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PubMedDate not supplied

[Comparative characteristics of the action of sydnocarb, phenamine and caffeine on multiple alteration in the orientation of the avoidance response in rats].

The ability of rats to alter orientation of the avoidance response in an Y-shaped maze was determined. Sydnocarb (20 mg/kg) improved the reversal learning of the animals, shortened the latent reaction periods and did not upset passive avoidance. Amphetamine (0.5 mg/kg) and caffein (25 mg/kg) shortened the latency of reactions, but did not affect the reversal learning. In large doses (2 and 5 mg/kg) amphetamine distinctly disturbed the reversal learning, while sydnocarb (50 mg/kg) did not impair the alteration of the avoidance response. In rats poorly amenable to reversal learning during control testing syndnocarb facilitated the alteration of the habit better than other drugs. In animals well amenable to reversal learning, in contrast to amphetamine and caffein, it did not derange their behavior.

Amphetamine↗
PubMed1999

Impairment of cingulothalamic learning-related neuronal coding in rabbits exposed to cocaine in utero: general and sex-specific effects.

Neuronal activity was recorded in the cingulate cortex and the limbic thalamus in Dutch-belted rabbits (Oryctolagus cuniculus) exposed to cocaine (8 mg/kg/day i.v.) or saline in utero during acquisition and reversal learning of a discriminative avoidance response. Anterior cingulate cortical excitatory training-induced activity (TIA) was attenuated in cocaine-exposed female rabbits during acquisition and reversal learning, but only during reversal learning in male rabbits. Posterior cingulate cortical excitatory TIA was lessened in cocaine-exposed rabbits during acquisition, whereas discrimination between the positive and negative cues was enhanced. Neuronal firing was attenuated in the anterior ventral thalamus in cocaine-exposed rabbits during acquisition and reversal learning. Behavioral learning was normal in cocaine-exposed rabbits. Other data suggest that rabbits exposed to cocaine in utero exhibit a learning deficit when trained with nonsalient cues.

Animals↗
PubMedDate not supplied

Involvement of the rat anterior cingulate cortex in control of instrumental responses guided by reward expectancy.

The anterior cingulate cortex (ACC) plays a critical role in stimulus-reinforcement learning and reward-guided selection of actions. Here we conducted a series of experiments to further elucidate the role of the ACC in instrumental behavior involving effort-based decision-making and instrumental learning guided by reward-predictive stimuli. In Experiment 1, rats were trained on a cost-benefit T-maze task in which they could either choose to climb a barrier to obtain a high reward (four pellets) in one arm or a low reward (two pellets) in the other with no barrier present. In line with previous studies, our data reveal that rats with quinolinic acid lesions of the ACC selected the response involving less work and smaller reward. Experiment 2 demonstrates that breaking points of instrumental performance under a progressive ratio schedule were similar in sham-lesioned and ACC-lesioned rats. Thus, lesions of the ACC did not interfere with the effort a rat is willing to expend to obtain a specific reward in this test. In a subsequent task, we examined effort-based decision-making in a lever-press task where rats had the choice between pressing a lever to receive preferred food pellets under a progressive ratio schedule, or free feeding on a less preferred food, i.e. lab chow. Results show that sham- and ACC-lesioned animals had similar breaking points and ingested comparable amounts of less-preferred food. Together, the results of Experiment 1 and 2 suggest that the ACC plays a role in evaluating how much effort to expend for reward; however, the ACC is not necessary in all situations requiring an assessment of costs and benefits. In Experiment 3 we investigated learning and reversal learning of instrumental responses guided by reward predictive stimuli. A reaction time (RT) task demanding conditioned lever release was used in which the upcoming reward magnitude (five vs. one food pellet) was signalled in advance by discriminative visual stimuli. Results revealed that rats with ACC lesions were able to discriminate reward magnitude-predictive stimuli and to adapt instrumental behavior to reversed stimulus-reward magnitude contingencies. Thus, in a simple discrimination task as used here, the ACC appears not to be required to discriminate reward magnitude-predictive stimuli and to use the learned significance of the stimuli to guide instrumental behavior.

Animals↗
PubMed2004

Incidental information acquired by the amygdala during acquisition of a stimulus-response habit task.

In the present paper we tested the hypothesis that the amygdala incidentally acquires information during the acquisition of a task sensitive to damage to the dorso-lateral striatum. Two groups of rats were trained on a stimulus-response (S-R) habit task on the eight-arm radial maze. Prior to initial acquisition, one group received NMDA lesions of the amygdala and the other received sham surgeries. After reaching a strict learning criterion, both groups underwent reversal training in either the same or different context from original training. Consistent with our previous work, the sham group showed enhanced reversal learning in a context different from original training. The rats with amygdala damage showed a deficit in reversal learning in both contexts, although the deficit was more apparent in the different context. Both groups of rats that underwent reversal training in the context different from original training showed a normal competition effect for this task (chance performance) when they were returned to the initial training context. This data supports the idea that the second S-R association, acquired during reversal training, and the context-specific inhibitory association, acquired during original training, were unaffected by the amygdala damage. Taken together, this pattern of data suggests that the amygdala incidentally acquired information during the acquisition of the S-R habit task. The nature of the association acquired in this learning paradigm, and the implications of this finding for theories dealing with the organization and functions of mammalian learning and memory are discussed.

Amygdala↗
PubMed2000

Probabilistic learning and reversal deficits in patients with Parkinson's disease or frontal or temporal lobe lesions: possible adverse effects of dopaminergic medication.

Three groups of patients with Parkinson's disease (PD) - mild, unmedicated (UPD), mild, medicated (MPD) and severe, medicated (SPD) - and patients with lesions of the frontal lobe (FLL) or temporal lobe (TLL) were compared with matched controls on the learning and reversal of probabilistic and two-pair concurrent colour discriminations. Both of the cortical lesion groups showed reversal deficits, with no increase in perseverative responding. The UPD group, although impaired on a spatial recognition task, showed intact discrimination learning and reversal; the MPD and SPD patients showed non-perseverative reversal impairments on both reversal tasks. Two hypotheses - based on disease severity and possible deleterious effects of medication - are offered to explain the reversal impairments of the PD patients and the results are discussed in terms of the role of dopamine in reward-based learning.

Adult↗
PubMedDate not supplied

The effect of beta-(Tyr9)melanotropin-(9-18) on active avoidance behavior, electroconvulsive shock-induced amnesia and T-discrimination learning of rats.

The effect of beta-(Tyr9)melanotropin-(9-18) was investigated on active avoidance behavior, electroconvulsive shock (ECS)-induced amnesia and T-discrimination learning in rats. The decapeptide inhibited the extinction of active avoidance behavior. It was also able to block ECS-induced amnesia if the treatment was performed immediately, or 4 hr or 20 hr after the ECS. In the T-discrimination paradigm the peptide facilitated spatial discrimination learning and reversal learning. These results suggest that beta-(Tyr9)melanotropin-(9-18) can influence learning and memory processes in different behavioral tests.

Amnesia↗
PubMed1984

Comparative studies with somatostatin and cysteamine in different behavioral tests on rats.

In the present study the effects of somatostatin and cysteamine (a selective decreaser of the somatostatin level in the body) were compared in different behavioral tests on rats. Somatostatin inhibited the extinction of active avoidance behavior 8 hr and 24 hr after intracerebroventricular (ICV) treatment, while cysteamine facilitated it 4 hr and 8 hr after subcutaneous (SC) treatment. Somatostatin did not significantly influence the cysteamine-induced facilitation of the extinction. Somatostatin did not have a significant effect on T-maze spatial discrimination learning and reverse learning, whereas cysteamine markedly attenuated the performance 4 hr (1st day) after treatment. Somatostatin in a dose of 4 micrograms (ICV) increased the locomotor activity 10 min after treatment, while cysteamine markedly decreased all parameters of the open-field test. These effects of the drug had disappeared 24 hr after treatment. If different doses of somatostatin (4 micrograms or 10 micrograms ICV) were administered to cysteamine-pretreated rats, the peptide did not modify the drug-induced changes in the open-field test. The data suggest that the brain somatostatin might have a physiological role in the organization of certain types of behavior.

Animals↗
PubMed2001

Episodic-like memory in animals: psychological criteria, neural mechanisms and the value of episodic-like tasks to investigate animal models of neurodegenerative disease.

The question of whether any non-human species displays episodic memory is controversial. Associative accounts of animal learning recognize that behaviour can change in response to single events but this does not imply that animals need or are later able to recall representations of unique events at a different time and place. The lack of language is also relevant, being the usual medium for communicating about the world, but whether it is critical for the capacity to represent and recall events is a separate matter. One reason for suspecting that certain animals possess an episodic-like memory system is that a variety of learning and memory tasks have been developed that, even though they do not meet the strict criteria required for episodic memory, have an 'episodic-like' character. These include certain one-trial learning tasks, scene-specific discrimination learning, multiple reversal learning, delayed matching and non-matching tasks and, most recently, tasks demanding recollection of 'what, where and when' an event happened. Another reason is that the neuronal architecture of brain areas thought to be involved in episodic memory (including the hippocampal formation) are substantially similar in mammals and, arguably, all vertebrates. Third, our developing understanding of activity-dependent synaptic plasticity (which is a candidate neuronal mechanism for encoding memory traces) suggests that its expression reflects certain physiological characteristics that are ideal components of a neuronal episodic memory system. These include the apparently digital character of synaptic change at individual terminals and the variable persistence of potentiation accounted for by the synaptic tag hypothesis. A further value of studying episodic-like memory in animals is the opportunity it affords to model certain kinds of neurodegenerative disease that, in humans, affect episodic memory. An example is recent work on a transgenic mouse that over-expresses a mutation of human amyloid precursor protein (APP) that occurs in familial Alzheimer's disease, under the control of platelet derived (PD) growth factor promoter (the PDAPP mouse). A striking age- and amyloid plaque-related deficit is seen using a task in which the mice have to keep changing their memory representation of the world rather than learn a single fact.

Alzheimer Disease↗
PubMed1975

Origins of anthropoid intelligence.

The development of the extrastriate visual system relative to the striate system was estimated indirectly by measuring the volumes of the lateral posteriorpulvinar complex and lateral geniculate nucleus in six varieties of mammals selected on the basis of their propinquity with Anthropoidea [oppossums, hedgehogs, rats, squirrels, tree shrews and bushbabies]. The same animals were tested on two related behavioral tasks [spatial and visual reversal learning] whose successful achievement requires a simple sort of abstraction. The results show that the ability to learn visual reversal, but not spatial reversal, corresponds closely to the relative degree of development of the extrastriate system. Since the variation in both these behavioral and morphological characteristics also parallels the phylogenetic dimension, the recency of common ancestry to anthropoids, the evolutionary origin of the anthropoid capacity for visual abstraction is suggested.

Animals↗
PubMed1975

Comparison of the septal lesion effects on visual and spatial discriminations in rats.

Postoperative performance in acquisition and reversal learning of septal rats was investigated and compared with control rats in three experiments. Experiment I involved a simultaneous black-white discrimination task. The number of errors in normal and septal rats was similar in acquisition and reversal learning. Both septal and normal rats manifested directional response sets. Experiment II examined a position habit discrimination. Acquisition was similar in septal and normal rats, while reversal learning was impaired in septal rats. Experiment III, which investigated a position habit discrimination with available irrelevant visual stimuli indicated that both acquisition and reversal learning were impaired in operated animals. Results suggested that septal rats utilize response produced cues to control their behavior, but the enhanced orienting response to the visual stimuli interferes with the proprioceptive stimuli.

Animals↗
PubMed2005

The involvement of the orbitofrontal cortex in learning under changing task contingencies.

Previous investigations examining the rat prefrontal cortex subregions in attentional-set shifting have commonly employed two-choice discriminations. To better understand how varying levels of difficulty influence the contribution of the prefrontal cortex to learning, the present studies examined the effects of orbitofrontal cortex inactivation in a two- or four-choice odor reversal learning test. Long-Evans rats were trained to dig in cups that contained distinct odors. In the two-choice odor discrimination, one odor cup was always associated with a cereal reinforcement in acquisition while the opposite odor cup was associated with a cereal reinforcement in reversal learning. In the four-choice odor discrimination, an additional two cups containing distinct odors were used that were never associated with reinforcement in acquisition or reversal learning. Bilateral infusions of the GABA-A agonist, muscimol (0.5 microg) into the orbitofrontal cortex did not impair acquisition of either the two- or four-choice discrimination task. However, muscimol infusions into the orbitofrontal cortex impaired two- and four-choice reversal learning. In the two-choice odor reversal, muscimol treatment selectively increased perseverative errors. In the four-choice odor reversal, muscimol treatment increased perseverative, regressive, as well as irrelevant errors. These findings suggest that the orbital prefrontal cortex not only enables task switching by supporting the initial inhibition of a previously relevant choice pattern, but under increasing task demands also enables the reliable execution of a new choice pattern and reduction of interference to irrelevant stimuli.

Animals↗
PubMed2005

The contribution of NMDA receptors in the dorsolateral striatum to egocentric response learning.

The present study examined the effects of the N-methyl-D-aspartate (NMDA) competitive antagonist, 2-amino-5-phosphonopentanoic acid (AP-5), injected into the dorsolateral striatum on the acquisition and reversal learning of a response discrimination. Male Long-Evans rats were tested across 2 consecutive days in a modified cross-maze. An infusion of either saline or AP-5 (5 or 25 nM) occurred 5 min prior to testing. In acquisition rats learned to turn left or right. In reversal learning rats learned to turn in the opposite direction. An AP-5 infusion at 25 nmol, but not 5 nmol, impaired response acquisition. Neither AP-5 dose impaired response reversal learning. The results suggest that NMDA receptors in the dorsolateral striatum are critical for the initial learning of an egocentric response discrimination.

Analysis of Variance↗
PubMed1984

The hippocampus, context, and information processing.

Two experiments are described in which groups of rats with bilateral hippocampal lesions, cortical lesions, and operated controls are compared on tests of discrimination learning, retention, and reversal learning. Experiment 1 examined the effects of varying prior training and context on new learning. Experiment 2 used a transfer paradigm to compare extent of original learning by hippocampal and control groups in a discrimination task involving multiple discriminanada . The major findings were that rats with hippocampal damage were less efficient at processing information and were more constrained by contextual influences than control rats.

Animals↗
PubMed1986

Discrimination learning and reversal following electrolytic lesions of the median raphe nucleus.

The current study examined the effects of electrolytic median raphe lesions on the performance of several T-maze discrimination tasks. Raphe lesions were found to impair the reversal, but not the acquisition, of a learned position habit, but to be without effect on either the acquisition or reversal of simultaneous brightness discrimination task. Rats with raphe damage were severely impaired in the acquisition of either a successive brightness discrimination task or of a delayed spatial alternation task. These results are similar to those which have been reported after limbic damage, and support the view that the paramedian midbrain tegmentum may play an important role in the functioning of limbic structures.

Animals↗
PubMed2006

The impact of tryptophan depletion and 5-HTTLPR genotype on passive avoidance and response reversal instrumental learning tasks.

Transient reductions in serotonin levels during tryptophan depletion (TD) are thought to impair reward processing in healthy volunteers, while another facet of the serotonergic system, the serotonin transporter (5-HTTLPR) short allele polymorphism, is implicated in augmented processing of aversive stimuli. We examined the impact and interactions of TD and the serotonin promoter polymorphism genotype on reward and punishment via two forms of instrumental learning: passive avoidance and response reversal. In this study, healthy volunteers (n=35) underwent rapid TD or control procedures and genotyping (n=26) of the 5-HTTLPR for long and short allele variants. In the passive avoidance task, tryptophan-depleted volunteers failed to respond sufficiently to rewarded stimuli compared to the control group. Additionally, long allele homozygous individuals (n=11) were slower to learn to avoid punished stimuli compared to short allele carriers (n=15). TD alone did not produce measurable deficits in probabilistic response reversal errors. However, a significant drug group by genotype interaction was found indicating that in comparison to short allele carriers, tryptophan-depleted individuals homozygous for the long allele failed to appropriately use punishment information to guide responding. These findings extend prior reports of impaired reward processing in TD to include instrumental learning. Furthermore, they demonstrate behavioral differences in responses to punishing stimuli between long allele homozygotes and short allele carriers when serotonin levels are acutely reduced.

Adult↗
PubMed2004

Central blockade of muscarinic cholinergic receptors disrupts affective and attentional set-shifting.

Impairments in multiple aspects of attentional and executive function follow damage to cholinergic neurons in the central nervous system. Affective and attentional set-shifting represent two aspects of executive function controlled by different sectors of the prefrontal cortex. The involvement of cholinergic neural mechanisms in these aspects of executive function has not been specified. To determine whether central muscarinic cholinergic receptors were involved in affective and/or attentional set-shifting, we tested rats on a series of discrimination learning problems, which included affective (reversal learning) and attentional set (extradimensional shift)-shifting components, under the systemic influence of scopolamine, a muscarinic antagonist. Scopolamine impaired both reversal learning and extradimensional shifting, but was without effect on learning new discrimination problems that did not require an affective or attentional shift. Systemic administration of methylscopolamine, which does not cross the blood-brain barrier, did not impair affective or attentional set-shifting, indicating that the scopolamine effects were centrally mediated. These data implicate muscarinic receptors in the central nervous system in the control of executive function. Taken together with other recent data, they may also suggest an important role for cholinergic receptors outside of the neocortex in regulating these aspects of attention and executive function.

Animals↗