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At least 1,297 records · Page 72Linked to original sources
PubMed1979

An exploration of perception of body boundary, personal space, and body size in elderly persons.

A study of 108 elderly persons using the Body Distortion Questionnaire and the personal space simulation technique test did not support hypotheses that elderly persons with a large personal space will have a larger distortion of body boundary, a larger perception of large body size, a smaller perception of small body size, a larger distortion of body size, and a larger body distortion than elderly persons with a small personal space. The analyses with one-tail t tests showed elderly persons with a small personal space have a larger perception of large body size and a larger distortion of body size than elderly persons with a large personal space. When the extremes of personal space were used the results were the same. Males have a larger personal space and greater distortion of skin perceptions than females.

Aged↗
PubMed2005

Perisaccadic perception of continuous flickers.

To realize perceptual space constancy, the visual system compensates for the retinal displacement caused by eye movements. It has been reported that the compensation process does not function perfectly around the time of a saccade--a perisaccadic flash is systematically mislocalized. However, observations made with transient flash stimuli do not necessarily indicate a general perisaccadic failure of space constancy. To investigate how the visual system realizes perisaccadic space constancy for continuous stimuli, we examined the time course of localization for a perisaccadic 500 Hz flicker with systematic variation of the onset timing, the offset timing and the duration. If each flash in the flicker is localized individually in the same way as a single flash, the apparent position and length of the flicker should be predicted from the time course of mislocalization of a perisaccadic flash. However, the results did not support this prediction in many respects. A dot array (of half the length of the retinal image) was perceived when the flicker was presented during a saccade, while only a single dot was perceived when the flicker was presented only before or after the saccade. A flash in a flicker was localized at a different position, depending on the onset timing, the offset timing and the duration of the flicker, even if the flash was presented at the same timing to the saccade. In general, our results support a two-stage localization in which the local geometrical configuration is first generated primarily based on the retinal information, and then localized as a whole in the egocentric or exocentric space. The localization is based on the eye position signal sampled at a time temporally distant from the saccade, which enables precise localization and space constancy for continuous stimuli.

Adult↗
PubMed2000

The emergence of visual objects in space-time.

It is natural to think that in perceiving dynamic scenes, vision takes a series of snapshots. Motion perception can ensue when the snapshots are different. The snapshot metaphor suggests two questions: (i) How does the visual system put together elements within each snapshot to form objects? This is the spatial grouping problem. (ii) When the snapshots are different, how does the visual system know which element in one snapshot corresponds to which element in the next? This is the temporal grouping problem. The snapshot metaphor is a caricature of the dominant model in the field-the sequential model-according to which spatial and temporal grouping are independent. The model we propose here is an interactive model, according to which the two grouping mechanisms are not separable. Currently, the experiments that support the interactive model are not conclusive because they use stimuli that are excessively specialized. To overcome this weakness, we created a new type of stimulus-spatiotemporal dot lattices-which allow us to independently manipulate the strength of spatial and temporal groupings. For these stimuli, sequential models make one fundamental assumption: if the spatial configuration of the stimulus remains constant, the perception of spatial grouping cannot be affected by manipulations of the temporal configuration of the stimulus. Our data are inconsistent with this assumption.

Humans↗
PubMed1998

Impairments of mental rotation in Parkinson's disease.

It is controversial whether parkinsonian patients are impaired on visuospatial tasks. In the present study, patients and normal control subjects judged whether pairs of wire-frame figures in different orientations were the same or different. The orientation difference between the figures was either in the picture plane (around the z-axis, or two-dimensional) or in depth (around the y-axis, or three-dimensional). Reaction times and error rates were measured. For the two-dimensional task, there were no significant differences in errors between the two groups, though Parkinsonian subjects were significantly slower to respond than the control group. In the three-dimensional task, patients had a different pattern of reaction times from the controls and made significantly more errors, which were systematic at large angular differences. The results suggest a visuospatial deficit in Parkinson's disease, which reflects problems in some aspect of the perception of extra-personal space.

Aged↗
PubMed2001

Unilateral spatial neglect.

Unilateral spatial neglect is a complex, but fascinating, deficit in attention that may occur following stroke. The phrase "unilateral spatial neglect" belies the complex mixture of disorders in representational memory, hypokinesia in the opposite hemispace, and inattention to sensory stimuli in the opposite hemispace. Unilateral spatial neglect occurs as a result of damage to the posterior parietal cortex, frontal lobe, cingulate gyrus, striatum, thalamus, or specific brain-stem nuclei. This neural network for attention is an excellent example of how different anatomic areas work together to produce a specific behavior. Traditional treatment strategies for USN have focused on training attention in the left hemispace using a variety of techniques, including sensory awareness, visual scanning, and spatial organization. Recently, additional treatment strategies have emerged that focus on representational aspects of brain functioning. These strategies have included visual and movement imagery,30 manipulation of sensory input that conveys perception of the head in space, and manipulation of visual input using prisms and eye patches. The complex nature of USN provides numerous directions for future research. Continued research will play a pivotal role in devising effective treatment strategies for patients with USN.

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