Search PubMed⌕ Search

Biomedical subjects

M Simpson

Publications and source records attributed to M Simpson.

116 records · Page 7Linked to original sources
PubMedDate not supplied

Stimulus deviance and evoked potentials.

In many studies on the effect of selective attention and stimulus significance on evoked potentials, the target, or otherwise significant, stimuli were also infrequent stimuli. Repetitive homogeneous auditory stimuli were presented at short constant intervals. One of two deviant stimuli, one slightly lower and the other slightly higher in pitch than the repetitive stimulus ('standard'), randomly replaced it at the same low probability. One at a time of these two physically equally deviant and equally infrequent stimuli was designated as a target and the subject's task was to count its number in a run and to ignore the other deviant stimulus. The two deviant stimuli elicited very similar potentials; hence, no target effect was obtained. On the other hand, both potentials were much larger and more complex than those elicited by standard stimuli. Additionally, a 'probe' stimulus, a widely deviant auditory stimulus randomly replaced, with a very small probability, a standard stimulus in these conditions. Even this irrelevant, physically widely deviant, stimulus elicited a wave complex basically similar to that elicited by slightly deviant stimuli, but of much larger amplitude. The comparison of these brain-wave sequences to those elicited by the same stimuli in reading subjects led to the conclusion that in detection conditions, deviant stimuli elicit two overlapping sequences of brain events: exogeneous and endogeneous. The former sequence, mainly including the processes producing the N1 and the N2 (neuronal mismatch) components, is an automatic, inflexible set of brain processes which appears as if providing a central-level stimulus to the endogeneous sequence. The latter seems to include a triphasic frontocentral complex overlapping the mismatch N2 and preceding the parietal late positive component and frontal late negative component. This endogeneous set of brain waves was regarded as a sign of detection of stimulus deviance. Consequently, it did not occur in response to the slightly deviant stimuli in reading, but the widely deviant stimuli which were also (involuntarily) perceived by the subject tended to elicit it in attenuated and delayed form.

Adolescent↗
PubMedDate not supplied

Raspberry leaf in pregnancy: its safety and efficacy in labor.

OBJECTIVE: Many women consume the raspberry leaf herb during their pregnancies in the belief that it shortens labor and makes labor "easier." METHODOLOGY: Because of the paucity of research regarding this herb, particularly in relation to pregnancy and birth, the authors undertook a double-blind, randomized, placebo-controlled trial. The sample consisted of 192 low-risk, nulliparous women who birthed their babies between May 1999 and February 2000 at a large tertiary-level hospital in Sydney, Australia. The aim of the study was to identify the effect and safety of raspberry leaf tablets (2 x 1.2 g per day), consumed from 32 weeks' gestation until labor, on labor and birth outcomes. RESULTS: Raspberry leaf, consumed in tablet form, was found to cause no adverse effects for mother or baby, but contrary to popular belief, did not shorten the first stage of labor. The only clinically significant findings were a shortening of the second stage of labor (mean difference = 9.59 minutes) and a lower rate of forceps deliveries between the treatment group and the control group (19.3% vs. 30.4%). No significant relationship was found between tablet consumption and birth outcomes. CONCLUSION: The lack of significant differences between the groups on measures expected to demonstrate the effect of raspberry leaf ingestion during pregnancy on labor prompted consideration of the issue of effectiveness of dosage level. Suggestions for further research are offered.

Double-Blind Method↗
PubMedDate not supplied

TCI left ventricular assist device: nursing implications.

The use of left ventricular devices as a bridge to transplantation has gained considerable acceptance in transplant centers nationwide. A new, innovative assist device that allows for greater patient mobility with a decreased incidence of patient complications is now being used at St. Luke's Episcopal Hospital to support the potential transplant recipient while waiting for a donor heart. The authors discuss the pathophysiology related to this type of assist device, along with two case studies and the nursing diagnoses indicated for patients using this unique device as a bridge to transplant.

Adult↗
PubMedDate not supplied

Phosphate, alkaline phosphatase and bone mineralization in preterm neonates.

We examined the relationship between bone mineralization, measured by single photon absorptiometry, and blood phosphate and alkaline phosphatase concentration in 71 preterm neonates. Although both alkaline phosphatase and phosphate concentrations were significantly related to bone mineral content, and alkaline phosphatase concentrations were related to bone mineral content relative to weight, each could only explain a small amount of the variation in bone mineralization. Hence, concentrations of neither could be used to identify those neonates with the greatest bone mineral deficits.

Absorptiometry, Photon↗