Illusory motion produced by dichoptic stimuli during saccades

A new motion illusion is reported in which saccadic eye movements can produce a perceived jump of a static stimulus presented dichoptically. In three experiments, observers made saccades while viewing a stationary stimulus consisting of a disk and random dots presented separately to the two eyes. In experiments 1 and 2, by measuring the strength of the perceived motion and the velocity of binocular eye movements, we found that (a) motion ratings were high for the stimulus that contained a large interocular difference in luminance, and (b) the saccadic strategy of the observer was virtually identical across different stimulus conditions. In experiment 3, by measuring the detectability of a short temporal gap introduced into the stimulus around saccades, we found that saccadic suppression was normal in the dichoptic presentation. We discuss possible mechanisms underlying the illusory motion.     

Cognitive Bias for the Distribution of Ball Landing Positions in Amateur Tennis Players (Cognitive Bias for the Motor Variance in Tennis)

This study aimed to investigate whether the isotropy bias (estimating one's own motor variance as an approximately circular distribution rather than a vertically elongated distribution) arises in tennis players for the estimation of the two-dimensional variance for forehand strokes in tennis (Experiment 1), as well as the process underlying the isotropy bias (Experiment 2). In Experiment 1, 31 tennis players were asked to estimate prospectively their distribution of ball landing positions. They were then instructed to hit 50 forehand strokes. We compared the eccentricity of the ellipse calculated from estimated and observed landing positions. Eccentricity was significantly smaller in the estimated ellipse than in the observed ellipse. We assumed that the isotropy bias for the estimated ellipse comes from the process of variance estimation. In Experiment 2, nine participants estimated the 95% confidence interval of 300 dots. Eccentricity was significantly smaller in their estimated ellipses than it was in the ellipses for the dots, though the magnitude of bias decreased for the estimation of dots. These results suggest that the isotropy bias in tennis ball landing position includes the bias of recognizing landing position and the bias of estimating the ellipse confidence interval from the recognized landing position.     

Selective attention to stimulus features modulates interocular suppression

Psychological and neurophysiological studies have shown that attention modulates various sorts of perceptual processing. Here, we report that attention affects the perceptual dominance of binocular rivalry. Experiments using a dichoptic masking paradigm revealed that when an observer was attending to one of the two orientations of the elements of a monocular texture, a texture briefly presented to the opposite eye suppressed the perception of the elements with the attended orientation, while the elements with the orientation which was ignored sustained their dominance. Moreover, subsequent experiments indicated that the suppression depended on the orientation of the texture elements constituting the mask, but was independent of their locations. These results suggest that attention to specific features modulates interocular suppression in a mode which is different from that found in a previous study [Ooi and He, 1999 Perception 28 551 -574].     

The aperture problems in the Pulfrich effect

The Pulfrich effect yields a perceived depth for horizontally moving objects but not for vertically moving ones. In this study the Pulfrich effect was measured by translating oblique lines seen through a circular window, which made motion direction ambiguous. Overlaying random dots that moved horizontally, vertically, or diagonally controlled the perceptual motion direction of the lines. In experiment 1, when the lines were seen to move horizontally, the effect was strongest in spite of the same physical motion of the lines. Experiment 2 was performed to test the above conditions again, excluding the Pulfrich effect of the dots on the depth of the lines. The overlaid dots were presented to one eye only. The result showed that the Pulfrich effect of the lines was persistently strong in spite of the perceptual changes in motion direction. Experiment 3 also showed that the Pulfrich depth was independent of the perceived horizontal speed in a plaid display. The Pulfrich effect was determined by measuring the horizontal disparity component, independently of the perceived motion direction. These results demonstrate that the aperture problems in motion and stereopsis in the Pulfrich effect are solved independently.     

Information regarding structure and lightness based on phenomenal transparency influences the efficiency of visual search

Phenomenal transparency reflects a process which makes it possible to recover the structure and lightness of overlapping objects from a fragmented image. This process was investigated by the visual-search paradigm. In three experiments, observers searched for a target that consisted of gray patches among a variable number of distractors and the search efficiency was assessed. Experiments 1 and 2 showed that the search efficiency was greatly improved when the target was distinctive with regard to structure, based on transparency. Experiment 3 showed that the search efficiency was impaired when a target was not distinctive with regard to lightness (ie perceived reflectance), based on transparency. These results suggest that the shape and reflectance of overlapping objects when accompanied by transparency can be calculated in parallel across the visual field, and can be used as a guide for visual attention.     

Modification of depth and distance perception caused by long-term wearing of left-right reversing spectacles

For 35 to 39 days, four observers wore continuously left-right reversing spectacles which pseudoscopically reverse the order of binocular disparity and direction of convergence. In three tests, we investigated how the visual system copes with the transformation of depth and distance information due to the reversing spectacles. In stereogram observation, after a few days of wearing the spectacles. the observers sometimes perceived a depth order which was opposite to the depth order that they had perceived in the pre-spectacle-wearing period. Monocular depth cues contributed more to depth perception in the spectacle-wearing period than they did in the pre-spectacle-wearing period. While the perceived distance significantly decreased during the spectacle-wearing period, we found no evidence of adaptive change in distance perception. The results indicate that the visual system adapts itself to the transformed situation by not only changing the processing of disparity but also by changing the relative efficiency of each cue in determining apparent depth.     

Object–Color Associations in Preschool Children’s Drawings

This study examines children’s abilities to identify a color-specific object by associating it with a given color. During the experimental sessions in preschool classrooms, 156 children aged 3–5 years were engaged in a drawing and coloring task. The experiment investigated whether the color of the object drawn by the child was congruent to the color that he/she had previously chosen. The results showed that children older than four years of age used object color knowledge to associate the given color with an object, suggesting that children acquire this ability at the same age that they learn to choose a typical color from a color-specific object. The developmental model of object representations is discussed on the basis of these results.     

Impaired Interpretation of Others’ Behavior is Associated with Difficulties in Recognizing Pragmatic Language in Patients with Schizophrenia

Much attention has been paid to the pragmatic language function in schizophrenia. This study of Japanese patients with schizophrenia examined the relationship between impaired interpretation of the behaviors of other people in social contexts and the ability to recognize metaphor and irony. We assessed 34 patients with schizophrenia and 34 normal subjects using first- and second-order theory of mind tasks, the Metaphor and Sarcasm Scenario Test, and the Dewey Story Test (which tests the ability to judge others’ social behaviors). We compared the performance between the groups and analyzed correlations between the tasks. All tasks revealed significant deficits in the patients compared with the controls. In the patient group, metaphor comprehension was correlated with the ability to judge normal behaviors, and irony comprehension was correlated with the ability to judge abnormal behaviors, suggesting that deficits of social cognition in schizophrenia include these two types of factors associated with pragmatic language.     

Additivity of retinal and pursuit velocity in the perceptions of depth and rigidity from object-produced motion parallax

Two psychophysical experiments were conducted to investigate the mechanism that generates stable depth structure from retinal motion combined with extraretinal signals from pursuit eye movements. Stimuli consisted of random dots that moved horizontally in one direction (ie stimuli had common motion on the retina), but at different speeds between adjacent rows. The stimuli were presented with different speeds of pursuit eye movements whose direction was opposite to that of the common retinal motion. Experiment 1 showed that the rows moving faster on the retina appeared closer when viewed without eye movements; however, they appeared farther when pursuit speed exceeded the speed of common retinal motion. The 'transition' speed of the pursuit eye movement was slightly, but consistently, larger than the speed of common retinal motion. Experiment 2 showed that parallax thresholds for perceiving relative motion between adjacent rows were minimum at the transition speed found in experiment 1. These results suggest that the visual system calculates head-centric velocity, by adding retinal velocity and pursuit velocity, to obtain a stable depth structure.     

慢性应激对大鼠海马Akt/FKHRL1信号通路活性的影响

探讨慢性应激对大鼠海马Akt/FKHRL1信号通路活性的影响,及其应激源特异性。将24只雄性SD大鼠随机分为心理应激组、束缚应激组和正常对照组（n=8）。用Western-blotting方法测定28天应激后海马Akt、FKHRL1蛋白含量及其磷酸化水平。结果表明,应激后三组大鼠海马磷酸化Akt、FKHRL1含量差异有统计学意义（p < 0.01;p < 0.001）,束缚应激组低于正常对照组（p < 0.01）。提示慢性应激能导致海马磷酸化Akt、FKHRL1表达水平降低,但其影响程度与应激源特异性有关