Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perceptual Distortion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1978

A quantitative confirmation of visual capture of curvature.

An investigation was performed to quantify the experience of contour curvature formed under sensory discrepancy inspection conditions. N = 80 male and female undergraduates were used. Experimental Ss finger-tracked a horizontal straight edge while viewing limb movements through a curve inducing lens. Control Ss inspected the edge unimodally, either through vision (distorted) or proprioception. Rather than relying on verbal reports all Ss were required to match their impressions of contour shape with an adjustable metal curve. Findings indicated that (a) the mean impression of contour shape derived from discrepant visual and proprioceptive information was curved and did not differ from that derived from distorted visual information, (b) proprioceptive inspection alone resulted in accurate judgements of physical straightness, (c) response modality effects did not emerge, and (d) a manipulation designed to direct Ss attention to the left contour shape and during sensory discrepancy inspection did not affect mean curvature matches but created sizeable variability among matches. A sensory organization versus a selective processing interpretation of visual capture was discussed.

Attention↗
PubMed2003

Distortion-product otoacoustic emissions in ears with normal hearing sensitivity: test-retest variability.

4 women and 4 men with normal hearing sensitivity were tested for variability in distortion-product otoacoustic emissions, with two measurement sessions per day for 4 days spread over a 2-wk. period. Most test-retest variations were small, on the order of 2 dB. Extreme variations of 6 dB or greater occurred most often at the highest test frequency and should not be considered clinically positive unless such differences are found at lower frequencies also.

Acoustic Stimulation↗
PubMed1996

Modulation of neglect hemianesthesia by transcutaneous electrical stimulation.

The effects of transcutaneous electrical stimulation on deficits of tactile perception contralateral to a hemispheric lesion were investigated in 10 right brain-damaged patients and in four left brain-damaged patients. The somatosensory deficit recovered, transiently and in part, after stimulation of the side of the neck contralateral to the side of the lesion, in all 10 patients with lesions in the right hemisphere, both with (six cases) and without (four cases) left visuo-spatial hemineglect, and in one left brain-damaged patient with right hemineglect. In three left brain-damaged patients without hemineglect, the treatment had no detectable effects. In one right brain-damaged patient, the stimulation of the side of the neck ipsilateral to the side of the lesion temporarily worsened the somatosensory deficit. These effects of transcutaneous electrical stimulation are similar to those of vestibular stimulation. The suggestion is made that these treatments modulate, through afferent sensory pathways, higher-order spatial representations of the body, which are pathologically distorted toward the side of the lesion. The modulatory effect is direction-specific: the defective internal representation of the contralesional side may be either partly restored, improving the disorder of tactile perception, or further impoverished, worsening the deficit. The possible neural basis of this modulation is discussed.

Adult↗
PubMed2006

[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↗
PubMed1981

The Poggendorff illusion: an illusion of linear extent?

In the standard version of the Poggendorff figure a transversal intersects two parallel verticals and the segment of the transversal between the two intersection points, A and B, is not shown. The two portions of the transversal outside the parallels then seem to be misaligned. Besides this illusion of direction, there is also an illusion of size, the distance AB being underestimated in the standard figure. The influence of configural components in determining this spatial distortion of the Poggendorff figure was examined by having subjects reproduce the inner oblique (at 45 degrees) extent AB in variations of the figure. This distance was found to be underestimated in Poggendorff variations which contained parallel (vertical) components that formed an acute angle with AB; and the underestimation increased as the number of these components present in the figure increased. The distance AB was found not be significantly distorted in figures which contained only those parallel (vertical) components that formed an obtuse angle with AB, yet their presence in the figure tended to counteract the underestimation. When the transversals were omitted, the underestimation was found to increase. The findings are interpreted in support of an explanation that reduces the Poggendorff effect to those factors which mediate the Müller-Lyer illusion.

Distance Perception↗
PubMed1985

Visual half-field symmetry in orientation perception.

The perception of orientation in the left and right visual half-fields has been investigated. No evidence for interfield differences was obtained for the discrimination of single lines by line matching or in magnitude of the systematic orientation distortion in orientation contrast and rod-and-frame experiments. Furthermore, increasing the time interval between test and comparison lines in successive matching provides no evidence for a differential operation of short-term spatial memory in the two hemispheres. It is concluded that hemispheric asymmetries do not arise at the level of sensory processing of spatial signals.

Female↗
PubMed2005

Adaptation to asymmetrically distorted faces and its lack of effect on mirror images.

Previous research showed that viewing symmetrically distorted faces for a few minutes causes undistorted faces to appear distorted in the opposite manner (face-distortion aftereffect, FDAE). Three experiments with 90 observers demonstrated that adaptation to an asymmetrically distorted face also causes FDAE, but does not affect perception of its mirror image. The results suggested the FDAE occurs at the level of visual processing where distinct neural populations respond to a non-frontal facial image and its mirror image. Unlike most aftereffects, this FDAE lasts at least 30 min. Spatial and temporal characteristics of the FDAE and its relevance to portrait drawing and painting are discussed.

Adaptation, Physiological↗
PubMedDate not supplied

Perceived length across the physiological blind spot.

Objects falling across the physiological blind spot appear "complete" despite the absence of photoreceptors. Completion of objects may occur across the blind spot because (1) the blind spot is filled in with the background (the associative explanation); (2) the opposite sides of the blind spot may be contiguously represented in the cortex (i.e. the blind spot is simply sewn up-the retinotopic explanation); or (3) the blind spot may be sewn up, with compensatory expansion occurring around the blind spot (the compensation explanation). These theories would predict no size distortions regardless of object size; constant size distortions regardless of object size; and distortions that depend on the size of the object, respectively. To evaluate these explanations, we measured size distortions at the blind spot. We measured length distortions at the blind spot using a criterion-free two-alternative forced-choice method with feedback. Observers compared the lengths of test bars presented across the blind spot with lengths of reference bars presented at the corresponding location in the fellow eye. Test bar lengths ranged from 7-14 deg. Reference bar lengths were in the range of +/- 3 deg of test bar length. From the observers' responses the perceived length of each bar at the blind spot was estimated. Estimates of the precision of length discrimination at the blind spot were also obtained. Our results were consistent with the associative explanation. In all seven observers, length distortions at the blind spot were smaller than 1 deg (< 20% of the vertical height of the blind spot) for all bar lengths tested. For bars that were presented across the blind spot, the precision with which observers could discriminate length was comparable to that of normal periphery (Weber fraction approximately 20%). Both the veridicality and precision of perceived length are preserved around the blind spot.

Distance Perception↗
PubMed1979

Levels of processing in visual illusions: the combination and interaction of distortion-producing mechanisms.

In order to assess the mode and sequence of interaction of visual-geometric illusion mechanisms, responses to simple and composite overestimation configurations were measured in 72 observers. Analysis suggests that some illusion mechanisms add their distortions to the outputs of others and that other mechanisms average. A logarithmic or near-logarithmic transformation seems to occur when illusory effects combine. A path analysis of the results suggests that some illusory mechanisms combine in a serial manner and that others operate on separate parallel channels. Notions based on simple addition of illusory effects and on serial linear processing are not supported by these analyses.

Discrimination Learning↗
PubMed2004

The Interpersonal Cognitive Distortions Scale: development and psychometric characteristics.

In this study, an Interpersonal Cognitive Distortions Scale was developed to assess cognitive distortions in individuals' interpersonal relationships. The sample comprised 425 university students. A factor analysis yielded three factors: Interpersonal Rejection, Unrealistic Relationship Expectation and Interpersonal Misperception. To examine construct validity the correlations between the scores on the Interpersonal Cognitive Distortions Scale and the Automatic Thoughts Scale (.54), the Irrational Belief Scale (.54), and the Conflict Tendency Scale (.53) were estimated. The first factor, the second factor, and the total scale discriminated married individuals who had low and high conflict intensity and conflict frequency. The reliability of the scale was estimated by performing a test-retest correlation (.74). Cronbach internal consistency coefficient alpha was .67.

Adolescent↗
PubMed2001

Hypnotic intervention for ambiguity as a depressive risk factor.

In the face of ambiguous life events, depressed individuals are more likely to make negative and depressing interpretations than nondepressed individuals. Fundamental to the success of cognitive-behavioral treatments, one of the most empirically supported treatments for depression is teaching the client to recognize and self-correct so-called cognitive distortions. To facilitate that learning process, clients can learn to better recognize and tolerate ambiguity inherent in many situations, and thereby diminish the drive to form subjective interpretations (either negative or positive) when more objective evidence is unavailable. This article describes ambiguity as a risk factor for depression and details a strategy employing hypnosis for teaching the skills of both recognizing and tolerating ambiguity.

Cognitive Behavioral Therapy↗
PubMed1999

Fluctuating olfactory sensitivity and distorted odor perception in allergic rhinitis.

OBJECTIVE: To characterize the relationship between allergic rhinitis, the severity and duration of nasal disease, olfactory function, and self-reported olfactory symptoms, including fluctuations or distortions in odor perception. DESIGN: Assessment of olfactory function and symptoms of 90 patients with allergic rhinitis. SETTING: A clinic of a university teaching hospital and research facility. PATIENTS: Sixty patients who presented to the Taste and Smell Clinic who had positive allergy test results and 30 patients who presented to the Allergy-Immunology Clinic. The Taste and Smell Clinic patients were grouped by nasal-sinus disease status (30 without chronic rhinosinusitis or nasal polyps, 14 with chronic rhinosinusitis but without polyps, and 16 with nasal polyps). MAIN OUTCOME MEASURES: Subjective olfactory symptom questionnaire and objective olfactory function tests. RESULTS: The Allergy-Immunology Clinic patients were diagnosed as being normosmic and the Taste and Smell Clinic patients as being hyposmic or anosmic with olfactory loss that increased significantly with nasal-sinus disease severity. Comparisons with normative data confirm that olfactory scores observed in all groups were significantly lower than expected because of the aging process alone. The self-reported duration of olfactory loss increased significantly with nasal-sinus disease severity. The Taste and Smell Clinic patients without chronic rhinosinusitis or nasal polyps reported the greatest incidence of olfactory distortions and olfactory loss associated with upper respiratory tract infections. CONCLUSIONS: There appears to be a continuum of duration and severity of olfactory loss in allergic rhinitis that parallels increasing severity of nasal-sinus disease. As a result of the increased frequency of respiratory infection associated with allergic rhinitis, these patients are at risk for damage to the olfactory epithelium.

Adolescent↗
PubMed2004

Body image, eating behaviors, and attitudes toward exercise among gay and straight men.

Gay men tend to be more dissatisfied with their bodies and may be at greater risk for symptoms of eating disorders compared to heterosexual men. However, the majority of research conducted with gay and heterosexual men has implemented instruments designed to assess eating disorder symptomatology in women. The present study assessed differences between gay and heterosexual men using the Male Eating Behavior and Body Image Evaluation (MEBBIE), an instrument designed to assess attitudes and behaviors related to eating, exercise and body image specifically in men. Analyses of MEBBIE scale means with body mass index (BMI) as the covariate indicated that, relative to their heterosexual counterparts, gay men diet more, are more fearful of becoming fat, and are more dissatisfied with their bodies in general as well as with their degree of muscularity. Gay men were also more likely than heterosexual men to hold distorted cognitions about the importance of having an ideal physique. Contrary to hypotheses, however, gay and straight men did not differ in the degree to which they exercised or felt guilty about missing a workout. Results are discussed in light of previous findings, and implications for clinical practice and future research are considered.

Adult↗
PubMed2002

Evoked otoacoustic emissions in patients with Ménière's disease.

HYPOTHESIS: This study investigated whether otoacoustic emissions (OAEs) in patients with Ménière's disease show abnormal properties. BACKGROUND: Patients with Ménière's disease experience vertigo, tinnitus, and hearing loss. OAEs are sounds generated in the inner ear, and their presence is associated with normal hearing. METHODS: Click-evoked OAEs and distortion product OAEs were measured in 100 patients with Ménière's disease. RESULTS: The incidence of the emissions in affected ears (56%) was lower than in unaffected (i.e., contralateral) ears (85%). The mean emission amplitude in affected ears was also significantly lower (2.6 dB), and the mean amplitude in unaffected ears was lower than in normal-hearing ears (5.3 dB). These differences were likely caused by the hearing loss involved. Further, ears with OAEs clearly showed smaller hearing losses than ears without OAEs (24-dB difference). The average hearing loss showed correlations with the emission amplitudes, although this correlation was not very strong; when plotted against the smallest hearing loss, a certain upper boundary for the emission amplitude was present. Also, the amplitude of click-evoked OAEs showed a considerable correlation with the largest of the three distortion product OAEs. CONCLUSION: OAEs in patients with Ménière's disease differed from those in normal-hearing ears but did not differ from those in non-Ménière's ears with equivalent hearing loss. This was best observed by comparing emission amplitude with smallest hearing loss instead of mean hearing loss.

Acoustic Stimulation↗
PubMed1995

The unconscious experience.

BACKGROUND: Although considerable research has been done on pathophysiology, metabolic and physical causes, and prognostic indicators, little is known about unconsciousness or coma from the perspective of the patient. OBJECTIVE: To describe the experiences of patients who were once documented as being unconscious. METHODS: Phenomenologic interviews were conducted with 100 patients whose records indicated that they had been unconscious during hospitalization. Interviews were also attempted with primary family members, significant others, or other external observers. Chart audits documenting the unconscious episode, medications, and diagnoses were also carried out. Data were compared, using van Kaam's method, and contrasted. RESULTS: Patients experienced one or more of five states: unconsciousness, inner consciousness, perceived unconsciousness, distorted consciousness, and paranormal experiences. They described hearing, understanding, and responding emotionally to what was being said when it was assumed they were not aware. In addition, 23 subjects reported near-death experiences or visits, out-of-body experiences, or some other paranormal experience. CONCLUSION: Patients' unconscious experiences can cause long-term effects. Patients often need reassurance that other patients subjected to similar conditions also have these experiences.

Auditory Perception↗
PubMed1997

[Effect of perilymphatic fistula on distortion product otoacoustic emissions in guinea pigs].

Perilymphatic fistula was induced in 11 healthy guinea pigs to study its effects on distortion product otoacoustic emissions (DPOAEs). DPOAE amplitudes decreased significantly right after formation of the fistula (P < 0.01), and recurred to near pretreatment level in animals whose fistula healed. The amplitude remained below pretreatment level 18 days after fistulization in those animals whose fistula failed to heal. Under light microscope, the organ of Corti was seen normal. The authors feel that DPOAEs may be helpful in detecting perilymphatic fistula.

Acoustic Stimulation↗
PubMed2005

Reduced gamma-band coherence to distorted feedback during speech when what you say is not what you hear.

BACKGROUND: Communication between the frontal lobes, where speech is generated, and the temporal lobes, where it is perceived, may occur through the action of an efference copy/corollary discharge mechanism that prepares the temporal lobes for the expected sound. We suggest that coherence of EEG in gamma-band between frontal and temporal lobes may reflect the successful action of such a mechanism. We tested the hypothesis that there would be a disruption of gamma-band coherence when the expected auditory consequence of speech does not match the auditory experience. METHOD: EEG was recorded from 21 healthy adult subjects as they uttered the sound [a:] (Talking condition) and as they heard these recorded sounds played back (Listening condition). As they spoke, subjects heard real-time feedback of the sounds that were: (1) pitch-shifted down one semi-tone, (2) pitch-shifted down one-half of a semi-tone, or (3) not pitch-shifted (veridical), each in separate runs. Event-related gamma coherence between frontal and temporal sites was calculated relative to the onset of the sound, as it was being spoken during Talking, and as it was being played back during Listening. RESULTS: Frontal-temporal gamma-band coherence spanning 33-43 Hz was greater during Talking than Listening and greater when speech was veridical than when it was distorted a whole semi-tone. CONCLUSIONS: Gamma-band fronto-temporal synchrony may reflect a "binding of expectation with experience." Disruption of this synchrony may provide feedback to the frontal lobes, particularly regions subserving vocalization, to implement sensorimotor adaptations to either adjust motor programs for speech production in the short run, or to reorganize expectations in the long run.

Adult↗
PubMed2005

[Age-related macular degeneration].

In the western world, macular degeneration is the most common cause of severe loss of vision and blindness in persons older than 50. The underlying cause of the condition is a disturbance in the interaction between the retina and choroid of the macula. Apart from age itself, genetic disposition and smoking are confirmed risk factors. In the initial stages, the patient experiences merely a mild blurring of vision. The wet form, which is usually progressive, is experienced as an acute loss of vision or distortion of the objects viewed. Underlying this wet macular degeneration is of new vessel growth from the choroid, known as choroidal neovascularization, which as a result of exudation of fluid and bleeding into the macula, destroys central vision. Apart from the administration of vitamins to slow down progression, laser coagulation, photodynamic treatment or vitreoretinal surgery may be helpful in some cases. A specific causal therapy is, however, not available.

Aged↗