scholarly journals Suppression of Luminance Contrast Sensitivity by Weak Color Presentation

2021 ◽  
Vol 15 ◽  
Author(s):  
Ippei Negishi ◽  
Keizo Shinomori
Keyword(s):  
Brain Activity ◽  
Luminance Contrast ◽  
Psychophysical Experiment ◽  
Dorsal Pathway ◽  
Color System ◽  
Ventral Pathway ◽  
Visual Cortices ◽  
Contrast Perception ◽  
Psychophysical Studies ◽  
Lower Saturation

The results of psychophysical studies suggest that color in a visual scene affects luminance contrast perception. In our brain imaging studies we have found evidence of an effect of chromatic information on luminance information. The dependency of saturation on brain activity in the visual cortices was measured by functional magnetic resonance imaging (fMRI) while the subjects were observing visual stimuli consisting of colored patches of various hues manipulated in saturation (Chroma value in the Munsell color system) on an achromatic background. The results indicate that the patches suppressed luminance driven brain activity. Furthermore, the suppression was stronger rather than weaker for patches with lower saturation colors, although suppression was absent when gray patches were presented instead of colored patches. We also measured brain activity while the subjects observed only the patches (on a uniformly black background) and confirmed that the colored patches alone did not give rise to differences in brain activity for different Chroma values. The chromatic information affects the luminance information in V1, since the effect was observed in early visual cortices (V2 and V3) and the ventral pathway (hV4), as well as in the dorsal pathway (V3A/B). In addition, we conducted a psychophysical experiment in which the ability to discriminate luminance contrast on a grating was measured. Discrimination was worse when weak (less saturated) colored patches were attached to the grating than when strong (saturated) colored patches or achromatic patches were attached. The results of both the fMRI and psychophysical experiments were consistent in that the effects of color were greater in the conditions with low saturation colors.

A Measure of Localization of Brain Activity for the Motion Aperture Problem Using Electroencephalograms

2012 ◽  
pp. 208-223 ◽  
Author(s):  
Isao Hayashi ◽  
Hisashi Toyoshima ◽  
Takahiro Yamanoi
Keyword(s):  
Visual Processing ◽  
Brain Activity ◽  
Inferior Frontal Gyrus ◽  
Dipole Source ◽  
Circular Aperture ◽  
Current Dipole ◽  
Aperture Problem ◽  
Dorsal Pathway ◽  
Ventral Pathway ◽  
Spatio Temporal

When viewed through a limited-sized aperture, bars appear to move in a direction normal to their orientation. This motion aperture problem is an important rubric for analyzing the early stages of visual processing particularly with respect to the perceptual completion of motion sampled across two or more apertures. In the present study, a circular aperture was displayed in the center of the visual field. While the baseline bar moved within the aperture, two additional circular apertures appeared; within each aperture, a “flanker bar” appeared to move. For upwards movement of the flanker lines, subjects perceived the flanker bar to be connected to the base bar, and all three parts to move upward. The authors investigated the motion perception of the moving bars by changing the line speeds, radii of the apertures, and distances between the circular apertures and then analyzed spatio-temporal brain activities by electroencephalograms (EEGs). Latencies in the brain were estimated by using equivalent current dipole source (ECD) localization for one subject. Soon after the flankers appear, ECDs, assumed to be generated by the recognition of the aperture’s form, were localized along the ventral pathway. After the bars moved, the ECDs were localized along the dorsal pathway, presumably in response to motion of the bars. In addition, for the perception of grouped motion and not normal motion, ECDs were localized to the middle frontal gyrus and the inferior frontal gyrus.

Temporal Dynamics of Shape Processing Differentiate Contributions of Dorsal and Ventral Visual Pathways

2019 ◽  
Vol 31 (6) ◽  
pp. 821-836 ◽  
Author(s):  
Elliot Collins ◽  
Erez Freud ◽  
Jana M. Kainerstorfer ◽  
Jiaming Cao ◽  
Marlene Behrmann
Keyword(s):  
Visual Information ◽  
Temporal Dynamics ◽  
Object Perception ◽  
Visual Pathway ◽  
Shape Sensitivity ◽  
Shape Information ◽  
Dorsal Pathway ◽  
Ventral Visual Pathway ◽  
Shape Processing ◽  
Ventral Pathway

Although shape perception is primarily considered a function of the ventral visual pathway, previous research has shown that both dorsal and ventral pathways represent shape information. Here, we examine whether the shape-selective electrophysiological signals observed in dorsal cortex are a product of the connectivity to ventral cortex or are independently computed. We conducted multiple EEG studies in which we manipulated the input parameters of the stimuli so as to bias processing to either the dorsal or ventral visual pathway. Participants viewed displays of common objects with shape information parametrically degraded across five levels. We measured shape sensitivity by regressing the amplitude of the evoked signal against the degree of stimulus scrambling. Experiment 1, which included grayscale versions of the stimuli, served as a benchmark establishing the temporal pattern of shape processing during typical object perception. These stimuli evoked broad and sustained patterns of shape sensitivity beginning as early as 50 msec after stimulus onset. In Experiments 2 and 3, we calibrated the stimuli such that visual information was delivered primarily through parvocellular inputs, which mainly project to the ventral pathway, or through koniocellular inputs, which mainly project to the dorsal pathway. In the second and third experiments, shape sensitivity was observed, but in distinct spatio-temporal configurations from each other and from that elicited by grayscale inputs. Of particular interest, in the koniocellular condition, shape selectivity emerged earlier than in the parvocellular condition. These findings support the conclusion of distinct dorsal pathway computations of object shape, independent from the ventral pathway.

Impaired Speed Perception but Intact Luminance Contrast Perception in People With One Eye

2013 ◽  
Vol 54 (4) ◽  
pp. 3058 ◽  
Author(s):  
Krista R. Kelly ◽  
Sarah R. Zohar ◽  
Brenda L. Gallie ◽  
Jennifer K. E. Steeves
Keyword(s):  
Luminance Contrast ◽  
Speed Perception ◽  
Contrast Perception

scholarly journals Fusion and Fission in the Visual Pathways

2014 ◽  
pp. 625-635
Author(s):  
P. KAPOSVÁRI ◽  
A. BOGNÁR ◽  
P. CSIBRI ◽  
G. UTASSY ◽  
GY. SÁRY
Keyword(s):  
Temporal Resolution ◽  
Vision System ◽  
Visual Pathways ◽  
Inconsistent Information ◽  
Dorsal Pathway ◽  
Ventral Pathway ◽  
Double Flash

Inconsistent information from different modalities can be delusive for perception. This phenomenon can be observed with simultaneously presented inconsistent numbers of brief flashes and short tones. The conflict of bimodal information is reflected in double flash or fission, and flash fusion illusions, respectively. The temporal resolution of the vision system plays a fundamental role in the development of these illusions. As the parallel, dorsal and ventral pathways have different temporal resolution we presume that these pathways play different roles in the illusions. We used pathway-optimized stimuli to induce the illusions on separately driven visual streams. Our results show that both pathways support the double flash illusion, while the presence of the fusion illusion depends on the activated pathway. The dorsal pathway, which has better temporal resolution, does not support fusion, while the ventral pathway which has worse temporal resolution shows fusion strongly.

scholarly journals More than noise: Context-dependant luminance contrast discrimination in a coral reef fish (Rhinecanthus aculeatus)

2020 ◽  
Author(s):  
Cedric P. van den Berg ◽  
Michelle Hollenkamp ◽  
Laurie J. Mitchell ◽  
Erin J. Watson ◽  
Naomi F. Green ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Luminance Contrast ◽  
Individual Species ◽  
Diverse Range ◽  
Bright Spots ◽  
Context Dependent ◽  
Luminance Discrimination ◽  
Contrast Perception ◽  
Contrast Discrimination ◽  
Contrast Thresholds

AbstractAchromatic (luminance) vision is used by animals to perceive motion, pattern, space and texture. Luminance contrast sensitivity thresholds are often poorly characterised for individual species and are applied across a diverse range of perceptual contexts using over-simplified assumptions of an animal’s visual system. Such thresholds are often estimated using the Receptor Noise Limited model (RNL) using quantum catch values and estimated noise levels of photoreceptors. However, the suitability of the RNL model to describe luminance contrast perception remains poorly tested.Here, we investigated context-dependent luminance discrimination using triggerfish (Rhinecanthus aculeatus) presented with large achromatic stimuli (spots) against uniform achromatic backgrounds of varying absolute and relative contrasts. ‘Dark’ and ‘bright’ spots were presented against relatively dark and bright backgrounds. We found significant differences in luminance discrimination thresholds across treatments. When measured using Michelson contrast, thresholds for bright spots on a bright background were significantly higher than for other scenarios, and the lowest threshold was found when dark spots were presented on dark backgrounds. Thresholds expressed in Weber contrast revealed increased contrast sensitivity for stimuli darker than their backgrounds, which is consistent with the literature. The RNL model was unable to estimate threshold scaling across scenarios as predicted by the Weber-Fechner law, highlighting limitations in the current use of the RNL model to quantify luminance contrast perception. Our study confirms that luminance contrast discrimination thresholds are context-dependent and should therefore be interpreted with caution.

Asymmetrical retinoic acid synthesis in the dorsoventral axis of the retina

Development ◽  
1992 ◽  
Vol 115 (2) ◽  
pp. 371-382 ◽  
Author(s):  
P. McCaffery ◽  
M.O. Lee ◽  
M.A. Wagner ◽  
N.E. Sladek ◽  
U.C. Drager
Keyword(s):  
Retinoic Acid ◽  
Spatial Arrangement ◽  
Acid Synthesis ◽  
Early Embryo ◽  
Entire Body ◽  
Dorsoventral Axis ◽  
Adult Retina ◽  
Dorsal Pathway ◽  
Ventral Pathway ◽  
Dorsal Retina

An aldehyde dehydrogenase present at high levels in the dorsal retina of the embryonic and adult mouse was identified as the isoform AHD-2 known to oxidize retinaldehyde to retinoic acid. Comparative estimates of retinoic acid levels with a reporter cell line placed the retinas among the richest tissues in the entire body of the early embryo; levels in ventral retina, however, exceeded dorsal levels. Retinoic acid synthesis from retinaldehyde in the dorsal pathway was less effective than the ventral pathway at low substrate levels and more effective at high levels. The dorsal pathway was preferentially inhibited by disulfiram, while ventral synthesis was preferentially inhibited by p-hydroxymercuribenzoate. When protein fractions separated by isoelectric focusing were analyzed for retinoic acid synthesizing capacity by a zymography-bioassay, most of the synthesis in dorsal retina was found to be mediated by AHD-2, and ventral synthesis was mediated by dehydrogenase activities distinct in charge from AHD-2. Postnatally, levels of highest retinoic acid synthesis shifted from ventral to dorsal retina. In the adult retina, the dorsal pathway persisted, but the preferential ventral pathway was no longer detectable. Our observations raise the possibility that retinoic acid plays a role in the determination and maintenance of the dorsoventral axis of the retina, and that the morphogenetically significant asymmetry here lies in the spatial arrangement of synthetic pathways.

scholarly journals Visual Perception in the Periphery: The Role of Covert Attention Vectors in the Extraction of Semantic Information

2020 ◽  
Author(s):  
Ikaasa Suri ◽  
Patrick McGranor Wilson ◽  
Saba Doustmohammadi ◽  
Anna De Schutter ◽  
Thida Sandy Chunwatanapong ◽  
...  
Keyword(s):  
Visual Perception ◽  
Semantic Information ◽  
Ganglion Cells ◽  
Covert Attention ◽  
Retinal Ganglion ◽  
Scale Invariant ◽  
Dorsal Pathway ◽  
Ventral Pathway ◽  
Foveal Center

AbstractUnder covert attention, our visual perception deteriorates dramatically as eccentricity increases. This reduction of peripheral visual acuity (PVA) is partially due to the coarse sampling of the retinal ganglion cells towards the periphery, but this property cannot be solely responsible. Other factors, such as character crowding, have been studied, yet the origin of the poor PVA is not entirely understood. This gap motivated us to investigate the PVA by varying the crowding conditions systematically. Under completely crowded conditions (i.e. resembling a full page of text), PVA was observed to be eight times worse than the PVA under uncrowded conditions. By partially crowding the periphery, we obtained PVA values between the fully crowded and uncrowded conditions. On the other hand, crowding the fovea center while leaving the periphery uncrowded improved PVA relative to the uncrowded case. These results support a model for a top-down “covert attention vector” that assists the resulting PVA in a manner analogous to saccadic eye movement for overt attention. We speculate that the attention vector instructs the dorsal pathway to transform the peripheral character to the foveal center. Then, the scale-invariant log-polar retinotopy of the ventral pathway can scale the centered visual input to match the prior memory of the specific character shape.

How Does the Brain Discriminate Familiar and Unfamiliar Faces?: A PET Study of Face Categorical Perception

2001 ◽  
Vol 13 (7) ◽  
pp. 1019-1034 ◽  
Author(s):  
Bruno Rossion ◽  
Christine Schiltz ◽  
Laurence Robaye ◽  
David Pirenne ◽  
Marc Crommelinck
Keyword(s):  
Categorical Perception ◽  
Brain Activity ◽  
Principal Component ◽  
Neural Responses ◽  
Lexical Information ◽  
Ventral Pathway ◽  
Middle Occipital Gyrus ◽  
The Right ◽  
The Brain ◽  
Unfamiliar Faces

Where and how does the brain discriminate familiar and unfamiliar faces? This question has not been answered yet by neuroimaging studies partly because different tasks were performed on familiar and unfamiliar faces, or because familiar faces were associated with semantic and lexical information. Here eight subjects were trained during 3 days with a set of 30 faces. The familiarized faces were morphed with unfamiliar faces. Presented with continua of unfamiliar and familiar faces in a pilot experiment, a group of eight subjects presented a categorical perception of face familiarity: there was a sharp boundary in percentage of familiarity decisions between 40% and 60% faces. In the main experiment, subjects were scanned (PET) on the fourth day (after 3 days of training) in six conditions, all requiring a sex classification task. Completely novel faces (0%) were presented in Condition 1 and familiar faces (100%) in Condition 6, while faces of steps of 20% in the continuum of familiarity were presented in Conditions 2 to 5 (20% to 80%). A principal component analysis (PCA) indicated that most variations in neural responses were related to the dissociation between faces perceived as familiar (60% to 100%) and faces perceived as unfamiliar (0 to 40%). Subtraction analyses did not disclose any increase of activation for faces perceived as familiar while there were large relative increases for faces perceived as unfamiliar in several regions of the right occipito-temporal visual pathway. These changes were all categorical and were observed mainly in the right middle occipital gyrus, the right posterior fusiform gyrus, and the right inferotemporal cortex. These results show that (1) the discrimination between familiar and unfamiliar faces is related to relative increases in the right ventral pathway to unfamiliar/novel faces; (2) familiar and unfamiliar faces are discriminated in an all-or-none fashion rather than proportionally to their resemblance to stored representations; and (3) categorical perception of faces is associated with abrupt changes of brain activity in the regions that discriminate the two extremes of the multidimensional continuum.

Sign in / Sign up

Export Citation Format

Share Document