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Biomedical subjects

R Shoup

Publications and source records attributed to R Shoup.

7 recordsLinked to original sources
PubMed2000

Response selection processes for conjunctive targets.

A model is proposed for identification and response selection of cross-dimensional conjunctive stimuli. The model assumes that the formation of conjunction representations involves processes similar to those used in response selection for single-feature targets. It predicts that discrimination between conjunctive targets leads to separate competitions in each of the relevant component dimensions and that detection of a predefined single conjunctive target is done at the conjunctive map level. Experiments 1 and 2 support these two sets of predictions. Experiment 3 demonstrates that responses to conjunctions of features within the orientation dimension are qualitatively different from those for cross-dimensional conjunctive targets. It is speculated that line-orientation conjunctions are handled by the visual object-recognition system, whereas cross-dimensional conjunctions, as exemplified by the model, may be performed by a different system that is closely associated with response selection processes.

Adult↗
PubMed1999

Localization of the human frontal eye fields and motor hand area with transcranial magnetic stimulation and magnetic resonance imaging.

We localized the neuroanatomical correlates for control of saccadic eye movements and for finger movements using a combined transcranial magnetic stimulation (TMS) and magnetic resonance imaging (MRI) approach. Two participants underwent TMS while performing an endogenous saccade task. The motor hand area was localized by TMS and the region anterior to it was mapped to identify the borders of a region where TMS produced delays in generating contralateral saccades. MRI scans were then obtained with fiducial markers placed over the motor hand area and 2 cm anterior to it, the common cortical region that produced saccadic delays in these two subjects. It was also shown that the structural anatomy of the hand area, physiologically defined by visible contractions of the contralateral hand following TMS, corresponded to the knob-like structure recently reported [18, 19]. These results demonstrate that TMS can be a precise, non-invasive tool for neuroanatomical mapping of cortical structures when combined with structural images of the brain.

Adult↗
PubMed1997

Perceptual dimensional constraints in response selection processes.

Most processing stages theorists assume that response selection processes are largely autonomous from earlier perceptual analysis of information. We report findings that challenge this assumption and suggest that a much more complex interaction exists between perception and action. Specifically our study demonstrates that the initial analysis of visual objects into features from different dimensions strongly constrains postperceptual processes of response selection. When a target that is associated with a response on the basis of one dimension is presented simultaneously with flankers that are associated with a response on the basis of another dimension, the response to the target is not affected by the identity of the flankers. These findings hold under a variety of conditions and appear to be specific to perceptual dimensions. When both target and flankers are associated with a response on the basis of the same dimension, the response to the target is affected by the identity of the flankers even when the target and flankers are perceptually dissimilar or belong to different semantic categories (digits and letters). We propose a model of response selection that can account for these findings. The model assumes that initial response selection processes for simple features are performed within dimensional modules and suggests a specific mediating role for spatial attention. We argue that this model is compatible with several other lines of research.

Analysis of Variance↗
PubMed1997

Body composition and health-related quality of life in patients with obstructive airways disease.

This study evaluated the effects of body weight and lean mass abnormalities on health-related quality of life (HRQL) in obstructive airways disease. Body weight, lean mass (using dual-energy X-ray absorptiometry), and HRQL (using the St George's Respiratory Questionnaire (SGRQ)) were measured in 50 patients. Low lean mass was defined as a lean mass index (lean mass/height2) below the fifth percentile of a control population. Dyspnoea was measured by the baseline dyspnoea index. The mean (SD) age was 69+/-9 yrs; the forced expiratory volume in one second (FEV1) was 39+/-19% of predicted. Patients had 2.4+/-4.1 kg less lean mass than predicted. Increased dyspnoea was the most influential predictor of poor HRQL. Compared to normal-weight patients, those who were underweight had significantly greater impairment in activity, impact, and total SGRQ scores, while those who were overweight had greater impairment in impact and total SGRQ scores. Low lean mass was associated with greater impairment in symptoms, activity and impact subscores and the total SGRQ score. When dyspnoea was added to the model as a covariate, neither weight nor lean mass remained significantly related to HRQL. Thus, although body weight and lean mass abnormalities influence health-related quality of life, their effects appear to be mediated through increased levels of dyspnoea.

Absorptiometry, Photon↗