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Biomedical subjects

R C Petersen

Publications and source records attributed to R C Petersen.

139 records · Page 8Linked to original sources
PubMed1977

Retrieval failures in alcohol state-dependent learning.

Retrieval processes subject to disruption by alteration of drug conditions were studied in a state-dependent learning experiment. On the first day of the 2-day experiment, 28 human subjects performed four verbal learning tasks in either an alcohol state (1.0 ml/kg) or a sober state, and the next day they attempted to recall the material in either the same or in an altered condition. Two of the tasks involved recall cues or prompts, and the other two required the subjects to recall the material unaided. Results indicated state-dependency on the two tasks that did not involve recall cues and no state-dependency on the two tasks involving cues. This finding indicates that memory failures resulting from a changed drug state can be reversed by appropriate experimental cueing or prompting, and implies that a learner's drug state has stimulus properties for recall. The role of drugs in contributing to a person's cognitive context and the resultant effects on memory are discussed.

Adolescent↗
PubMed1977

Scopolamine induced learning failures in man.

Two experiments were performed to determine the locus of the amnestic effects of scopolamine in man. The first experiment involved 24 volunteers receiving one of three doses of scopolamine (5, 8 or 10 microng/kg) or a placebo, intravenously. The subjects were tested for retention of material learned prior to administration of the drug, acquisition of new information, and retention of material learned while under the influence of the drug. Results indicated that scopolamine has its primary effect on the acquisition of new material and less of an effect on the retrieval of information already learned. The second experiment was designed to refine and expand upon the results of the first and involved 18 volunteers receiving eith 5 or 10 microng/kg of scopolamine or a placebo, intravenously. The subjects were given four trials to learn a list of verbal materials, and their recall for that material was measured at various intervals up to 24 h. These results confirmed those of the first experiment in that the predominant influence of the drug was to impair the acquisition of new information. Implications of these results for memory mechanisms are discussed.

Adult↗
PubMed1977

History of cocaine.

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Anesthetics, Local↗
PubMedDate not supplied

MR findings in normal-pressure hydrocephalus: significance and comparison with other forms of dementia.

This study was undertaken to identify findings on magnetic resonance (MR) imaging that might possibly differentiate among several dementia states in the elderly or predict response to shunt therapy in patients with normal-pressure hydrocephalus (NPH). The MR findings were retrospectively reviewed in 54 patients who were divided into four clinical categories: NPH (17 patients), obstructive hydrocephalus (eight patients), Alzheimer disease (eight patients), and non-Alzheimer dementia (21 patients). Three MR findings were evaluated in each case: increased periventricular (PVS) and white matter (WMS) signal on T2-weighted images, CSF flow void sign (CFVS) in the aqueduct, and corpus callosum thinning. Neither the PVS/WMS nor corpus callosum thinning patterns were useful for distinguishing among the four clinical groups. At low field strength, the absence of a marked or moderate CFVS, however, may militate against a diagnosis of NPH. All 17 patients with NPH underwent a shunt procedure after the MR study. A better response to shunt therapy occurred in patients without WMS and with more severe PVS.

Adult↗
PubMedDate not supplied

An enriched-population, double-blind, placebo-controlled, crossover study of tacrine and lecithin in Alzheimer's disease. The Tacrine 970-6 Study Group.

We studied the effects of 40 and 80 mg/day of tacrine on patients with probable Alzheimer's disease (AD) in an 8-week, randomized, double-blind, placebo-controlled crossover trial with an enriched-population design. In the initial dose titration phase, an intent-to-treat analysis showed significantly more improvement with 80 mg/day of tacrine than placebo. In the subsequent crossover trial that included only 'responders', no significant improvement was observed with tacrine, whether or not it was given with lecithin. We found that individualized dose titration and enrichment strategies were not helpful and had the effect of reducing the power of the study. In the dose titration phase of this study we found that more impaired subjects were as likely to improve as those who were less impaired, suggesting that tacrine should be further investigated in more severely demented AD patients.

Aged↗