Many researchers have explored the way younger people perceive weight ratios using a variety of methodologies; however, very few researchers have used a more direct ratio estimation procedure, in which participants estimate an actual ratio between two or more weights. Of the few researchers who have used a direct method, the participants who were recruited were invariably younger adults. To date, there has been no research performed to examine how older adults perceive weight-ratios, using direct estimation or any other technique. Past research has provided evidence that older adults have more difficulty than younger adults in perceiving small differences in weight (i.e., the difference threshold for older adults is higher than that of younger adults). Given this result, one might expect that older adults would demonstrate similar impairments in weight ratio estimation compared to younger adults. The current experiment compared the abilities of 17 younger and 17 older adults to estimate weight ratios, using a direct ratio estimation procedure. On any given trial, participants were presented with two weights, and were asked to provide a direct estimate of the ratio, with the heavier in relation to the lighter. The results showed that the participants’ perceived weight ratios increased as a linear function of the actual weight ratios and that compared to younger adults, the older adults overestimated the weight ratios. The age-related overestimation was especially pronounced at higher weight ratios.

La mesure de la perte du volume cérébral est un marqueur IRM de la neurodégénérescence dans la sclérose en plaques. Les techniques actuelles permettent de quantifier soit directement la perte de volume cérébral entre deux examens, soit de la mesurer indirectement à partir du volume cérébral de chaque examen. La fiabilité de ces techniques reste difficile à évaluer en l’absence de gold standard. Ce travail a consisté premièrement, en une étude de reproductibilité réalisée chez 9 patients à partir d’acquisitions semestrielles (3 IRM), sur deux machines différentes et post-traitées par sept algorithmes : BBSI, FreeSurfer, Intégration Jacobienne, KNBSI, un algorithme Segmentation / Classification, SIENA et SIENAX. Deuxièmement, un suivi longitudinal et prospectif a été effectué chez 90 patients SEP. L’étude des variabilités inter-techniques et inter-sites a montré que les techniques de mesures indirectes (Segmentation/Classification, FreeSurfer) et SIENAX fournissaient des pourcentages d’atrophie hétérogènes. A l’inverse, les techniques de mesures directes telles que BBSI, KNBSI, Intégration Jacobienne et à un moindre degré SIENA obtenaient des résultats reproductibles. Toutefois BBSI, KNBSI et l’Intégration Jacobienne obtenaient des pourcentages faibles, suggérant une possible sous-estimation de l’atrophie. L’évaluation de la perte du volume cérébral par Intégration Jacobienne a montré sur 2½ ans de suivi, une atrophie de 1,21% pour les 90 patients et de 1,55%, 1,51%, 0,84%, 1,21% respectivement pour les patients CIS, RR, SP et PP. A l’avenir l’évaluation de la perte de volume cérébral impose des défis d’ordre technique afin d’améliorer la fiabilité des algorithmes actuels. / Brain volume loss is currently a MRI marker of neurodegeneration in MS. The available algorithms for its quantification perfom either direct measurements, or indirect measurements. Their reliability remains difficult to assess especially since there is no gold standard technique. This work consisted first, in a reproducibility study performed on nine patients’ biannual MRI acquisitions (3 time points). These acquisitions were performed on two different MRI systems. Post-processing was applied using seven algorithms: BBSI, FreeSurfer, Jacobian Integration, KNBSI, an algorithm based on segmentation/classification, SIENA and SIENAX. Second, a longitudinal and prospective study was performed in 90 MS patients. The study of inter-technique and inter-site variabilities showed that direct measurement techniques and SIENAX provided heterogeneous values of atrophy. In contrast, indirect measurement algorithms such as BBSI, KNBSI, Jacobian Integration and to a lesser extent SIENA obtained reproducible results. However BBSI, KNBSI and Jacobian Integration algorithms showed lower percentages, suggesting a possible underestimation of atrophy. The evaluation of brain volume loss by Jacobian Integration has shown an atrophy rate of 1.21% over 2 ½ years of the 90 patients’ follow up, and of 1.55%, 1.51%, 0.84%, 1.21% for CIS, RR, SP and PP patients respectively. Jacobian Integration showed its importance in individual monitoring. In the future, assessing brain volume loss requires overcoming of some technical challenges to improve the reliability of the currently available algorithms.

Both stroke and depression are major health problems in the elderly. In this study, the prevalence of major depression after stroke was investigated in a well-defined sample of acute stroke patients (n=80), followed up at 3 months, 1 year, 2 and 3 years after the stroke event. Links to biological and psychosocial factors were examined. Hypercortisolism was studied by the dexamethasone suppression test and compared with healthy elderly. Living conditions (including demographic caracteristics, economic resources, health, functional ability, activity/leisure, social network) and life satisfaction were described before and after stroke in relation to a general elderly population. Demographic caracteristics, economic resources, social network and psychiatric morbidity prestroke did not differ from the general elderly population. Already prior to the stroke, patients reported more health problems and lower functional ability in many aspects of daily life, more passive leisure time and a lower global life satisfaction. After stroke, contacts with children were maintained, whilst contacts outside the family declined and remained lower than in the general elderly population. Stroke involved a marked reduction in global life satisfaction. Poor life satisfaction at 1 year remained poor for the entire three years; these stroke victims had a higher frequency of major depression early after stroke. The prevalence of major depression was 25% at the acute stage, 31% at 3 months, decreased to 16% at 1 year, was 19% at 2 years and increased to 29% at 3 years. The most important predictors of immediate major depression were left anterior brain lesion, dysphasia, and living alone. Dependence in self-care ability and loss of social contacts outside the family were the most important predictors at 3 months. From 1 year onwards, loss of social contacts contributed most to depression and at 3 years also cerebral atrophy. Sixty percent of patients with early depression (0-3 months) had recovered at 1 year; those not recovered at 1 year had a high risk of chronicitation. Hypercortisolism as measured by the dexamethasone suppression test was associated with major depression late (3 years) but not early (0-3 months) after stroke. At 3 years, the dexamethasone suppression test had a sensitivity of 70%, a specificity of 97%, a positive predictive value of 88%, a negative predicitive value of 91%, and a diagnostic accuracy of 90%. Nonsuppression of dexamethasone at 3 months was a significant predictor of major depression at 3 years. / <p>Härtill 5 uppsatser</p> / digitalisering@umu