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At least 793 records · Page 44Linked to original sources
PubMed2006

Dynamic object recognition in pigeons and humans.

We investigated the role of dynamic information in human and pigeon object recognition. Both species were trained to discriminate between two objects that each had a characteristic motion, so that either cue could be used to perform the task successfully. The objects were either easy or difficult to decompose into parts. At test, the learned objects could appear in their learned motions, the reverse of the learned motions, or an entirely new motion, or a new object could appear in one of the learned motions. For humans, any change in the learned motion produced a decrement in performance for both the decomposable and the nondecomposable objects, but participants did not respond differentially to new objects that appeared in the learned motions. Pigeons showed the same pattern of responding as did humans for the decomposable objects, except that pigeons responded differentially to new objects in the learned motions. For the nondecomposable objects, pigeons used motion cues exclusively. We suggest that for some types of objects, dynamic information may be weighted differently by pigeons and humans.

Animals↗
PubMed2006

Priming or executive control? Associative priming of cue encoding increases "switch costs" in the explicit task-cuing procedure.

The explicit task-cuing procedure involves presenting a cue that indicates which task to perform on a target. Responses are typically faster when tasks repeat than when they alternate, and this difference is often interpreted as a measure of the time required for executive control processes to change task set. This article suggests that the difference reflects priming of cue encoding when successive cues are identical or associatively related. Subjects responded to task repetitions more quickly when the cue on the current trial was associatively related to the cue on the previous trial (e.g., day --> night) than when the cues were unrelated (e.g., verb --> night). Models applied to the time course function--generated by manipulating the interval between the onsets of the cue and the target--showed that the facilitation was due to cue encoding, a process that does not require online executive control.

Attention↗
PubMed1975

Long-term transfer of a mediational strategy by moderately retarded children.

Moderately retarded children were instructed to produce prepositional mediatros by physically manipulating PA objects in learning three nine-term PA lists. Mediational training, distributed across days or weeks, consisted of one or three different prepositions supplied for two-thirds or for all of the items. It was found that mediation subjects performed significantly better than control subjects on an unaided test list administered 2 weeks after training, regardless of distribution of training, degree of aid or number of prepositions provided during training sessions. The degress of transfer, which was larger than in previously reported studies, was attributed to the instructional procedures requiring active production of prepositional mediators, coupled with an emphasis on their value. It was suggested that individual variability in mediational transfer should be considered in future research on mediational transfer.

Adolescent↗
PubMedDate not supplied

Autoshaped discrimination learning in chicks incubated under normobaric hyperoxia.

White Leghorn chicken eggs were exposed to either 60% O2 or room air (21% O2) for the first 19 days of incubation. Chicks that hatched from these eggs were then tested in discrimination learning tasks in which keypecking was autoshaped to colored lights that were paired with either access to food (Experiment 1) or heat (Experiment 2). Chronic prenatal exposure to 60% O2 reduced hatchability but did not affect mean hatching time. Although previous research has shown that hyperoxic treatment accelerates growth in chick embryos until the 18th day of incubation, experimental chicks weighed either the same (Experiment 1) or less (Experiment 2) than controls at hatching. Prenatal exposure to hyperoxia depressed rate of acquisition, but not final performance level in both discrimination tasks. The initial performance deficit appeared to reflect a temporary depression of activity or arousal, possibly due to a relatively greater hypothermia in experimental chicks. This general pattern of results was attributed to premature depletion of essential nutrients within the egg as a result of oxygen-induced growth acceleration.

Animals↗
PubMedDate not supplied

Visual-discrimination learning ability and beta-amyloid accumulation in the dog.

Young, middle-aged, and old beagle dogs were tested on several visual-discrimination tasks: reward- and object-approach learning, object discrimination and reversal, long-term retention of a reversal problem, and a size-discrimination task. Beta-amyloid accumulation in the entorhinal, prefrontal, parietal, and occipital cortices was quantified using immunohistochemical and imaging techniques at the conclusion of cognitive testing. Middle-aged and old dogs were impaired in size-discrimination learning. In each task, a subset of aged dogs was impaired relative to age-matched peers. Beta-amyloid accumulation was age-dependent. However, not all middle-aged and old dogs showed beta-amyloid accumulation in the entorhinal cortex. The error scores from dogs tested with a nonpreferred object during visual discrimination learning and from reversal learning were correlated with beta-amyloid in the prefrontal but not entorhinal cortex. Size-discrimination and reward and object-approach learning error scores were correlated with beta-amyloid accumulation in the entorhinal but not prefrontal cortex. The results of these studies support an association between cognitive test and the location and extent of beta-amyloid pathology.

Amyloid beta-Peptides↗
PubMedDate not supplied

The effects of hippocampal-area parahippocampalis lesions on discrimination learning in the pigeon.

Three experiments examined the behavioural effects of bilateral ablation of the avian hippocampus-area parahippocampalis (Hp-APH), a region which is considered to be the homologue of the mammalian hippocampal formation. Pigeons with lesions of the Hp-APH were impaired in learning the reversal (but not the acquisition) of a position (left/right) discrimination (Expt. 1). In contrast, lesion birds were unimpaired relative to controls in both the acquisition and reversal of a visual (pattern) discrimination (Expt. 2) in terms of errors to criterion; there was evidence, however, that the pattern of responding differed between groups during reversal. Finally, Hp-APH pigeons were impaired in the acquisition of a conditional discrimination (Expt. 3). The results are compared with the effects of hippocampal ablation in mammals, and their implications for a behavioural homology between the avian Hp-APH and the mammalian hippocampal formation are considered.

Animals↗
PubMed2005

Dynorphin A (2-13) improves mecamylamine-induced learning impairment accompanied by reversal of reductions in acetylcholine release in rats.

Accumulating evidence indicates that the endogenous opioid peptides dynorphin A (1-17) and synthetic dynorphin A (1-13) interact not only with opioid receptors but also with as yet poorly characterized non-opioid binding sites. Dynorphin A (1-13) improved impairments of learning and memory via not only kappa-opioid receptor-mediated, but also 'non-opioid' mechanisms. In the present study, the effects of des-tyrosine(1) dynorphin A (2-13) as a non-opioid metabolite of dynorphin A, and dynorphin A (1-13) on mecamylamine-induced impairment of the acquisition of learning in rats were investigated using a step-through type passive avoidance task. Further, hippocampal acetylcholine release was examined using in vivo microdialysis. Mecamylamine significantly shortened the step-through latency when given 30 min before the acquisition trial. Not only dynorphin A (1-13) but also dynorphin A (2-13) attenuated the mecamylamine-induced impairment of the acquisition of learning. The effect of dynorphin A (2-13) was not blocked by pre-treatment with nor-binaltorphimine (nor-BNI), a selective kappa-opioid receptor antagonist. Dynorphin A (2-13) completely abolished the decrease in the extracellular acetylcholine concentration induced by mecamylamine and this effect was not blocked by nor-BNI. Taken together with our previous findings, the present results may indicate that dynorphin A (2-13) improves impairment of learning and/or memory in 'non-opioid' mechanisms and dynorphin A (1-13) ameliorates impairment of the acquisition of learning via not only kappa-opioid receptor-mediated mechanisms but also 'non-opioid' mechanisms, by regulating the release of extracellular acetylcholine.

Acetylcholine↗
PubMed1992

Ventrolateral prefrontal cortex lesions in rats impair the acquisition and retention of a tactile-olfactory configural task.

Rats with aspirative lesions of the ventrolateral frontal cortex were tested on acquisition and postsurgical retention of an associative learning task that required that they learn a tactile-olfactory configural discrimination. The task required that they pull up a string to obtain attached food and that they identify the correct string using a compound of string size and odor. The rats were not impaired in initial learning or reversal of the olfactory elements of the discrimination. They were impaired in acquisition and retention of the compound, and their deficit was proportional to lesion size. The results confirm that the ventrolateral frontal cortex is involved in processing of olfactory information and imply that the prefrontal cortex is involved in at least certain types of cross-modal configural associative learning.

Animals↗
PubMed1981

Differential effects of neuropeptides on short-term memory in primates.

In a within-subject design, six rhesus monkeys (3 males and 3 females) received a 100 micrograms/kg injection of one of seven neuropeptides or a diluent control solution and were then tested for activity level, learning (discrimination reversal), short-term memory (delayed response), and for responsiveness to noxious stimuli. One daily injection was made with a different peptide for 10 consecutive days, including pre- and post tests on th first and last days with the diluent control. DSIP and D-Phe4-Met enkephalin seemed to produce some interference with short-term memory, while alpha-MSH showed some facilitation of it, as indicated by interactions of the peptides with the delay periods of 0, 15, or 30 sec. Sex differences were found in the learning task and the responsiveness to a noxious stimulus, suggesting the possibility of interactions between the peptides and endogenous hormones.

Animals↗
PubMed2003

Enrichment enhances the expression of sgk, a glucocorticoid-induced gene, and facilitates spatial learning through glutamate AMPA receptor mediation.

We have previously demonstrated that the serum and glucocorticoid-inducible kinase (sgk) gene plays a causal role in facilitating memory performance in rats. Environment enrichment is known to facilitate spatial learning. We therefore examined the effect of enrichment on sgk expression. We also examined the role of sgk in spatial and nonspatial learning and the regulation of sgk expression by activation of different glutamate receptors. Both real-time polymerase chain reaction and Western blot analyses revealed that enrichment training preferentially increased sgk mRNA and protein levels in the hippocampus. Transfection of sgk mutant DNA to the hippocampal CA1 area markedly impaired spatial learning, fear-conditioning learning and novel object-recognition learning in rats, but enrichment training effectively reversed these learning deficits. Meanwhile, S422A mutant DNA transfection prevented enrichment-induced spatial learning facilitation. In studying glutamate receptor regulation of sgk expression, we found that blockade of N-methyl-d-aspartate (NMDA) receptors in general, and the NR2B subunit in particular both effectively blocked enrichment-induced spatial learning facilitation, but they did not block enrichment-induced sgk expression. Upon various glutamate agonist infusions, only alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) increased sgk mRNA levels significantly in the hippocampus. Furthermore, blockade of AMPA receptors effectively blocked both enrichment-induced spatial learning facilitation and sgk expression. These results indicate that there is a dissociation between NMDA receptor activation and sgk expression. Enrichment enhanced spatial learning through both NMDA and AMPA receptor activation, whereas enrichment-induced sgk expression is specifically mediated through AMPA receptors. These results suggest that sgk could serve as a novel molecular mechanism, in addition to the NMDA receptor NR2B, underlying enrichment-induced learning facilitation.

Age Factors↗
PubMed1999

Comparative effects of prenatal and postnatal undernutrition on learning and memory in rats.

Effects of pre- and post-natal undernutrition on learning and memory parameters were studied in albino rats. Prenatal undernutrition was induced in rat pups by restricting the mother's diet by 50% during the entire gestation period, whereas postnatal undernutrition was induced in rat pups by restriction of their diet by rotating them between lactating and non-lactating maternalised females for 12 hr each day during suckling period from 2nd day to 18th day after birth. At 2.5 to 3 months of age all the rat offsprings were subjected to (i) original and reversal discrimination learning, (ii) passive avoidance, and (iii) active avoidance and its retention tests. The results indicate that both pre- and post-natal undernutrition in rat pups caused significant deficits in original and reversal discrimination learning, retention of passive avoidance after one week retention interval, and retention of active of avoidance learning. However, both pre- and post-natal undernutrition did not show significant effect on acquisition of active avoidance and retention of passive avoidance after 24 hr retention interval.

Animals↗
PubMed2004

Free operant and discrete trial performance of mice in the nine-hole box apparatus: validation using amphetamine and scopolamine.

RATIONALE: To determine the suitability of the nine-hole box to characterise mouse performance on a free operant task and a discrete trials task, and to validate the tests by probing whether d-amphetamine and scopolamine modify performance of the task as predicted. OBJECTIVES: To demonstrate the functionality and efficiency of the mouse nine-hole box for the evaluation of performance under fixed- (FR) and progressive-ratio (PR) operant schedules, as well as under a three-choice visual discrimination task and subsequent reversals of the task. In addition, sensitivity of the apparatus was assessed using pharmacological challenges. METHODS: C57BL/6J were tested on CRF, FR5, FR10, FR20, and a modified PR3 schedule. Behavioural response to d-amphetamine sulphate (0.1, 0.3, and 2.0 mg/kg for FR and 0.1, 0.3, and 1.0 mg/kg for PR) was assessed. In a separate group of mice trained on a three-choice visual discrimination task, the task was reversed (light+, dark+, light+, dark+) 3 times to determine acquisition and reversal of the visual discrimination rule. Scopolamine hydrobromide was examined in this paradigm with the reversal task, and was used to determine learning acquisition and rule reversal learning. RESULTS: Mice rapidly acquired the FR and PR schedules, as well as both three-choice visual discrimination procedures in the nine-hole box. d-Amphetamine significantly reduced performance on the FR5 and FR10 schedules as shown by the reduction in the number of rewarded responses and the increases in various latency measurements. As expected, d-amphetamine induced an increase in the break point and eliminated the pauses that occurred on high ratio schedules under the PR3 paradigm. Pretreatment of scopolamine decreased accuracy in the three-choice visual discrimination task. CONCLUSIONS: The nine-hole box is an effective tool to assess operant behaviours in mice following pharmacological manipulation validating the utility of this apparatus for the behavioural evaluation of drug-induced and transgenic models of neurodegenerative disorders.

Amphetamine↗
PubMed2006

Hippocampal cell proliferation regulation by repeated stress and antidepressants.

A recent hypothesis suggests reduced hippocampal neurogenesis in depression. Here, we examined cell proliferation in the dentate gyrus and the subventricular zone of rats given repeated stress, a paradigm that prolongs learned helplessness behavior, and whether antidepressants modulate the learned helplessness-associated altered cell proliferation. Decreased cell proliferation, number of clusters, and cells/cluster were noted in the dentate gyrus, but not in the subventricular zone, of learned helplessness rats. Both fluoxetine and desipramine reversed the learned helplessness behavior and increased the cell proliferation and the number of clusters in learned helplessness rats; only fluoxetine did so significantly. Both fluoxetine and desipramine significantly increased the number of cells/cluster. Our results suggest modified hippocampal neurogenesis in prolonged depression and in the mechanism of antidepressant action.

Analysis of Variance↗
PubMed1975

Effects of structural variations in elaboration on learning by EMR and nonretarded children.

The effects of three elaboration structures (compound sentences, complex sentences, and paragraphs) on the paired-associate learning and reversal of 30 8- to 10-year-old nonretarded and 30 8- to 10-year-old EMR children were investigated. Analyses of trials-to-criterion, first trial errors, and reversal errors did not reveal any differences in the effects of the three elaboration structures. Results of the present study indicate that given constant meaning and relational factors, some forms of surface structure differneces (compound sentences vs. complex sentence vs. paragraph) are not significant in determining a child's ability to understand an elaboration or to use it in a learning situation. There was no population difference found in the analysis of first-trial errors, although small significant differences between the nonretarded and EMR children were found in the analyses of trials-to-criterion and reversal performance.

Child↗
PubMed1994

Scopolamine induces recovery of shuttle box avoidance behavior after frontal cortex ablation.

The learning and reversal of shuttle box active avoidance behavior in animals with a bilateral frontal cortex ablation was investigated during and after scopolamine or pilocarpine treatment. Scopolamine facilitated the performance of the avoidance task in normal animals and in those with frontal cortex lesions and also increased the number of intertrial responses, while pilocarpine increased the deleterious effects of the lesions. Furthermore, in the absence of scopolamine, the animals previously treated with the drug showed that its beneficial effects persisted while the number of intertrial responses were no longer increased. The results indicate that the beneficial effects of scopolamine treatment on active avoidance behavior are independent from the effects observed on intertrial activity since only the former are observed after drug withdrawal. Therefore, scopolamine treatment seems to induce a long lasting recovery process in frontal cortex ablated animals.

Animals↗