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At least 883 records · Page 49Linked to original sources
PubMed2000

Noradrenergic receptor blockade of the NTS attenuates the mnemonic effects of epinephrine in an appetitive light-dark discrimination learning task.

These experiments examined the contribution of noradrenergic neurons in the nucleus of the solitary tract (NTS) in mediating the memory-facilitating effects of epinephrine. In Experiment 1, saline or 0.05 or 0.1 mg/kg of epinephrine was given intraperitoneally (ip) to rats after the second day of training in a light-dark Y-maze discrimination task. On a 20-trial retention test given 2 and 7 days later, the 0.1 mg/kg epinephrine group made significantly more correct responses than controls and required fewer trials to reach criterion. In Experiment 2, phosphate-buffered saline or the noradrenergic antagonist dl-propranolol (0.3 or 1.0 microg/0.5 microl) was infused into the NTS prior to an ip injection of saline or 0.1 mg/kg of epinephrine. The memory-enhancing effects of epinephrine were attenuated by the infusion of 0.3 microg/0.5 microl of dl-propranolol into the NTS. These findings indicate an involvement of NTS noradrenergic neurons in mediating the effects of peripheral epinephrine on memory storage processes.

Animals↗
PubMed1981

Role of mediodorsal thalamic nucleus in olfactory discrimination learning in rats.

Severe deficits in the acquisition of an olfactory learning-set task resulted from lesions of the central (olfactory) component of the mediodorsal thalamic nucleus but not from large lesions that destroyed olfactory projections to the amygdala. Complex olfactory learning may be mediated by the olfactory thalamocortical system and not by olfactory projections to the limbic system.

Amygdala↗
PubMed1967

Discrimination learning by Macaca mulatta with option to switch between S+ and S-.

Three rhesus monkeys were trained to press either of two response keys. A response on the reinforcement key during presentation of the reinforced stimulus produced a sucrose pellet followed by an intertrial interval, but during presentation of the unreinforced stimulus produced only the intertrial interval. A response on the switching key changed the discriminative stimulus from reinforced to unreinforced or from unreinforced to reinforced. The reinforced stimulus was presented automatically on half the trials, but could be produced only by a switching response on the other half. Switching tended to occur in three distinct stages during acquisition of discriminative behavior. The first stage was identified as "nondiscriminative switching"; the second as "nonswitching"; and the third as "discriminative switching".

Animals↗
PubMed1996

Discrimination learning and multiple reversals in young adult and older monkeys (Macaca arctoides).

Two groups of five young adult an older stumptailed macaques (Macaca arctoides) were tested on a visual discrimination task followed by a reversal upon attainment of criterion; task and reversal were repeated until 20 reversals with the same pair of objects had been completed. Both groups required more trials to learn the first reversal than the original discrimination, with no significant difference between the groups. Older monkeys tended to show more perseverative errors on early reversals, but a striking improvement in their scores across successive blocks of reversals culminated in performances virtually indistinguishable from those of the young group by the end of testing.

Age Factors↗
PubMed1980

[The influence of object sort and early experience on the discrimination learning in domestic chickens].

Main subject of the reported investigation is the question in which way the acquisition of a conditional discrimination is modified on the one hand by the kind of objects presented, on the other hand by early experience. 40 newly hatched chickens grew up either with all the wooden eggs or cubes used for training and test, or without these objects, or in a 'natural' (enriched) environment. The results prove an influence of the kind of objects--cubes are discriminated twice or three times as fast as wooden eggs--but no effects of the different environments on acquisition (number of trials for reaching learning criterion). Results are discussed under aspects of species-specific constraints on learning.

Animals↗
PubMed1990

A computer-aided procedure for measuring discrimination learning.

A computer program is described for a two-choice black-white T-maze discrimination task involving 10 trials per day for 5 days. A Gellerman series of 44 semirandom L/R sequences is included within the program to specify the location of the reinforcing stimulus on each trial. A picture of the T-maze appears on the screen, and the experimenter tracks the animals's movements as it goes through the maze. At the end of the 10 trials, the following statistical information is obtained: number of initial choices into the left alley, number of correct choices, number of trials in which no choice was made, median time to make a choice, and a learning score based upon the path taken by the animal. These data are then sent to Excel for statistical processing.

Animals↗
PubMed2002

Role of the dorsomedial striatum in behavioral flexibility for response and visual cue discrimination learning.

These experiments examined the effects of dorsomedial striatal inactivation on the acquisition of a response and visual cue discrimination task, as well as a shift from a response to a visual cue discrimination, and vice versa. In Experiment 1, rats were tested on the response discrimination task followed by the visual cue discrimination task. In Experiment 2, the testing order was reversed. Infusions of 2% tetracaine did not impair acquisition of the response or visual cue discrimination but impaired performance when shifting from a response to a visual cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was not due to perseveration of the previously learned strategy, but to an inability to maintain the new strategy. These results contrast with findings indicating that prelimbic inactivation impairs behavioral flexibility due to perseveration of a previously learned strategy. Thus, specific circuits in the prefrontal cortex and striatum may interact to enable behavioral flexibility, but each region may contribute to distinct processes that facilitate strategy switching.

Animals↗
PubMed1999

The effect of excitotoxic hippocampal lesions on simple and conditional discrimination learning in the rat.

The effect of excitotoxic lesions of the hippocampus on acquisition and reversal of simple and conditional tasks was investigated using a Y-maze. Hippocampal-lesioned rats were severely impaired on acquisition and reversal of a conditional visuo-spatial task (where different pairs of visually distinctive choice arms indicated whether a left or right arm choice was correct on that trial) and were unable to acquire a visuo-visual conditional discrimination (where the appearance of the start arm indicated which of the visually distinctive choice arms was correct irrespective of their left/right position). They were not impaired on acquisition or reversal of a simple spatial left/right discrimination task (where all arms had the same visual appearance) nor on acquisition of a visual discrimination (where the correct, visually distinctive, choice arm varied in its left/right position). Hippocampal-lesioned rats were, however, impaired on reversal of this visual discrimination task and on acquisition and reversal of another visual discrimination task in which the visually distinctive choice arms were less different from each other than in the first version of this task. The degree of impairment in the lesioned rats was related to task difficulty for the sham-operated rats and was not specific to tasks requiring spatial choices, visual discrimination or conditional responding. The impairment on conditional tasks was greater than the impairment on those non-conditional tasks which happened to be matched for task difficulty for the sham-operated rats, suggesting that the conditional demand may target the function of the hippocampus rather closely. Statistically worse than chance performance by hippocampal-lesioned (and sham-operated) rats at the beginning of reversal testing, which was given 24 h after achieving criterion on acquisition of that task, indicated that hippocampal-lesioned rats simultaneously exhibited good memory but impaired learning for the type of information required for those tasks.

Animals↗
PubMed1989

Effects of delayed monocular enucleation after birth upon black-white discrimination learning in the albino rat.

Many investigators have demonstrated that enucleation of one eye in rats and hamsters soon after birth results in an increased number of uncrossed optic nerve terminals in the main visual centers, and that they are physiologically functional. Such changes, however, became less evident as the time of enucleation is delayed after birth. We also have found that rats with one eye removed at birth were able to relearn a black-white discrimination task faster than rats monocularly enucleated at maturity when relearning was conducted after destruction of the visual cortex contralateral to the remaining eye. This faster relearning phenomenon is considered to be a behavioral expression of such morphological and physiological changes. The present study was then undertaken to examine the question of how this faster relearning phenomenon is affected by the delay of enucleation time after birth. Two experiments were conducted. In Experiment 1 the effects of the removal of one eye at 0, 5, 10, 15, 20 days and at three months of age were compared, and in Experiment 2 those at 10, 11, 12, 13, 14 and 15 days of age were compared. Experiment 1 showed that enucleation at 0, 5 and 10 but not at 15, 20 days and at three months of age facilitated relearning, and that the degree of facilitation decreased as age increased. And, although the results were not unequivocal, Experiment 2 did suggest that the removal of one eye at and beyond 13 days of age was no longer able to facilitate relearning.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed2001

Evidence for a conceptual account of same-different discrimination learning in the pigeon.

We trained pigeons to peck two different buttons in response to 16-icon same arrays versus 16-icon different arrays. In the same arrays, the icons were all the same as one another, whereas in the different arrays, the icons were all different from one another. In Experiment 1, we upset the spatial regularities of the displays by disarranging the icons--randomly displacing each icon to reduce the degree of perceptual order. The pigeons' discriminative performance was unaffected by disarranging. In Experiment 2, spatial regularities were disturbed by varying the rotation of the icons within a display. Again, no disruption in discriminative performance was observed. These and other findings suggest that pigeons treat the 16 icons as either the same or different despite changes in the spatial organization or orientation of the icons, thus implicating a conceptual rather than a perceptual process in same-different discrimination.

Animals↗
PubMed1982

The relative importance of reinforced versus nonreinforced stimuli in visual discrimination learning by redwinged blackbirds (Agelaius phoeniceus).

Redwinged blackbirds were trained to locate and peck apple slices in two discrimination problems with four times more training on one problem than on the other. The birds were then given transfer tests with the stimuli re-paired. Nonreinforced (S-) stimuli exerted greater control over behavior than did reinforced (S+) stimuli. We inferred that the blackbirds learned more about what to avoid than what to approach when searching for food in the two-choice situation. That inference is contrary to the notion that, by being alert to the visual cues which signal foods (i.e., S+ stimuli), birds can more successfully cope with irrelevant visual information encountered during foraging. Rather, being alert to cues which signal the absence of food (i.e., S- stimuli) may be relatively more important.

Animals↗
PubMed1993

Effects of ageing on visual discrimination learning in Drosophila melanogaster.

Two experiments examined conditioned suppression of the Proboscis Extension Response (PER), unconditionally released by sucrose stimulation of gustatory tarsal receptors, in young (7-day-old), middle-aged (30-day-old) and old (50-day-old) Drosophila melanogaster males, reared at 25 degrees C. Individual flies were trained in a differential conditioning procedure in which a white stimulus signalled a quinine reinforcer, whereas a black stimulus was non-reinforced. When trained from the outset with the discriminative procedure, flies of all ages acquired the discrimination, although the acquisition of PER suppression to the white stimulus was retarded in middle-aged and old flies. The retardation of the acquisition of PER suppression in middle-aged and old flies was replicated in a second study in which the files received simple conditioning to the white stimulus prior to discrimination training.

Age Factors↗
PubMed1978

Influence of prenatal and postnatal lead exposure on discrimination learning in rats.

The animals in this study were the offspring of dams, who, from 21-99 days of age, were exposed to 1000 mg/kg of lead acetate via a daily restricted watering schedule with exposure continuing throughout gestation and nursing. Control dams received distilled water under the same watering schedule. Offspring were weaned at 21 days of age and did not received lead treatment from that point. Testing began at 30 days of age with animals receiving 10 trials/day for 10 days on a brightness discrimination task conducted in a water-escape T-maze. This task was followed by a shape discrimination problem in the same apparatus. Analysis of results revealed that the lead-exposed pups made significantly more errors than the controls but had significantly shorter swimming times on both the brightness and shape discrimination tasks. The failure to attend to relevant discriminative cues may account for the observed deficits in lead-exposed animals.

Animals↗
PubMed1977

Pattern structure and relational discrimination learning.

McGonigle and Jones take exception to Dodwell's explanation of anomalous transfer (AT) as the outcome of relational discriminations among a set of stimulus patterns which vary along a single dimension of orientational salience, from 'horizontal' to 'vertical'. In particular they do not think that the continuum is generated by units with Hubel-and-Wiesel type retinal receptive fields. Instead, they invoke Garner's notions about stimulus structure to explain Dodwell's results, as well as their own finding of two situations where AT fails to occur. It seems that McGonigle and Jones missed the point of the relational discrimination explanation of AT. In fact, it is shown that AT is not predicted by this model for the conditions in which they failed to obtain it. The relational model makes definite predictions about conditions under which AT will occur; as this is not true of their invocation of Garner's ideas, the former is to be preferred. Whether or not outputs are coded by Hubel-and Wiesel type units is not particularly relevant to the main point, that AT is a result of relational learning. In fact, the model is an instance of how structure, in Garner's sense, can be generated.

Animals↗
PubMed1995

Changes in c-fos mRNA expression in rat brain during odor discrimination learning: differential involvement of hippocampal subfields CA1 and CA3.

Levels of c-fos mRNA were measured with in situ hybridization to test for behaviorally dependent changes in neuronal activity in three subdivisions of hippocampus and in components of the olfactory and visual systems. In rats that performed a well-learned nose-poke response for water reward, c-fos mRNA levels were broadly increased, relative to values in home cage-control rats, in visual cortex, superior colliculus, olfactory bulb, and, to comparable levels, regions CA3 and CA1 of hippocampus; hybridization was not increased in the dentate gyrus. In rats first trained on the nose-poke behavior and then required to discriminate between two odors for water reward, the increase in c-fos mRNA was generally not as great and was more regionally differentiated. Thus, in olfactory bulb, hybridization was more greatly elevated in lateral than medial fields, thereby exhibiting regional activation corresponding to the topographic representation of the predominant odor sampled in the discrimination task. In hippocampus of odor-discrimination rats, c-fos mRNA levels were far greater in the region CA3 than region CA1, but remained at cage control values in stratum granulosum. Interestingly, c-fos mRNA levels in each hippocampal subdivision were highly correlated with levels in other regions (e.g., visual cortex) for home cage controls but not for rats in the two behavioral groups. Thus, c-fos mRNA levels in cage-control rats appeared to be regulated by some generalized factor acting throughout much of the brain (e.g., arousal), while odor-discrimination performance changed the pattern of expression within hippocampus, and allowed for a differentiated response by olfactory regions to emerge. These findings suggest that hippocampus possesses multiple modes of functioning and makes contributions to behavior that vary according to task demands.

Animals↗
PubMed2006

Holeboard discrimination learning in mice.

We have adapted to mice a holeboard-learning task, which allows simultaneous assessment of spatial working and reference-memory performance. The holeboard apparatus consists of an open-field chamber with a 16-hole floor insert. Across trials, animals have to learn that the same four holes of 16 are always baited. Here, we show that C57BL/6 mice readily acquire this task within 4 days when submitted to six trials per day or within 8 days when submitted to only four trials per day. We also show that C57BL/6, Swiss-Webster, CD-1 and DBA/2 mice acquire this task similarly, despite the fact that some differences could be observed in measures of exploratory activity during habituation and training. Moreover, the muscarinic antagonist scopolamine disrupts learning at doses of 0.1 and 1.0 mg/kg, although the highest dose appeared to have side-effects. Lastly, we found that amyloid precursor protein transgenic mice have a selective disruption in their working-memory performance only during reversal training (i.e. after a change in the configuration of the baited holes). Overall, our data indicate that this spatial learning task is well adapted to mice and will be useful to characterize spatial memory in various genetic or pharmacological mouse models.

Amyloid beta-Protein Precursor↗
PubMed1988

Effects of superior colliculus lesion upon a black-white discrimination learning in the albino rat with one eye removed at birth.

It has previously been shown that, following original training of a black-white discrimination task, rats with one eye removed at birth (OEB) relearned the task faster than rats monocularly enucleated at three months of age (OET) when relearning was conducted after extirpation of the visual cortex contralateral to the remaining eye. The aim of the present study was to examine the role of the crossed and uncrossed retina-superior colliculus-lateral posterior nucleus of the thalamus-visual cortex pathway in mediation of original learning and relearning of OEBs in comparison with OETs. For this purpose the superior colliculus was destroyed bilaterally either before or after original learning. It was found that SC lesions did not affect original learning nor its retention in both OEBs and OETs, and there was no difference in the learning rate between the two. In relearning, it was also found that only when SC lesions were made before original learning, did OEBs fail to show faster relearning. Based on these findings it was suggested that enhanced functioning of the uncrossed retina-superior colliculus-lateral posterior nucleus of the thalamus-visual cortex pathway in original learning plays an indispensable role in enabling OEBs to relearn the discrimination task faster than OETs.

Animals↗