Biomedical subjects

Jun Saiki

Publications and source records attributed to Jun Saiki.

4 recordsLinked to original sources

PubMed2003

Spatiotemporal characteristics of dynamic feature binding in visual working memory.

It has been proposed that visual working memory can hold a set of four to five coherent object representations. As a test of this proposal, I devised a paradigm called multiple object permanence tracking (MOPT) that measures memory for feature-location binding in dynamic situations. Observers were asked to detect any feature switch in the middle of a regular rotation of a pattern with multiple objects behind an occluder. The feature switch detection performance dramatically declined as the pattern rotation velocity increased. The behavioral evidence for the use of multiple color-shape conjunction was observed only when the objects were stationary. These results cast doubt on the view that the functional unit of visual working memory involves coherent object representation, where object features are tightly bound and dynamically updated.

Color Perception↗

PubMed2003

Feature binding in object-file representations of multiple moving items.

Maintenance of episodic representations by feature-location binding is important for visual cognition. It has been proposed that we can hold and update coherent episodic representations of up to four objects. This study investigated the dynamic maintenance of feature-location bindings with multiple objects. In a series of seven experiments, participants judged whether a sequence of rotating patterns of three or four colored disks contains any color switch between two disks. Color-switch detection is in general difficult, even when tracking of objects' motions is successful, suggesting that our ability for dynamic maintenance is limited. The performance improved when the interframe rotation angle became sufficiently small. Moreover, spatiotemporal predictability was necessary for this improvement, suggesting that the maintenance of multiple episodic representations is an interactive process between our prediction and sensory mechanisms.

Cognition↗

PubMed2003

[Perceptual judgments of novel contour shapes and hierarchical descriptions of geometrical properties].

Previous studies of pattern psychophysics have suggested that a form property such as the number of turns and a structural property such as symmetry were useful cues for perceptual judgments of simple forms. However, it is necessary for complete descriptions of more complex forms to use hierarchical indices reflecting global and local characteristics. In this study, we clarified what geometrical properties contributed to complexity and similarity judgments of novel shapes, and examined differences between the two judgments, using Fourier descriptors as a form property, and symmetropy as a structural property. Global and local unevenness were derived from the amplitude of Fourier descriptors, and the hierarchical representation was found in both judgment data. Whereas complexity judgment was based on local unevenness and global symmetry, similarity judgment was, it was suggested, mainly based on global unevenness and symmetry. Moreover, it became clear that geometrical properties important for complexity data were a subset of those for similarity data. These results suggested that more dimensions in geometrical properties were necessary for similarity judgment than complexity judgment.

Form Perception↗

PubMed2002

Multiple-object permanence tracking: limitation in maintenance and transformation of perceptual objects.

Research on change blindness and transsaccadic memory revealed that a limited amount of information is retained across visual disruptions in visual working memory. It has been proposed that visual working memory can hold four to five coherent object representations. To investigate their maintenance and transformation in dynamic situations, I devised an experimental paradigm called multiple-object permanence tracking (MOPT) that measures memory for multiple feature-location bindings in dynamic situations. Observers were asked to detect any color switch in the middle of a regular rotation of a pattern with multiple colored disks behind an occluder. The color-switch detection performance dramatically declined as the pattern rotation velocity increased, and this effect of object motion was independent of the number of targets. The MOPT task with various shapes and colors showed that color-shape conjunctions are not available in the MOPT task. These results suggest that even completely predictable motion severely reduces our capacity of object representations, from four to only one or two.

Algorithms↗