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Percep??o visual de contraste em humanos: evidência psicofísica para canais de freqüência angular alta
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Psicologia: Reflex?o e Crítica , 2007, DOI: 10.1590/S0102-79722007000100005
Abstract: the aim of this study was to measure narrow-band frequency response curves for four angular frequency filters. the test frequencies were 32, 48, 64 and 96 cycles/360o. six humans observers with normal or corrected visual acuity measured nine curves for each filter, with a supra-threshold response summation psychophysical method allied with a forced-choice method. the results showed maximum summation effects at test frequency for filter frequencies 32, 48, 64 and 96 cycles/360o, as well as a strong inhibition for neighboring frequencies. these results are consistent with the existence of narrow-band angular frequency filters in the human visual system either through summation or the inhibition of specific high angular frequency ranges.
Visual processing of form: evidences for angular narrow-band frequency channels in human / Processamento visual da forma: evidências para canais múltiplos de freqüências angulares em humanos
Natanael Antonio dos Santos,Renata Maria Toscano Barreto Lyra Nogueira,Maria Lúcia de Bustamante Simas
Psicologia: Reflex?o e Crítica , 2005,
Abstract: The aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/360o defined in polar coordinates. We measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. The results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360o) filters surrounded on both sides by strong inhibition. These results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.
We Are Humor Beings: Understanding and Predicting Visual Humor  [PDF]
Arjun Chandrasekaran,Ashwin K Vijayakumar,Stanislaw Antol,Mohit Bansal,Dhruv Batra,C. Lawrence Zitnick,Devi Parikh
Computer Science , 2015,
Abstract: Humor is an integral part of human lives. Despite being tremendously impactful, it is perhaps surprising that we do not yet have a detailed understanding of humor. In this work, we explore the novel problem of studying visual humor and designing computational models of humor using abstract scenes. We collect and make publicly available two datasets of abstract scenes: one that enables the study of humor at the scene-level and the other at the object-level. We study the funny scenes in our dataset and explore different types of humor depicted in these scenes. We model two tasks that we believe demonstrate an understanding of visual humor -- predicting the funniness of a scene and altering the funniness of a scene. We show that our models perform well using automatic evaluation as well as human studies.
Sistema visual humano: evidência psicofísica para filtros de freqüência angular baixa
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Estudos de Psicologia (Natal) , 2005, DOI: 10.1590/S1413-294X2005000100012
Abstract: the aim of this work was to measure narrow-band frequency response curves for four angular frequency filters whose test frequencies were 1, 2, 3 and 4 cycles/360o. five human observers with normal or corrected visual acuity measured nine curves for each filter with a supra-threshold response summation psychophysical method allied within a forced-choice method. the results showed maximum summation effects at test frequency for filters 1, 2, 3 and 4 cycles/360o surrounded on both sides by strong inhibition. these results are consistent with the existence of narrow-band angular frequency filters operating in human visual system either through summation or inhibition of specific low angular frequency ranges.
Psychophysical Responses Comparison in Spatial Visual, Audiovisual, and Auditory BCI-Spelling Paradigms  [PDF]
Moonjeong Chang,Nozomu Nishikawa,Zhenyu Cai,Shoji Makino,Tomasz M. Rutkowski
Computer Science , 2012,
Abstract: The paper presents a pilot study conducted with spatial visual, audiovisual and auditory brain-computer-interface (BCI) based speller paradigms. The psychophysical experiments are conducted with healthy subjects in order to evaluate a difficulty and a possible response accuracy variability. We also present preliminary EEG results in offline BCI mode. The obtained results validate a thesis, that spatial auditory only paradigm performs as good as the traditional visual and audiovisual speller BCI tasks.
Clinical Psychophysical Assessment of the ON- and OFF-Systems of the Magnocellular and Parvocellular Visual Pathways  [PDF]
Marcelo Fernandes Costa
Neuroscience & Medicine (NM) , 2011, DOI: 10.4236/nm.2011.24043
Abstract: We developed a psychophysical paradigm for the clinical assessment of the contrast sensitivity (CS) mediated by the ON- and OFF-systems of the Magnocellular and Parvocellular pathways. We designed a stimulus considering two dimensions: two spatial frequencies (0.5 and 4.5 cpd) and two temporal rates of flicker (33 ms and 1500 ms). To evidence the ON- and OFF responses, the CS was measured for two polarities of light with luminance changes of 0.6 dB steps above and below the medium luminance grey background. We tested 38 healthy volunteers. The results shows that Magnocellular contrast sensitivity was higher than Parvocellular for the 33 ms flickering stimulus and the Parvocellular contrast sensitivity was higher than Magnocellular for 1500 ms stimuli. The reliability of the test was checked and confirmed. We concluded that the test performs a rapid measurement of the CS mediated by the ON and OFF systems of Magnocellular and Parvocellular pathways. It is useful in clinical protocols due to its high sensitivity and good reliability.
Visual Stability and the Motion Aftereffect: A Psychophysical Study Revealing Spatial Updating  [PDF]
Ulrich Biber,Uwe J. Ilg
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016265
Abstract: Eye movements create an ever-changing image of the world on the retina. In particular, frequent saccades call for a compensatory mechanism to transform the changing visual information into a stable percept. To this end, the brain presumably uses internal copies of motor commands. Electrophysiological recordings of visual neurons in the primate lateral intraparietal cortex, the frontal eye fields, and the superior colliculus suggest that the receptive fields (RFs) of special neurons shift towards their post-saccadic positions before the onset of a saccade. However, the perceptual consequences of these shifts remain controversial. We wanted to test in humans whether a remapping of motion adaptation occurs in visual perception.
Psychophysical Tests of the Hypothesis of a Bottom-Up Saliency Map in Primary Visual Cortex  [PDF]
Li Zhaoping ,Keith A May
PLOS Computational Biology , 2007, DOI: 10.1371/journal.pcbi.0030062
Abstract: A unique vertical bar among horizontal bars is salient and pops out perceptually. Physiological data have suggested that mechanisms in the primary visual cortex (V1) contribute to the high saliency of such a unique basic feature, but indicated little regarding whether V1 plays an essential or peripheral role in input-driven or bottom-up saliency. Meanwhile, a biologically based V1 model has suggested that V1 mechanisms can also explain bottom-up saliencies beyond the pop-out of basic features, such as the low saliency of a unique conjunction feature such as a red vertical bar among red horizontal and green vertical bars, under the hypothesis that the bottom-up saliency at any location is signaled by the activity of the most active cell responding to it regardless of the cell's preferred features such as color and orientation. The model can account for phenomena such as the difficulties in conjunction feature search, asymmetries in visual search, and how background irregularities affect ease of search. In this paper, we report nontrivial predictions from the V1 saliency hypothesis, and their psychophysical tests and confirmations. The prediction that most clearly distinguishes the V1 saliency hypothesis from other models is that task-irrelevant features could interfere in visual search or segmentation tasks which rely significantly on bottom-up saliency. For instance, irrelevant colors can interfere in an orientation-based task, and the presence of horizontal and vertical bars can impair performance in a task based on oblique bars. Furthermore, properties of the intracortical interactions and neural selectivities in V1 predict specific emergent phenomena associated with visual grouping. Our findings support the idea that a bottom-up saliency map can be at a lower visual area than traditionally expected, with implications for top-down selection mechanisms.
Processamento visual da forma: evidências para canais múltiplos de freqüências angulares em humanos
Santos, Natanael Antonio dos;Nogueira, Renata Maria Toscano Barreto Lyra;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2005, DOI: 10.1590/S0102-79722005000100013
Abstract: the aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/360o defined in polar coordinates. we measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. the results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360o) filters surrounded on both sides by strong inhibition. these results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.
An Usage Measure Based on Psychophysical Relations  [PDF]
V. Kromer
Computer Science , 2000,
Abstract: A new word usage measure is proposed. It is based on psychophysical relations and allows to reveal words by its degree of "importance" for making basic dictionaries of sublanguages.
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