Biomedical subjects

Chie Nakatani

Publications and source records attributed to Chie Nakatani.

6 recordsLinked to original sources

PubMed2005

Phase synchronization analysis of EEG during attentional blink.

The attentional blink (AB) phenomenon occurs when perceivers must report two targets embedded in a sequence of distracters; if the first target precedes the second by 200-600 msec, the second one is often missed. We investigated AB by measuring dynamic cross-lag phase synchronization for 565 electrode pairs in 40-Hz-range EEG. Phase synchrony, on average, was higher in experimental conditions, where two targets are reported, than in control conditions, where only the second target is reported. The effect occurred in electrode pairs covering the whole head. Timing of the synchrony was crucial: Brief episodes of enhanced synchrony occurred 100-500 msec before expected target onset in AB conditions where the second target was correctly reported. These results show that intrinsic brain dynamics produce anticipatory synchronization in transient assemblies of cortical areas. Enhanced levels of anticipatory synchronization occur in response to the demands of the task in conditions where the system's limited capacity is under strain.

Adolescent↗

PubMed2004

Amodal completion as reflected by gaze durations.

In two experiments amodal completion of partly occluded shapes was investigated by recording eye movements in a directed visual-search task. Participants searched arrays of shapes in a prescribed order for target figures that could partly be occluded. Longer gaze durations were found on occlusion patterns than on truncated control patterns for targets but not for non-targets. This effect of occlusion was restricted to a subset of the stimuli. A second experiment was carried out to establish whether this restriction resulted from structural properties of the stimuli or their familiarity. Occlusion patterns in this experiment were ambiguous with respect to structure, allowing both local and global completions. One of the completions was always less familiar than the other. The results showed longer gazes only for the less familiar completions, irrespective of whether they were local or global.

Adult↗

PubMed2004

An eye movement analysis of "mental rotation" of simple scenes.

Participants saw a standard scene of three objects on a desktop and then judged whether a comparison scene was either the same, except for the viewpoint of the scene, or different, when one or more of the objects either exchanged places or were rotated around their center. As in Nakatani, Pollatsek, and Johnson (2002), judgment times were longer when the rotation angles of the comparison scene increased, and the size of the rotation effect varied for different axes and was larger for same judgments than for different judgments. A second experiment, which included trials without the desktop, indicated that removing the desktop frame of reference mainly affected the y-axis rotation conditions (the axis going vertically through the desktop plane). In addition, eye movement analyses indicated that the process was far more than a simple analogue rotation of the standard scene. The total response latency was divided into three components: the initial eye movement latency, the first-pass time, and the second-pass time. The only indication of a rotation effect in the time to execute the first two components was for z-axis (plane of sight) rotations. Thus, for x- and y-axis rotations, rotation effects occurred only in the probability of there being a second pass and the time to execute it. The data are inconsistent either with an initial rotation of the memory representation of the standard scene to the orientation of the comparison scene or with a holistic alignment of the comparison scene prior to comparing it with the memory representation of the standard scene. Indeed, the eye movement analysis suggests that little of the increased response time for rotated comparison scenes is due to something like a time-consuming analogue process but is, instead, due to more comparisons on individual objects being made (possibly more double checking).

Concept Formation↗

PubMed2003

Perceptual switching, eye movements, and the bus paradox.

According to a widely cited finding by Ellis and Stark (1978 Perception 7 575-581), the duration of eye fixations is longer at the instant of perceptual reversal of an ambiguous figure than before or after the reversal. However, long fixations are more likely to include samples of an independent random event than are short fixations. This sampling bias would produce the pattern of results also when no correlation exists between fixation duration and perceptual reversals. When an appropriate correction is applied to the measurement of fixation durations, the effect disappears. In fact, there are fewer actual button-presses during the long intervals than would be expected by chance. Moving-window analyses performed on eye-fixation data reveal that no unique eye event is associated with switching behaviour. However, several indicators, such as blink frequency, saccade frequency, and the direction of the saccade, are each differentially sensitive to perceptual and response-related aspects of the switching process. The time course of these indicators depicts switching behaviour as a process of cascaded stages.

Adult↗

PubMed2002

Viewpoint-dependent recognition of scenes.

Three experiments investigated scene recognition across viewpoint changes, involving same/different judgements on scenes consisting of three objects on a desktop. On same trials, the comparison scene appeared either from the same viewpoint as the standard scene or from a different viewpoint with the desktop rotated about one or more axes. Different trials were created either by interchanging the locations of two or three of the objects (location change condition), or by rotating either one or all three of the objects around their vertical axes (orientation change condition). Response times and errors increased as a function of the angular distance between the standard and comparison views, but this effect was bigger for rotations around the vertical axis than for those about the line of sight or horizontal axis. Furthermore, the time to detect location changes was less than that to detect orientation changes, and this difference increased with increasing angular disparity between the standard and comparison scenes. Rotation times estimated in a double-axis rotation were no longer than other rotations in depth, indicating that alignment was not necessarily simpler around a "natural" axis of rotation. These results are consistent with the hypothesis that scenes, like many objects, may be represented in a viewpoint dependent manner and recognized by aligning standard and comparison views, but that the alignment of scenes is not a holistic process.

Feedback↗

PubMed2002

A case of angiosarcoma of the nose.

A case of angiosarcoma arising from the nose of a 69-year-old man is presented in this report. The patient was treated with a combination of recombinant interleukin-2 (rIL-2, Celeuk), electron beam irradiation, and surgery. He died 27 months after diagnosis, but there was no apparent remote metastasis.

Aged↗