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At least 1,423 records · Page 79Linked to original sources
PubMed1986

Incidental learning is impaired during early-life undernutrition.

Rats were either well-nourished (control) or undernourished (PU) during the suckling and early post-weaning periods (birth to 45 days), after which all animals were fed ad libitum. From 25 to 45 days half of the rats in each group were exposed continuously in their home cases to shape stimuli (triangles and circles). Half of each of these 4 groups were given "reminders" of the stimuli through exposure for 2 h every 10-12 days from 55 to 131 days. Beginning on day 132, ability to discriminate these same visual stimuli was tested using a nonappetitively motivated version of the Lashley jumping stand technique. Discrimination learning per se was unimpaired by previous undernutrition (control and PU rats not viewing the stimuli prior to training performed equally well). However, early-life exposure led to improved learning performance only in control rats; it had no effect on the performance of PU rats (significant exposure X nutrition interaction). These findings indicate that undernutrition interfered with early "incidental learning", that is, learning about features of the environment which are not, at the time, biologically relevant. Finally, retention of the discrimination was assessed 9 weeks after the rats had attained criterion performance. There were no effects of nutrition or prior exposure on long-term memory.

Animals↗
PubMed1998

Protective effects of fetal neocortical transplants on cognitive function and neuron size in rats with congenital micrencephaly.

The rat with micrencephaly, produced by prenatal exposure to methylazoxymethanol, provides a useful model to study neurobehavioral abnormalities associated with congenital brain defects. The micrencephalic animals have a life-long learning impairment. As they age, their already impaired learning competence deteriorates further. To determine whether the aging-associated functional deterioration could be ameliorated by a neural transplant, micrencephalic rats bearing solid transplants of normal fetal neocortical tissue since infancy were evaluated on a visual pattern discrimination learning at 15 months and a spatial navigation test at 24 months of age. The transplant-bearing rats learned both tasks significantly better than the micrencephalic rats without transplants. Morphometric analyses revealed that cortical pyramidal neurons were larger in the transplant-bearing rats than in micrencephalic rats without transplants. The life-long presence of a transplant appeared to have protected the micrencephalic brain against aging-associated deterioration. This is the first demonstration that a neural transplant, placed in a congenitally defective infant brain, can ameliorate aging-associated cognitive deficits.

Animals↗
PubMed1984

Effects of kainic acid and radiofrequency lesions of the pulvinar on visual discrimination in the monkey.

Monkeys with thermocoagulation or kainic acid lesions of the pulvinar and unoperated control monkeys were tested in two tasks: pattern discrimination retention and color discrimination learning in which the stimuli were located at the response sites or were separated spatially from them (S-R separation). The monkeys with kainic acid pulvinar lesions were mildly impaired in retention of the pattern discrimination, but were unimpaired in the color discrimination tasks with or without the S-R separation. The monkeys with thermocoagulation lesions, like monkeys with superior colliculus lesions in a prior study, were severely impaired in performing one of the color discrimination tasks with S-R separation. These findings suggest that: (a) the inferior pulvinar, unlike the superior colliculus, does not contribute to the performance of discriminations involving S-R separation; and (b) corticotectal projections traversing the pulvinar and destroyed by the thermocoagulation lesions are crucial to the performance of discriminations involving S-R separation. The results of an earlier experiment also suggested that interruption of corticotectal fibers passing through the pulvinar impairs performance in another task sensitive to superior colliculus lesions--spatial localization of light flashes. Thus, corticotectal projections may be crucial for the contribution of the colliculus to performance in a variety of visual tasks.

Animals↗
PubMed1981

Transfer of perceptual learning: role of tactual-kinesthetic feedback reexamined.

Albino rats were pre-exposed to stimuli in an otherwise visually sparse environment, with visibility and opportunity to manipulate the forms controlled during rearing. Analysis indicated that pre-exposing animals to stimuli which provided either tactual-kinesthetic feedback or highly visible forms significantly facilitated subsequent discrimination learning. The findings question the adequacy of either an attention-getting or tactual-kinesthetic feedback to account for differences in transfer effects in studies using two- and three-dimensional forms. It is suggested that the visibility of the forms and the opportunity to inspect the forms during pre-exposure is the important variable in studies of this type.

Animals↗
PubMed1996

A behavioural preparation for the study of human Pavlovian conditioning.

Conditioned suppression is a useful technique for assessing whether subjects have learned a CS-US association, but it is difficult to use in humans because of the need for an aversive US. The purpose of this research was to develop a non-aversive procedure that would produce suppression. Subjects learned to press the space bar of a computer as part of a video game, but they had to stop pressing whenever a visual US appeared, or they would lose points. In Experiment 1, we used an A+/B- discrimination design: The US always followed Stimulus A and never followed Stimulus B. Although no information about the existence of CSs was given to the subjects, suppression ratio results showed a discrimination learning curve-that is, subjects learned to suppress responding in anticipation of the US when Stimulus A was present but not during the presentations of Stimulus B. Experiment 2 explored the potential of this preparation by using two different instruction sets and assessing post-experimental judgements of CS A and CS B in addition to suppression ratios. The results of these experiments suggest that conditioned suppression can be reliably and conveniently used in the human laboratory, providing a bridge between experiments on animal conditioning and experiments on human judgements of causality.

Animals↗
PubMed2001

A simple and reliable test of olfactory learning and memory in mice.

The present paper describes a quick and efficient method for assessing olfactory discrimination learning in mice. In training mice received trials in which one odor (CS+) was paired with sugar and another odor (CS-) was paired with no sugar. When the mice were subsequently placed in a chamber with CS+ odor at one end and CS- odor at the other, they spent more time digging in CS+ than in CS- odor. In Experiment 2 mice trained with this procedure and tested after 60 days also spent more time digging in CS+ than CS- in the test phase, indicating that this olfactory discrimination task is effective for assessing long-term memory. In addition to the outbred strain of CD1 mice used in Experiments 1 and 2, C57Bl/6NCr/BR and DBA/2NCr/BR mice used in Experiment 3 also acquired this learned odor discrimination. Moreover, Experiment 4 showed that DBA animals were capable of acquiring this odor discrimination after receiving only two training trials (one exposure each to CS+ and CS-) per day for 4 days.

Animals↗
PubMed1999

Fos protein expression induced by intracerebroventricular injection of vasopressin in unconditioned and conditioned mice.

Arginine8-vasopressin (AVP) has been shown to improve memory consolidation in various mnemonic tasks. Our previous studies have pointed out the involvement of the hippocampus in memory consolidation and retrieval processes during discriminative learning by mice. The present study attempts to determine what other brain areas besides the hippocampus might be involved in the enhancing effect of intracerebroventricularly (i.c.v.) injected AVP on memory consolidation in a visual discrimination task using a polyclonal antibody that acts against Fos and Fos-like proteins. For behavioral testing, AVP was i.c.v. injected at the behaviorally active dose of 2 ng after the last learning session and improvement in consolidation processes was assessed in a retention session. Changes in Fos and Fos-like protein expression were determined in non-conditioned and conditioned mice. In non-conditioned mice, AVP i. c.v. injected at a dose of 2 ng evoked a time-dependent increase in Fos and Fos-like protein expression in the dentate gyrus (DG), CA1 and CA3 hippocampal fields, lateral septum (LS), bed nucleus of the stria terminalis, and basolateral and central amygdaloid nuclei, with a peak 120 min after the injection in most of the these brain areas. In contrast, in conditioned mice, an increase in the level of Fos expression, assessed 120 min after the end of learning and the injection of AVP, was detected only in the DG, ventral CA3 hippocampal field, and LS. Thus, the pattern observed after post-training injection of AVP was not the same as that evoked by AVP alone, since among the limbic structures activated following AVP alone, only the DG, the CA3 hippocampal field, and the LS seem to be involved in the enhancing effect of AVP on memory consolidation in discriminative learning.

Amygdala↗
PubMedDate not supplied

Colour discrimination in the black-tufted-ear marmoset (Callithrix penicillata): ecological implications.

The dietary diversity of marmosets is substantial, which may reflect differences in their colour vision. This study examined the colour discrimination ability of a gummivore/insectivore callitrichid, Callithrix penicillata, which inhabits the Brazilian cerrado (bush savanna). A series of ecologically relevant tasks, involving a behavioural paradigm of discrimination learning in semi-natural conditions and the usage of ecologically relevant stimuli, was executed. Three marmosets, 2 males and a female, behaved like human dichromats, showing an impaired performance when orange and green stimuli had to be discriminated. In contrast, 2 females resembled human trichromats, discriminating those kinds of pairs. Our data suggest that Callithrix penicillata presents a polymorphic trichromacy, with dichromatic males and dichromatic or trichromatic females.

Animals↗
PubMed1984

Time-dependent effects of posttraining intrahippocampal injections of corticosterone on retention of appetitive learning tasks in mice.

In previous studies we suggested that corticosterone may modulate hippocampal functioning during memory formation. To test this assumption, we studied the effects of posttrial administration of corticosterone (1 microgram) injected bilaterally in the hippocampus. The treatment was applied at different time intervals after the learning session and the retention session took place 24 h later. Using appetitive operant conditioning tasks in a Skinner box, we found that the posttrial treatment 1) did not affect the retention of a continuously reinforced schedule, 2) improved the retention of a successive discrimination learning task, and 3) was still effective when given 3 h after the acquisition of this task, but not after 6 h. Taken together, the results suggest that corticosterone modulates the hippocampal mechanisms involved in behavioral suppression during memory formation.

Animals↗
PubMedDate not supplied

Chlorpyrifos exposure of developing zebrafish: effects on survival and long-term effects on response latency and spatial discrimination.

Chlorpyrifos (CPF) is a widely used insecticide, which has been shown to interfere with neurobehavioral development. Rat models have been key in demonstrating that prenatal CPF exposure causes choice accuracy deficits and motor alterations, which persist into adulthood. Complementary nonmammalian models can be useful in determining the molecular mechanisms underlying the persisting behavioral effects of developmental CPF exposure. Zebrafish with their clear chorion and extensive developmental information base provide an excellent model for assessment of molecular processes of toxicant impacted neurodevelopment. To facilitate the use of the zebrafish model and to compare it to the more typical rodent models, the behavioral phenotype of CPF toxicity in zebrafish must be well characterized. Our laboratory has developed methods for assessing spatial discrimination learning in zebrafish, which can differentiate response latency from choice accuracy in a three chambered fish tank. Low and high doses of CPF (10 and 100 ng/ml on days 1-5 postfertilization) both had significant persisting effects on both spatial discrimination and response latency over 18 weeks of testing. The high, but not the low dose, significantly accelerated mortality rates of the fish during the study from 20-38 weeks of age. Developmental exposure to either 10 or 100 ng/ml of CPF caused significant spatial discrimination impairments in zebrafish when they were adults. The impairment caused by 10 ng/ml was seen during early but not later testing, while the impairment caused by 100 ng/ml became more pronounced with continued testing. The higher dose caused a more pervasive impairment. The 10 and 100 ng/ml doses had opposite effects on response latency. The low 10 ng/ml dose significantly slowed response latency, while the high 100 ng/ml dose significant increased response latency. Both of these effects diminished with continued testing. CPF exposure during early development caused clear behavioral impairments, which lasted throughout adulthood in zebrafish. The molecular mechanisms by which early developmental CPF exposure produces these behavioral impairments expressed in adulthood can now be studied in the zebrafish model.

Animals↗
PubMedDate not supplied

Size and reversal learning in the beagle dog as a measure of executive function and inhibitory control in aging.

Several studies converge on the idea that executive processes age earlier than other cognitive processes. As part of a larger effort to investigate age-related changes in executive processes in the dog, inhibitory control was measured in young, middle-aged, old, and senior dogs using size discrimination learning and reversal procedures. Compared to young and middle-aged dogs, old and senior dogs were impaired on both the initial learning of the size task and the reversal of original reward contingencies. Impaired performance in the two aged groups was characterized as a delay in learning the correct stimulus-reward contingencies and, among the senior dogs in particular, an increase in perseverative responding. These separate patterns of reversal impairments in the old and senior dogs may reflect different rates of aging in subregions of the frontal cortex.

Aging↗
PubMed1984

Developments of a water-maze procedure for studying spatial learning in the rat.

Developments of an open-field water-maze procedure in which rats learn to escape from opaque water onto a hidden platform are described. These include a procedure (A) for automatically tracking the spatial location of a hooded rat without the use of attached light-emitting diodes; (B) for studying different aspects of spatial memory (e.g. working memory); and (C) for studying non-spatial discrimination learning. The speed with which rats learn these tasks suggests that they may lend themselves to a variety of behavioural investigations, including pharmacological work and studies of cerebral function.

Animals↗
PubMed2006

Rhesus monkeys (Macaca mulatta) immediately generalize the uncertain response.

Rhesus monkeys (Macaca mulatta) have learned, like humans, to use an uncertain response adaptively under test conditions that create uncertainty, suggesting a metacognitive process by which human and nonhuman primates may monitor their confidence and alter their behavior accordingly. In this study, 4 rhesus monkeys generalized their use of the uncertain response, without additional training, to 2 familiar tasks (2-choice discrimination learning and mirror-image matching to sample) that predictably and demonstrably produce uncertainty. The monkeys were significantly less likely to use the uncertain response on trials in which the answer might be known. These results indicate that monkeys, like humans, know when they do not know and that they can learn to use a symbol as a generalized means for indicating their uncertainty.

Adaptation, Psychological↗
PubMed2004

Cocaine-experienced rats exhibit learning deficits in a task sensitive to orbitofrontal cortex lesions.

Addictive drugs, such as cocaine, cause long-lasting neural changes in prefrontal cortex. It has been hypothesized that these changes affect the behavioural control mediated by orbitofrontal cortex. To test this hypothesis, rats were given injections of cocaine (30 mg/kg/d, i.p.) or vehicle for 14 days and then trained after a 2-week withdrawal period in an odor discrimination task sensitive to the effects of orbitofrontal cortex lesions. We found that cocaine-treated rats, who demonstrated long-lasting sensitization to the locomotor activating effects of cocaine, failed to show normal changes in response latency during discrimination learning and were also slower than controls to acquire serial reversals. These behavioural impairments are identical to the effects of orbitofrontal cortex lesions in this task and show that cocaine exposure in rats can cause long-lasting effects on orbitofrontal-dependent functions. Notably, these effects were not correlated with increases in locomotor activity linked to cocaine-induced psychomotor sensitization observed before or after training, suggesting that the brain changes underlying the behavioural effects in the discrimination task are different from those mediating psychomotor sensitization.

Anesthetics, Local↗
PubMed1982

Improving the visual discrimination of mentally retarded children: a training strategy.

Mentally retarded children were asked to judge whether a series of visual stimuli matched a standard. With each judgment the investigator verbalized "right" or "wrong" and then provided full feedback of particulars, indicating with gesture and words the cue similarities and differences that supported each correct and each incorrect judgment. Control subjects were either given no training (test--retest only) or were asked to make the judgments but given no feedback. Attesting to the efficacy of the training procedure, the trained subjects exhibited total intradimensional transfer; the control subjects, none. The results were related to the attention-retention theory of discrimination learning developed by Fisher and Zeaman and to the "differentiation" methodology and theory presented by Gibson and Gibson.

Adolescent↗
PubMed1992

Delayed matching to sample and concurrent learning in nonamnesic humans with alcohol dependence.

Small samples of alcohol-dependent subjects who showed no clinical signs of Wernicke-Korsakoff syndrome were compared with nonalcohol-dependent controls on two animal memory tests which are performed poorly by human amnesics. Compared to the control subjects, the alcohol-dependent subjects' performance was impaired on a version of the delayed matching to sample task. On concurrent discrimination learning the overall group difference just failed to reach significance. The results are interpreted as suggesting that behavioural impairment may occur in alcohol-dependent subjects who are not clinically amnesic, and that the impairment is similar in type to that observed in cases of severe Wernicke-Korsakoff syndrome.

Adolescent↗
PubMed1988

Intracortical auditory evoked potentials during classical aversive conditioning in cats.

Auditory evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. In a classical aversive learning paradigm the change of the pitch of regularly given acoustic stimuli served as warning signal. With conditioning the amplitude of a middle latency negative component increased and its latency decreased. Based on laminar analysis of EP profiles we propose that the observed EP changes were generated within the upper cortical layers and reflected a temporary aurousal reaction induced by the signal as a result of discrimination learning. For the description of this effect the term "learned aversive arousal" is suggested.

Animals↗
PubMed2000

Associative olfactory learning in the moth Manduca sexta.

The proboscis extension response conditioning protocol has been used to explore olfactory-based associative learning in an array of insects. We have monitored a different feeding reflex, which involves activation of the cibarial pump, to demonstrate olfactory learning in the moth Manduca sexta. In the first experiment, four different treatment conditions were used to assess associative (Pavlovian) learning. The results indicate that an excitatory cibarial pump response develops and is retained for at least 24 h only when odor is forward-paired with the presentation of sucrose. Three control treatments, backward pairing, air (no odor) pairing and random pairing, failed to increase the cibarial pump response. However, an excitatory cibarial pump response developed when the backward- and air-paired groups received forward pairing of odor and sucrose on the following day. In contrast, moths experiencing random pairing on day 1 displayed a slower rate of acquisition during forward pairing on day 2, which may indicate inhibition. The second experiment investigated discrimination learning. Two odors were randomly presented, one odor being forward-paired with sucrose (+), the other presented alone (-) in a counterbalanced design. Again, only when odor was forward-paired with sucrose did learning occur. We discuss the implication of these findings for a broader comparative analysis of learning in insects.

Animals↗