PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Visual 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 1,081 records · Page 60Linked to original sources
PubMed1985

[Activation of processes of perception and visual memory in teaching pathological anatomy].

The comparative study of different methods of student work with macroscopical preparations and different variants of slides presentation is performed. The volume of the demonstrative material reproduction was checked one week after the presentation. It was required to list in a control card a full name of macro- and microscopical preparations presented. The results of assimilation of the macroscopical preparations in collective stand demonstration and in work with the preparations in small groups or individually were evaluated. The highest level of remembering is established when every student works individually in a special room having the possibility to use textbooks and gets a preliminary notice on the reproduction of the information obtained (evaluation, control of the knowledge). The efficiency of remembering depends on both quantity and quality of the material, the presence of logical and associative links, the imagery of words in the accompanying text.

Education, Medical, Undergraduate↗
PubMed1998

[Correction of left handedness worsened mirror writing in a girl with spastic diplegia].

We experienced a 4-year-11-month old girl with right side dominant spastic diplegia caused by preterm birth and neonatal asphyxia. She tended to use the left hand but showed mirror writing on both hands, which was aggravated by correction of handedness to the right. Magnetic resonance T2-weighted imaging revealed a localized high intensity lesion in the white matter of her left parietal lobe, caused by hypoxic insult and suggested a damage of spatial orientation center. Wechsler Preschool and Primary Scale of Intelligence showed a total IQ of 76, VIQ of 86 and PIQ of 74, revealing borderline intelligence with insufficient visual perception. Frostig visual perception test revealed lower scores of position in space. Spatial confusion caused by a lesion in the left parietal lobe might have induced the mirror writing of this case. Forced correction to use the right hand with damaged left parietal lobe may aggravate spatial confusion and consequently worsen mirror writing.

Cerebral Palsy↗
PubMedDate not supplied

Visual testing for readiness to drive after stroke: a multicenter study.

OBJECTIVE: The purpose of this study was to determine the ability of a visual-perception assessment tool, the Motor-Free Visual Perception Test, to predict on-road driving outcome in subjects with stroke. DESIGN: This was a retrospective study of 269 individuals with stroke who completed visual-perception testing and an on-road driving evaluation. Driving evaluators from six evaluation sites in Canada and the United States participated. Visual-perception was assessed using the Motor-Free Visual Perception Test. Scores range from 0 to 36, with a higher score indicating better visual perception. A structured on-road driving evaluation was performed to determine fitness to drive. Based on driving behaviors, a pass or fail outcome was determined by the examiner. RESULTS: The results indicated that, using a score on the Motor-Free Visual Perception Test of < or =30 to indicate poor visual-perception and >30 to indicate good visual perception, the positive predictive value of the Motor-Free Visual Perception Test in identifying those who would fail the on-road test was 60.9% (n = 67/110). The corresponding negative predictive value was 64.2% (n = 102/159). Univariate logistic regression analyses revealed that older age, low Motor-Free Visual Perception Test scores and a right hemisphere lesion contributed significantly to identifying those who failed the on-road test. CONCLUSIONS: The predictive validity of the Motor-Free Visual Perception Test is not sufficiently high to warrant its use as the sole screening tool in identifying those who are unfit to undergo an on-road evaluation.

Aged↗
PubMed1999

Surface formation and depth in monocular scene perception.

The visual perception of monocular stimuli perceived as 3-D objects has received considerable attention from researchers in human and machine vision. However, most previous research has focused on how individual 3-D objects are perceived. Here this is extended to a study of how the structure of 3-D scenes containing multiple, possibly disconnected objects and features is perceived. Da Vinci stereopsis, stereo capture, and other surface formation and interpolation phenomena in stereopsis and structure-from-motion suggest that small features having ambiguous depth may be assigned depth by interpolation with features having unambiguous depth. I investigated whether vision may use similar mechanisms to assign relative depth to multiple objects and features in sparse monocular images, such as line drawings, especially when other depth cues are absent. I propose that vision tends to organize disconnected objects and features into common surfaces to construct 3-D-scene interpretations. Interpolations that are too weak to generate a visible surface percept may still be strong enough to assign relative depth to objects within a scene. When there exists more than one possible surface interpolation in a scene, the visual system's preference for one interpolation over another seems to be influenced by a number of factors, including: (i) proximity, (ii) smoothness, (iii) a preference for roughly frontoparallel surfaces and 'ground' surfaces, (iv) attention and fixation, and (v) higher-level factors. I present a variety of demonstrations and an experiment to support this surface-formation hypothesis.

Cues↗
PubMed2002

Visual imagery of famous faces: effects of memory and attention revealed by fMRI.

Complex pictorial information can be represented and retrieved from memory as mental visual images. Functional brain imaging studies have shown that visual perception and visual imagery share common neural substrates. The type of memory (short- or long-term) that mediates the generation of mental images, however, has not been addressed previously. The purpose of this study was to investigate the neural correlates underlying imagery generated from short- and long-term memory (STM and LTM). We used famous faces to localize the visual response during perception and to compare the responses during visual imagery generated from STM (subjects memorized specific pictures of celebrities before the imagery task) and imagery from LTM (subjects imagined famous faces without seeing specific pictures during the experimental session). We found that visual perception of famous faces activated the inferior occipital gyri, lateral fusiform gyri, the superior temporal sulcus, and the amygdala. Small subsets of these face-selective regions were activated during imagery. Additionally, visual imagery of famous faces activated a network of regions composed of bilateral calcarine, hippocampus, precuneus, intraparietal sulcus (IPS), and the inferior frontal gyrus (IFG). In all these regions, imagery generated from STM evoked more activation than imagery from LTM. Regardless of memory type, focusing attention on features of the imagined faces (e.g., eyes, lips, or nose) resulted in increased activation in the right IPS and right IFG. Our results suggest differential effects of memory and attention during the generation and maintenance of mental images of faces.

Adult↗
PubMed2003

Visual object and face processing in mild-to-moderate Alzheimer's disease: from segmentation to imagination.

Little is known about the fate of higher level visual perception and visual mental imagery in the early stages of Alzheimer's disease (AD). In this study, we assessed these abilities in a group of mild-to-moderate AD patients using tasks selected to satisfy two main criteria. First, they have been shown to be sensitive to impairments of perception and imagery caused by other neurological conditions. Second, they test specific stages of visual perception and cognition in a reasonably selective manner. These stages were (in their normal order of occurrence during perception): the segmentation of different local points of the visual field into regions belonging to distinct objects; the representation of the shapes of these segmented regions in the image; the construction of more abstract shape representations that possess constancy over changes in size, location, orientation or illumination (assessed separately for faces and objects); the use of these perceived shape representations to access stored shape representations; and the access of lexical semantic representations from these high-level visual representations. Additional tasks tested the top-down activation of earlier visual representations from the semantic level in visual mental imagery. Our findings indicate small, but in most cases reliable, impairments in visual perception, which are independent of degree of cognitive decline. Deficits in basic shape processing influenced performance on some higher level visual tasks, but did not contribute to poor performance on face processing, or to the profound deficit on object naming. The latter of these is related to semantic-lexical impairment.

Aged↗
PubMed1979

Visual field-cerebral hemisphere differences in perception of visual nonverbal stimuli.

16 subjects were tested for differences between left and right visual fields in accuracy of recognition for paired verbal and nonverbal stimuli presented at below threshold duration and at minimal intensity. Performance on the visual recognition task was also compared with scores on a written n-Ach test. The data clearly indicated superior recognition of physiognomic stimuli presented in the left visual field and above-chance-level performance of subjects' manual responses for these below-threshold stimuli. The data also hint at a possible relationship between n-Ach and accuracy of visual recognition in the left hemisphere.

Achievement↗
PubMed1989

The role of visual information in the processing of place and manner features in speech perception.

Visual information provided by a talker's mouth movements can influence the perception of certain speech features. Thus, the "McGurk effect" shows that when the syllable (bi) is presented audibly, in synchrony with the syllable (gi), as it is presented visually, a person perceives the talker as saying (di). Moreover, studies have shown that interactions occur between place and voicing features in phonetic perception, when information is presented audibly. In our first experiment, we asked whether feature interactions occur when place information is specificed by a combination of auditory and visual information. Members of an auditory continuum ranging from (ibi) to (ipi) were paired with a video display of a talker saying (igi). The auditory tokens were heard as ranging from (ibi) to (ipi), but the auditory-visual tokens were perceived as ranging from (idi) to (iti). The results demonstrated that the voicing boundary for the auditory-visual tokens was located at a significantly longer VOT value than the voicing boundary for the auditory continuum presented without the visual information. These results demonstrate that place-voice interactions are not limited to situations in which place information is specified audibly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2004

Adolescents with learning disorders have atypical EEG correlation indices. I. Correlation indices during visual discrimination.

OBJECTIVE: To find out whether 14-16-year-old pupils with visual perception disabilities have atypical EEG activation patterns during visual discrimination. METHODS: EEG correlation indices (EEGCIs), based on the waveform characteristics of two EEG signals, were used as measures of slow joint activation of cortical regions during visual discrimination in pupils with visual perception disabilities. RESULTS: During visual discrimination low EEGCIs were seen between the left temporal and both parieto-occipital EEG channels in pupils with visual perception disabilities and in pupils with a poor occupational outcome. The pupils with low performance intelligence and those with difficulties in the visual discrimination task had low EEGCIs within the left hemisphere. The left hemispheric dominance of the findings is suggested to reflect the psychophysiology of the task since visual discrimination demands attention to details (local processing) and is thus supposed to be more strongly represented in the left hemisphere. CONCLUSIONS: During visual discrimination, low EEGCIs were seen in the posterior and left hemispheric regions of pupils with disabilities in visual perception and visual discrimination and with a poor occupational outcome. SIGNIFICANCE: Low EEGCIs in posterior and left hemispheric regions during visual discrimination can to some extent be seen as neurophysiological markers for visual perception disabilities and a poor occupational outcome and imply an increased need for adjustment of the educational curriculum and a need for occupational guidance.

Adolescent↗