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At least 199 records · Page 11Linked to original sources
PubMed1999

Keeping perception accurate.

Perception should change if an error in perception is detected. Yet how can information that comes through the senses ever indicate that those very senses aren't accurate? Knowledge of objects that arises independently of sensory experience can be used to check the sensory information for errors. For instance, an a priori constraint that one object cannot be in two places at the same time would lead to error detection if the sensory systems suggest that one object is in two places. Variants on the classic prism-adaptation phenomenon have revealed new rules about changes in space perception. These variants involve specifying new unusual mappings between visual space and motor (proprioceptive) space, and testing for generalization to novel untrained locations. The research has suggested that there is a preference for changes in space perception that shift space rigidly everywhere, that shrink or expand space uniformly, and that preserve the one-to-one relationship between modalities. Finally, this review discusses the issue that perception must change to remain accurate in the face of childhood growth and adult drift.

Journal Article↗
PubMed1994

Two metric solutions to three-dimensional reconstruction for an eye in pure rotations.

A problem in space perception concerns how a mobile observer acquires information about the structure of objects. Earlier research derived the optic-flow equations for an eye undergoing pure rotations. It was suggested that, by utilizing three points and two views, one can recover the distance of points and the motion parameters. The radius of the eyeball was the metric unit. Yet the common view regards this problem as indeterminate. We derived a unique solution in the discrete case, which required three points and two views. However, when we observed a single bright point, a substantial amount of visual stability existed. We therefore derived a solution in the differential approach for a single point, which is based on a distinction that we made between mathematical and visual points. Both solutions were checked with a computer simulation and were found to be accurate, supporting the space perception in navigation (SPIN) theory.

Computer Simulation↗
PubMed2006

Identification of latent variables in a semantic odor profile database using principal component analysis.

Many classifications of odors have been proposed, but none of them have yet gained wide acceptance. Odor sensation is usually described by means of odor character descriptors. If these semantic profiles are obtained for a large diversity of compounds, the resulting database can be considered representative of odor perception space. Few of these comprehensive databases are publicly available, being a valuable source of information for fragrance research. Their statistical analysis has revealed that the underlying structure of odor space is high dimensional and not governed by a few primary odors. In a new effort to study the underlying sensory dimensions of the multivariate olfactory perception space, we have applied principal component analysis to a database of 881 perfume materials with semantic profiles comprising 82 odor descriptors. The relationships identified between the descriptors are consistent with those reported in similar studies and have allowed their classification into 17 odor classes.

Cluster Analysis↗
PubMed2004

Cognitive changes in patients with Huntington's disease (HD) and asymptomatic carriers of the HD mutation--a longitudinal follow-up study.

OBJECTIVE: Objective information about the onset and progression of cognitive impairment in Huntington's disease (HD) is very important in the light of appropriate outcome measures when conducting clinical trials. Therefore, we evaluated the progression of cognitive functions in HD patients and asymptomatic carriers of the HD mutation (AC) over a 2.5-year period. We also sought to detect the earliest markers of cognitive impairment in AC. METHODS: A prospective study comparing HD patients, clinically asymptomatic HD mutation-carriers (AC) and non-carriers (NC). These groups were examined three times during a period of 2.5 years. At baseline the study sample consisted of 49 subjects. Forty-two subjects (19 HD patients, 12 AC and 11 NC) completed three assessments. A battery of neuropsychological tests measuring intelligence, attention, memory, language, visuospatial perception, and executive functions was performed. RESULTS: The performance of HD patients deteriorated on the following cognitive tests: Symbol Digit Modalities Test (SDMT), Stroop Colour and Word, Boston Naming Test (BNT), Object and Space Perception and Trail Making Test-B. Longitudinal comparison of AC and NC revealed that performances on SDMT, Block Span, Digit Span Backwards, Hopkins Verbal Learning Test (learning and delayed recall) and Conditional Associative Learning Test are impaired in AC. CONCLUSIONS: Tasks measuring mainly attention, object and space perception and executive functions adequately assess the progression of HD disease. Other cognitive functions do not significantly deteriorate. Furthermore, problems in attention, working memory, verbal learning, verbal long-term memory and learning of random associations are the earliest cognitive manifestations in AC.

Adult↗
PubMedDate not supplied

[The perceptive brightness space in the carp (Carpio cyprinus L.)].

Brightness discrimination of black-white (in the range of 0.0082-0.214 W/m2; CIE chromaticity coordinates X = 0.340, Y = 0.354) and red (in the range of 0.0035-0.106 W/m2; CIE chromaticity coordinates X = 0.641, Y = 0.342) stimuli was studied during using choice conditioning paradigm in two carps. Confusion matrices for black-white and red stimuli separately were constructed from probabilities of instrumental responses (catching of a bead) to conditioned and differential stimuli in sequential six series in which one of ten intensities used in the experiment served as a conditioned stimulus. Confusion matrices were transformed into correlation matrices between the vectors which corresponded to the applied stimuli. Principal component analysis revealed two-dimensional circular structure of carp's brightness perceptual space both for achromatic and for red stimuli. This space was principally similar to that in humans. Two eigenvectors which constitute two-dimensional Euclidean space of brightness may be interpreted as bright and dark neuronal channels.

Animals↗
PubMed2000

Perceiving binocular depth with reference to a common surface.

A common surface is a spatial regularity of our terrestrial environment. For instance, we walk on the common ground surface, lay a variety of objects on the table top, and display our favorite paintings on the wall. It has been proposed that the visual system utilizes this regularity as a reference frame for coding objects' distances. Presumably, by treating the common surface as such--i.e. an anticipated constant--the visual system can reduce its coding redundancy, and divert its resources to representing other information. For intermediate-distance space perception, it has been found that absolute distance judgment is most accurate when a common ground surface is available. Here we explored if the common surface also serves as the reference frame for the processing of binocular-disparity information, which is a predominant cue for near-distance space perception. We capitalized on an established observation where the perceived slant of a surface with linear binocular-disparity gradient is underestimated. Clearly, if the visual system utilizes this incorrectly represented slant surface as a reference frame for coding the objects' locations, the perceived depth separation between the objects will be adversely affected. Our results confirm this, by showing that the depth judgment of objects (two laterally separated vertical lines) on, or in the vicinity of, the surface is underestimated. Furthermore, we show that the impact of the common surface on perceived depth separation most likely occurs at the surface-representation level where the visual surface has been explicitly delineated, rather than at the earlier disparity-processing level.

Cues↗
PubMed2002

Illusions in action: consequences of inconsistent processing of spatial attributes.

Many authors have performed experiments in which subjects grasp objects in illusory surroundings. The vast majority of these studies report that illusions affect the maximum grip aperture less than they affect the perceived size. This observation has frequently been regarded as experimental evidence for separate visual systems for perception and action. In order to make this conclusion, one assumes that the grip aperture is based on a visual estimate of the object's size. We believe that it is not, and that this is why size illusions fail to influence grip aperture. Illusions generally do not affect all aspects of space perception in a consistent way, but mainly affect the perception of specific spatial attributes. This applies not only to object size, but also to other spatial attributes such as position, orientation, displacement, speed, and direction of motion. Whether an illusion influences the execution of a task will therefore depend on which spatial attributes are used rather than on whether the task is perceptual or motor. To evaluate whether illusions affect actions when they influence the relevant spatial attributes we review experimental results on various tasks with inconsistent spatial processing in mind. Doing so shows that many actions are susceptible to visual illusions. We argue that the frequently reported differential effect of illusions on perceptual judgements and goal-directed action is caused by failures to ensure that the same spatial attributes are used in the two tasks. Illusions only affect those aspects of a task that are based on the spatial attributes that are affected by the illusion.

Cues↗
PubMedDate not supplied

[The perceptive color space of the rabbit].

Discrimination of colors was studied using instrumental learning paradigm in three rabbits (Oryctolagus cuniculus). The rabbits were able to discriminate all but red stimuli by their color. The red stimulus could not be discriminated from the black one. The confusion matrix composed of probabilities of instrumental reactions was subjected to factor analysis in order to reveal the basic axes of the color perceptual space. The four-dimensional spherical structure of perceptual color space was obtained, which was different from that of trichromatic species in a reduction of color axes in red and yellow parts. The evidence characterizes rabbit as a protanopic animal.

Animals↗
PubMedDate not supplied

[The perceptive color space in the carp (Carpio cyprinus L.)].

Discrimination of colours was studied using choice conditioning paradigm (one of a pair of colour stimuli) in carps. Matrix of probabilities of instrumental reactions (catching a bead) was constructed by the results of eight experimental sessions with successive reinforcement of one of the eight colours. It was processed by factor analysis. The spherical structure of carp's perceptual colour space revealed by factor analysis was similar to that of monkeys and humans. Four eigenvectors which constituted four-dimensional Euclidean hypersphere corresponded to excitation of four colour-encoding neuronal channels, i.e., red-green, blue-yellow, bright and dark.

Animals↗
PubMed2003

Two different streams form the dorsal visual system: anatomy and functions.

There are two radically different views on the functional role of the dorsal visual stream. One considers it as a system involved in space perception. The other is of a system that codes visual information for action organization. On the basis of new anatomical data and a reconsideration of previous functional and clinical data, we propose that the dorsal stream and its recipient parietal areas form two distinct functional systems: the dorso-dorsal stream (d-d stream) and the ventro-dorsal stream (v-d stream). The d-d stream is formed by area V6 (main d-d extrastriate visual node) and areas V6A and MIP of the superior parietal lobule. Its major functional role is the control of actions "on line". Its damage leads to optic ataxia. The v-d stream is formed by area MT (main v-d extrastriate visual node) and by the visual areas of the inferior parietal lobule. As the d-d stream, v-d stream is responsible for action organization. It, however, also plays a crucial role in space perception and action understanding. The putative mechanisms linking action and perception in the v-d stream is discussed.

Animals↗