Anisotropic distortion in the perceived orientation of stimuli on the arm

Mechanoreceptors on the skin are heterogeneously distributed, and the sampling of neural signals in the brain can vary depending on the part of the body. Therefore, it can be challenging for the brain to consistently represent stimuli applied to different body sites. Here, we report an example of a regional perceptual distortion of the tactile space. We used a piezoelectric braille display to examine shape perception on the volar surface of the arm and to compare it to that on the palm. We found that the orientation of perceived stimuli on the arm was distorted in certain areas. In particular, an inwardly-inclined line shape was perceived as being more inwardly-inclined than it actually was. On the other hand, an outwardly-inclined line was perceived accurately. When the same stimuli were applied to the palm, this anisotropic bias was not observed. We also found that changing the posture of the arm changed the angle at which this anisotropic distortion occurred, suggesting the influence of the skin frame of reference on this illusion. This study showed a clear example of how the representation of even simple stimuli is complexly distinct when the stimuli are applied to different body sites.

Dynamic arm movements attenuate the perceptual distortion of visual vertical induced during prolonged whole-body tilt

Concurrent body movements have been shown to enhance the accuracy of spatial judgment, but it remains unclear whether they also contribute to perceptual estimates of gravitational space not involving body movements. To address this, we evaluated the effects of static or dynamic arm movements during prolonged whole-body tilt on the subsequent perceptual estimates of visual or postural vertical. In Experiment 1, participants were asked to continuously perform static or dynamic arm movements during prolonged tilt, and we assessed their effects on the prolonged tilt-induced shifts of subjective visual vertical (SVV) at a tilted position (during-tilt session) or near upright (post-tilt session). In Experiment 2, we evaluated how static or dynamic arm movements during prolonged tilt subsequently affected the subjective postural vertical (SPV). In Experiment 1, we observed that the SVV was significantly shifted toward the direction of prolonged tilt in both sessions. The SVV shifts decreased when performing dynamic arm movements in the during-tilt session, but not in the post-tilt session. In Experiment 2, as well as SVV, the SPV was shifted toward the direction of prolonged tilt, but it was not significantly attenuated by the performance of static or dynamic arm movements. The results of the during-tilt session suggest that the central nervous system utilizes additional information generated by dynamic body movements for perceptual estimates of visual vertical.

Verification of the accommodative responses in viewing an on-axis analog reflection hologram

Vergence and accommodation responses of human vision are very important factors when a 3D image is observed, and a vergence-accommodation conflict (VAC) causes perceptual distortion, visual discomfort, and fatigue for an observer. Theoretically, a hologram is expected to provide a 3D image without such a conflict. In this article, natural focusing was verified by human accommodation response (A-R) measurement during on-axis analog reflection Denisyuk hologram observation. The A-R of a group of participants were measured for a real marker and its Denisyuk hologram at various visualization distances using an Nvision K5001 autorefractor. The experimental results statistically confirmed the equivalence of the responses to the Denisyuk hologram and its real counterpart, as well as the absence of a VAC.

Dynamic arm movements attenuate perceptual distortion of visual vertical induced during prolonged whole-body tilt

Additional gravitational cues generated by active body movements may play a role in the perception of gravitational space, but no experimental evidence has been shown on this. To investigate this possibility, we evaluated how arm movements made against gravity influenced the perceptual distortion of visual and postural vertical induced by prolonged whole-body tilt. In Experiment 1, participants were asked to perform static or dynamic arm movements during prolonged whole-body tilt and we assessed their effects on subjective visual vertical (SVV) at the tilt position (during-tilt session) and after tilting back to the upright position (post-tilt session). In Experiment 2, we evaluated how static or dynamic arm movements during prolonged tilt subsequently affected the subjective postural vertical (SPV). In Experiment 1, we observed that prolonged tilt induced the SVV shifts toward the side of body tilts in both sessions. The prolonged tilt-induced SVV shifts effectively decreased when performing dynamic arm movements in the during-tilt session, but not in the post-tilt session. In Experiment 2, the SPV shifted toward the side of prolonged body tilt, which was not significantly influenced by the performance of static or dynamic arm movements. Results of the during-tilt session suggest that the central nervous system utilizes additional cues generated by dynamic body movements for the perception of the visual vertical.

High-Payload Data-Hiding Method for AMBTC Decompressed Images

Data hiding is the art of embedding data into a cover image without any perceptual distortion of the cover image. Moreover, data hiding is a very crucial research topic in information security because it can be used for various applications. In this study, we proposed a high-capacity data-hiding scheme for absolute moment block truncation coding (AMBTC) decompressed images. We statistically analyzed the composition of the secret data string and developed a unique encoding and decoding dictionary search for adjusting pixel values. The dictionary was used in the embedding and extraction stages. The dictionary provides high data-hiding capacity because the secret data was compressed using dictionary-based coding. The experimental results of this study reveal that the proposed scheme is better than the existing schemes, with respect to the data-hiding capacity and visual quality.

On Why Objects Appear Smaller in the Visual Periphery

An object appears smaller in the periphery than in the center of the visual field. In two experiments ( N = 24), we demonstrated that visuospatial attention contributes substantially to this perceptual distortion. Participants judged the size of central and peripheral target objects after a transient, exogenous cue directed their attention to either the central or the peripheral location. Peripheral target objects were judged to be smaller following a central cue, whereas this effect disappeared completely when the peripheral target was cued. This outcome suggests that objects appear smaller in the visual periphery not only because of the structural properties of the visual system but also because of a lack of spatial attention.