SEARCH · PubMed Health

Results for “Space Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources

PubMed1999

Some recent studies on the extraretinal contribution to distance perception.

Some recent studies on the extraretinal contribution to distance perception are reviewed. These experiments demonstrate that vergence can provide reliable information for judgments on the distance of proximal targets in the absence of all other cues. We argue that, although vergence is an unreliable cue at large fixation distances and is subject to a strong contraction bias when studied in isolation, these facts do not imply a minor role for vergence in near-space perception. When additional depth and distance cues are added, the contribution of vergence information becomes more complicated. We present results which indicate that the different cues to depth and distance are combined in a manner that can result in unexpected distortions of visual space. A simple heuristic model which can produce the observed distortions is outlined.

Accommodation, Ocular↗

PubMedDate not supplied

[The 4-dimensional spherical color space in the monkey].

Discrimination of colours by macaque rhesus was studied by the method of elaboration of differentiation inhibition of instrumental conditioned responses to colour stimuli. Matrix of probabilities of instrumental reactions to presentation of colour stimuli, the columns of which corresponded to the colours applied, and the lines--to series of experiments with definite reinforced colour--was processed by the method of factor analysis. Four factors describing the used colours in four-dimensional Euclidean space were singled out. Spatial structure of the seven used colours satisfies the equation of four-dimensional sphere. Two first factors are interpreted as colour-opponent red-green and yellow-blue and the third and fourth ones as achromatic light and dark neuronal channels. Perceptive space of colour stimuli based on the data of instrumental behaviour of the monkey corresponds to analogous results obtained by the method of multidimensional scaling of subjective evaluations of super-threshold colour differences for the man.

Animals↗

PubMed2003

A case of acute loss of binocular vision and stereoscopic depth perception. (The misery of acute monovision, having been binocular for 68 years).

PURPOSE: There are few personal reports in the literature, by knowledgeable vision scientists, of the loss of binocular vision. This case is reported. CASE REPORT: This 68 year old retired pediatric ophthalmologist suffered an almost total loss of vision, OD, as a result of a sudden massive hemorrhage into the vitreous body from a bridging retinal vessel, which remained after repair of a spontaneous large horseshoe retinal tear. This caused significant problems with both remaining monocular vision, cognition, and space perception. It was surprisingly disabling. A diary is included. RESULT: The author now appreciates better: 1. that the overlap and cross compensation of monocular vision is quite significant; 2. that monocular depth perception may be impaired by any type of intervening optical media; 3. that a two dimensional world is very different and vastly inferior to a three dimensional world. COMMENT: Such problems are not ordinarily expected or described in these circumstances, but considering what is in the literature, they may be more common and serious than assumed by eye care professionals, and should be taken into consideration in rendering eye care in similar situations. Loss of binocular vision results in a significant handicap even when the vision remaining in the good dominant eye is normal. It is truly remarkable to this victim that so many mature patients are willing to accept this situation in the form of surgical or optical monovision to avoid spectacles for presbyopia.

Acute Disease↗

PubMed1979

Perception: a model comprising two modes of consciousness.

A model of human perception is proposed in which conscious awareness is assumed to be the result of two separate mechanisms each involving consciousness, one outer, sensori-produced, and one inner, conceptual. By mediation of flexible memory representations the sensory data of the outer consciousness give rise to a matched "copy" in the inner consciousness which conceptually organizes the former and also serves as input to the memory store. The model is applied to some perceptual problems in vision such as ambiguous stimuli, subjective contours, space perception, a case of metacontrast, and subliminal perception.

Awareness↗

PubMed1999

Increasing confidence in vergence as a cue to distance.

Multiple cues contribute to the visual perception of an object's distance from the observer. The manner in which the nervous system combines these various cues is of considerable interest. Although it is accepted that image cues play a significant role in distance perception, controversy exists regarding the use of kinaesthetic information about the eyes' state of convergence. We used a perturbation technique to explore the contribution of vergence to visually based distance estimates as a function of both fixation distance and the availability of retinal information. Our results show that the nervous system increases the weighting given to vergence as (i) fixation distance becomes closer; and (ii) the available retinal image cues decrease. We also identified the presence of a strong contraction bias when distance cues were studied in isolation, but we argue that such biases do not suggest that vergence provides an ineffectual signal for near-space perception.

Adolescent↗

PubMedDate not supplied

[Current concepts concerning the genesis of vestibulo-vegetative disorders in weightlessness].

The up-to-date hypotheses of the genesis of vestibulo-vegetative disorders in weightlessness are taken under critical analysis. Preference is given to the concept which attaches greatest importance to the changes in stereotyped interactions of analyzers responsible for space perception. It is, however, emphasized that neither hypothesis can account for all the phenomena seen in crewmembers in orbital flight. It is, therefore, indicated that mechanisms of vestibulo-vegetative disorders need further study. It is believed that the most promising line of research is to study the role of endogenous factors determining individual variations of motion sickness susceptibility.

Autonomic Nervous System↗

PubMed2001

Perception, attention, and working memory are disproportionately impaired in dementia with Lewy bodies compared with Alzheimer's disease.

OBJECTIVE: To test the hypotheses that visuoperceptual and attentional ability are disproportionately impaired in patients having dementia with Lewy Bodies (DLB) compared with Alzheimer's disease (AD). METHODS: A comprehensive battery of neuropsychological tasks designed to assess working, episodic, and semantic memory, and visuoperceptual and attentional functions was given to groups of patients with DLB (n=10) and AD (n=9), matched for age, education, and mini mental state examination (MMSE), and to normal controls (n=17). RESULTS: Both patient groups performed equally poorly on tests of episodic and semantic memory with the exception of immediate and delayed story recall, which was worse in the AD group. Digit span was by contrast spared in AD. The most striking differences were on tests of visuoperceptual/spatial ability and attention. Whereas patients with AD performed normally on several subtests of the visual object and space perception battery, the DLB group showed substantial impairments. In keeping with previous studies, the AD group showed deficits in selective attention and set shifting, but patients with DLB were more impaired on virtually every test of attention with deficits in sustained, selective, and divided attention. CONCLUSIONS: Patients with DLB have substantially greater impairment of attention, working memory, and visuoperceptual ability than patients with AD matched for overall dementia severity. Semantic memory seems to be equally affected in DLB and AD, unlike episodic memory, which is worse in AD. These findings may have relevance for our understanding of the genesis of visual hallucinations, and the differential diagnosis of AD and DLB.

Aged↗

PubMed1996

Bisection and perception of horizontal lines in normal children.

Simple line bisection is a complex task in which both perceptual/attentional factors and motor factors are involved. Using a judgment task on prebisected lines it is possible to assess independently the role of perceptual/attentional factors. The judgment-bisection relationship was investigated in 37 preschool children aged 4-5 and 70 school children aged 10-12. At bisection, a clear shift of the right hand with age from right to left bisections was observed, more pronounced in right- than in left-handers, and probably related to learned patterns. At judgment, a slight but significant left side overestimation was observed. In right-handers, judgment was related to left-hand but not to right-hand bisection. It is concluded that motor (manual) factors strongly influence visuo-motor bisection in normal children, and it is suggested that the judgment-bisection relationship has to be systematically investigated when bisection is used as a task informing on space perception or on direction of attention.

Adolescent↗

PubMed1987

On the late invention of the stereoscope.

It was not until 1838, when Wheatstone published his account of the stereoscope, that stereoscopic depth perception entered into the body of binocular phenomena. It is argued that the stereoscope was not invented earlier because the phenomenon of stereopsis based on disparity had not been adequately described. This was the case despite the fact that there had been earlier descriptions of tasks that could be performed better with two eyes than with one; the perceptual deficits attendant upon the loss of one eye had been remarked upon; analyses of the projections to each eye were commonplace, and binocular disparities were accurately illustrated; moreover, binocular microscopes and telescopes had been made over a century earlier. Theories of binocular vision were generally confined to accounting for singleness of vision with two eyes, and the concepts employed to account for this were visible direction, corresponding retinal points, and union in the brain. The application of these concepts inhibited any consideration of disparities, other than for yielding diplopia. When perception of the third dimension was addressed by Berkeley at the beginning of the eighteenth century, it was in the context of monocular vision and binocular convergence. Thereafter visual direction became the province for binocular vision and it was analysed in terms of geometrical optics, whereas visual distance was examined in the context of learned associations between vision and touch. This artificial division was challenged initially with respect to visual direction and later with respect to stereopsis. An additional factor delaying the invention of the stereoscope was that experiments on binocular vision generally involved abnormal convergence on extended objects. Wheatstone's accidental observation of stereopsis was under artificial conditions in which disparity alone defined the binocular depth perceived. Once invented the stereoscope was enthusiastically embraced by students of vision. It is suggested that the ease with which retinal disparity could be manipulated in stereopairs has led to an exaggeration of its importance in space perception. "The appearances, which are by this simple instrument rendered so obvious, may be easily inferred from the established laws of perspective; for the same object in relief is, when viewed by a different eye, seen from the two points of sight at a distance from each other equal to the line joining the two eyes. Yet they seem to have escaped the attention of every philosopher and artist who has treated of the subjects of vision and perspective." (Wheatstone 1838, page 371).

Depth Perception↗

PubMed1992

[A study of perspective vision].

The present study describes the structure of monocular depth perception using an experimental basis. It regards the traditional theory of perspective, which is a subset of descriptive geometry, only as a construction guide for flat, albeit depth eliciting, visual stimuli. The investigation starts with a definition of structure as a set with an automorphism on it. In the present context the projection of the physical stimuli onto the retina provide a suitable ground set. After suitable confinement of the stimuli to a horizontal plane, the effects of eye and head movements of the subject can be represented as projective mappings of the retinal image onto itself. The present approach represents these as visual automorphisms. They are each characterized by a special visual invariance. The automorphisms form a group which comprises the affine, the affine unimodular and the orthogonal groups (in this order) as subgroups. Experimental studies of the different invariants of these subgroups as well as the consideration of other empirical observations lead to the conclusion that the structure of monocular space perception is characterized by the affine unimodular subgroup of the projective group. There are indications that the phenomena of size constancy can be represented by affine unimodular maps instead of orthogonal (metric) maps as sometimes has been conjectured.

Attention↗

PubMed2006

The assessment of fitness to drive in people with dementia.

OBJECTIVE: To determine whether cognitive tests predict fitness to drive in patients with dementia. DESIGN: Two group comparison of patients with dementia and healthy elderly volunteers, and comparison of patients with dementia who were found safe to drive and those found unsafe, followed by a validation study. PARTICIPANTS: Forty-two people with dementia and 33 healthy elderly volunteers with no known memory problems who were driving. Of the 42 people with dementia 37 were assessed on the road. A second sample of 17 people with dementia was also assessed on the road. MAIN MEASURES: Stroke Drivers Screening Assessment, Mini Mental State Examination, Salford Objective Recognition Test, Stroop Test, Test of Everyday Attention, Visual Object and Space Perception Battery, Behavioural Assessment of the Dysexecutive Syndrome, Adult Memory and Information Processing Battery. RESULTS: All healthy elderly volunteers were safe to drive but 10 of the 27 patients with dementia were unsafe. Discriminant function analysis identified a combination of tests, which correctly classified 92% of drivers with dementia as safe or unsafe. Validation of this prediction on an independent sample had 59% accuracy using a cut-off of 0 but 88% accuracy using a cut-off of 5. CONCLUSIONS: Safety to drive in people with dementia could be predicted from a combination of six cognitive tests. These correctly identified 67% of safe drivers in a validation sample. This assessment could be used to identify those who need evaluation of their safety on the road.

Aged↗

PubMed2003

Spatiotemporal activation of the two visual pathways in form discrimination and spatial location: a brain mapping study.

To address the question of the relationship between the two visual pathways, a ventral stream for object and form vision and a dorsal stream for spatial and motion vision, we measured the spatiotemporal activation patterns in the two pathways responding to an integrated visuospatial task to which form discrimination and spatial location were assigned simultaneously. The two cognitive components of form discrimination and spatial location were interwoven in the task; however, the fMRI data demonstrated that such a task still activated both ventral GTi/GF (the inferior temporal gyrus/the fusiform gyrus) and dorsal Ga/PCu (the angular gyrus/Precuneus), which are supposed to mediate form discrimination and spatial location, respectively. In addition, the source waveforms of the fMRI foci based on the source analysis of the fMRI-seeded dipole modeling and the moving dipole modeling indicated that in responding to the task combining simultaneously form perception and spatial location, the activity in Ga/PCu begins earlier than that in GTi/GF, but it peaks later and lasts longer.

Adult↗

PubMed1998

Sex differences in right hemisphere tasks.

We tested the hypothesis that sex differences in spatial ability and emotional perception are due to sex differences in intrahemispheric organization of the right hemisphere. If the right hemisphere is differently organized by sex-primarily specialized for spatial ability in men, but primarily specialized for emotional perception in women-then there should be a negative correlation between spatial ability and emotional perception within sex, and the greatest disparity between abilities should be found in people with characteristic arousal of the right hemisphere. Undergraduate men (N = 86) and women (N = 132) completed tests of Mental Rotation, Surface Development, Profile of Nonverbal Sensitivity, Progressive Matrices, and Chimeric Faces. Although the expected pattern of sex differences was observed, there was no evidence for the hypothesized negative correlation between spatial ability and emotional perception, even after statistical control of general intelligence.

Adult↗

PubMed1999

Change of spatial field effects in 16- to 20-week-old infants.

Infants from 16 to 20 weeks were presented with objects moving across a 60-cm distance. Tracking increased between 16 and 18 weeks, reaching increased at 18 weeks, and arm lifts (swipes) showed no age change. A right spatial field bias in tracking disappeared gradually. Swipes occurred most often in front of the object, when it was moving in the center field, presumably as reactions due to spatial proximity. Reaching occurred in the peripheral spatial fields in the younger infants, but in the older infants most often in the center spatial field. Moreover, reaching occurred generally more often toward the left spatial field and predicted the emergence of tracking the left spatial field. Thus, it appeared that a bias in reaching corrected a bias in tracking. Similar effects of limb movements, especially when reaching, were found in the successful treatment of visual neglect patients in neuropsychological research.

Female↗

PubMed1997

Development of size modification of human figure drawings in spatial axes systems of varying complexity.

In the present study, intraindividual development of the ability to modify the size of the human figure drawing was investigated. In a longitudinal data set with repeated measurement at ages 7, 9, and 12 it was shown that size was reduced between 7 and 9 years. Three factors were found to be responsible for size variation of the human figure drawing: The larger the figure initially, the more complex the level of the spatial axes system and the more persons in the picture, the greater size reduction.

Age Factors↗

PubMed2002

A parametric study of mental spatial transformations of bodies.

TWO CLASSES OF MENTAL SPATIAL TRANSFORMATION CAN BE DISTINGUISHED: Object-based spatial transformations are imagined movements of objects; and egocentric perspective transformations are imagined movements of one's point of view. The hypothesis that multiple neural systems contribute to these mental imagery operations was tested with functional MRI. Participants made spatial judgments about pictures of human bodies, and brain activity was analyzed as a function of the judgment required and the time taken to respond. Areas in right temporal, occipital and parietal cortex and the medial superior cerebellum appear to be differentially involved in object-based spatial transformations. Additionally, midline structures and lateral parietal cortex were found to decrease in activity during the spatial reasoning tasks, independently of the judgment required or of the latency of response. The results are discussed in terms of a model of spatial reasoning that postulates specialized subsystems for performing object-based and egocentric perspective image transformations.

Adult↗

PubMed1988

Perception of the immediate extrapersonal space through proprioceptive inputs.

In the present work we sought to examine the idea that an internalized representation of space can be formed and used in the absence of visual information. To this end human subjects were trained to locate 5 points within a horizontal plane at shoulder level, under guidance of an acoustic signal. Next, reaching accuracy was determined for both the trained and the untrained hands without external cues. This allowed comparison of hand positioning that could be based upon a memory trace or proprioceptive inputs (trained hand) to hand positioning that must be based upon a more abstract internal representation than proprioceptive memory (untrained hand). The effect of training on reach accuracy of the two hands and the effect of prolongation the time interval between guided and recall (unguided) trials were studied. Finally, subjects were asked to interpolate between already learned target positions, a procedure which tested their ability to utilize an abstract construct of space. The relative contribution of the elbow and shoulder joints to reaching errors was determined. This analysis served to evaluate whether representation of spatial locations was based on joint angle coordinates, or on a more abstract extracorporeal reference system. Our results indicate that a memorized sensory image of the limb, which corresponds to the hand being at the target position, is used whenever possible. An abstract representation of position is used whenever comparison of the actual sensory input to a memorized sensory trace is made impossible, costing an approximately 25% reduction in accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1979

The electroencephalogram (EEG) as a research tool in human behavior genetics: psychological examinations in healthy males with various inherited EEG variants. III. Interpretation of the results.

Interpretation of the results from psychological examinations of 298 probands with inherited EEG variants requires (1) critical evaluation of previous literature on psychological EEG correlates, (2) knowledge of the main concepts and experimental approaches for elucidating the basic mechanisms of EEG rhythms, (3) discussion of previous attempts to link psychological variation in human populations with corresponding variation in brain function, and (4) interpretation of results from considerations at these three levels with the data from our own study. At the first level (previous psychological studies), comparison with Schmettau's study proved to be especially revealing: Her conclusions about personality correlates with high alpha-index and with "flat" EEGs were very similar to ours with the monotonous alpha- (R) and low-voltage (N) EEGs, respectively. Her EEG type with high beta-index overlaps with our beta-diffuse (BD) type; a tendency to psychasthenia and low resistance to stress is less obvious in our group, but is expressed indirectly by reduced speed and accuracy in tests requiring attentiveness and persistence. The correlation between alpha-frequency and intelligence found in other studies was confirmed by the especially high intelligence scores of our group with occipital fast alpha-variants (BO). At the second and third levels of the discussion (EEG mechanisms; neurophysiological theories), the cooperation of cerebral cortex (EEG battery), thalamus (pacemaker), and ARAS (tonic arousal) is discussed, and the personality typologies of Eysenck and Claridge are mentioned. From this and other evidence, the following hypotheses are discussed: 1) The personality profiles of the R group are influenced by high activity and efficiency of the thalamic alpha-pacemaker(s), which leads to a high degree of modulation, selection, and amplification of afferent stimuli. 2) In the countertype of this EEG variant, the N EEG, a low modulation and amplification by the thalamic alpha-pacemaker is assumed. This leads to relatively low intensity of feeling and to low spontaneous activity, but to faster information processing. Combined with an increased level of tonic arousal in the ARAS, it may cause certain 'neurotic' complaints (our low-voltage borderline (NG) group). 3) The EEG with diffuse beta-waves (BD) is caused by a high level of tonic arousal in the ARAS, which tends to distrub the thalamocortical circuit. This leads to reduced stress resistance and to impairment of intellectual functions, especially space perception. Due to limited evidence, the next two hypotheses are advanced only tentatively: 4) alpha-rhythm with very high frequency 16--19 c/s) leads to improvement of information processing and, hence, to high intellectual performance and motor dexterity. 5) Probands with frontoprecentral beta-groups (BG) show no psychological signs of increased tonic arousal; therefore, these beta-groups are caused not by increased tonic arousal of the ARAS, but by a genetic variant of a thalamic subsystem.

Adult↗