JND) profile is an efficient model to represent those perceptual redundancies. Human eyes are usually not sensitive to the distortion below the JND threshold. In this paper, a DCT based JND model for monochrome pictures is proposed. This model incorporates the spatial contrast sensitivity function (CSF), the luminance adaptation effect, and the contrast masking effect based on block classification. Gamma correction is also considered to compensate the original luminance adaptation effect which gives more accurate results. In order to extend the proposed JND profile to video images, the temporal modulation factor is included by incorporating the temporal CSF and the eye movement compensation. Moreover, a psychophysical experiment was designed to parameterize the proposed model. Experimental results show that the proposed model is consistent with the human visual system (HVS). Compared with the other JND profiles, the proposed model can tolerate more distortion and has much better perceptual quality. This model can be easily applied in many related areas, such as compression, watermarking, error protection, perceptual distortion metric, and so on.