Addison's disease: after 40 years much remains the same.
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Addison Disease↗
Biomedical subjects
K G White
Publications and source records attributed to K G White.
Generalization of delayed matching to sample following training at different delays.
Four groups of pigeons were trained to perform a delayed matching-to-sample task with a single delay of 0, 2, 4, or 6 s from the outset of training. The longer the training delay, the more sessions were required for all birds to reach the same level of response accuracy. Following initial training, five test sessions that included nonreinforced trials with delay intervals of 0, 2, 4, 6, 8, and 10 s were interspersed between training sessions. Unlike typical forgetting functions in which accuracy decreases monotonically with increasing delay, the forgetting functions from test sessions resembled generalization gradients with the peak of the functions occurring at the training delay. Following additional training for all birds with a 0-s delay, forgetting functions decreased monotonically with increasing delay. The results suggested that remembering can be trained at a specific delay interval, and generalizes to similar delay intervals. Generalization along the temporal dimension of delay may contribute to typical forgetting functions in which accuracy decreases from 0-s delay.
Animals↗
Glucose attenuation of memory impairments.
The performance of pigeons in a short-term memory procedure (delayed matching-to-sample) was studied over a range of retention intervals from 0.2 s to 24.0 s. The authors examined the ability of 3 dose levels of glucose (0, 50, and 100 mg/kg) to alleviate memory impairments produced by administration of scopolamine (0.03 mg/kg), by a reduction in the sample-response requirement and by interpolating retroactive interference in the retention interval (houselight illumination). Glucose administration attenuated the deficit produced by scopolamine and by the reduced sample-response requirement, by reversing the decrement in accuracy at 0 delay. Glucose did not, however, reverse the increase in rate of forgetting generated by retroactive interference. The results suggest that the mode of action by which glucose is able to attenuate drug-induced and behavioral impairments in memory may be through an effect on attentional or encoding processes.
Acetylcholine↗
Facilitation of memory performance by a novel muscarinic agonist in young and old rats.
AF150(S), a partial M1 muscarinic receptor agonist, was tested for its ability to improve performance in rats in a delayed matching-to-position task. Young and old rats received intraperitoneal injections of 0, 1, and 4 mg/kg of AF150(S). AF150(S) significantly enhanced matching accuracy for both young and old rats. Fits of exponential functions to discriminability measures showed that the enhancement was manifest as a reduction in the rate of forgetting. These results indicate that AF150(S) may be a useful therapeutic agent for improving cognitive function.
Aging↗
Psychophysics of remembering.
We present a new model of remembering in the context of conditional discrimination. For procedures such as delayed matching to sample, the effect of the sample stimuli at the time of remembering is represented by a pair of Thurstonian (normal) distributions of effective stimulus values. The critical assumption of the model is that, based on prior experience, each effective stimulus value is associated with a ratio of reinforcers obtained for previous correct choices of the comparison stimuli. That ratio determines the choice that is made on the basis of the matching law. The standard deviations of the distributions are assumed to increase with increasing retention-interval duration, and the distance between their means is assumed to be a function of other factors that influence overall difficulty of the discrimination. It is a behavioral model in that choice is determined by its reinforcement history. The model predicts that the biasing effects of the reinforcer differential increase with decreasing discriminability and with increasing retention-interval duration. Data from several conditions using a delayed matching-to-sample procedure with pigeons support the predictions.
Animals↗
Quantitative reanalysis of lesion effects on rate of forgetting in macaques.
In Ringo's reanalysis (Behav. Brain Res., 42 (1991) 123-124), differences between d' discriminability measures of memory performance by macaque monkeys in normal and lesioned groups did not change systematically with retention-interval duration. There was therefore no evidence of an effect of brain lesion on rate of forgetting. Our quantitative analysis in which power and negative exponential functions were fitted to the d' measures yielded a different conclusion. The rate parameter of the best-fitting functions provided a measure of rate of forgetting. Parameter values for rate of forgetting were significantly greater for lesioned groups than for normal groups, whereas the parameter describing performance in the absence of a delay did not differ between normal and lesion conditions.
Animals↗
Memory procedures, performance and processes in pigeons.
Short-term memory in pigeons is studied in the delayed matching-to-sample procedure where information is forgotten over short periods of time. Performance in this task reflects the separate influences of attention to the sample stimuli and memorial processes and is determined by a range of procedural variables. Forgetting functions can be obtained by varying the duration of the retention interval and can be quantified in terms of the parameters of a fitted function, such as the negative exponential. These parameters provide measures of initial discriminability and rate of forgetting and are sensitive to the effects of drugs known to influence the cholinergic, GABA and dopaminergic systems. The results of behavioral pharmacological studies suggest that the effects of a variety of drugs on initial discriminability and rate of forgetting are quite similar for pigeons and monkeys. We conclude that pigeons serve as an effective model to examine the effects of agonist and antagonist drugs on memory.
Animals↗
Resting energy expenditure of patients with gynecologic malignancies.
OBJECTIVE: To evaluate resting energy expenditure compared to predicted energy expenditure in patients with cervical or ovarian carcinoma who require specialized nutritional support. DESIGN: Women with biopsy-proven cervical or ovarian carcinoma referred to the Nutrition Support Service were studied. Resting energy expenditure was measured by indirect calorimetry and compared to predicted energy expenditure (PEE) as determined by the Harris-Benedict equation for females. RESULTS: Sixty one patients were studied. Patients with ovarian cancer (n = 31) had a significantly higher measured resting energy expenditure (% PEE) than patients with cervical cancer (109 +/- 18% vs. 98 +/- 16%, p < 0.02, respectively). This difference in measured resting energy expenditure between groups could not be explained by differences in the extent of disease, nutritional status, body temperature, or nutrient intake between groups. A greater proportion of patients with ovarian cancer were hypermetabolic (> 110% of predicted) in comparison to patients with cervical cancer (55% vs. 13%, p < 0.01, respectively). Measured resting energy expenditure varied between 53% and 157% of predicted for the entire population. CONCLUSION: Ovarian cancer patients are more hypermetabolic than cervical cancer patients. The Harris-Benedict equation for females is a unreliable estimate of caloric expenditure in patients with cervical or ovarian cancer receiving specialized nutritional support.
Adult↗
Action at a temporal distance: Component transition as the relational basis for successive discrimination.
In a successive discrimination, red and green hues signaled component variable-interval schedules. The exponent of the power function relating ratios of responses in the red and green components to ratios of reinforcers provided a reinforcement-free measure of discrimination or stimulus control. Responses were recorded in successive 10-s subintervals of the 50-s components. The power-function exponent decreased systematically with increasing time since component transition in most conditions of five experiments. This reduction was not influenced by the absolute rate of reinforcement, consistent with the interpretation of the exponent as a measure of stimulus control. A reduction in the overall level of stimulus control by increasing the duration of response-produced keylight offset did not influence the decrease in discrimination with increasing time since component transition. The results support the conclusion that discriminative responding in successive discriminations is governed by several sources of stimulus control including delayed control by component transition.
Journal Article↗
Biasing the pacemaker in the behavioral theory of timing.
In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.
Journal Article↗
Effects of chronic phenobarbital administration on forgetting functions in pigeons.
The present study examined the effect of chronic phenobarbital administration on forgetting functions based on delayed matching-to-sample performance in pigeons. The effects of IP injections of 10 and 20 mg/kg administered over five consecutive training sessions were compared to each other and a baseline (no drug) condition. Percent correct was reduced as a function of both increasing delay and dose of phenobarbital. A quantitative analysis using a negative-exponential function fitted to bias-free measures of discriminability demonstrated that impaired performance following administration of phenobarbital was reflected in both an increase in the rate of forgetting as well as a decrease in initial discriminability. Furthermore, the influence of proactive interference arising from stimuli on previous trials was attenuated at the highest dose level (20 mg/kg). Thus, chronic phenobarbital administration impairs memorial function and limits the influence of information gained from previous trials on subsequent performance. The current effects of chronic phenobarbital administration are consistent with the effects of acute administration on forgetting functions reported in prior studies.
Animals↗
The behavioral theory of timing: Reinforcer rate determines pacemaker rate.
In the behavioral theory of timing, pulses from a hypothetical Poisson pacemaker produce transitions between states that are correlated with adjunctive behavior. The adjunctive behavior serves as a discriminative stimulus for temporal discriminations. The present experiments tested the assumption that the average interpulse time of the pacemaker is proportional to interreinforcer interval. Responses on a left key were reinforced at variable intervals for the first 25 s since the beginning of a 50-s trial, and right-key responses were reinforced at variable intervals during the second 25 s. Psychometric functions relating proportion of right-key responses to time since trial onset, in 5-s intervals across the 50-s trial, were sigmoidal in form. Average interpulse times derived by fitting quantitative predictions from the behavioral theory of timing to obtained psychometric functions decreased when the interreinforcer interval was decreased and increased when the interreinforcer interval was increased, as predicted by the theory. In a second experiment, average interpulse times estimated from trials without reinforcement followed global changes in interreinforcer interval, as predicted by the theory. Changes in temporal discrimination as a function of interreinforcer interval were therefore not influenced by the discrimination of reinforcer occurrence. The present data support the assumption of the behavioral theory of timing that interpulse time is determined by interreinforcer interval.
Journal Article↗
An investigation of the differential-outcomes effect within sessions.
The differential-outcomes effect is manifest as more accurate performance of a delayed conditional discrimination when alternative choice responses are followed by different reinforcers than when they are followed by the same reinforcer. In Experiment 1, a differential-outcomes effect was demonstrated within sessions by signaling the duration of food access for correct responses with stimuli appearing in conjunction with the sample stimuli. The delayed matching-to-sample performance of 5 pigeons was more accurate when green choice responses (matching a green sample) were followed by 3.5-s food access and red choice responses (matching a red sample) were followed by 0.5-s food access (different-outcome trials) than when the correct choice responses were both followed by 1.5-s reinforcers (same-outcome trials). In Experiment 2, the acquisition of this differential-outcomes effect was characterized by a progressive decrease in rate of forgetting on different-outcome trials and no change in rate of forgetting on same-outcome trials. In addition, accuracy at the shortest delay intervals for both different-outcome and same-outcome trials increased over acquisition, but to a greater extent for different-outcome trials. These data suggest that both memorial and attentional (time-dependent and time-independent) factors contribute to the differential-outcomes effect.
Journal Article↗
Use of vitamin and mineral supplements by pharmacy students.
Use of vitamin and mineral supplements by undergraduate pharmacy students and the students' perceptions and beliefs about these products were studied. Undergraduate pharmacy students from two schools in Philadelphia completed a questionnaire in which they were asked whether they had taken vitamin or mineral supplements within the preceding two weeks, the reason for taking the supplements, and the identity of the type of products taken. General demographic information and a self-assessment of health and diet were also obtained. In addition, using a five-point Likert scale, students were asked to rate the degree to which they agreed with five controversial statements regarding vitamin and mineral supplements. Of the 692 students completing the questionnaire, 47% had taken supplements in the preceding two weeks. This percentage is higher than that determined in surveys of the general population and of professionals in other health disciplines. No significant difference was noted in the percentage of men and women who took supplements, but the types of products taken by men and women differed significantly. The most common reasons for taking supplements were inadequate diet, to improve energy, for stress, and for colds. Year in school had a modest influence on the beliefs about vitamin and mineral supplement use expressed by students. The use of vitamin and mineral supplements among pharmacy students was high. Pharmacy schools should devote time in the curriculum to the sociological and clinical aspects of vitamin and mineral therapy.
Adult↗
Sample-stimulus discriminability and sensitivity to reinforcement in delayed matching to sample.
Five pigeons were trained in a delayed matching-to-sample task with red and green stimuli. The retention interval between sample-stimulus presentation and the availability of the choice stimuli was varied between 0.01 s and 12 s within each session. The probability of food produced by correct-red and correct-green responses was varied across conditions. Sample-stimulus discriminability and response bias were measured at four different retention intervals. The results of these analyses showed an interaction between the discriminability of the sample stimuli and the control exerted by differential reinforcement. At longer retention intervals, sample discriminability decreased and sensitivity of choice behavior to changes in the red/green reinforcer ratio increased. An analogous relation has been reported in conditional discriminations in which the physical disparity of stimuli has been varied. This correspondence suggests that increasing the delay between presentation of one of two stimuli and an opportunity to respond discriminatively to it may be functionally similar to increasing the physical similarity of the two stimuli.
Journal Article↗
Successive independence and behavioral contrast in a closed economy.
Two pigeons had access to multiple concurrent schedules of reinforcement for 24 hours per day in their home cages. The variable-interval schedules comprising the multiple concurrent schedules were varied across 16 conditions. In three sets of conditions, one schedule was varied while its concurrent alternative and the concurrent schedules in the other component were held constant. Behavioral contrast was observed; that is, as the rate of reinforcement arranged by the varied schedule decreased, response rates on the constant schedules typically increased. These conditions formed part of two larger sets of conditions in which the concurrent schedules in one multiple-schedule component remained constant while the concurrent schedules in the other component were varied. Successive independence was found, in that behavior allocation during the constant component did not vary as a function of the reinforcer ratios in the varied component. Successive independence between components in multiple concurrent schedules is a robust result that occurs in closed economies and under conditions that promote behavioral contrast.
Animals↗
Delayed and current stimulus control in successive discriminations.
In a successive discrimination in which successively alternating red and green hues signaled component variable-interval schedules, sensitivity of the ratio of responses in the two components to variation in the component reinforcer ratio decreased systematically during the course of the component. This decrease in stimulus control or discrimination over the course of the component was shown to be the result of delayed control of responding during the component by the stimulus transition between components. When the red-green stimulus transition was altered by interpolating a white stimulus at the end of each 60-s component, discrimination at the beginning of the component (measured by the power-function exponent for sensitivity to reinforcement) was reduced. Conditions with the white stimulus inserted in other quarters of the component indicated that the current discriminative stimulus exerts control over responding throughout the component, whereas during about the first half of the component, response differentials are influenced by the transition between discriminative stimuli.
Journal Article↗
Cognition and behavior analysis.
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Journal Article↗