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Query: UMLS:C0598853 (forgetting)
 3,232 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some years ago Underwood (1964) grappled with the problem of explaining his finding that rate of forgetting was not a function of the rate of learning but rather seemed to reflect the level of learning achieved. He likened different rates of learning to filling an Erlenmeyer flask of water at different rates and the process of forgetting to the rate of evaporation, which in turn is a function of the exposed surface area. Since an Erlenmeyer flask is cone-shaped, the surface area becomes smaller as the flask is filled, thus the greater the amount of learning achieved, or water added, the less the rate of evaporation independent of how quickly or slowly the flask was filled. I give this example because it is such a clear description of history kept simple, in the psychological process of learning and forgetting. Indeed it is as simple as Charles Dickens' description of how students are to be taught, that is, by considering them to be "little vessels...ready to have imperial gallons of facts poured into them until they were full to the brim" (Dickens, 1961, p. 12). The object of this paper is to show how our neglect in specifying the history of reinforcement and other behavior analytic concepts has resulted in our ceding much of our field to cognitive psychologists even though our knowledge of conditioning enables us to study it more thoroughly than they can.
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PMID:Reinforcement history: a concept underutilized in behavior analysts. 895 21

Two experiments examined retention of spatial learning in rats using a Morris water maze. Retention was scored in terms of probe trial performance when the platform was removed. Latency to reach the platform location, percent of time in the quadrant that had contained the platform, and relative frequency of visits to the platform location were analyzed. Results of the first experiment showed that preweanlings and juveniles exhibited substantial forgetting at 3- and 7-day retention intervals. Forgetting in adults was much lower than that found in the younger animals, and no differences in amount of forgetting appeared between the 3- and 7-day retention intervals at any age. The second experiment showed that forgetting in juveniles was alleviated by a single training trial administered just prior to the probe trial. These results are discussed in terms of ontogenetic differences in memory processing and measurement issues pertinent to the Morris water maze test procedure.
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PMID:Ontogenetic differences in retention of spatial learning tested with the Morris water maze. 914 8

Rats with bilateral, electrolytic lesions of perirhinal cortex (PRC), lateral entorhinal cortex (LEC), or combined lesions (PRLE) were impaired relative to controls (sham) during initial acquisition in the Morris water maze, although all groups were eventually able to learn to locate the platform. A further deficit in the performance of PRC and PRLE, but not LEC groups, was evident, however, when a probe trial was conducted 2 min (but not 24 hours) after training. When the performance of sham- and PRC-lesioned rats was tested with variable memory delays inserted between training and probe trials, lesioned rats displayed an increase in the rate of forgetting for information made available during the training trial. This finding suggests that the PRC normally stores information regarding the cue-platform relationship and transfers this information to related structures during water maze performance.
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PMID:Perirhinal cortex contributions to performance in the Morris water maze. 958 80

Two new behavioural tests in rats are described which demonstrate the fast consolidation of the long-term memory (LTM) in a dangerous natural situation (water escape). It is shown that after one-trial learning of the motor skill (jumping out of the water), long-term memory traces are retained without forgetting and are resistant to the blockade of M-cholinoreceptors by scopolamine (2 mg/kg) and of D1/D2 dopamine receptors by haloperidol (10 mg/kg) as well as electroconvulsive shock applied tank wall, learning of necessary motor skills, automatization and minimization of the skilled movements in 1.5-3.0 min, after 5 to 7 trials at two-second intervals (superfast learning) is demonstrated. It is suggested that the superfast consolidation of LTM (several minutes) is possible in life-threatening situations, the necessary time being 1-2 orders of magnitude less than it is generally accepted in the modern theories of memory. The proposed behavioural models may be helpful in investigation of some fundamental physiological and molecular mechanisms of stable neuronal interactions, as a basis for LTM consolidation.
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PMID:Possibility of "superfast" consolidation of long-term memory. 971 71

Alterations in N-methyl-d-aspartate receptor (NMDAR)-dependent synaptic plasticity, characteristic of aged rodents, may contribute to impaired memory with advanced age. The purpose of the current research was to examine whether NMDARs contribute to rapid forgetting on a spatial memory task. Aged (22-24 months) and adult (3-6 months) male Fischer 344 rats received 18 training trials, over a period of 3 to 4 h, on the spatial version of the Morris water maze. Immediately after training, a standard free-swim probe trial was administered to assess the acquisition of spatial bias, which was determined by the percent of time spent in the goal quadrant and the number of platform crossings. Rats then received injections of the noncompetitive NMDAR antagonist, (+)-10, 11-dihydro-5methyl-5H-dibenzo(a,b)cycloheptene-5,10 imine (MK-801, 0. 05 mg/kg, i.p.), or a vehicle injection of equal volume. Approximately 24 h later, rats were administered a second free-swim probe trial to assess retention of spatial bias. All age/drug groups exhibited a spatial bias on the acquisition probe, with adults generally outperforming the aged rats. On the retention probe, this spatial bias continued to be shown by adult rats, regardless of treatment. For the aged group, in contrast, only MK-801-injected rats maintained a spatial bias on the retention probe, suggesting that NMDAR activity may be involved in rapid forgetting during aging. Because blockade of NMDARs also may impair new learning, which may, in turn, protect previously stored information from retroactive interference, rats in a second experiment received post-training injections of scopolamine (0.05 mg/kg), a compound known to inhibit learning. However, scopolamine did not enhance retention in the aged group, consistent with the hypothesis that MK-801 influenced memory in aged rats through its actions on NMDAR-dependent synaptic plasticity.
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PMID:MK-801 improves retention in aged rats: implications for altered neural plasticity in age-related memory deficits. 1008 39

In order to observe the consequences of chronic ingestion of high fluoride-rich water on plasma potassium levels of hemodialysed subjects, we have conducted a retrospective study on 25 patients with chronic renal failure, treated with a substitute method, six of whom (consumers group, group C) were drinkers of a bicarbonate (about 4500 mg/l) and fluoride-rich (9 mg/l) mineral water, the Vichy Saint-Yorre water. With respect to sodium polystyrene sulfonate consumption (n = 17), there was no significant difference between group C and NC (non-consumers group). A significant correlation between plasma fluoride and potassium levels was observed only before dialysis (P < 1 x 10(-7)) but not after dialysis. A group by group analysis revealed that this correlation was linked to group C (P < 5 x 10(-6)), in which kalemia before dialysis was higher than that observed in group NC (P < 0.005). Moreover, it appeared that the higher fluoride levels were, the higher the kalemia was inclined to be. Thus, the risks of hyperkalemia in dialysed patients, who also drink Vichy St-Yorre water or other fluoride-rich waters, are more important, while not forgetting the risk of fluorosis. The mechanisms by which chronically administered fluoride could increase kalemia are also discussed.
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PMID:Hyperkalemia risks in hemodialysed patients consuming fluoride-rich water. 1021 24

While the delayed nonmatching-to-position (DNMTP) behavioral paradigm has often been used by neuroscientists to assess working memory in rats, its measure of working memory is compromised by floor and ceiling effects. Specifically, these floor and ceiling effects undermine the ability to detect a significant interaction in a two-factor repeated-measures ANOVA, which is required in order to conclude that impaired performance has resulted from disrupted working memory and not from a change in another psychological process (i.e. that the impairment is 'specific' to working memory). The present study was conducted to evaluate if these limitations could be overcome in a DNMTP by adjusting the length of time that the rat was required to remember (the 'delay') so as to avoid the floor and ceiling. The general procedure for two experiments presented subjects with trials where there was either a minimal (1 s) delay or a longer delay of varying length, with the goal of maintaining nonmatch-to-position accuracy near 75%. The procedure was such, that if the average accuracy was at or above 75%, then the next trial would be a long-delay trial. If it were below 75%, then the next trial would be a 1 s delay trial. In the first experiment, the subjects were presented with trials where the value of the longer delay was systematically varied between-sessions. This was done to simulate the faster rate of forgetting found in persons with amnesia. DNMTP accuracy diminished at the longer delay but not the short delay as the second interval was lengthened. However, other measures, including accuracy at the 1 s delay, discrimination accuracy during the sample phase, and the number of trials completed per session, did not change. This experiment suggested that this DNMTP could precisely measure small changes in the rate of forgetting. In a second experiment, a potential non-mnemonic confound, the level of motivation, was directly manipulated by giving the water-restricted subjects access to water immediately prior to the start of the session. The number of trials completed per session diminished, but the accuracy at both the 1 s and the longer delays did not change. These results indicated that the measures of working memory in this DNMTP were insensitive to changes in motivation. Together, these experiments confirmed that adjusting the delay in the DNMTP improves the validity of the measures in this task.
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PMID:Specificity of memory measures in an adjusting delayed nonmatching-to-position task for rats. 1084 Jan 37

The present study examined the influence of dexefaroxan, a potent and selective alpha(2)-adrenoceptor antagonist, on cognitive performance in rodents. In young adult rats, dexefaroxan reversed the deficits induced by UK 14304 [5-bromo-N-(4,5-dihydro-1-H-imidazol-2-yl)-6-quinoxalinamine], scopolamine, and diazepam in a passive avoidance task. In this test, dexefaroxan also attenuated the spontaneous forgetting induced by a 15-week training-testing interval. Moreover, dexefaroxan, given immediately after training, increased the memory performance of rats trained with a weak electric footshock in the passive avoidance test, facilitated spatial memory processes in the Morris water maze task in rats, and increased the performance of mice in an object recognition test. Thus, dexefaroxan appears to have a promnesic effect in these tests by facilitating the processes of memory retention, rather than acquisition or other noncognitive influences. The facilitatory effects of dexefaroxan in young adult rats persisted even after a 21- to 25-day constant subcutaneous infusion by using osmotic minipumps, indicating that tolerance to the promnesic effect of the drug did not occur during this prolonged treatment interval. Furthermore, in the passive avoidance and Morris water maze tests, dexefaroxan ameliorated the age-related memory deficits of 24-month-old rats to a level that was comparable to that of young adult animals, and reversed the memory deficits induced by excitotoxin lesions of the nucleus basalis magnocellularis region. Together, these findings support a potential utility of dexefaroxan in the treatment of cognitive deficits occurring in Alzheimer's disease.
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PMID:Effects of acute and subchronic administration of dexefaroxan, an alpha(2)-adrenoceptor antagonist, on memory performance in young adult and aged rodents. 1190 73

In this paper five multivariable adaptive and classical control strategies have been studied and implemented in a simulator of the copper grinding plant of CODELCO-Andina. The strategies presented were compared and, according to theory, exhibit good behavior. The extended horizon, pole-placement and model reference multivariable adaptive control strategies were formulated in discrete-time and use a model of the plant whose parameters are updated on line using the recursive least squares method along with UD factorization of the covariance matrix and variable forgetting factor. The direct Nyquist array and sequential loop closing techniques were also studied and simulated. The two-by-two multivariable system chosen to represent the grinding plant has the percentage of solids (density) of the pulp fed to the hydrocyclones (which is highly correlated with the percentage of +65 mesh in the overflow of hydrocyclones) and the sump level as output (controlled) variables. The water flow added to the sump and the speed of the pump are its input (manipulated) variables. All the algorithms tested by simulation exhibited good performance and were able to control the grinding plant in a stable fashion. Adaptive algorithms showed better performance than classical techniques, with the extended horizon and pole-placement algorithms proving to be the best. The fact that adaptive algorithms continuously adjust their parameters renders such controllers superior to those based on fixed parameters.
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PMID:Multivariable control of grinding plants: a comparative simulation study. 1201 4

The endocannabinoid system has been proposed to modulate a variety of physiological processes, including those that underlie cognition. The present study tested whether this system is tonically active in learning and memory by comparing CB(1) receptor knockout mice (CB(1)(-/-)) to wild-type mice (CB(1)(+/+)) in several Morris water maze tasks. Also, the effects of three cannabinoid agonists, Delta(9)-tetrahydrocannabinol (Delta(9)-THC), R-(+)-[2,3-dihydro-5-methyl-3[morpholinyl)methyl]-pyrrolo[1,2,3-de]-1, 4-benzoxazinyl]-(1-naphthalenyl)methanone mesylate (WIN 55,212-2), and methanandamide, were evaluated in a working memory procedure. Both genotypes exhibited identical acquisition rates in a fixed platform procedure; however, the CB(1)(-/-) mice demonstrated significant deficits in a reversal task in which the location of the hidden platform was moved to the opposite side of the tank. This phenotype difference was most likely due to an increased perseverance of the CB(1)(-/-) mice in that they continued to return to the original platform location, despite being repeatedly shown the new platform location. In addition, Delta(9)-THC (ED(50) = 1.3 mg/kg), WIN 55,212-2 (ED(50) = 0.35 mg/kg), and methanandamide (ED(50) = 3.2 mg/kg) disrupted the performance of CB(1)(+/+) mice in the working memory task at doses that did not elicit motivational or sensorimotor impairment as assessed in a cued version of the task. Furthermore, doses of each drug that were maximally disruptive in CB(1)(+/+) mice were ineffective in either N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR 141716A)-treated CB(1)(+/+) or CB(1)(-/-) mice. These results provide strong evidence that cannabinoids disrupt working memory through a CB(1) receptor mechanism of action, and suggest that the endocannabinoid system may have a role in facilitating extinction and/or forgetting processes.
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PMID:Evaluation of CB1 receptor knockout mice in the Morris water maze. 1202 19


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