Influence of arthritis and non-arthritis related factors on areal bone mineral density (BMDa) in women with longstanding inflammatory polyarthritis: a primary care based inception cohort

<p>Abstract</p> <p>Background</p> <p>The aim of this analysis was to determine the relative influence of disease and non-disease factors on areal bone mineral density (BMD_a) in a primary care based cohort of women with inflammatory polyarthritis.</p> <p>Methods</p> <p>Women aged 16 years and over with recent onset inflammatory polyarthritis were recruited to the Norfolk Arthritis Register (NOAR) between 1990 and 1993. Subjects were examined at both baseline and follow up for the presence of tender, swollen and deformed joints. At the 10^thanniversary visit, a sub-sample of women were invited to complete a bone health questionnaire and attend for BMD_a(Hologic, QDR 4000). Linear regression was used to examine the association between BMD_awith both (i) arthritis-related factors assessed at baseline and the 10^thanniversary visit and (ii) standard risk factors for osteoporosis. Adjustments were made for age.</p> <p>Results</p> <p>108 women, mean age 58.0 years were studied. Older age, decreasing weight and BMI at follow up were all associated with lower BMD_aat both the spine and femoral neck. None of the lifestyle factors were linked. Indices of joint damage including 10^thanniversary deformed joint count and erosive joint count were the arthritis-related variables linked with a reduction in BMD_aat the femoral neck. By contrast, disease activity as determined by the number of tender and or swollen joints assessed both at baseline and follow up was not linked with BMD_aat either site.</p> <p>Conclusion</p> <p>Cumulative disease damage was the strongest predictor of reduced femoral bone density. Other disease and lifestyle factors have only a modest influence.</p

The analysis of slant-from-texture in early vision

A considerable amount of research exists on the subjective perception of three-dimensional structure from texture gradients. The present set of experiments extends these tests of phenomenal perception by examining the underlying processes used in interpreting slant-from-texture. The first two experiments show that measures of subjective perception predict speeded performance in a visual search task, and that the mediating representation relies on an assumption of projective size (i.e., discriminating the size of the target is difficult when the short target is far or the long target is near). The third experiment shows that sensitivity to apparent depth in the texture display is present even in rapid and parallel search conditions where early vision is known to operate. The fourth experiment assesses the relative contribution of two dominant dimensions of the texture gradient -- "perspective" (i.e., a radial pattern) and "compression" (i.e., a foreshortened pattern). Both dimensions are detected by early vision as signals for apparent depth. The fmal experiment examines how early vision codes these two dimensions. Sternberg's (1969) Additive Factors Method (AFM) is used to assess separability of encoding, and Blalock's path analysis (1962, 1985) is used to examine the order of encoding. AFM shows that perspective and compression have independent influences on search performance in the most rapid search conditions, but that their interaction increases as search slows. The path analysis shows further that when both texture dimensions are available, perspective exerts a more immediate and perhaps even an exclusive influence on performance. These findings support the view that perspective and compression are coded separately at the earliest stages of visual processing and share a common code only later in visual processing.Arts, Faculty ofPsychology, Department ofGraduat

Visual search for direction of shading is influenced by apparent depth

Recentreports ofrapid visual search for some feature conjunctions-suggestedthat preattentive vision might be sensitive to scene-based as well as to image-based features (Enns &amp; Rensink, 1990a, 1990b). This study examined visual search for targets defined by the direction of a luminance gradient, a conjunction of luminance and relative location that often: corresponds to ob-= ject curvature and direction of lighting in naturalistic scenes. Experiment 1 showed that such search is influenced by several factors, including the type of gradient, the shape of the contour enclosing the gradient, and the background luminance. These factors were variedsystematically in Experiment 2 in a three-dimensionality rating task and in a visual-search task. The factors combined interactively in the rating task, supporting the presence of an emergent property of three-dimensionality. In contrast, each factor contributed only additively tothe speed of the visualsearch task. This is inconsistent with the view that search is guided by specialized detectors for surface curvature or direction of lighting. Rather, it is in keeping with the view that search is governed by a number of “quick and dirty ” processes that are implemented rapidly and inparallel across the visual field. Conventional theories of preattentive vision claim that simple features such as size, orientation, luminance, and motion are registered automatically and in parallel, whereas the serial spotlight of attention is required todetect conjunctions of these features (Beck, Prazdny, &amp; Rosenfeld, 1983; Julesz, 1984; Treisman, 1986). This claim is based on data from visual-search and texture-segmentation tasks: preattentive sensitivity is implicated by visual-search rates that are relatively independent of display size (i.e., less than 10 msec per item) and by textureboundaries that are perceived spontaneously (i.e., within 50-100 msec of display onset). Recently, there havebeen several reports of very rapid search andlor texture segmentation based on complex conjunctions of these features. Ramachandran (1988) showed that it is possible to segment a texture on the basis of the direction of the luminance gradients within circular textur

Visual search for size is influenced by a background texture gradient

Research on the perception of texture gradients has relied heavily on the subjective reports of observers engaged in free-viewing. We asked whether these findings generalized to speeded performance. Experiment 1 showed that an important aspect of subjective perception—sizeconstancy scaling with perceived distance—also predicted the speed of pop-out visual search for cylinders viewed against a texture gradient. Experiment 2 showed that this finding could not be attributed to the local contrast between search items and the background texture. Experiment 3 assessed the relative contributions of 2 separable dimensions of texture gradients—perspective (radial spreading) and compression (foreshortening)—finding them to be independent in the more rapid search conditions (long target among shorter distractors) but combined in their influence in the slower conditions (short target among longer distractors). When observers view the texture gradient shown in Figure 1A they usually report seeing a flat surface recede into the distance, despite the fact that a two-dimensional (2-D) image alone cannot specify the three-dimensional (3-D) surface that gave rise to the projection. This study asked whether the factors influencing the perceived slant of such texture gradients also influences rapid visual search for objects placed on their surface. Although a large number of previous studies have examined the perception of slant in texture gradients (e.g., Flock