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Results for “Perceptual Distortion”

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At least 307 records · Page 17Linked to original sources
PubMed2006

Temporal instability in the perception of strabismic amblyopia.

Amblyopia is a developmental disorder of spatial vision resulting from an abnormal visual stimulation in early childhood. The aim of our study was to investigate the spatial and temporal distortions that occur in strabismic and anisometropic amblyopic vision. The main focus was on the temporal instability of amblyopic perception of low and high spatial frequencies. Our results indicate that temporal instability is perceived mainly by strabismic and strabismic-anisometropic amblyopes and occurs only at high spatial frequencies. We found two categories of temporal distortions in high spatial frequency patterns: a) the whole pattern is perceived as jittering, b) single lines or parts in a pattern are perceived as moving. Our data suggest that strabismus, in addition to amblyopia, is needed to elicit significant temporal distortions.

Adult↗
PubMed2001

Neurocognitive evidence favors "top down" over "bottom up" mechanisms in the pathogenesis of body size distortions in anorexia nervosa.

Perceptually-based disturbances in body image, or body size distortions, have been posited to occur in anorexia nervosa (AN). Perception does not result from a simple flow of sensory information from periphery to cortex ("bottom-up" processing), but involves the selection of inputs most likely to be relevant in light of an individual's experience and expectations ("top-down" processing). Most investigations of body size distortion in AN have used procedures likely to engage top-down processing, raising the possibility that attitudinal disturbances may play a role. To our knowledge, there have been no studies that assess the presence, in AN, of neurocognitive deficits associated with neurologically based disturbances in body schema. Such deficits, if found, could provide evidence of body image distortion unlikely to result from top-down processing. We tested 20 inpatients with AN on measures of proprioception, finger identification, right/left orientation, general cognition and eating disorders symptomatology, both before and after treatment. Matched normal controls were tested on the same measures over the same time intervals. Significant differences between the two groups occurred only prior to treatment, and only on those measures which involved executive, in addition to more body-schema-specific functions. This suggests that patients with AN do not have enduring deficits in the domain of body-schema, but may have subtle cognitive dysfunction, in the acute state, which is not specific to, but can interact with processing of body-schema-related information. This, in turn, suggests that their body image distortion may not be secondary to bottom-up perceptual disturbances.

Adolescent↗
PubMed2002

Recognizing the un-real McCoy: priming and the modularity of face recognition.

Fodor (1983) has proposed that face perception is carried out by an informationally encapsulated module, whose operation is unaffected by context or expectancies. We tested the modularity hypothesis by examining whether discriminations between normal and distorted versions of famous faces can be primed, either by the name of an associated person (semantic context) or by a valid cue as to the identity of the target face (expectancy). A preliminary experiment showed that, in the absence of priming, discriminations between normal and distorted versions of a face were unaffected by whether the target faces were familiar or not, confirming that these judgments tap perceptual, not postperceptual (semantic), coding processes. In Experiment 1, accuracy was significantly higher when target face pairs were preceded by related name primes, as compared with unrelated ones. In Experiment 2, reaction times were significantly faster for targets preceded by a valid identity cue than for targets preceded by an invalid one. Neither effect could be explained as a speed-accuracy tradeoff. These results fail to support Fodor's conjecture that face processing is encapsulated.

Adult↗