SEARCH · PubMed Health

Results for “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 1,315 records · Page 73Linked to original sources

PubMed2000

[Simple retinal detachment: computer reconstruction of visual perception during the first month after surgery].

Visual function during the first month following ab externo surgery for retinal detachment with raised macula has been inadequately investigated. We present through pictures the patient's perception of his visual function after surgical intervention consisting of cryotherapy, draining, scleral buckling, and gas. The patient used image processing software to modify the pictures seen by the nonoperated eye in order to reproduce his visual perception with the operated eye. Results show the relation between visual perception and clinical examination. When the surgical procedure is undergone early, visual recovery only requires a few days and color vision returns quickly. Hyalitis and gas perception prevails at first, then visual acuity increases progressively and efficiently.

Color Perception↗

PubMed2002

Object-based and action-based visual perception in children with spina bifida and hydrocephalus.

Children with spina bifida and hydrocephalus (SBH) have long been known to have difficulties with visual perception. We studied how children with SBH perform 12 visual perception tasks requiring object identification, multistable representations of visual space, or visually guided overt actions. Four tasks required object-based processing (visual constancy illusions, face recognition, recognition of fragmented objects, line orientation). Four tasks required the representation of visual space in egocentric coordinates (stereopsis, visual figure-ground identification, perception of multistable figures, egocentric mental rotation). Four tasks required the coupling of visual space to overt movement (visual pursuit, figure drawing, visually guided route finding, visually guided route planning). Effect sizes, measuring the magnitude of the difference between SBH children and controls, were consistently larger for action-based than object-based visual perception tasks. Within action-based tasks, effect sizes were large and roughly comparable for tasks requiring the representation of visual space and for tasks requiring visually guided action. The results are discussed in terms of the physical and brain problems of children with SBH that limit their ability to build effective situation models of space.

Adolescent↗

PubMed2001

[Change of cone's motion perception in patients with primary open angle glaucoma].

OBJECTIVE: To assess the change of cone's motion perception in primary open angle glaucoma (POAG). METHODS: Equi-luminance random dots moving test was used to determine the change of motion perception of blue, green and red cones in 51 eyes with POAG. To isolate the three kinds of cones, the blue, green and red visual targets were displayed on the yellow, purple and blue-green background respectively. RESULTS: The direction discrimination thresholds of motion perception from blue, green and red cones were all damaged in POAG compared to that of the normal group, and among them the blue cone was the most obviously damaged. CONCLUSIONS: These findings indicate that cone's motion perception, especially the blue cone's, may reveal pre-clinical visual nerve damage in POAG.

Adolescent↗

PubMed2005

Vertical linear self-motion perception during visual and inertial motion: more than weighted summation of sensory inputs.

We evaluated visual and vestibular contributions to vertical self motion perception by exposing subjects to various combinations of 0.2 Hz vertical linear oscillation and visual scene motion. The visual stimuli presented via a head-mounted display consisted of video recordings of the test chamber from the perspective of the subject seated in the oscillator. In the dark, subjects accurately reported the amplitude of vertical linear oscillation with only a slight tendency to underestimate it. In the absence of inertial motion, even low amplitude oscillatory visual motion induced the perception of vertical self-oscillation. When visual and vestibular stimulation were combined, self-motion perception persisted in the presence of large visual-vestibular discordances. A dynamic visual input with magnitude discrepancies tended to dominate the resulting apparent self-motion, but vestibular effects were also evident. With visual and vestibular stimulation either spatially or temporally out-of-phase with one another, the input that dominated depended on their amplitudes. High amplitude visual scene motion was almost completely dominant for the levels tested. These findings are inconsistent with self-motion perception being determined by simple weighted summation of visual and vestibular inputs and constitute evidence against sensory conflict models. They indicate that when the presented visual scene is an accurate representation of the physical test environment, it dominates over vestibular inputs in determining apparent spatial position relative to external space.

Adolescent↗

PubMed1985

Effect on perception of hue of imposed oscillatory movements of a stabilized retinal image.

A stabilized image of a coloured square seen against a black background was produced. After the image had faded, oscillatory movements were applied in a direction parallel to a diagonal so that all boundaries had an equal component of motion normal to themselves. Movements of different frequency, amplitude and wave-form were studied. Most of the experiments were carried out at fairly high retinal illuminance (80-500 td). The objective was to find the amplitude and frequency required for perception of hue and saturation. It was found that these movements had (i) a minimum amplitude of about 5' (10' peak-to-peak), (ii) a minimum velocity of 15'(-1) and (iii) a frequency range from about 1 Hz to about 4 Hz. The movements required are larger than those required for perception of the shape of the target and also larger than the normal movements which remain when a subject fixates a well-defined mark. Also the movements associated with the perception of hue and saturation are restricted to a narrower frequency range. These features probably imply that it is necessary to excite numbers of cones covering a minimum area to give perception of hue and saturation.

Color Perception↗

PubMed1984

[Emotional and meaningful regulation of perception in psychopathic personalities of the excitable and hysterical type].

An experimental psychological study of the emotional and meaningful perception control involved 83 psychopaths of the excitable and hysterical types and 80 mentally normal test subjects. It has been revealed that unlike normal people, perception in psychopathic personalities is based on a smaller number of emotional-evaluation categories; under emotional stress their perception is more dependent on the subjective significance of the perceived stimuli; the process of perception in such individuals is less hierarchical and structural. The data obtained indicate an inadequately structuralized and unstable hierarchy of meaningful formations in psychopathic patients of the excitable and hysterical types.

Adult↗

PubMed1995

[Motion discrimination as as test for visual motion perception].

Recent neurophysiological studies have indicated that there are two parallel pathways in vision processing independently shape and motion. There are many methods for examining perception of color and shape, but none for examining visual motion perception. In this study, we devised a "motion discrimination task (MDT)" for evaluating motion perception, which was displayed on a computer monitor, and recorded normal responses to the MDT in 90 normal subjects. Responses to MDT were not affected by visual acuity, but were affected by dot speed of the MDT. There was little trial-to-trial or subject variability in the MDT. These findings indicate that our MDT is a good clinical test for evaluating motion perception in human subjects.

Adolescent↗

PubMed1998

Anomalies of motion perception in infantile esotropia.

PURPOSE: To quantify motion sensitivity in patients with infantile esotropia who, as a subgroup, have been previously reported to have abnormal oculomotor control. In addition, to probe abnormal binocular development as a factor underlying abnormal motion perception in infantile esotropia (IE), motion sensitivity was compared among participants with and without stereopsis. METHODS: Monocular sensitivity to leftward and rightward motion was assessed across the horizontal meridian, using partially coherent random dot kinematograms. Participants included 11 observers with IE, 5 observers with acquired esotropia, and 11 observers with normal eye alignment. RESULTS: Participants with IE showed no deficits in motion sensitivity to any visual field locations when motion thresholds were collapsed across direction. However, they showed an abnormal variation in directional anisotropy. Although sensitivity to centripetal motion was superior in both hemifields of control participants and in the temporal hemifields of participants with IE, a centrifugal bias was revealed in the nasal hemifields of IE. Stereoblind observers with acquired esotropia showed a normal centripetal directional anisotropy, whereas binocular observers with acquired esotropia showed directional anisotropy similar to that in the IE group. CONCLUSIONS: Motion perception, like oculomotor function in IE, is characterized by a variation of directional anisotropy for stimuli presented to the nasal hemifields. This finding supports the hypothesis that abnormal oculomotor control and motion perception in IE reflect a common disruption of the visual system. A similar variation of directional sensitivity in patients with acquired esotropia with normal stereopsis suggests that the interruption of binocularity is not the underlying cause of abnormal motion perception in IE.

Adolescent↗

PubMed1996

Visual perception elicited by electrical stimulation of retina in blind humans.

OBJECTIVE: To evaluate the feasibility of bypassing damaged photoreceptors and electrically stimulating the remaining viable retinal layers to provide limited visual input to patients who are blind because of severe photoreceptor degeneration. METHODS: In the operating room with the patient under local anesthesia, focal electrical stimulation of the retinal surface with brief biphasic pulses was performed using small probes inserted through the sclera. The procedure was performed in five subjects who had little or no light perception. Three subjects had retinitis pigmentosa, one had age-related macular degeneration, and one had unspecified retinal degeneration from birth. RESULTS: Stimulation elicited visual perception of a spot of light (phosphene). Subjects who previously had useful vision accurately localized the phosphenes according to the retinal area stimulated. Two subjects could track the movement of the stimulating electrode by reporting movement of the elicited phosphene, and could perceive two simultaneous phosphenes on independent stimulation with two electrodes. In a resolution test, one of the subjects with no light perception in his left eye resolved phosphenes at 1.75 degrees center-to-center distance (ie, 4/200 OS visual acuity). CONCLUSIONS: Local electrical stimulation of the retinal surface in patients blind from outer retinal disease results in focal light perception that seems to arise from the stimulated area. Such findings in an acute experiment warrant further research into the possibility of prolonged retinal stimulation, improved resolution, and ultimately, an intraocular visual prosthesis.

Adult↗

PubMed2000

Lesions of the anterior forebrain song control pathway in female canaries affect song perception in an operant task.

We tested whether the avian anterior forebrain pathway functions in song perception in female canaries, and whether it is specialized for conspecific song perception or functions more generally in auditory perception. Using operant conditioning methods, we trained female canaries to discriminate among synthetic sound stimuli, canary songs, and song sparrow songs. We also trained each bird to discriminate among visual stimuli to test for general effects of lesions on performance. When canaries had learned the discrimination tasks, bilateral electrolytic lesions of the lateral portion of the magnocellular nucleus of the anterior neostriatum (lMAN) were made. The lesioned birds were then tested on the previously learned discrimination tasks. Lesions that destroyed most or all of lMAN decreased the ability of female canaries to discriminate between previously learned pairs of acoustic stimuli of all types, while visual discrimination was unaffected. These results suggest that the female canary anterior forebrain pathway contributes to the perception of acoustic stimuli, with this contribution including heterospecific song and other acoustic stimuli as well as canary song.

Acoustic Stimulation↗

PubMedDate not supplied

Maternal perception of preterm labor: is it reliable?

The objective of this study was to determine the reliability of maternal perception of uterine contractions and the influence of gestational age and maternal training on the perception level. Three hundred fifty patients at high risk for preterm delivery were followed from 20 to 35 weeks of gestation. The average maternal perception (79%) of contractions did not significantly vary as a function of gestational age. Four groups of women were identified according to the perception index (PI) defined as the ratio of contractions felt by the mother and the contractions documented by tocodynamometer. Within each group, the PI did not significantly vary during consecutive monitoring sessions, as the women become more familiar with self detection of uterine contractions (R < .65, P > .95). Twenty-one percent (+/-5%) of all preterm uterine contractions were not perceived by the pregnant women from 21 to 35 weeks. Thirty-two patients (9.1%) fail to perceive most or all uterine contractions while 189 (54%) detect most or all at any time during the study period.

Female↗

PubMed2006

Left hemispheric lateralization of brain activity during passive rhythm perception in musicians.

The nature of hemispheric specialization of brain activity during rhythm processing remains poorly understood. The locus for rhythmic processing has been difficult to identify and there have been several contradictory findings. We therefore used functional magnetic resonance imaging to study passive rhythm perception to investigate the hypotheses that rhythm processing results in left hemispheric lateralization of brain activity and is affected by musical training. Twelve musicians and 12 nonmusicians listened to regular and random rhythmic patterns. Conjunction analysis revealed a shared network of neural structures (bilateral superior temporal areas, left inferior parietal lobule, and right frontal operculum) responsible for rhythm perception independent of musical background. In contrast, random-effects analysis showed greater left lateralization of brain activity in musicians compared to nonmusicians during regular rhythm perception, particularly within the perisylvian cortices (left frontal operculum, superior temporal gyrus, inferior parietal lobule). These results suggest that musical training leads to the employment of left-sided perisylvian brain areas, typically active during language comprehension, during passive rhythm perception.

Acoustic Stimulation↗

PubMed2006

Impact of the diagnostic label of osteoarthritis on perceptions of disability and willingness to help a parent in African Americans and whites.

OBJECTIVE: Family members are central to arthritis care, but little is known about public perceptions of osteoarthritis (OA) and how cultural diversity affects these perceptions. We examined the effects of participant race and diagnostic label of OA on family members' perceptions and willingness to help a parent with OA. METHODS: A total of 105 young adult African American and 308 young adult white participants were randomly assigned to read 1 of 2 vignettes (OA label versus no label) describing an older mother with marked pain and disability. Effects for race and diagnostic label were examined. RESULTS: Participants who were told that the mother had OA were more likely to believe the mother's problems were due to illness, but were less likely to believe that better health care would improve her condition than participants not told a diagnosis. African Americans attributed less blame to the mother, showed less anger, more sympathy, and were more willing to help compared with whites. CONCLUSION: The finding that the OA label leads to pessimism concerning the benefits of health care for a parent suggests a need for public education on the effectiveness of arthritis care. Race differences in perceptions of the parent and willingness to provide care are consistent with previous literature on race and family caregiving, and indicate that cultural values regarding family caregiving may be important in arthritis care. Family members could serve as important allies for elderly individuals with OA, and public health efforts should not just target older adults but should also provide information on arthritis care for families.

Adolescent↗

PubMed2005

No influence on selected parameters of human visual perception of 1970 MHz UMTS-like exposure.

In recent years several studies regarding possible effects of radio frequency (RF) electromagnetic fields (EMFs) on cognitive brain function were reported. In many of these studies on awake humans the working tasks were presented visually to the test subjects, e.g., on a computer screen. Therefore, the question of where in the chain of visual perception, brain processing and response a possible effect could be induced seems to be of interest. In this study, possible effects of exposure to a generic 1.97 GHz UMTS-like signal on human visual perception were investigated in a double blinded, crossover study including 58 healthy volunteer subjects (29 male, 29 female), aged 29 +/- 5.1 years (mean +/- SD). Each test subject underwent a battery of four different clinical tests three times (two different exposure levels and sham exposure) to assess selected parameters of visual perception. The generic signals applied to the subjects' head represented the RF emissions of an UMTS mobile phone under constant receiving conditions and the under condition of strongly varying transmit power, i.e., the signal envelope contained low frequency components. In the high exposure condition the resulting average exposure of the test subjects in the cortex of the left temporal lobe of the brain was 0.63 W/kg (1 g averaged SAR) and 0.37 W/kg (10 g averaged SAR). Low exposure condition was one tenth of high exposure and sham was at least 50 dB (corresponding to a factor of 100,000) below low exposure. Statistical evaluation of the obtained test results revealed no statistically significant differences in the investigated parameters of visual perception between the exposure conditions and sham exposure.

Adult↗

PubMed2002

Project NEMESIS: perception of a 50 Hz electric and magnetic field at low intensities (laboratory experiment).

The Electrical Hypersensitivity Syndrome (EHS) is a condition where people suffer from various nonspecific health symptoms attributed to an assumed adverse effect of electric and magnetic fields (EMF). Many EHS patients report the ability to consciously perceive EMF at very low intensities. The existence of a direct EMF perception could be the key to explain at least partially the aetiology of EHS through stress mechanisms and allow the comparison with well known environmental stressors such as noise or odor. The double blind laboratory experiment tested the hypothesis that there are subjects with the ability to perceive 50 Hz EMF at 100 V/m and 6 microT (EMF sensitive) and to investigate the prevalence of EMF sensitivity in a group consisting of subjects with or without self-reported EHS. A total of 63 volunteers, 49 with EHS and 14 controls, took part in the EMF perception experiment, where 10 sham and 10 exposed 2 min blocks had to be judged in randomized sequence (field on/field off). Seven out of 63 subjects reached a statistically significant result which points to the existence of a small EMF sensitive subgroup within the study group. There was no relevant difference between the subjects with self reported EHS and those without in terms of the success rate in the field perception experiment, as well as the number and types of symptoms encountered during the test. The results of the EMF perception experiment suggest that EHS is not a prerequisite for the ability to consciously perceive weak EMF and vice versa.

Adolescent↗

PubMed1978

Nonlinear modeling of multistable perception.

Multistable figures show that the stimulus-percept relation is not a single valued function. We therefore propose a tentative nonlinear model on the hypothesis that the graph of this relation is the equilibrium set of a dynamic system. For simplicity and to obtain testable predictions, we consider a system whose bifurcations are gradient-like and thus generically described by the elementary catastrophes. We motivate this general model, and then show how, in conjunction with the principle of minimal singularity, it implies cusp catastrophe geometry in a specific perceptual example. Indeed, we argue for canonical cusp geometry in this case. The model incorporates naturally certain observed features of multistable perception, such as hysteresis and bias effects. Despite being a continuum model it is naturally compatible with the subjective dichotomy of bistable perception. The model makes testable predictions which may easily be extended to other specific examples of multistable perception.

Humans↗

PubMed2005

Perceptions of insurance coverage for screening mammography among women in need of screening.

BACKGROUND: Breast carcinoma remains a significant health problem in the U.S., especially among underserved populations. Although screening mammography is recommended for early detection, in 2002, approximately 25% of women age > 40 years had not had a mammogram within the past 2 years. The current study examined perceptions of insurance coverage and cost as barriers to screening mammography within an underserved, predominantly low-income population of women in need of a mammogram. METHODS: Between 1998 and 2002, face-to-face interviews were conducted with 897 women age > or = 40 years. All women were part of a randomized, controlled study evaluating a health education intervention designed to improve mammography screening. They were asked questions at baseline about cost and insurance coverage as barriers to mammography screening. Women's reports of their level of insurance coverage for mammography were compared with actual coverage by their insurance type to determine the accuracy of their perception of insurance coverage for mammography. The relation between perception of insurance coverage and the barrier of cost was investigated. RESULTS: Greater than half of the women who needed a mammogram identified cost as a barrier to mammography; however, 40% of these women had an inappropriate perception of their insurance coverage. Underestimating or not knowing the level of mammography coverage was strongly associated with reporting cost-related difficulty (odds ratio [OR] = 4.57, 95% confidence interval [95% CI], 1.95-10.70 for the underestimate category; OR = 4.42, 95% CI, 1.80-10.88 for the don't know category), regardless of true coverage levels. CONCLUSIONS: Providing women with information regarding their actual coverage for mammograms may reduce the impact of cost as a barrier to screening mammography.

Adult↗

PubMed1995

Quantitative measurement of cutaneous perception in diabetic neuropathy.

To determine the diagnostic value of various cutaneous sensory modalities in diabetic neuropathy, we studied cutaneous perception at the dominant hallux of 113 subjects (32 normal healthy controls and 81 diabetic subjects). The cutaneous sensory perception tests included warm and cold thermal perception, vibration, touch-pressure sensation, and current perception testing (CPT). The sensitivity of each modality when specificity is held greater than 90% was as follows: warm = 78%, cold = 77%, vibration = 88%, tactile-pressure = 77%, 5-Hz CPT = 52%, 250-Hz CPT = 48%, and 2000-Hz CPT = 56%. Combination thermal and vibratory gave optimum sensitivity (92-95%) and specificity (77-86%). We conclude that vibratory and thermal testing should be the primary screening tests for diabetic peripheral neuropathy. Other modalities may be of use only in specific situations.

Adult↗