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K A Kimball

Publications and source records attributed to K A Kimball.

6 recordsLinked to original sources
PubMed1992

Titrating matching-to-sample performance: effects of drugs of abuse and intertrial interval.

Previous reports have shown that increasing the length of the intertrial interval (ITI) in a matching-to-sample schedule of reinforcement results in increased matching accuracy. This has traditionally been interpreted in the context of proactive inhibition, the disruption of memory for a stimulus as a consequence of events that occurred prior to the presentation of the stimulus. In an effort to more fully characterize a titrating matching-to-sample baseline, the effect of ITI ranging from 0-30 s was determined in pigeons trained to respond under the titrating matching-to-sample procedure. In addition, the effect of ITI length on the dose-response curve for pentobarbital, phencyclidine, D-amphetamine, and cocaine were determined. Surprisingly, performance under the titrating matching-to-sample was not altered as a function of ITI length, nor did the effects of the four drugs of abuse change as a function of ITI length. These results suggest that performance under the titrating matching-to-sample is under a different control than matching-to-sample using fixed delays.

Amphetamine↗
PubMed1991

Aging: changes in cardiac alpha 1-adrenoceptor responsiveness and expression.

Several investigators have reported a diminished responsiveness of senescent cardiac muscle to norepinephrine and beta-adrenoceptor agonists. In contrast, relatively little is known regarding the effects of aging on myocardial actions mediated specifically by alpha-adrenoceptor stimulation. Thus, the current study examined aging-dependent changes in: (a) the inotropic response to methoxamine, an alpha-adrenoceptor agonist; (b) characteristics of myocardial alpha 1-adrenoceptors as monitored by specific [3H]prazosin binding; and (c) steady state levels of alpha 1-adrenoceptor mRNA as determined by Northern blot analysis. Cardiac preparations were isolated from 4-, 14-, and 25-month-old F344 rats. An aging-associated decline was observed in the maximum positive inotropic effect elicited by methoxamine in right ventricular strips (160 +/- 23, 134 +/- 13 and 79 +/- 26% increase above control developed tension in 4, 14 and 25 months, respectively) with no change in ED50 values. [3H]Prazosin binding to ventricular sarcolemmal membranes revealed a reduction in receptor number (82 +/- 7, 69 +/- 6 and 59 +/- 5 fmol/mg protein in 4, 14 and 25 months, respectively); the apparent dissociation constant was not affected. Steady state levels of alpha 1-adrenoceptor mRNA decreased progressively between 4 and 25 months of age (14- and 25-month levels were approximately 71 and 38% of 4 months, respectively), while steady state levels of beta-actin mRNA did not change with age. These results suggest that the aging-related decline in alpha 1-adrenergic responsiveness in rat ventricular muscle is mediated, at least in part, by a decrease in cardiac alpha 1-adrenoceptor density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1980

A human performance/workload evaluation of the AN/PVS-5 bifocal night vision goggles.

Eight experienced U.S. Army aviators performed various maneuvers in an instrumented helicopter to test the relative usability of two bifocal-configured night vision goggles. Both configurations were statistically better than the unmodified arrangement when looking at a pilot's ability to fly a standard traffic pattern and to hold a precise altitude at night. The subjective data, supported by comparative flight performances with the two bifocals, further suggested that a 24% bifocal version was more desirable than a 14% configuration. The inference is that the reduced inside field of view presented by the 14% bifocal interferes with a pilot's ability to readily locate instruments once he has directed his attention inside the cockpit.

Aerospace Medicine↗
PubMed1978

Inflight measurement of pilot workload: a panel discussion.

A group of U.S. scientists engaged in inflight measurements of pilot workload discussed the problems and aspects of workload; the techniques used for inflight measurements; the various workload models, such as design-oriented, operational, psychological, and physiological concepts; different experimental approaches; and experiences, results and further plans, during the 48th Annual Scientific Meeting of the Aerospace Medical Association in Las Vegas, Nv, on May 10, 1977. The contributions by the chairman and the five panel members are summarized.

Aerospace Medicine↗