Biomedical subjects

Shigeru Ichihara

Publications and source records attributed to Shigeru Ichihara.

3 recordsLinked to original sources

PubMed2004

Effects of illusory stripes on the Helmholtz illusion.

This study examined the Helmholtz illusion by using "illusory stripes." A square patch is perceived as wider when vertical lines are drawn on it and is perceived as taller when horizontal lines are drawn on it, i.e., Helmholtz illusion. With vertical lines curved sinusoidally, horizontal "illusory stripes" are perceived; and with horizontal lines curved sinusoidally, vertical "illusory stripes" are perceived. The purpose of the present study was to test whether the "illusory stripes" produce the Helmholtz illusion. We measured the apparent size of a square patch filled with sinusoidal lines. Our subjects (N=27) judged the patch with horizontal "illusory stripes" taller than the square patch filled with vertical straight lines. The subjects also judged the square patch with vertical "illusory stripes" wider than the square patch filled with horizontal straight lines. These results demonstrate that "illusory stripes" can produce the Helmholtz illusion.

Adult↗

PubMed2004

Vision of a pictorial hand modulates visual-tactile interactions.

The participants in this study discriminated the position of tactile target stimuli presented at the tip or the base of the forefinger of one of the participants' hands, while ignoring visual distractor stimuli. The visual distractor stimuli were presented from two circles on a display aligned with the tactile targets in Experiment 1 or orthogonal to them in Experiment 2. Tactile discrimination performance was slower and less accurate when the visual distractor stimuli were presented from incongruent locations relative to the tactile target stimuli (e.g., tactile target at the base of the finger with top visual distractor) highlighting a cross-modal congruency effect. We examined whether the presence and orientation of a simple line drawing of a hand, which was superimposed on the visual distractor stimuli, would modulate the cross-modal congruency effects. When the tactile targets and the visual distractors were spatially aligned, the modulatory effects of the hand picture were small (Experiment 1). However, when they were spatially misaligned, the effects were much larger, and the direction of the cross-modal congruency effects changed in accordance with the orientation of the picture of the hand, as if the hand picture corresponded to the participants' own stimulated hand (Experiment 2). The results suggest that the two-dimensional picture of a hand can modulate processes maintaining our internal body representation. We also observed that the cross-modal congruency effects were influenced by the postures of the stimulated and the responding hands. These results reveal the complex nature of spatial interactions among vision, touch, and proprioception.

Adult↗

PubMed2002

Hearing visual motion in depth.

Auditory spatial perception is strongly affected by visual cues. For example, if auditory and visual stimuli are presented synchronously but from different positions, the auditory event is mislocated towards the locus of the visual stimulus-the ventriloquism effect. This 'visual capture' also occurs in motion perception in which a static auditory stimulus appears to move with the visual moving object. We investigated how the human perceptual system coordinates complementary inputs from auditory and visual senses. Here we show that an auditory aftereffect occurs from adaptation to visual motion in depth. After a few minutes of viewing a square moving in depth, a steady sound was perceived as changing loudness in the opposite direction. Adaptation to a combination of auditory and visual stimuli changing in a compatible direction increased the aftereffect and the effect of visual adaptation almost disappeared when the directions were opposite. On the other hand, listening to a sound changing in intensity did not affect the visual changing-size aftereffect. The results provide psychophysical evidence that, for processing of motion in depth, the auditory system responds to both auditory changing intensity and visual motion in depth.

Acoustic Stimulation↗