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Biomedical subjects

T M Cowan

Publications and source records attributed to T M Cowan.

27 records · Page 2Linked to original sources
PubMed1986

Drosophila mutations that alter ionic conduction disrupt acquisition and retention of a conditioned odor avoidance response.

We have previously found that genetic alterations in neuronal ion channel function have specific effects on learning and memory of a conditioned courtship behavior in Drosophila. Using a behavioral assay of conditioned odor avoidance, we report here that shaker mutants, in which potassium-channel function is abnormal, are defective in both their rate and maximum level of acquisition when compared to wild-type flies. napts (no action potential, temperature sensitive) mutants, in which nerve excitability is decreased due to faulty sodium-channel function, can achieve a normal (wild-type) level of learning, but the rate of acquisition is reduced. Neither the shaker nor the napts mutations affect memory decay following rest periods greater than 30 min. However, memory may decay more rapidly in both shaker and napts flies during the initial 30-min period following training. These results suggest that neuronal sodium- and potassium-channel function may be of general importance to the processes of acquisition and short-term memory in Drosophila.

Animals↗
PubMed1984

Mutational and pharmacological alterations of neuronal membrane function disrupt conditioning in Drosophila.

Neuronal membrane channels of Drosophila melanogaster were altered either genetically or pharmacologically in order to investigate the role of specific ionic currents in the acquisition and retention of a conditioned behavior. Conditioning could not be detected for Shaker mutants, in which the fast transient potassium current (IA) is altered; a second potassium channel mutant, eag (ether a go-go) is conditioned like wild type, but the retention period is abnormally short. The napts mutant (no action potential, temperature sensitive), in which nerve excitability is reduced, also expresses normal acquisition and a shortened period of retention. Double mutants of Sh5 and napts as well as Sh5 treated with tetrodotoxin, are essentially normal with respect to acquisition; in both cases these flies remain retention-defective. These experiments therefore reveal a behavioral phenotype of Drosophila mutants in which the primary physiological defect seems to be in the functioning of specific neuronal ionic channels.

Animals↗
PubMed1978

An investigation of the cues responsible for figure impossibility.

Two different perceptual confrontations produced by two different cues (sides that seem to twist and apparent levels of depth), which were thought to influence the perception of the degree of possibility of impossible torus figures, were examined in two experiments. In Experiment 1 it was found that net change in depth experienced with one scan around the figure was inversely related to magnitude estimates of possibility, whereas the number of apparently twisted sides was not. These results were verified in Experiment 2, a replication of Experiment 1 using stereograms of the figures, in which an interpretation of multiple levels of depth was more difficult.

Cues↗
PubMed1977

Organizing the properties of impossible figures.

The empirical study of impossible figures requires that independent variables be well-specified. This paper provides an aid for such a task by developing a classification system which partitions cornered torus figures into meaningful subsets. These can be used to identify both formal and psychological properties of known as well as unknown possible and impossible figures in much the same manner as with the periodic table of chemical elements. The classification is polytopic (for demensional) and is formally, not empirically, derived. Coherent three-dimensional and two-dimensional forms of the system are possible without loss of information.

Classification↗
PubMedDate not supplied

Using a clinical practice guideline to measure physician practice: translating a guideline for the management of heart failure.

BACKGROUND: Effective clinical practice guidelines should improve clinical outcomes, and measures of physician use of clinical practice guidelines should correlate with improved outcomes. This study translates a clinical practice guideline on heart failure into review criteria to measure physician performance and the effectiveness of the clinical practice guideline. METHODS: A panel of 11 family physicians and 1 cardiologist systematically reviewed the clinical practice guideline for its clinical importance, educational relevance, and evaluative appropriateness. Then a subset of 4 family physicians rigorously applied each recommendation to established criteria for measurability and developed an evaluation tool useful in medical record review. RESULTS: The heart failure clinical practice guideline was found to be an excellent educational tool. Using it to measure physician performance, however, was limited to diagnostic tests and drug prescribing. Of 45 recommendations, 5 fulfilled criteria for measurability; 1 recommendation had A-level evidence, whereas 2 recommendations had B-level and 2 had C-level evidence. CONCLUSION: This study illustrates the logistic issues and challenges in developing a measure of physician adherence to clinical practice guidelines. Medical record review is inadequate to measure many recommendations. Physicians use of this clinical practice guideline must be evaluated as an intermediate step to measuring the effectiveness of clinical practice guidelines based on patient outcomes.

Evidence-Based Medicine↗