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Crowding changes appearance.

ABSTRACT: Crowding is the breakdown in object recognition that occurs in cluttered visual environments and the fundamental limit on peripheral vision, affecting identification within many visual modalities and across large spatial regions. Though frequently characterized as a disruptive process through which object representations are suppressed or lost altogether, we demonstrate that crowding systematically changes the appearance of objects. In particular, target patches of visual noise that are surrounded ("crowded") by oriented Gabor flankers become perceptually oriented, matching the flankers. This was established with a change-detection paradigm: under crowded conditions, target changes from noise to Gabor went unnoticed when the Gabor orientation matched the flankers (and the illusory target percept), despite being easily detected when they differed. Rotation of the flankers (leaving target noise unaltered) also induced illusory target rotations. Blank targets led to similar results, demonstrating that crowding can induce apparent structure where none exists. Finally, adaptation to these stimuli induced a tilt aftereffect at the target location, consistent with signals from the flankers "spreading" across space. These results confirm predictions from change-based models of crowding, such as averaging, and establish crowding as a regularization process that simplifies the peripheral field by promoting consistent appearance among adjacent objects.

SUBMITTER: Greenwood JA

PROVIDER: S-EPMC2849014 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Crowding changes appearance.

Greenwood John A JA Bex Peter J PJ Dakin Steven C SC

Current biology : CB 20100304 6

Crowding is the breakdown in object recognition that occurs in cluttered visual environments and the fundamental limit on peripheral vision, affecting identification within many visual modalities and across large spatial regions. Though frequently characterized as a disruptive process through which object representations are suppressed or lost altogether, we demonstrate that crowding systematically changes the appearance of objects. In particular, target patches of visual noise that are surround ...[more]

PMID: 20206527

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Project description:Many protein functions can be directly linked to conformational changes. Inside cells, the equilibria and transition rates between different conformations may be affected by macromolecular crowding. We have recently developed a new approach for modeling crowding effects, which enables an atomistic representation of "test" proteins. Here this approach is applied to study how crowding affects the equilibria and transition rates between open and closed conformations of seven proteins: yeast protein disulfide isomerase (yPDI), adenylate kinase (AdK), orotidine phosphate decarboxylase (ODCase), Trp repressor (TrpR), hemoglobin, DNA beta-glucosyltransferase, and Ap(4)A hydrolase. For each protein, molecular dynamics simulations of the open and closed states are separately run. Representative open and closed conformations are then used to calculate the crowding-induced changes in chemical potential for the two states. The difference in chemical-potential change between the two states finally predicts the effects of crowding on the population ratio of the two states. Crowding is found to reduce the open population to various extents. In the presence of crowders with a 15 A radius and occupying 35% of volume, the open-to-closed population ratios of yPDI, AdK, ODCase and TrpR are reduced by 79%, 78%, 62% and 55%, respectively. The reductions for the remaining three proteins are 20-44%. As expected, the four proteins experiencing the stronger crowding effects are those with larger conformational changes between open and closed states (e.g., as measured by the change in radius of gyration). Larger proteins also tend to experience stronger crowding effects than smaller ones [e.g., comparing yPDI (480 residues) and TrpR (98 residues)]. The potentials of mean force along the open-closed reaction coordinate of apo and ligand-bound ODCase are altered by crowding, suggesting that transition rates are also affected. These quantitative results and qualitative trends will serve as valuable guides for expected crowding effects on protein conformation changes inside cells.

Project description:INTRODUCTION:Living with an altered facial appearance as a result of treatment for cancer requires considerable psychological adjustment. As such it is essential that health care professionals understand the lived experience of people affected. This systematic review provides a meta-ethnography of studies that have explored the experience of changed facial appearance as a result of cancer. METHODS:A search of four databases (Web of Science, CINAHL, PsycInfo, and Scopus) took place using terms relating to qualitative research, cancer, and changed facial appearance. Thirteen studies were identified, appraised, and included in the synthesis. The findings and interpretations within the studies were subject to meta-ethnography procedures so as to elicit novel cross-cutting themes. FINDINGS:The experience of changed facial appearance after cancer was clustered into three contexts. In the context of the disease, subthemes were the primacy of survival, the changing relationship with the disease, and the impact of the care team on the experience of changed appearance. In the context of the social world, subthemes were positive reactions, negative reactions, and coping strategies. In the context of the self, subthemes were the self under attack, self-to-self relating, the self in the world, and rebuilding the self. CONCLUSIONS:The findings indicate that health care professionals must conduct holistic assessments, so as to fully recognize and where necessary address the impact upon self. The meta-ethnography shows that the experience of facial appearance change following cancer is complex and requires awareness of a number of theoretical areas including identity construction, social support, stigmatization, and the specific literature on visible difference. Statement of contribution What is already known on this subject? Changed facial appearance after cancer can cause significant social difficulties and impact on the sense of self. The experience of managing the specific dual challenges of cancer and altered facial appearance is not clearly understood. Recent studies that have focused specifically on the experience of changes in appearance after cancer have been limited in scope and transferability. What does this study add? To our knowledge, this is the first meta-ethnography to bring together the literature on the impact of altered facial appearance following cancer. Patients may feel unable to talk about appearance with health care professionals because it is seen as a frivolous issue. Clinicians should facilitate open, person-centred opportunities for patients to discuss the impact of changed appearance and where necessary facilitate access to support.

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Crowding changes appearance.

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Crowding changes appearance.

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