Takeharu Seno

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.

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.

Independent modulation of motion and vection aftereffects revealed by using coherent oscillation and random jitter in optic flow.

We added simulated vertical viewpoint jitter and oscillation to radial optic flow displays designed to induce forward vection. Display jitter and oscillation were both found to increase vection strength during, and reduce motion aftereffects (MAE) following, exposure to the optic flow (compared to no-jitter controls). Display jitter, which induced the strongest vection of all the conditions tested, was also found to increase the duration of vection aftereffects (VAE).

Perceptually plausible sounds facilitate visually induced self-motion perception (vection)

We examined whether and how sounds influence visually induced illusory self-motion (vection). Visual stimuli were presented for 40 s. They were made radially, expanding or contracting visual motion field and luminance-defined gratings drifting in a vertical or horizontal direction. Auditory stimuli were presented with the visual stimuli in most conditions; we employed sounds that increased or decreased in intensity, or ascended or descended in frequency. As a result, the sound which increased in intensity facilitated forward vection, and the sound which ascended/descended in frequency facilitated upward/downward vection. The perceptual plausibility of the sound for the corresponding self-motion seemed an important factor of enhancing vection.

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.

Vection is Modulated by the Semantic Meaning of Stimuli and Experimental Instructions

Vection strength is modulated by the semantic meanings of stimuli. In experiment 1—even though vection stimuli were of uniform size, color, and luminance—when they also had semantic meaning as falling objects, vection was inhibited. Specifically, stimuli perceived as feathers, petals, and leaves did not effectively induce vection. In experiment 2 we used the downward motion of identical dots to induce vection. Participants observed stimuli while holding either an umbrella or a wooden sword. Results showed that vection was inhibited when participants held the umbrella and the stimuli was perceived as rain or snow falling. The two experiments suggest that vection is modulated by the semantic meaning of stimuli.

Emotional Sounds Influence Vertical Vection

While viewing a large vertically moving sinusoidal luminance grating, the perception of upward self-motion (vection) was modulated by positive sounds (eg a babys laughter). This may be because positive emotion and the spatial metaphor of vertical directions were unified in the mind.

More rapid and stronger vection in elementary school children compared with adults.

We compared vection (visually induced illusory self-motion perception) among elementary school children and adults by measuring latency to onset, cumulative duration, and estimated strength of vection. Significantly stronger vection with shorter latency was observed in children compared with adults. Several possible causes (eg size-difference of the effective visual field) of the age-related differences are discussed.