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PubMedDate not supplied

Situational cues in visual speech perception by geriatric subjects.

Situational cues have been known to enhance visual speech perception. In the present study the influence of relevant and nonrelevant visual and auditory background information on visual perception of everyday sentences was measured in geriatric subjects using videotaped material. Results indicated that visual speech perception with relevant situational cues was significantly different from performance when nonrelevant cues were provided and when situational cues were absent. Individual subject deviations in performance were noted and their therapeutic implications were presented.

Acoustic Stimulation↗
PubMed1980

Effects of a remedial program on visual-motor perception in spina bifida children.

Most studies dealing with spina bifida children concentrate on medical or physical factors, largely ignoring any psychosocial and educational consequences. The present study assessed the effect of a remedial program on visual-motor perception in spina bifida children. Thirty-six spina bifida boys and girls (mean age 82.87 months) with a myelomeningocele and an associated hydrocephalus were assigned randomly to either a control, attention-placebo, or experimental group. Following the administration of the Frostig Program for the Development of Visual Perception, the experimental group significantly improved on a global index of visual perception and the five subtests of Frostig's Development Test of Visual Perception; at a maintenance test two months later, all treatment gains (except on the visual spatial perception subtest) were still evident. These results are discussed in terms of the provision of remedial education for spina bifida children, and a possible cognitive mechanism mediating the behavioral change in the experimental group.

Child↗
PubMed2002

Visual spatial perception and surgical competence.

BACKGROUND: Proficiency in visual spatial perception (VSP) is a hypothetical component of surgical competence. METHODS: Four tests of VSP, taken from the Cognitive Laterality Battery (CLB), were administered to 301 surgeons and surgical residents. Mean scores on each test were compared by Student t tests to those of the normative sample (n = 251) on which the test was originally standardized. RESULTS: Mean scores on two of the tests (Orientation, Touching Blocks) were significantly greater (P <0.01) for the study sample than for the normative sample, while mean scores on the other two subtests (Form Completion, Localization) were not. CONCLUSIONS: Surgeons tend to outperform the general population on tests of high-level VSP abilities (ie, envisioning depth and mentally manipulating two-dimensional representations of three-dimensional structures) identified previously as correlates of surgical skill acquisition. VSP proficiency is a valid component of surgical competence that should perhaps be included in career selection discussions with medical students and in assessment of the competence of surgeons.

Adult↗
PubMed1995

Role of peripheral vision in terms of critical perception--its relevance to the visually impaired.

It is recognised that discrimination of fine detail is dependent on an intact macula with the peripheral retina being responsible for motion detection. There is evidence, however, to suggest that the peripheral retina does play a critical part in such discrimination. Studies of the performance of visually impaired school children have revealed levels of visual perception far exceeding anything that would be expected for individuals so severely handicapped. The art work of visually impaired youngsters was compared with the predicted results based on their visual acuity. The results showed detail that in theory could not have been resolved with such low acuity levels. All the youngsters had dense central scotomata. The peripheral retina, therefore, must have been involved in the discrimination of such detail. These results have implications not only for the visually impaired in terms of what they are capable of doing, but also for our understanding about the way the visual cortex processes information from the peripheral retina and the use that it makes of this relatively poor quality information.

Blindness↗
PubMed1998

Bilateral vestibular failure impairs visual motion perception even with the head still.

Visual motion perception of a single object, moving with a constant angular velocity of 40 min of arc/s in four orthogonal directions, was measured in eight patients with chronic bilateral vestibular failure (BVF) with the head stationary. Perception of object motion was more severely impaired for horizontal than for vertical directions and the impairment was more pronounced in the dominant eye than the nondominant eye. Impaired motion perception in patients with BVF is best explained by a central visual mechanism that suppresses oscillopsia due to the involuntary retinal slip caused by the defective vestibulo-ocular reflex (VOR). This mechanism cannot be switched off with the head stationary (inactive VOR) and thus causes a measurable deficit of motion perception.

Adult↗
PubMedDate not supplied

[Effect of genotype on evoked potentials of the left and right hemispheres during perception of visual stimuli].

Intrapair similarity of evoked potentials (EPs) to light flash, checkerboard, house picture, the word "house" and a number of other stimuli was estimated in 20 pairs of monozygotic and 20 pairs of dizygotic adult twins of the same gender. In the right temporal area the level of the genotypic control of amplitude-temporal parameters of EPs on the whole is higher than in the left one; the more prominent this difference is in responses to spatial-structural stimuli. In the left temporal area, the genotypic control is manifested in latencies of components of EPs to linguistic stimuli.

Adolescent↗
PubMed1999

Attention to facial regions in segmental and prosodic visual speech perception tasks.

Two experiments were conducted to test the hypothesis that visual information related to segmental versus prosodic aspects of speech is distributed differently on the face of the talker. In the first experiment, eye gaze was monitored for 12 observers with normal hearing. Participants made decisions about segmental and prosodic categories for utterances presented without sound. The first experiment found that observers spend more time looking at and direct more gazes toward the upper part of the talker's face in making decisions about intonation patterns than about the words being spoken. The second experiment tested the Gaze Direction Assumption underlying Experiment 1--that is, that people direct their gaze to the stimulus region containing information required for their task. In this experiment, 18 observers with normal hearing made decisions about segmental and prosodic categories under conditions in which face motion was restricted to selected areas of the face. The results indicate that information in the upper part of the talker's face is more critical for intonation pattern decisions than for decisions about word segments or primary sentence stress, thus supporting the Gaze Direction Assumption. Visual speech perception proficiency requires learning where to direct visual attention for cues related to different aspects of speech.

Adult↗
PubMed1993

Clinicopathological correlations of visual depth perception in patients with cerebrovascular disease.

Visual depth perception in 100 patients with cerebrovascular disease was evaluated using the Titumus stereotest. Twelve patients showed depth perception impairment. CT scans revealed that the lesion was located on the right hemisphere in 6 patients and on the left hemisphere in 3 patients, and that the remaining 3 patients had multiple infarctions. 123I SPECT was performed in 7 patients with moderate to severe depth perception impairment, of whom 6 patients showed a reduced blood flow in the posterior half of both the right and left cerebral hemispheres. Moderate to severe impairment of depth perception was more frequently observed in patients with a lesion in the right hemisphere or in the posterior half of either hemisphere.

Aged↗
PubMed1993

On spatial frequencies and cerebral hemispheres: some remarks from the electrophysiological and neuropsychological points of view.

The spatial frequency hypothesis on hemispheric specialization gave rise to contradictory experimental results, commented on in Brain and Cognition by Christman (1989) and Peterzell (1991). The question is discussed through a review of the electrophysiological and neuropsychological research on hemispheric asymmetry of spatial frequency processing. The general hypothesis of the hemispheric specialization for this basic visual information appears to be supported by recent works on evoked potentials by gratings and checkerboards. However, an interaction between the cerebral hemisphere, spatial frequency, and temporal frequency was found more than a sharp dichotomy between low (right hemisphere) and high spatial frequencies (left hemisphere), as indeed it was proposed by the spatial frequency hypothesis. Other relevant physical parameters in generating the hemispheric asymmetry were found to be the contrast and the visual field size. The neuropsychological research on brain-injured patients has given some further evidence of the hemispheric asymmetry in spatial frequency processing. In conclusion, it is argued that the major merit of the spatial frequency hypothesis was in the attempt to investigate the hemispheric specialization of lower and higher levels of visual information processing from the perspective of a unified computational conception of visual perception.

Brain↗
PubMed1999

Serial attention mechanisms in visual search: a critical look at the evidence.

Until a few years ago, visual search tasks were of exclusive pertinence to psychophysicists and cognitive psychologists trying to understand the operating principles and computational constraints of visual perception and visual selective attention. In recent years, cognitive neuroscience, with its powerful tools, has started to explore more directly the neuronal mechanisms underlying search performance in humans and macaques, aiming at the same general goals. New observations from a number of cognitive neuroscience approaches are promising a near future of great excitement in this field of research. This article offers a critical review of some of these recent contributions and highlights some of the interpretational problems that they pose.

Animals↗
PubMed1987

Impaired emotional recognition following severe head injury.

Four tests of emotional recognition from facial expression and posture cues were administered to 15 male closed head injury patients who had previously shown no impairment on a visual perception task. An equivalent number of controls matched for sex, age and verbal IQ were administered the same tests. Only those stimuli which validly depicted the stated emotion, identified by the controls performance, were included in the final analyses. Head injury patients were impaired on emotional recognition across all four tests compared to controls. No relationship between age, verbal IQ and emotional recognition could be found in either subject group. Similarly, no significant correlation between head injured and control performance across the 31 affective stimuli was found. Results indicated that the head injured were more impaired on the recognition of negative emotions than positive emotions. These findings are discussed with reference to the psychosocial difficulties encountered by the severely head injured.

Adult↗
PubMed2002

Object-based visual neglect: a computational hypothesis.

Some patients with damage to the right parietal cortex show neglect for the left half of each of a series of objects shown in a horizontal row in the visual field. The neglect is thus not based on failure to see objects in any part of left visual space, but is object-based. We show that in a model of attention with separate V1, object (inferior temporal cortex, IT) and spatial (posterior parietal cortex, PP) modules the effect can arise after graded damage increasing towards the right of the PP module when the lateral inhibition between neurons in the PP and V1 modules is short-range. The local lateral inhibition produces high contrast effects at the edges of each object, and it is when this interacts with gradually increasing damage through the left visual field that the visibility of the left half of each object is especially impaired. This result was found in a formal model completely specified by mean field equations to quantify the dynamical interactions between the modules. This is the first quantitative account of object-based neglect found in humans with right parietal cortex damage, and provides evidence that the model of attention we describe can account for even detailed and extraordinary phenomena that can occur in visual perception.

Attention↗