Biomedical subjects

C Lortie

Publications and source records attributed to C Lortie.

3 recordsLinked to original sources

PubMed1992

Selective reaching: evidence for action-centered attention.

Most studies of selective attention briefly present static 2-dimensional stimuli and require arbitrary responses such as verbal naming or a keypress. Many of our perceptual-motor interactions with the environment, however, require reaching directly toward an object while ignoring other objects in the scene. A series of experiments examines selective attention in the latter reaching situation. Effects previously observed in the traditional experimental procedures were obtained, suggesting that the models developed (which propose inhibitory mechanisms, e.g.) apply to ecologically valid situations. Attention accesses action-centered internal representations during such tasks.

Adult↗

PubMed1990

Effects of dexamethasone on macrophages in fetal and neonatal rat lung.

The effects of injecting dexamethasone to pregnant and newborn rats on the subsequent production of macrophages in the lung and on their phagocytic activity and lysosomal enzyme content were evaluated from late gestation to postnatal day 10 using an organ culture system to collect macrophages. Pieces of lung tissue cultured 6 days on cover glasses produced a halo of macrophages adherent to the glass around the explants. Thymidine labeling showed that the macrophages were derived from dividing precursors in the pulmonary interstitium. DNA synthesis was reduced after steroid treatment, and fewer cells were obtained on cover glasses, particularly just after birth when the macrophage number usually increases. Phagocytic function was also diminished in cells collected after dexamethasone injection, particularly when derived from neonatal animals. In contrast, intracellular levels of non-specific esterase and glucosaminidase were increased, probably indicative of lower phagolysosome formation and lower enzyme secretion. These results demonstrate that steroid administration to fetal or newborn animals subsequently reduces the number and phagocytic activity of macrophages in the lungs. This could reduce the defense mechanisms of the neonate and increase susceptibility to infection.

Animals↗

PubMed1990

Evidence for early selection: precuing target location reduces interference from same-category distractors.

In this study, we evaluated whether uncertainty about target location and category overlap between the target and the flankers played a role in recent findings (Miller, 1987) of semantic interference of irrelevant stimuli. In each of four testing conditions, subjects were required to identify a target letter surrounded by irrelevant flankers whose identity predicted the correct response. We varied (1) whether or not the target location was precued, and (2) the flanker's category (digits vs. letters). We found a substantial effect of letter flankers when subjects were uncertain of the precise target location. However, this effect was greatly attenuated when attention was predirected to the target location. Similarly, a reduced flanker effect was observed when the flankers (digits) belonged to a different semantic category than the target. However, when the target location was precued, no effect of the semantic congruity of target and flankers was found. Coupled with previous research, these findings converge in establishing that both failures to maintain attention on the target location and the semantic congruity of target and flankers modulate the size of the effects from irrelevant stimuli. These results are discussed in the context of early and late selection views of selective attention.

Adult↗