Blood oxygenation level-dependent (BOLD) contrast appears through a variation in the transverse r... more Blood oxygenation level-dependent (BOLD) contrast appears through a variation in the transverse relaxation rate of magnetic resonance signals induced by neurovascular coupling and is known to have nonlinear characteristics along echo time (TE) due to the intra-vasculature. However, the physiological causes of this nonlinearity are unclear. We attempted to estimate the physiological information related to the nonlinearity of BOLD signals by using a two-compartment model. For this purpose, we used a multi-echo gradient-echo echo-planar imaging sequence and developed a computational method to estimate the physiological information from the TE-dependent BOLD signals. The results showed that the average chemical exchange time in the intra-vasculature varied during stimulation, which might be the essential source of the nonlinearity.
Despite numerous prior studies, important questions about the Japanese color lexicon persist, par... more Despite numerous prior studies, important questions about the Japanese color lexicon persist, particularly about the number of Japanese basic color terms and their deployment across color space. Here, 57 native Japanese speakers provided monolexemic terms for 320 chromatic and 10 achromatic Munsell color samples. Through k-means cluster analysis we revealed 16 statistically distinct Japanese chromatic categories. These included eight chromatic basic color terms (aka/red, ki/yellow, midori/green, ao/blue, pink, orange, cha/brown, and murasaki/purple) plus eight additional terms: mizu ("water")/light blue, hada ("skin tone")/peach, kon ("indigo")/dark blue, matcha ("green tea")/yellow-green, enji/maroon, oudo ("sand or mud")/mustard, yamabuki ("globeflower")/gold, and cream. Of these additional terms, mizu was used by 98% of informants, and emerged as a strong candidate for a 12th Japanese basic color term. Japanese and Ameri...
ABSTRACT Our previous study showed that the algorithm using quantified aerial perspective could c... more ABSTRACT Our previous study showed that the algorithm using quantified aerial perspective could control subjective depth in stereoscopic still pictures. Being integrated with a motion-estimation technique, this algorithm can be applied to motion pictures. In this paper, details of the algorithm and results of subjective assessment will be presented and discussed.
9th Congress of the International Colour Association, 2002
ABSTRACT Based on the psychophysical method of constant stimuli, an experiment was carried out, u... more ABSTRACT Based on the psychophysical method of constant stimuli, an experiment was carried out, using CRT-generated stimuli and in CIELAB color space, to test the visual color differences in relation to colorimetric scales. The CIE Gray and Blue color centers, the most basic color and, perceptually, the most different color, respectively, were chosen, and the maximum average size of test color difference was 12 CIELAB ΔE units. The resultant visual data, procesed via probit analysis, were used to analyze the relationship between color discrimination threshold and suprathreshold color-difference preception. The equal color-difference contours, corresponding to all the visual scales, 4.0, 8.0, and 12.0 CIELAB ΔE units, were well fitted into ellipses while maintaining the orientation of the threshold one, but the shapes were not completely the same, especially at Blue center. The comparisons between visual color differences and their colorimetric counterparts, in teh CIELAB ΔE units or threshold units, show linear relations at both color centers, but the slopes were, in general, not equal to 45° and differed for all directions. Thus the suprathreshold color differences can be derived by enlarging the thresholds linearly but not uniformly, i.e. with different ratios for individual directions.
2013 2nd IAPR Asian Conference on Pattern Recognition, 2013
ABSTRACT Despite a number of studies of computational models of visual saliency, it is still diff... more ABSTRACT Despite a number of studies of computational models of visual saliency, it is still difficult to predict where human would attend in a scene. One of the problems is the effect of self-motion on retinal images. Usually saliency is calculated with local motion signals, and high degree of saliency is found in motion components caused by self-motion. Since human observers usually ignore the motion caused by self-motion, the prediction accuracy of attention locations falls off. We developed a framework that reduces the saliency of the motion components caused self-motion, using a physiological model of optic flow processing that extracts object motion among self-motion signals.
ABSTRACT Background / Purpose: Motion in depth can be perceived based on interocular velocity dif... more ABSTRACT Background / Purpose: Motion in depth can be perceived based on interocular velocity differences (IOVDs) caused by monocular motion aftereffect (MAE). In order to investigate how the IOVD integrates signals from the luminance and colour motion channels, we conducted experiments to reveal whether this integration is implemented before or after the comparison of the velocity signals from the two eyes.We measured cross adaptation effects between luminance and colour motion signals in MAE of motion in depth (3D MAE). Adaptation stimulus was either luminance or red/green gratings drifting laterally in Experiment 1 and we also used yellow/blue gratings in Experiment 2. After adapting either the left or right eye to the drifting grating, the duration of 3D-MAE was measured with the static version of the colour or the luminance grating. To confirm colour motion system is concerned in colour motion conditions, we varied temporal frequency (with a fixed spatial frequency), expecting different temporal frequency characteristics between the luminance and colour motion systems. Main conclusion: After the colour adaptation, MAE duration showed longer with lower temporal frequencies (low pass) while it showed the longest around 5 Hz after the luminance adaptation (band pass) for both 2D- and 3D-MAEs with longer absolute duration for 2D-MAE. This trend was the same for the luminance and colour tests both in Experiments 1 and 2.These results indicate that colour motion signals are used to see motion in depth through the IOVD and that integration of colour and luminance motion signals occurs at a stage of 2D motion and the IOVD is calculated from the combined motion signals. The results also suggest that there is an energy based colour motion system since it is highly unlikely to calculate IOVDs through a high level mechanism such as feature tracking.
Blood oxygenation level-dependent (BOLD) contrast appears through a variation in the transverse r... more Blood oxygenation level-dependent (BOLD) contrast appears through a variation in the transverse relaxation rate of magnetic resonance signals induced by neurovascular coupling and is known to have nonlinear characteristics along echo time (TE) due to the intra-vasculature. However, the physiological causes of this nonlinearity are unclear. We attempted to estimate the physiological information related to the nonlinearity of BOLD signals by using a two-compartment model. For this purpose, we used a multi-echo gradient-echo echo-planar imaging sequence and developed a computational method to estimate the physiological information from the TE-dependent BOLD signals. The results showed that the average chemical exchange time in the intra-vasculature varied during stimulation, which might be the essential source of the nonlinearity.
Despite numerous prior studies, important questions about the Japanese color lexicon persist, par... more Despite numerous prior studies, important questions about the Japanese color lexicon persist, particularly about the number of Japanese basic color terms and their deployment across color space. Here, 57 native Japanese speakers provided monolexemic terms for 320 chromatic and 10 achromatic Munsell color samples. Through k-means cluster analysis we revealed 16 statistically distinct Japanese chromatic categories. These included eight chromatic basic color terms (aka/red, ki/yellow, midori/green, ao/blue, pink, orange, cha/brown, and murasaki/purple) plus eight additional terms: mizu ("water")/light blue, hada ("skin tone")/peach, kon ("indigo")/dark blue, matcha ("green tea")/yellow-green, enji/maroon, oudo ("sand or mud")/mustard, yamabuki ("globeflower")/gold, and cream. Of these additional terms, mizu was used by 98% of informants, and emerged as a strong candidate for a 12th Japanese basic color term. Japanese and Ameri...
ABSTRACT Our previous study showed that the algorithm using quantified aerial perspective could c... more ABSTRACT Our previous study showed that the algorithm using quantified aerial perspective could control subjective depth in stereoscopic still pictures. Being integrated with a motion-estimation technique, this algorithm can be applied to motion pictures. In this paper, details of the algorithm and results of subjective assessment will be presented and discussed.
9th Congress of the International Colour Association, 2002
ABSTRACT Based on the psychophysical method of constant stimuli, an experiment was carried out, u... more ABSTRACT Based on the psychophysical method of constant stimuli, an experiment was carried out, using CRT-generated stimuli and in CIELAB color space, to test the visual color differences in relation to colorimetric scales. The CIE Gray and Blue color centers, the most basic color and, perceptually, the most different color, respectively, were chosen, and the maximum average size of test color difference was 12 CIELAB ΔE units. The resultant visual data, procesed via probit analysis, were used to analyze the relationship between color discrimination threshold and suprathreshold color-difference preception. The equal color-difference contours, corresponding to all the visual scales, 4.0, 8.0, and 12.0 CIELAB ΔE units, were well fitted into ellipses while maintaining the orientation of the threshold one, but the shapes were not completely the same, especially at Blue center. The comparisons between visual color differences and their colorimetric counterparts, in teh CIELAB ΔE units or threshold units, show linear relations at both color centers, but the slopes were, in general, not equal to 45° and differed for all directions. Thus the suprathreshold color differences can be derived by enlarging the thresholds linearly but not uniformly, i.e. with different ratios for individual directions.
2013 2nd IAPR Asian Conference on Pattern Recognition, 2013
ABSTRACT Despite a number of studies of computational models of visual saliency, it is still diff... more ABSTRACT Despite a number of studies of computational models of visual saliency, it is still difficult to predict where human would attend in a scene. One of the problems is the effect of self-motion on retinal images. Usually saliency is calculated with local motion signals, and high degree of saliency is found in motion components caused by self-motion. Since human observers usually ignore the motion caused by self-motion, the prediction accuracy of attention locations falls off. We developed a framework that reduces the saliency of the motion components caused self-motion, using a physiological model of optic flow processing that extracts object motion among self-motion signals.
ABSTRACT Background / Purpose: Motion in depth can be perceived based on interocular velocity dif... more ABSTRACT Background / Purpose: Motion in depth can be perceived based on interocular velocity differences (IOVDs) caused by monocular motion aftereffect (MAE). In order to investigate how the IOVD integrates signals from the luminance and colour motion channels, we conducted experiments to reveal whether this integration is implemented before or after the comparison of the velocity signals from the two eyes.We measured cross adaptation effects between luminance and colour motion signals in MAE of motion in depth (3D MAE). Adaptation stimulus was either luminance or red/green gratings drifting laterally in Experiment 1 and we also used yellow/blue gratings in Experiment 2. After adapting either the left or right eye to the drifting grating, the duration of 3D-MAE was measured with the static version of the colour or the luminance grating. To confirm colour motion system is concerned in colour motion conditions, we varied temporal frequency (with a fixed spatial frequency), expecting different temporal frequency characteristics between the luminance and colour motion systems. Main conclusion: After the colour adaptation, MAE duration showed longer with lower temporal frequencies (low pass) while it showed the longest around 5 Hz after the luminance adaptation (band pass) for both 2D- and 3D-MAEs with longer absolute duration for 2D-MAE. This trend was the same for the luminance and colour tests both in Experiments 1 and 2.These results indicate that colour motion signals are used to see motion in depth through the IOVD and that integration of colour and luminance motion signals occurs at a stage of 2D motion and the IOVD is calculated from the combined motion signals. The results also suggest that there is an energy based colour motion system since it is highly unlikely to calculate IOVDs through a high level mechanism such as feature tracking.
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