Shoji Sunaga

Vection aftereffects from expanding/contracting stimuli.

We presented three types of visual stimuli (blank, static and dynamic random dots) following optic flow stimuli and measured the durations of the motion aftereffects (MAEs) and aftereffects of vection (vection aftereffects, VAEs). The VAEs were induced in the direction opposite to the MAEs. However, the VAEs were not the same as the vection induced by the MAEs because the VAEs were sustained even after the MAEs vanished. In addition, when vection was facilitated or inhibited by the static dot plane in front or in the back of the optic flow, only the VAE strength was modulated, while the MAE was constant between the two conditions. From these results, we conclude that the vection-inducing mechanism shares some neural units with the motion processing mechanisms but has an additional aspect that adapts independently of the motion processing mechanisms.

Attentional load inhibits vection

In this study, we examined the effects of cognitive task performance on the induction of vection. We hypothesized that, if vection requires attentional resources, performing cognitive tasks requiring attention should inhibit or weaken it. Experiment 1 tested the effects on vection of simultaneously performing a rapid serial visual presentation (RSVP) task. The results revealed that the RSVP task affected the subjective strength of vection. Experiment 2 tested the effects of a multiple-object-tracking (MOT) task on vection. Simultaneous performance of the MOT task decreased the duration and subjective strength of vection. Taken together, these findings suggest that vection induction requires attentional resources.

Evaluation of an organic light-emitting diode display for precise visual stimulation

A new type of visual display for presentation of a visual stimulus with high quality was assessed. The characteristics of an organic light-emitting diode (OLED) display (Sony PVM-2541, 24.5 in.; Sony Corporation, Tokyo, Japan) were measured in detail from the viewpoint of its applicability to visual psychophysics. We found the new display to be superior to other display types in terms of spatial uniformity, color gamut, and contrast ratio. Changes in the intensity of luminance were sharper on the OLED display than those on a liquid crystal display. Therefore, such OLED displays could replace conventional cathode ray tube displays in vision research for high quality stimulus presentation. Benefits of using OLED displays in vision research were especially apparent in the fields of low-level vision, where precise control and description of the stimulus are needed, e.g., in mesopic or scotopic vision, color vision, and motion perception.

Inconsistent locomotion inhibits vection

We measured the strength of illusory self-motion perception (vection) with and without locomotion on a treadmill. The results revealed that vection was inhibited by inconsistent locomotion, but facilitated by consistent locomotion.

Inhibition of vection by red

We investigated the effects of colors on vection induction. Expanding optical flows during one’s forward self-motion were simulated by moving dots. The dots and the background were painted in equiluminant red and green. Experiments 1 and 2 showed that vection was weaker when the background was red than when the background was green. In addition, Experiment 3 showed that vection was weaker when the moving dots were red than when the dots were green. Experiment 4 demonstrated that red dots on a red background induced very weak vection, as compared with green dots on a green background. In Experiments 5 and 6, we showed that the present results could not be explained by a luminance artifact. Furthermore, Experiment 7 showed that a moving red grating induced weaker vection than did a green one. We concluded that a red visual stimulus inhibits vection.

Temporonasal motion projected on the nasal retina underlies expansion–contraction asymmetry in vection

Contracting visual stimuli have been found to induce stronger vection than expanding stimuli. We sought to determine which component of motion underlies the advantage of contraction over expansion in inducing vection. Either the right or left hemi-visual field of an optic flow was presented to either the right or left eye. Our results revealed that without temporonasal motion projected on the nasal retina, vection was weak even with contracting stimuli. Conversely, vection was strong even with expanding stimuli if this type of motion was present. The advantage of contracting stimuli in inducing vection may be caused by anisotropy in processing motion on the nasal retina.

The mental number line in depth revealed by vection.

To explore how numbers are represented in depth in our mental space, we asked participants to sequentially speak random numbers while they observed forward/backward vection. We found that participants tended to generate larger numbers when they perceived backward self-motion. The results suggest that numerical magnitudes were topographically mapped onto our mental space from front to rear in an ascending order.

Effect of additive salts on ion conductivity characteristics in solid polymer electrolytes

Abstract Effects of lattice energy of the additive salt on ionic species and ion conductivity characteristics were studied in the solid polymer electrolyte. Poly[oligo(oxyethylene) methacrylate] and several lithium salts were used as matrix and additive salt for solid polymer electrolytes, respectively. Salt and salt content deeply affected the ion conductivity characteristics as well as morphology even for amorphous type solid polymer electrolytes. The relationship between ion conductivity at constant reduced temperature ( T − T g = 90°C) and lattice energy of the additive salt was evaluated at each salt content. A different relationship was found for each salt content. Multiple ion aggregate formation was considerably affected by the salt, and was revealed to be effective to increase the ion conductivity.

Coherent Modulation of Stimulus Colour Can Affect Visually Induced Self-Motion Perception

The effects of dynamic colour modulation on vection were investigated to examine whether perceived variation of illumination affects self-motion perception. Participants observed expanding optic flow which simulated their forward self-motion. Onset latency, accumulated duration, and estimated magnitude of the self-motion were measured as indices of vection strength. Colour of the dots in the visual stimulus was modulated between white and red (experiment 1), white and grey (experiment 2), and grey and red (experiment 3). The results indicated that coherent colour oscillation in the visual stimulus significantly suppressed the strength of vection, whereas incoherent or static colour modulation did not affect vection. There was no effect of the types of the colour modulation; both achromatic and chromatic modulations turned out to be effective in inhibiting self-motion perception. Moreover, in a situation where the simulated direction of a spotlight was manipulated dynamically, vection strength was also suppressed (experiment 4). These results suggest that observers perception of illumination is critical for self-motion perception, and rapid variation of perceived illumination would impair the reliabilities of visual information in determining self-motion.

Self-Motion Perception Compresses Time Experienced in Return Travel

It is often anecdotally reported that time experienced in return travel (back to the start point) seems shorter than time spent in outward travel (travel to a new destination). Here, we report the first experimental results showing that return travel time is experienced as shorter than the actual time. This discrepancy is induced by the existence of self-motion perception.