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 595 records · Page 33Linked to original sources
PubMed1996

Effects of diminished and conflicting sensory information on balance in patients with cerebellar deficits.

We studied the effects of altered sensory information on standing balance in 25 patients with cortical cerebellar atrophy (CCA), nine patients with olivoponto-cerebellar atrophy (OPCA), and 10 normal subjects. The total sway path and its components, the anteroposterior (AP) sway path and the lateral sway path, were measured under six conditions: (1) standing on a fixed platform with the eyes open and visual surroundings fixed, (2) standing on a fixed platform with the eyes closed, (3) standing on a fixed platform with the eyes open and visual surroundings AP sway referenced, (4) standing on an AP sway-referenced platform with the eyes open and visual surroundings fixed, (5) standing on an AP sway-referenced platform with the eyes closed, and (6) standing on an AP sway-referenced platform with the eyes open and visual surroundings AP sway referenced. Patients swayed more than normal subjects during normal stance (condition 1), when the visual information was absent (condition 2) or distorted (condition 3), and when the proprioceptive information from the ankles was distorted (condition 4). Patients swayed much more than normal, and most fell, when two sensory modalities were affected under condition 5 (proprioceptive information distorted and visual information absent) and condition 6 (both proprioceptive information and visual information distorted). When the patients' sway was normalized to that of the first condition, however, only their lateral sway was greater than the sway in normal subjects. Unlike in normal subjects, the patients' lateral sway varied with the AP sway to approximately the same degree in each condition for conditions 1-5. Clinical ratings of gait and balance were highly correlated with the sway measures. Quantitative testing of standing balance with altered sensory information has better sensitivity than normal stance testing.

Adult↗
PubMed1989

Validity, reliability, and factor structure of the Anorectic Cognitions Questionnaire.

Several authors have hypothesized cognitive distortion as central to the psychopathology of anorexia nervosa and bulimia. However, there have been few investigations of these hypotheses. Equally as important, psychometrically sound devices for assessing these cognitions are notably lacking. The purpose of this investigation is to examine the psychometric characteristics of the Anorectic Cognitions Questionnaire (MAC). This study reports on initial item development, initial concurrent validity, factor structure, initial item refinement, and internal consistency. Results indicated that the MAC has good concurrent validity, three theoretically defined factors were empirically supported, and the scale is internally consistent.

Adult↗
PubMed1994

Psychophysical foundations of a model of amplified night vision in target detection tasks.

In this article we examine some of the basic psychophysics relevant to amplified night vision devices. These devices produce images that are substantially different from ordinary visual scenes. Distortions in contrast and luminance and the introduction of visual interference and geometrical artifacts contribute to unusual viewing conditions. We carried out experiments to determine the effect of these parameters of the image on a highly controlled visual target detection task simulated on a computer graphics system that closely models a night vision device. Our results indicate that display luminance and geometrical artifacts degrade detection performance only slightly, whereas contrast and visual interference have a substantial degrading effect.

Adult↗
PubMed1985

Amblyopic processing of positional information. Part II: Sensitivity to phase distortion.

Amblyopic sensitivities to spatial distortions of compound gratings and checker-board textures were studied. Iso-energy target signals were used by employing phase modulations which leave the stimulus power spectra unaltered. The non-amblyopic eyes of the 6 amplyopes tested showed supranormal sensitivities at 1 s exposure duration for both types of patterns. At 125 ms the amblyopic eyes were found virtually blind to the texture distortions while performance improved with prolonging the presentation time to 1 s. Comparable results were obtained with compound gratings. However, the correlation between amblyopic acuities and texture discrimination was higher than that between acuities and grating performance. This is probably due to the fact that both (misaligned) vernier targets and the texture are more 'natural' stimuli in the sense that they contain a broad range of spatial frequency components at many different orientations. Differences in behaviour between strabismic and anisometropic amblyopes did not occur. This suggests that the results depend upon defects of foveal visual function.

Amblyopia↗
PubMed1997

[Intraoperative evaluation of signal transduction of prototypes of implantable hearing aid transducers in the human].

During routine middle ear surgery prototypes of implantable piezoelectric hearing aid transducers were coupled to the ossicular chain of 28 patients. Pure tone thresholds in a broad frequency range (250 Hz-8 kHz) and perception of music were the basis of psychoacoustic evaluation of the transfer properties of the prototypes in this human study. The piezoelectric transducer reached an equivalent transducer sound-pressure level of up to 145 dB SPL and frequencies of 10 kHz. The dynamics for music reached 32 dB, which was identical with the results of the preoperative investigations using hi-fi headsets (33 dB). The low nonlinear distortions of around 0.1% and the frequency range up to 10 kHz are reflected in the positive evaluation of sound quality by 84% of the patients involved. The study is the basis for realizing a piezoelectric transducer designed for routine clinical implantations. The transducer is thought to be part of a totally implantable future hearing aid for rehabilitation of moderate and severe sensory neural hearing loss predominantly in the middle and high frequency range.

Adult↗
PubMed1979

Integration of verbal and visual information as evidenced by distortions in picture memory.

Subjects were presented with a series of pictures, some of which were general (girl walking down the path) and others specific (girl hiking down the path). These pictures were matched with sentences which were either general or specific ("The girl is walking [hiking] down the path.") Subsequently, a forced-choice picture recognition test was administered in which subjects saw pairs of pictures and indicated which member of each pair they had seen before. It was found that labelling the picture with a sentence containing a specific verb substantially increased the likelihood that the specific picture corresponding to that verb would subsequently be falsely recognized. The results are discussed in terms of current theories of memorial representation.

Cues↗
PubMed1991

Construct validity and factor stability of the anorectic cognitions questionnaire.

Specific cognitive distortions may be central to the psychopathology of anorexia nervosa and bulimia nervosa; however, few psychometrically adequate instruments exist to assess these cognitions. The Mizes Anorectic Cognitions (MAC) questionnaire was previously developed to fill this need. The present study examined the construct validity, temporal reliability, and factor stability of the MAC in a sample of 100 college females. Results suggested excellent construct validity and test-retest reliability. Moreover, the three previously identified factors (i.e., Self-Control, Weight and Approval, Rigid Weight Regulation) were cross-validated in this sample.

Adolescent↗
PubMed2000

Age-related changes in auditory function of rhesus monkeys (Macaca mulatta).

The purpose of this study was to investigate the changes in auditory function associated with aging in rhesus monkeys (Macaca mulatta) as a model for age-related changes in humans. One advantage of using monkeys from the Wisconsin Regional Primate Research Center was that lifestyle factors such as diet and excessive noise exposure were controlled. Twenty younger (mean: 10 years, 9 months, S.D.=+/-6 months) and 20 older (mean: 25 years, 11 months, S.D.=+/-11 months) monkeys were used in this study. Cochlear function in these monkeys was measured with distortion product otoacoustic emissions (DPOAEs); neural function was measured with auditory brainstem responses (ABRs) and middle latency responses (MLRs). Older monkeys had (1) significantly smaller DPOAEs, (2) significantly smaller ABR peak amplitudes, and (3) significantly longer ABR peak latencies compared to younger monkeys. Overall, these results suggest that older monkeys have decreased cochlear and neural function to the level of the brainstem as compared to younger monkeys. The decrease in DPOAE level and the increase in age accounted for approximately 70% of the increase in peak IV latency.

Aging↗
PubMed2002

Auditory perception in auditory neuropathy: clinical similarity with auditory verbal agnosia.

The precise features of auditory perception in patients with auditory neuropathy have not been well described. In the present study, we examined auditory perception in a patient with auditory neuropathy. The patient was a right-handed 7-year-old boy. His chief complaint was delayed speech and suspected of verbal learning disability. He could talk, read and repeat rather fluently but could not understand fully what was asked. V-IQ, P-IQ and F-IQ of Wechsler Scale for Children III-R were 53, 118 and 81, respectively. Pure tone audiogram was completely normal. His speech discrimination ability was very poor. He could identify environmental sounds with visual matching. He could differentiate intensity difference but not time difference. This phenomenon was reported in patients with hemispheric symptoms. These clinical features are very similar to verbal auditory agnosia. ABR showed no response at 90dBnHL alternating clicks and tone bursts. Click evoked and distortion product otoacoustic emissions (OAE) were normal. Electrocochleogram was also normal. Motor and sensory nerve conduction velocity was completely normal. Pa of MLR and N1 of SVR were present. His diagnosis should be "pure type" of auditory neuropathy or auditory nerve disease. Importance of both ABR and OAE examination should be widely announced and auditory neuropathy must be campaigned stressed to be clinical entity among personnel who take care of children with speech delay.

Agnosia↗
PubMed1998

Time course of the medial olivocochlear efferent effect on otoacoustic emissions in humans.

The time course of the medial olivocochlear efferent system has been studied in humans, using the suppressive effect of a contralateral broad-band noise (CBBN) on 2f1-f2 distortion product otoacoustic emissions (DPOAE) amplitude. DPOAE were recorded with F2 at 1.5 kHz, with a temporal resolution of 2.6 s, in the presence and absence of a 40 dB SL continuous CBBN, whose duration ranged between 30 s and 20 min. The CBBN suppressive effect on DPOAE amplitude was greatest from the first 2.6 s, and was sustained for 20 min. At the CBBN offset, when the CBBN duration was > or = 2 min, DPOAE amplitude continued to increase for > 1 min, showing an efferent effect outlasting CBBN stimulation.

Acoustic Stimulation↗
PubMed1982

Magnitude estimation of degraded speech quality by normal- and impaired-hearing listeners.

Speech quality magnitude estimates (SQME's) were obtained from 12 sensorineurally impaired-hearing listeners on connected speech samples degraded by changing low-pass filter cutoff frequency, high-pass filter cutoff frequency, or percent total harmonic distortion (THD) by linear rectification. Log SQME's varied linearly with log bandwidth for filtered signals and with log percent undegraded (100-% THD) for linearly rectified signals. Significant variations were found among the slopes of the log-log functions for degradation modes and group-by-degradation mode interactions. Slope differences appeared to represent differential sensitivity of the listeners to changes in mode and degree of degradation. The findings are sufficiently encouraging to suggest that direct scaling procedures be employed in future studies of the evaluation of communication systems and the perception of complex signals.

Adolescent↗
PubMed2006

Feeling and time: the phenomenology of mood disorders, depressive realism, and existential psychotherapy.

Phenomenological research suggests that pure manic and depressive states are less common than mixtures of the two and that the two poles of mood are characterized by opposite ways of experiencing time. In mania, the subjective experience of time is sped up and in depression it is slowed down, perhaps reflecting differences in circadian pathophysiology. The two classic mood states are also quite different in their effect on subjective awareness: manic patients lack insight into their excitation, while depressed patients are quite insightful into their unhappiness. Consequently, insight plays a major role in overdiagnosis of unipolar depression and misdiagnosis of bipolar disorder. The phenomenology of depression also is relevant to types of psychotherapies used to treat it. The depressive realism (DR) model, in contrast to the cognitive distortion model, appears to better apply to many persons with mild to moderate depressive syndromes. I suggest that existential psychotherapy is the necessary corollary of the DR model in those cases. Further, some depressive morbidities may in fact prove, after phenomenological study, to involve other mental states instead of depression. The chronic sub-syndromal depression that is often the long-term consequence of treated bipolar disorder may in fact represent existential despair, rather than depression proper, again suggesting intervention with existential psychotherapeutic methods.

Awareness↗
PubMed2003

The balanced electromagnetic separation transducer a new bone conduction transducer.

Conventional bone conduction transducers, which are relatively large, suffer from poor performance at low frequencies. A new type of electro-dynamic transducer, the balanced electromagnetic separation transducer (BEST), was developed to improve the performance of the conventional transducers. By using a balanced suspension principle, the quadratic distortion forces, as well as the static forces between the vibrating parts, are principally counterbalanced. Both the distortion and the size of the transducer can therefore be considerably reduced. Moreover, the static and dynamic magnetic fluxes are separated, except in the air gap regions, giving a more efficient transducer. For example, in comparison with a conventional B71 transducer, a prototype of the BEST has: Lower total harmonic distortion (THD), by 20-25 dB, and improved sensitivity by 10-20 dB for 100 to 1000 Hz and by 2-10 dB for 1 to 10 kHz. From a clinical point of view, the BEST offers a chance to measure bone thresholds, at 250 and 500 Hz, which are reliable at hearing levels not possible before. For example, at 250 Hz the BEST has 23 dB higher sensitivity than the B71; the THD is improved from 61% (B71) to 3.3% (BEST) at 40 dB HL (ISO 389-3, 1994).

Audiometry, Pure-Tone↗
PubMed1980

Reliability, sex difference, and Honi phenomenon in a distorted room.

Test-retest reliability and sex differences when viewed in a distorted room were investigated. The presence of the Honi phenomenon, which is less change in apparent size of a spouse than of a stranger, was examined. A reliability coefficient was obtained by testing 27 college men twice. Judgments of size from 25 of the men and 25 women who viewed black disc targets and also from 10 women viewing husbands' and strangers' photographs were compared. The reliability was high, .87. Sex difference was significant. Women's larger reading was interpreted as a more meaningful or valuable perception of things than men's. The Honi phenomenon does not exist.

Adult↗
PubMed1980

The influence of visual pattern on perceived speed.

The two experiments to be described are concerned with the instability of the relationship between objective and subjective speed as experienced by the driver of a motor vehicle. A number of factors that contribute to the instability are outlined, one of the most important of which is considered to be rectilinear speed adaptation. The hypothesis is made that by deliberately distorting the spatial geometry of the visual field it should be possible to counteract the effects of sensory adaptation. The first experiment tests the hypothesis on a motion simulator and confirms the possible value of such a technique. The second experiment describes a field study in which the proven technique is applied to a stretch of motorway at a site where the accident rate was exceptionally high owing to excessive speed. The observed reduction of relevant accidents at this and a number of other motorway sites where the system has been installed is discussed.

Accident Prevention↗
PubMedDate not supplied

Body size estimation in anorexia nervosa patients: the significance of overestimation.

Using the video distortion method on a life-size screen, we have studied body size estimation in 100 female restricting anorexia nervosa patients. About half of the patients were accurate in estimating their own body dimensions and only 20% clearly showed overestimation. We then tested whether differences in accuracy of estimation were related to scores on the following questionnaires: Eating Disorder Inventory; Body Attitude Test; and Symptom Checklist (SCL-90). Overestimators reported a more negative body attitude and a more "neurotic profile" on the SCL-90. These differences might have both prognostic and therapeutic implications.

Adolescent↗
PubMed1985

Nonlinear phenomena as observed in the ear canal and at the auditory nerve.

We report here several measures of nonlinear effects in the mammalian ear made in the external auditory meatus and in single neurons of the auditory nerve. We have measured the 2f1-f2 and the f2-f1 distortion products and we have found that the neural distortion product threshold curve for 2f1-f2 mirrors the low-frequency side of the frequency threshold curve, when the neural distortion product threshold curve of 2f1-f2 is plotted versus log(f2/f1) its slope is about 50 dB/oct and its intercept is 10-20 dB above the frequency threshold at the characteristic frequency CF, substantial 2f1-f2 distortion was seen in all animals studied while the f2-f1 distortion product was only rarely found at substantial levels, and the distortion product pressure observed in the ear canal was at a level equal to that detected at threshold by the neural units under study. We have also made measurements of two-tone rate suppression thresholds using two new and consistent threshold paradigms. We find that for high and intermediate characteristic frequency neural units the suppression threshold is independent of frequency and at a level of about 70 dB SPL, the suppression above CF is much less than below CF, and the tip of the frequency tuning curve can be suppressed by up to 40 dB by a low-frequency suppressor.

Animals↗
PubMed1997

Perception of body size and body satisfaction in recovered anorexic women: comparison with restrained and unrestrained eaters.

The perception of body size, measured by three different methods, and body satisfaction were assessed in 23 formerly anorexic inpatients with an "intermediate" (n = 9) or a "good" outcome (n = 14) and compared with the data obtained from 21 restrained and 20 unrestrained eaters. Using the Kinaesthetic Size Estimation Apparatus, overestimation and uncertainty in the perception of body size became apparent in both groups of former patients. The other two methods, Video Distortion Technique and Image Marking Procedure, did not produce comparable results. There was only a trend towards higher scores on body dissatisfaction, as measured by the Body Shape Questionnaire, in the patients' groups in comparison with the group of unrestrained eaters, whereas the patients' scores on body dissatisfaction were quite similar to those of the restrained eaters. None of these measures discriminated between the two outcome categories of "intermediate" and "good.". These findings suggest that restoration of body weight, by itself, obviously does not cause a normalization of body experience in all its components in patients with anorexia nervosa.

Adolescent↗