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.

SourceResearch connectionFrom yearThrough year

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

At least 685 records · Page 38Linked to original sources

PubMed1992

Caricature and face recognition.

Although caricatures are often gross distortions of faces, they frequently appear to be super-portraits capable of eliciting recognition better than veridical depictions. This may occur because faces are encoded as distinctive feature deviations from a prototype. The exaggeration of these deviations in a caricature may enhance recognition because it emphasizes the features of the face that are encoded. In two experiments, we tested the superportrait hypothesis and the encoding-by-caricature hypothesis. In the first experiment, caricatures were recognized better than faces, and true caricatures of previously seen faces were recognized better than the faces from which the caricatures had been developed. In the second experiment, faces and their caricatures were tachistoscopically presented in a sequential same/different reaction time task. Subjects were slower to distinguish the stimuli when the face preceded its caricature, indicating that caricatures are more similar to the encoded representation of a face than are stimuli in which the distinctive features are deemphasized.

Adult↗

PubMed2002

Effects of age on the distortion product otoacoustic emission growth functions.

Age-related hearing loss (presbycusis) is thought to result from age-related degeneration (aging) of the cochlea plus the cumulative effects of extrinsic damage (noise and other ototoxic agents) and intrinsic disorders (e.g. systemic diseases). Previous studies have implicated dysfunction of the hair cells (sensory presbycusis) as the principal mechanism of age-related hearing loss. However, recent evidence from quiet-reared gerbils suggests that cochlear aging results primarily from atrophy of the stria vascularis, which is associated with diminished endocochlear potential (EP), spiral ganglion atrophy, and a relatively flat audiometric loss, termed metabolic presbycusis. Because it is not currently possible to measure EP directly in the clinical setting, we wondered if cochlear metabolic dysfunction might be evidenced indirectly from existing clinical tests, specifically, the input-output (IO) growth function of the distortion product (DP) otoacoustic emissions in relation to behavioral hearing threshold levels (HTL). We anticipated finding discordance between the IO functions and HTL with either a greater decline with age in HTL than in IO functions if an age-related metabolic dysfunction of the cochlea was operant, or a greater loss of IO function than HTL if outer hair cell dysfunction was the dominant pathology. To address this supposition we analyzed existing auditory data from a large cohort of adults to determine the change with age in three aspects of the DP IO function: area under the curve, threshold, and slope. The analyses demonstrated a greater effect of age on HTL than on the DP IO measures. This effect supports the hypothesis that strial dysfunction is a substantive factor in cochlear aging. The etiology and mechanisms for this dysfunction are conjectural at present.

Adult↗

PubMed2003

Sound-evoked efferent effects on cochlear mechanics of the mustached bat.

The influence of the crossed medial efferent system on cochlear mechanics of the mustached bat was tested by measuring delayed evoked otoacoustic emissions (DEOAEs), cochlear microphonics, distortion product otoacoustic emissions (DPOAEs) and stimulus frequency otoacoustic emissions. Contralaterally delivered sinusoids, broadband noise and bat echolocation calls were used for acoustic stimulation of the efferent system. With all four measures we found a level-dependent suppression under stimulation with both broadband noise and echolocation calls. In addition, the sharply tuned cochlear resonance of the mustached bat which is involved in processing echolocation signals at 61 kHz shifted upward in frequency by several 100 Hz. Presentation of sinusoids did not have any significant effect. DEOAEs and DPOAEs were in some cases enhanced during contralateral presentation of the bat calls at moderate intensities. The most important function of the efferent system in the mustached bat might be the control of the extraordinarily fine-tuned resonator of this species, which is close to instability as evident from the very pronounced evoked otoacoustic emissions which sometimes convert into spontaneous otoacoustic emissions of high level.

Acoustic Stimulation↗

PubMed1992

Attentive fields are related to focal and contextual features: a study of Müller-Lyer distortions.

The mathematical model associated with integrative field theory was used to infer the size of attentive fields in a task involving judgments of size. A compounded Müller-Lyer task was employed in which fins between or outside the standard shafts were systematically removed. Performance on this task was simulated by a computer that generated families of theoretical functions varying in the parameter of attentive field size. Individual theoretical functions were then correlated with an empirical function obtained from real observers. The value of attentive field size that provided the best fit between functions was then selected. The results showed that, in almost all cases, the optimum size of the attentive field was smaller for the shrinkage form than for the expansion form of the Müller-Lyer pattern, that the attentive field changed more dramatically with changes in stimulus variables in the expansion form than in the shrinkage form, and that changes in viewing distance had little effect on the optimum size of the attentive field. It was concluded that the attention was involved both in figure-ground segregation and in maintaining object constancy. The similarity of these results to data obtained in recognition and detection tasks was noted.

Adult↗

PubMed2002

Effects of electrical stimulation of the inferior colliculus on 2f1-f2 distortion product otoacoustic emissions in anesthetized guinea pigs.

The effects of electrical stimulation of the inferior colliculus (IC) on the activation of olivocochlear nerve fibers were investigated in guinea pigs in which the 2f1-f2 distortion product otoacoustic emissions (DPOAE) were recorded. Animals were anesthetized with ketamine (33 mg/kg) and xylazine (6.6 mg/kg). Bipolar electrical stimulation of the IC by a train of pulses with currents less than the threshold for evoking muscle twitches resulted in a small depression of the DPOAE amplitude by 0.1-2 dB. The maximal effect was observed when the stimulating electrodes were located in the rostro-medial or ventral parts of the IC. The suppression of electrically evoked DPOAE was similar to the DPOAE suppression produced by acoustical stimulation of the contralateral ear by a broad-band noise. Suppression of DPOAE amplitude in response to both acoustical and electrical stimulation was abolished 1-2 h after a single intramuscular injection of gentamicin (210-250 mg/kg). The results indicate that electrical stimulation of the IC can activate the efferent system and produce DPOAE changes by similar mechanisms as does acoustical stimulation of the contralateral ear.

Animals↗

PubMed2003

Distortion-product otoacoustic emissions study of the noise-induced toughening effect in rats.

OBJECTIVE: To compare the toughening effects in rats induced by pure tones and a broadband noise (BBN). MATERIAL AND METHODS: Sprague-Dawley female albino rats (n = 148; 8-10 weeks old) were used. Three experimental groups were established as follows. Toughening only: 38 rats, divided into 3 subgroups, were exposed to different conditioning sounds (2 and 4 kHz and a BBN of 0.25-6 kHz, respectively) at 75-85 dB sound pressure limit (SPL) for 8 h/day for 10 days. Acoustic trauma only: 54 rats, divided into 3 subgroups, were exposed to different conditioning sounds as above for 24 h at 100-110 dB SPL. Toughening plus acoustic trauma: 56 rats, divided into 3 subgroups, were exposed to different conditioning sounds as above, followed 8 h later by traumatic exposure to the conditioning sound at 110 dB SPL for 24 h. 2f1-f2 distortion-product (DP) otoacoustic emission measurements were obtained from the right ear of each animal pre-exposure, immediately post-exposure and after 8 h of the traumatic or conditioning exposure. RESULTS: In our control DPgram response, the maximum amplitude occurred at the highest frequencies (2, 3, 4, 5 and 6 kHz). No statistical differences between the control DPgram and the DP toughening (2 and 4 kHz and BBN)responses were found. Only 2 and 4 kHz frequencies induced a protective effect against traumatic sound exposures to the same frequencies, and this finding was statistically significant. CONCLUSION: The toughening phenomenon induced using 2 and 4 kHz pure tones and BBN in rats does not modify the DPgram response. Nevertheless, only 2 and 4 kHz frequencies induce a protective effect against traumatic sound exposures to the same frequencies.

Adaptation, Physiological↗

PubMed1984

Distance distortions in children's cognitive maps: an examination of the information storage model.

Second graders (mean age = 7-8), fourth graders (mean age = 9-8), and sixth graders (mean age = 11-11) walked two paths located in and around their school. Children in the Unsegmented condition estimated the distance and time taken to walk a path that was relatively undifferentiated in terms of the number of qualitatively different areas of the school through which it passed. Children in the Segmented condition made the same estimates for a path that went through different areas (segments) of the school (i.e., cafeteria, hall, vestibule, and outside the building). Children at all three grade levels estimated that the distance traversed in the Segmented condition was longer than the distance in the Unsegmented condition. This difference was not significant on the time measure. It was concluded that (1) paths with a large number of segments are perceived as being longer than paths of the same length with fewer segments, (2) distances along paths with few segments are underestimated, (3) distances along paths with many segments may be overestimated as a function of developmental level, and (4) only younger children may have used time to estimate distance.

Child↗

PubMed2002

Evaluation of anesthesia effects in a rat animal model using otoacoustic emission protocols.

Anesthesia effects on otoacoustic emission (OAE) recordings were evaluated in a group of 72 Sprague-Dawley rats (mean weight 225+/-20 gr). Two anesthesia dosages (high and normal) and two anesthetic protocols (ketamine-xylazine, ketamine-xylazine-atropine) were tested. Transient evoked OAE (TEOAE) and distortion product OAE (DPOAE) responses were recorded in 10 min intervals, for a total period of 60 min. Analyses of the data with repeated measure models indicated the following: (1) The animals receiving a high dose of anesthesia (cumulative dose 66.6 mg of ketamine and 13.2 mg of xylazine/kg of body weight) presented significant alterations of the TEOAE response level and the signal to noise ratio at 3.0 kHz; (2) the animals receiving a normal dose of ketamine-xylazine anesthesia (cumulative dose 50 mg of ketamine and 10 mg of xylazine/kg of body weight) presented TEOAE and DPOAE responses invariant in terms of time; (3) significant differences were observed in the DPOAE responses from animals anesthetized with ketamine-xylazine and ketamine-xylazine-atropine. The data support the hypothesis that the ketamine anesthesia OAE suppressing mechanism is related to middle-ear mechanics.

Adjuvants, Anesthesia↗

PubMed2003

Cognitive basis of hallucinations in schizophrenia: role of top-down information processing.

Hallucinations in schizophrenia have been regarded to result from the erroneous attribution of internally generated information to an external source. Distortions in mental imagery may underlie such confusions. We investigated performance of 77 subjects on multiple behavioral measures of auditory and visual mental imagery and perception, and a measure of reality monitoring. Comparisons were made between performance of schizophrenia patients with (N=22) and without (N=35) hallucinations and matched normal comparison subjects (N=20), after controlling for attentional factors. No differences emerged on any of the mental imagery measures, nor on reality monitoring accuracy. This suggests that there is no stable disposition towards abnormal mental imagery associated with hallucinations. However, for patients with active hallucinations (N=12), hallucination severity correlated positively with a measure of imagery-perception interaction in the auditory modality, r=0.70, p=0.01. Although preliminary, this finding is consistent with recent theoretical proposals in which hallucinations have been suggested to result from an increased influence of top-down sensory expectations on conscious perception.

Adult↗

PubMed2001

Ouabain application to the round window of the gerbil cochlea: a model of auditory neuropathy and apoptosis.

The physiological and morphological changes resulting from acute and chronic infusion of ouabain onto the intact round-window (RW) membrane were examined in the gerbil cochlea. Osmotic pumps fitted with cannulas allowed chronic (0.5-8 days) infusions of ouabain. Acute and short-term applications of ouabain (1-24 h) induced an increase in auditory-nerve compound action potential (CAP) thresholds at high frequencies with lower frequencies unaffected. The resulting threshold shifts were basically all (no response) or none (normal thresholds), with a sharp demarcation between high and low frequencies. Survival times of 2 days or greater after ouabain exposure resulted in complete auditory neuropathy with no CAP response present at any frequency. Distortion product otoacoustic emissions (DPOAEs) and the endocochlear potential (EP) were largely unaffected by the ouabain indicating normal function of the outer hair cells (OHC) and stria vascularis. One to 3 days after short-term applications, apoptosis was evident among the spiral ganglion neurons assessed both morphologically and with TdT-mediated dUTP-biotin nick end labeling (TUNEL). With 4-8 day survival times, most spiral ganglion cells were absent; however, a few cell bodies remained intact in many ganglia profiles. These surviving neurons had many of the characteristics of type II afferents. Our working hypothesis is that the ouabain induces a spreading depression among the type I ganglion cells by blocking the Na,K-ATPase pump. Because of the constant spike activity of these cells, the ouabain rapidly alters potassium concentrations within ([K+]i) and external to ([K+]o) the ganglion cells, thereby initiating an apoptotic cascade.

Action Potentials↗

PubMed1988

Affine distortions of pictorial space: some predictions for Goldstein (1987) that La Gournerie (1859) might have made.

Goldstein (1987) studied the perception of pictures seen from the front and the side. Several distinctions arose from his results and analysis, but only one is central to the reanalysis presented here: The perceived orientation of objects within a picture with respect to the external world is a function of viewer position in front of the picture. For example, the eyes of a portrait subject appear to follow an observer who moves around a gallery. Viewed from many positions, such objects can be said to rotate, following a mobile viewer. Goldstein called this the differential rotation effect because those objects that point directly out of the picture (at 90 degrees) rotate most; those pointing at other angles rotate in decreasing amounts. Goldstein offered no theoretical model and little in the way of explanation for this effect. This Observation offers a model based on the affine geometry and the analyses of La Gournerie (1859). This analysis transforms pictorial space (the space behind a photograph or representational picture) by shears, compressions, and dilations according to the viewpoint of the observer in relation to the composition point of the picture. These effects account for Goldstein's differential rotation effect quite well.

Depth Perception↗

PubMed2002

Effects of noise on the intensity of distortion product otoacoustic emissions.

Distortion product otoacoustic emission (DPOAE) is a widely used differential diagnostic method for diagnosing inner ear disorders. It provides us information on the condition of the outer hearing cells (OHCs). Otoacoustic emission occurs only when the OHCs are functioning normally. Changes in thresholds of DPOAE curves can provide us important information on the activity of the OHCs. The inner ear shows nonlinear properties if the OHCs are functioning normally. If OHCs are injured and thus function improperly, the system stops showing nonlinear properties. If we have a system with periodic excitation and, with the addition of white noise, the signal-to-noise ratio on the output increases (at least for small noise intensities), we have witnessed what is called phenomenon stochastic resonance. Our goal was to elucidate how white noise influences the intensity of DPOAE. If there is emission, that specific ear surely exhibits nonlinear behavior, which in turn is the basic property needed for stochastic resonance.

Adult↗

PubMed2005

Responsibility attitude in a sample of Iranian obsessive-compulsive patients.

BACKGROUND: The study of distorted beliefs about responsibility attitude and interpretation has become the central theme in Salkovskis' (1985) and Rachman and Hodgson's (1980) models of Obsessive-Compulsive Disorder (OCD). AIMS: The aim of this research is to assess the responsibility attitude in Iranian OCD patients. METHODS: Twenty OCD patients were selected through available sampling from the case referred to psychology clinics. Two other patient groups comprised of 20 non-OCD anxiety disorder patients and 20 non-clinical participants were also chosen as comparison groups. All participants completed the Responsibility Attitude Scale (RAS) and Responsibility Interpretation Questionnaire (RIQ). RESULTS: Analyses revealed statistically significant differences between OCD group and comparison groups on both RAS and RIQ. In addition, both RAS and RIQ scores were associated with the severity of OCD assessed by the Yale-Brown scale. CONCLUSIONS: These findings suggest that responsibility attitude and interpretations are the prominent features of OCD in Iranian patients and are associated with the severity of illness.

Adult↗

PubMed1995

Body size estimation in eating disorder patients: testing the video distortion method on a life-size screen.

The video distortion method on a life-size screen is a new method for studying eating disordered patients' estimations of their own body width. Testing this method in female patients (53 with anorexia nervosa, 38 with bulimia nervosa) and 36 normal females, yielded high to very high reliability scores (consistency and test-retest stability). A careful analysis of the 'just noticeable difference' showed that a 5% deviation from the undistorted image should be considered as within the range of accuracy. Taking this into account, anorectic patients appear to score below, above, as well as within the normal range. Bulimia nervosa patients are either accurate in their body estimations or overestimate their body width. All control Ss are correct in their estimations. With this method no significant differences were found between the anorectic patients and the controls. Bulimics differ significantly from anorectics and controls on their optative responses (i.e. what they wanted to look like) and their affective responses (i.e. what they felt they looked like).

Adolescent↗

PubMed2003

Otoacoustic emissions and brainstem evoked potentials in compound carriers of connexin 26 mutations.

This study compares the effects of mutations in the gap junction protein connexin 26 (Cx26), on outer hair cells (OHCs), inner hair cells (IHCs) and auditory nerve/brainstem among carriers of these mutations. One hundred and twenty eight individuals, from a village with widespread consanguinity and congenital deafness, due to three Cx26 mutations, were selected among relatives of deaf persons, and divided into non-carriers, carriers of one mutation, homozygous to one mutation, or compound heterozygous carriers of two different mutations. Distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs) and audiometric evaluation were compared in these genetic groups. Hearing loss among homozygotes and compound heterozygotes was comparable and ranged from mild to profound. Most ABRs from these groups showed no responses or partial responses (peaks III, V) with prolonged latencies, but some individuals had all peaks at normal latencies. DPOAEs were absent, except sporadic responses. Carriers of one mutation had significantly smaller DPOAEs compared to non-carriers, although normal pure tone audiograms and ABRs were found in these groups. In conclusion, based on DPOAEs, Cx26 mutations may impact OHC function among carriers of one or two Cx26 mutations. IHC/nerve impairment among homozygotes and compound heterozygotes is variable. OHCs may be more susceptible to Cx26 mutations compared to IHCs and the auditory nerve and brainstem pathway activated by them.

Adolescent↗

PubMed1997

[Are negative cognitions symptoms of depression or also an expression of personality traits?].

This study examined the changes from hospital admission to discharge of different categories of cognitive distortions - automatic thoughts, self-concepts and dysfunctional attitudes - in 67 patients with an ICD-10 diagnosis of a depressive episode. Furthermore, the relationships were analyzed between cognitive distortions, degree of depression, and personality dimensions (isolation tendency, extraversion, rigidity, schizoidia, frustration tolerance and neuroticism). There was a significant correlation between automatic thoughts and negative self-concepts on the one hand, and severity of depression on the other upon admission. There was a significant reduction of automatic thoughts and the negativity of self-concepts from admission to discharge. No significant association was observed, however, between the severity of depression and dysfunctional attitudes. In addition, dysfunctional attitudes showed a significant decrease until discharge only in patients with a full remission of depressive symptoms. These results underline the fact that automatic thoughts and self-concepts are more state-dependent than dysfunctional attitudes. Moreover - even taking into account the degree of depression - there was a significant relationship between the personality dimension neuroticism and all cognitive scales upon admission. This indicates that a high degree of neuroticism may facilitate the emergence of negative cognitions during a depressive episode.

Adult↗

PubMed1990

The behavior of the acoustic distortion product, 2f1-f2, from the human ear and its relation to auditory sensitivity.

The acoustic intermodulation distortion product 2f1-f2 (ADP) was measured in human subjects to investigate (1) the dependence of ADP level on stimulus parameters and (2) the relationship between ADP level and auditory sensitivity. The frequency ratio (f2/f1), at which ADP level is maximal, varies only slightly across frequency and subjects. The average optimal ratio is 1.225. Beyond the maximum, the ADP level declines with increasing f2/f1 ratio, at rates of up to 250 dB/oct. As the level of one stimulus is increased relative to the other, the ADP grows, saturates, and in most cases shows a bendover. Maximum distortion is generated when L 1 exceeds L 2. Growth rate and saturation point are dependent on which stimulus is incremented and on the level of the stationary stimulus. With optimal stimulus parameters (levels below 60 dB SPL; L 1 greater than L 2 by 15 dB; f2/f1 = 1.225), ADP levels are commonly 30 dB below L 2. Patterns of ADP level across frequency vary between subjects, but are repeatable within each subject. As the frequency of one or both of the stimuli is varied, changes in ADP level exhibit a broadly featured pattern with a fine structure superimposed upon it. This fine structure was compared with the features in the stimulus frequency emission spectrum in one subject. With appropriate stimulus parameters, half of our subjects show a statistically significant correlation across frequency, between ADP level and auditory sensitivity at the corresponding f1 frequency. Our results suggest that, with low levels of stimulation, ADP measurements could form the basis of an objective measure of cochlear function in human subjects.

Adolescent↗

PubMed1987

Relations among temporal acuity, hearing loss, and the perception of speech distorted by noise and reverberation.

Eight normal listeners and eight listeners with sensorineural hearing losses were compared on a gap-detection task and on a speech perception task. The minimum detectable gap (71% correct) was determined as a function of noise level, and a time constant was computed from these data for each listener. The time constants of the hearing-impaired listeners were significantly longer than those of the normal listeners. The speech consisted of sentences that were mixed with two levels of noise and subjected to two kinds of reverberation (real or simulated). The speech thresholds (minimum signal-to-noise ratio for 50% correct) were significantly higher for the hearing-impaired listeners than for the normal listeners for both kinds of reverberation. The longer reverberation times produced significantly higher thresholds than the shorter times. The time constant was significantly correlated with all the speech threshold measures (r = -0.58 to -0.74) and a measure of hearing threshold loss also correlated significantly with all the speech thresholds (r = 0.53 to 0.95). A principal components analysis yielded two factors that accounted for the intercorrelations. The factor loadings for the time constant were similar to those on the speech thresholds for real reverberation and the loadings for hearing loss were similar to those of the thresholds for simulated reverberation.

Acoustic Stimulation↗