[Disorders of space and time perception with special reference to mescaline hallucinations].
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Hallucinations↗
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Results for “Space Perception”
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[Evaluation of the effects of psychomotor reeducation in aged patients with dementia].
Psychomotor re-education has been attempted experimentally with a population of demented patients in a geriatric ward. It draws on the methods employed at the Bel Air Psychiatric Clinic, in particular the principle of transfer of training. To assess the effect, if any, of the therapy, two psychological rating scales devised specially for demented patients, were established by the team of psychologists at the Grenoble Teaching Hospital. These rating scales are based on the theoretical notions of J. de AJURIAGUERRA and colleagues, that is, the concepts of structural analysis, of involution and homogeneity or inhomogeneity. The psychological test rating scale proposed explores four aspects of mental activity : memory, operating mechanisms, visual defects, space perception and orientation. The rating scale is described in detail, with its references, instructions and scoring.
Aged↗
Influence of the instructions on the performance and establishment of memorization strategies in space judgments.
Studies of visual space perception have been assuming that people have an internal representation of the physical space that surrounds them. A variety of psychophysical procedures has been used in an attempt to measure the properties of visual space. The goal of the present study was to evaluate the accuracy of the mental representation and the strategies adopted to acquire and retain visuo-spatial information of a configuration as a function of two types of instructions. Thirty-eight undergraduate and graduate students participated in the study and were distributed in perceptive and mnemonic experimental conditions. The effect of the instructions (intentional and incidental) on the representation of the distances among the objects of the scene was estimated using exponents of power function, based on the reproduction of the distances among the stimuli of the scene. The results revealed that judgments made under intentional instructions were more frequently based on strategies related to the location of the stimuli, whereas judgments originating from incidental instructions were based on strategies related to the name of the stimuli. It was observed that the intentional instruction facilitated a more accurate mental representation of the observed experimental configuration, enhancing participants' performance.
Adolescent↗
Studies in visual perception of architectural spaces and rooms.
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Architecture↗
Topographical amnesia.
The ability to learn to criterion a visually-guided stylus maze was found impaired in patients with right posterior cerebral damage, not only in comparison with controls but also with other hemisphere-damaged groups. The contribution of the corresponding left sided area to this task is dubious, and certainly not substantial. This finding points to the independent organisation of long-term spatial memory in the right posterior cerebral cortex, an inference that was further supported by the study of two cases. The first was a female patient with right temporo-parietal softening (as suggested by clinical, EEG, and brain scan data) who showed topographical amnesia and inability to learn the visual maze over 275 trials. On an extensive battery of tests she was found free from disorders of space perception, and from verbal and visual memory impairment. The second was a patient presenting with severe global amnesia who, nevertheless, had no difficulty in route finding, and reached the criterion on the maze in 31 trials.
Amnesia↗
A case study of space-time distortion during a total lunar eclipse following street use of LSD.
Although psychedelics can induce "cosmic" consciousness through severe distortions of time and space perceptions, little attention has been given to examination of this psychopharmacological property. With the hope of providing an impetus to further research in this area, a case of cosmic perception under the influence of LSD is reported which included the apparent movement of consciousness to the lunar surface combined with the experience of remote viewing of the Milky Way galaxy. While the possibility of veridical remote viewing is unlikely, it is speculated that the neurocognitive action of LSD can sensitize the user to focused bright light, associated memories, and creative elaborations during actual eclipse events. Experimenters are urged to adopt precautions to avoid potentially detrimental effects of pharmacologically manipulating the space-time continuum.
Adult↗
Motor and cognitive functions of the ventral premotor cortex.
Recent data show that the ventral premotor cortex in both humans and monkeys has motor and cognitive functions. The cognitive functions include space perception, action understanding and imitation. The data also show a clear functional homology between monkey area F5 and human area 44. Preliminary evidence suggests that the ventral part of the lateral premotor cortex in humans may correspond to monkey area F4. A tentative map of the human lateral premotor areas founded on the reviewed evidence is presented.
Anatomy, Comparative↗
Visuospatial functions in atypical parkinsonian syndromes.
OBJECTIVES: Visuospatial deficits have been occasionally reported but never systematically studied in atypical parkinsonian syndromes. The interpretation of existing studies is complicated by the possible influence of motor and frontal executive deficits. Moreover, no attempt has been made to distinguish visuoperceptual from visuospatial tasks. The aim of the present study was to assess visuoperceptual and visuospatial abilities in three atypical parkinsonian syndromes while minimising the influence of confounding variables. METHODS: Twenty patients with multiple system atrophy (MSA), 43 with progressive supranuclear palsy (PSP), and 25 with corticobasal degeneration (CBD) as well as 30 healthy age matched controls were examined with the Visual Object and Space Perception Battery (VOSP). RESULTS: Visuospatial functions were intact in MSA patients. PSP patients showed mild deficits related to general cognitive decline and the severity of oculomotor symptoms. The CBD group showed the most pronounced deficits, with spatial tasks more impaired than object based tasks. Performance on object based, but not spatial, tasks was related to general cognitive status. The extent of the visuospatial impairment could not be predicted from disease duration or severity. CONCLUSION: Visuospatial functions are not consistently impaired in atypical parkinsonian syndromes. The degree and pattern of impairment varies across the diseases, suggesting that the observed deficits could have a different neural basis in each condition. The distinction between the object based ("ventral stream") and the space oriented ("dorsal stream") processing might be useful in the interpretation of visuospatial deficits in parkinsonian syndromes, especially in CBD.
Aged↗
Monocular spatial distortion in strabismic amblyopia.
We examined monocular spatial vision of strabismic amblyopes by measuring errors of relative directionalization (specifying whether or not two targets are in vertical alignment) and partitioning (equating left- and right-field spaces). Abnormally large errors were made when fixation occurred with the amblyopic eye; these errors did not attributable to reduced acuity, unsteady fixation, or eccentric fixation. From the results we infer that monocular space perception of strabismic amblyopic eyes is severely distorted and is characterized by "bending" of vertical lines of direction and by local "compressions" and "expansions" of horizontal spatial values. Such distortions can readily account for many of the oculomotor abnormalities of the amblyopic eye as well as for the strabismic subject's phenomenological description of the difficulties experienced in using this eye--difficulties that are typically much worse than the reduced acuity would predict.
Amblyopia↗
[Adaptation of visual distortions in children with strabismic amblyopia following strabismus surgery and occlusion therapy].
BACKGROUND: Reduced visual acuity and deficient binocularity are well-known symptoms of amblyopia. Distortions of visual space perception were reported more recently in strabismic amblyopia. This study investigated whether strabismus surgery and occlusion therapy have an influence on these deficits in amblyopic children. MATERIALS AND METHODS: Two aspects of vertical alignment of amblyopic eyes, namely spatial distortion and spatial uncertainty, were investigated prospectively in 13 children (mean age 6 years 9 months) before and after strabismus surgery and in 12 children (mean age 6 years 11 months) during 6 months of occlusion therapy. RESULTS: A different impact of the two types of therapeutic intervention was observed: a slight (statistically not significant) increase of uncertainty was the only change noticed postoperatively after 1 week, spatial distortions were not affected. During occlusion treatment, both clear shifts of alignment and a decrease of uncertainty occurred. CONCLUSIONS: The geometry of visual space of amblyopic children showed modifications due to altered visual experience during treatment, most obviously during occlusion therapy. These changes are evidence for unknown features of plasticity of the amblyopic visual system initiated by treatment.
Amblyopia↗
Acoustical vision of neglected stimuli: interaction among spatially converging audiovisual inputs in neglect patients.
Cross-modal spatial integration between auditory and visual stimuli is a common phenomenon in space perception. The principles underlying such integration have been outlined by neurophysiological and behavioral studies in animals (Stein & Meredith, 1993), but little evidence exists proving that similar principles occur also in humans. In the present study, we explored such possibility in patients with visual neglect, namely, patients with visuospatial impairment. To test this hypothesis, neglect patients were required to detect brief flash of light presented in one of six spatial positions, either in a unimodal condition (i.e., only visual stimuli were presented) or in a cross-modal condition (i.e., a sound was presented simultaneously to the visual target, either at the same spatial position or at one of the remaining five possible positions). The results showed an improvement of visual detection when visual and auditory stimuli were originating from the same position in space or at close spatial disparity (16 degrees ). In contrast, no improvement was found when the spatial separation of visual and auditory stimuli was larger than 16 degrees. Moreover, the improvement was larger for visual positions that were more affected by the spatial impairment, i.e., the most peripheral positions in the left visual field (LVF). In conclusion, the results of the present study considerably extend our knowledge about the multisensory integration, by showing in humans the existence of an integrated visuoauditory system with functional properties similar to those found in animals.
Acoustic Stimulation↗
[Behavior of cats after unilateral section of the brachii of the inferior colliculi].
In experiments on 13 cats a unilateral section of the brachii of inferior colliculi produced a stable interhemispheric asymmetry not only in the auditory system, but in other (vestibular, visual, somatic, olfactory) analysers as well, which led to a disturbance of adequate space perception. This was manifested in orienting reactions directed only to the side of brain lesion. Animals were no more able to distinguish between the right and left troughs either by spatial or by modal cues. A complete "disregard" by the animals of the trough contralateral to the side of lesion suggests a hemispheric lateralization of conditioned connections providing for an adequate direction of the animals' running.
Animals↗
Underestimation of contralateral space in neglect: a deficit in the "where" task.
Space perception was investigated in right brain damaged patients with ( N=13) and without neglect ( N=5; control group). Patients were requested to localise a target tachistoscopically flashed at various eccentricities along the horizontal meridian. All patients had an intact visual field and spared ability to manually point to a target. To segregate magno- and parvo-pathway activity, stimuli modulated in either luminance or chromatic contrast were used. Patients were required to verbally report the stimulus position (verbal task) or to manually point to the stimulus (pointing task). Neglect patients reported the stimuli in the left visual field closer to the centre than they actually were. In the verbal test, underestimation was about 7 deg at the most eccentric position tested (20 deg), and decreased linearly for smaller eccentricities. The effect was similar but less marked in the pointing task. No difference was found for stimuli with luminance or chromatic contrast. Space underestimation was confined to the contralesional space; no evidence of misperception was detected in the ipsilesional hemifield. The present findings are consistent with the view that contralesional space representation is compressed in neglect patients.
Adult↗
Ocular scanning and perceptual size distortion in hemispatial neglect: effects of prism adaptation and sequential stimulus presentation.
When asked to compare two lateralized shapes for horizontal size, neglect patients often indicate the left stimulus to be smaller. Gainotti and Tiacci (1971) hypothesized that this phenomenon might be related to a rightward bias in the patients' gaze. This study aimed to assess the relation between this size underestimation and oculomotor asymmetries. Eye movements were recorded while three neglect patients judged the horizontal extent of two rectangles. Two experimental manipulations were performed to increase the likelihood of symmetrical scanning of the stimulus display. The first manipulation entailed a sequential, rather than simultaneous presentation of the two rectangles. The second required adaptation to rightward displacing prisms, which is known to reduce many manifestations of neglect. All patients consistently underestimated the left rectangle, but the pattern of verbal responses and eye movements suggested different underlying causes. These include a distortion of space perception without ocular asymmetry, a failure to view the full leftward extent of the left stimulus, and a high-level response bias. Sequential presentation of the rectangles and prism adaptation reduced ocular asymmetries without affecting size underestimation. Overall, the results suggest that leftward size underestimation in neglect can arise for a number of different reasons. Incomplete leftward scanning may perhaps be sufficient to induce perceptual size distortion, but it is not a necessary prerequisite.
Adaptation, Physiological↗
Two-dimensional spatial distortions in human strabismic amblyopia.
Two-dimensional space perception was measured in the central visual field of amblyopic subjects under special consideration of spatial distortions and spatial uncertainty. The subjects had to construct circles with different radii around a given fixation point. Subjects with deep strabismic amblyopia were showed to exhibit considerable distortion in the amblyopic eye. Each subject exhibited an individual distortion pattern. The dominant eye showed distortions similar to those seen in normal observers. Subjects with mild strabismic amblyopia, strabismic alternators and anisometropic amblyopes did not exhibit any significant spatial distortions. Data from dichoptic localization experiments indicate that anomalous retinal correspondence might contribute to monocular spatial distortions.
Adult↗
Modality-specific frontal and parietal areas for auditory and visual spatial localization in humans.
Although the importance of the posterior parietal and prefrontal regions in spatial localization of visual stimuli is well established, their role in auditory space perception is less clear. Using positron emission tomography (PET) during auditory and visual spatial localization in the same subjects, modality-specific areas were identified in the superior parietal lobule, middle temporal and lateral prefrontal cortices. These findings suggest that, similar to the visual system, the hierarchical organization of the auditory system extends beyond the temporal lobe to include areas in the posterior parietal and prefrontal regions specialized in auditory spatial processing. Our results may explain the dissociation of visual and auditory spatial localization deficits following lesions involving these regions.
Adult↗
"Acoustical vision" of below threshold stimuli: interaction among spatially converging audiovisual inputs.
Crossmodal spatial integration between auditory and visual stimuli is a common phenomenon in space perception. The principles underlying such integration have been outlined by neurophysiological and behavioral studies in animals; this study investigated whether the integrative effects observed in animals also apply to humans. In this experiment we systematically varied the spatial disparity (0 degrees, 16 degrees, and 32 degrees) and the temporal interval (0, 100, 200, 300, 400, and 500 ms) between the visual and the auditory stimuli. Normal subjects were required to detect visual stimuli presented below threshold either in unimodal visual conditions or in crossmodal audiovisual conditions. Signal detection measures were used. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a simple spatial and temporal rule, governing multisensory integration at the neuronal level.
Acoustic Stimulation↗
Shift in sound localization induced by rTMS of the posterior parietal lobe.
Neuroimaging studies in human subjects and single-unit recordings in monkeys have suggested the primate posterior parietal cortex (PPC) to be involved in auditory space perception. Here we tested this hypothesis by combining repetitive focal transcranial magnetic stimulation (rTMS) of the right PPC with a task of pointing to free-field-sound stimuli. After a period of 15 min rTMS at 1Hz, subjects exhibited an overall signed error in pointing by 2.5 degrees, directed to the left and downward, with reference to a baseline condition with "sham rTMS". No effects of rTMS on the general precision of sound localization (unsigned errors) were found. Thus, low-frequency offline rTMS may have specifically affected neuronal circuits transforming auditory spatial coordinates in both azimuth and elevation. This is in accordance with the view that the PPC may represent a neural substrate of the perceptual stability in spatial hearing.
Acoustic Stimulation↗