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Results for “Avoidance Learning”

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At least 973 records · Page 54Linked to original sources

PubMed2000

Phosphorylated cAMP response element-binding protein as a molecular marker of memory processing in rat hippocampus: effect of novelty.

From mollusks to mammals the activation of cAMP response element-binding protein (CREB) appears to be an important step in the formation of long-term memory (LTM). Here we show that a 5 min exposure to a novel environment (open field) 1 hr after acquisition of a one-trial inhibitory avoidance training hinders both the formation of LTM for the avoidance task and the increase in the phosphorylation state of hippocampal Ser 133 CREB [phosphorylated CREB (pCREB)] associated with the avoidance training. To determine whether this LTM deficit is attributable to the reduced pCREB level, rats were bilaterally cannulated to deliver Sp-adenosine 3', 5'-cyclic monophosphothioate (Sp-cAMPS), an activator of PKA. Infusion of Sp-Adenosine 3',5'-cyclic monophosphothioate Sp-cAMPS to CA1 region increased hippocampal pCREB levels and restored normal LTM of avoidance learning in rats exposed to novelty. Moreover, a 5 min exposure to the open field 10 min before the avoidance training interferes with the amnesic effect of a second 5 min exposure to the open field 1 hr after avoidance training and restores the hippocampal levels of pCREB. In contrast, the avoidance training-associated activation of extracellular signal-regulated kinases (p42 and p44 mitogen-activated protein kinases) in the hippocampus is not altered by novelty. Together, these findings suggest that novelty regulates LTM formation by modulating the phosphorylation state of CREB in the hippocampus.

Amnesia, Retrograde↗

PubMed1979

Ontogeny of active avoidance in the rat: learning and memory.

Ontogenetic development of active avoidance learning, extinction and retention was studied in rats. The learning of a 1-way active avoidance was most rapid between Weeks 4 and 6, although some slight gender-related differences were evident. No such unambiguous development was detected in forced extinction. The 24-hr retention of avoidance peaked at the age of 4 weeks whereas 1-month retention was best in animals trained at the age of 8 weeks. The retrieval of memory trace also had best values at these ages. Retention of forced extinction was found to peak in 6-week animals. The existence of developmental "critical periods" must be considered cautiously as various functions have different time courses depending upon the chosen parameters in assessment.

Animals↗

PubMed2005

Explaining Dioscorides' "double difference": why are some mushrooms poisonous, and do they signal their unprofitability?

The adaptive significance of toxins in mushrooms has received very little consideration, although it is clear that poisons have appeared (and/or disappeared) many times in mushrooms' evolutionary history. One possibility is that poisons have evolved in some mushroom species to deter their consumption by would-be fungivores before spore dispersal. If this is so, then one might expect poisonous mushrooms to signal their unprofitability in some way. In this study, we have conducted the first formal analysis of the ecological and morphological traits associated with edible and poisonous mushrooms in North America and Europe. Poisonous mushrooms do not tend to be more colorful or aggregated than edible mushrooms, but they are more likely to exhibit distinctive odors even when phylogenetic relationships are accounted for. This raises the intriguing possibility that some poisonous species of mushrooms have evolved warning odors (and perhaps tastes) to enhance avoidance learning by fungivores.

Agaricales↗

PubMed2004

Role of hippocampal CaMKII in serotonin 5-HT(1A) receptor-mediated learning deficit in rats.

The serotonin 5-HT(1A) receptor agonist, 8-OH-DPAT (8-hydroxy-2-di-n-propylamino-tetralin), impairs retention performance in a passive avoidance learning task in rats. In the hippocampus of rats trained on this procedure and killed 1 h after the acquisition trial, an increase in the membrane levels of both Ca2+/calmodulin-dependent protein kinase II (CaMKII) and phosphorylated CaMKII, as well as in total and Ca2+-independent enzyme activity in tissue lysates was found. These effects were learning-specific as no changes in CaMKII levels or activity were found in rats receiving a footshock identical to the trained rats. The effect of training on CaMKII was prevented by a low 8-OH-DPAT dose. The 5-HT(1A) agonist also reduced protein kinase A (PKA) activity and increased the membrane levels of phosphatase 1 (PP1) and PP1 enzyme activity in the hippocampus. All of the changes induced by 8-OH-DPAT were reversed by the selective 5-HT(1A) antagonist WAY-100635, indicating receptor-specific effects. We suggest that 5-HT(1A) receptor-mediated disruption of retention performance is a consequence of the reduced PKA activity and the ensuing enhancement in PP1 activity, possibly through decreased phosphorylation/activation of endogenous PP1 inhibitors, that cause a reduced activity of phosphorylated CaMKII, a key enzyme in early stages of memory formation. This study provides an in vivo molecular basis for the cognitive deficits induced by stimulation of hippocampal 5-HT(1A) receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMedDate not supplied

Effects of scopolamine on spontaneous alternation and shuttle avoidance in rats exposed to alcohol in utero.

The behavioral effects of the anticholinergic scopolamine were examined in rats exposed to alcohol prenatally. Pregnant Long-Evans rats received isocaloric liquid diets containing either 35% or 0% ethanol-derived calories on Days 6-20 of gestation. A pair-feeding procedure was used, and a lab chow control group was also included. In Experiment 1, adult offspring were tested on a spontaneous alternation task following 1 mg/kg scopolamine or saline. Independent of prenatal treatment, scopolamine caused an increase in the number of trials to alternate. In Experiment 2, offspring were tested on a two-way shuttle avoidance learning task following a 1 mg/kg injection of scopolamine or methylscopolamine. Alcohol-exposed animals injected with methylscopolamine made fewer avoidances than controls on the second day of testing while treatment with scopolamine enhanced avoidance performance to control levels. These data suggest that prenatal exposure to alcohol does not interfere with scopolamine-induced changes in the behavior of adult rats.

Animals↗

PubMedDate not supplied

[Role of amygdalar nuclei in alimentary and defensive conditioned reflexes in the rat].

Ninety experimentally naive male white rats were divided into groups with lateral (AL), medial (AME) and central (ACE) amygdalar nuclei lesions, sham-operated and normal controls. The AL-rats showed a facilitation of instrumental conditioned alimentary reflexes (CAR) acquisition and retardation of initial avoidance learning in a shuttle box; the AME-rats exhibited a slower acquisition of the CAR and a facilitation of avoidance conditioning; in the ACE-rats acquisition of the CAR was the same as in controls but avoidance performance was significantly impaired as compared with all experimental groups. It has been assumed that functional non-identity of the amygdalar nuclei in alimentary and avoidance behaviour is caused by dominant drive and by presence of "specific" amygdalar neurones participating in functional systems of the studied behavioural reactions.

Amygdala↗

PubMed1988

Facilitative effects of cross-modality training on recovery of a conditioned avoidance response following striate cortex ablations in the rat.

Two experiments with visual decorticate rats examined the effects of cross-modality transfer on the recovery of a preoperatively learned avoidance task using high intensity light cues. In both experiments, brief postoperative cross-modality training with high intensity noise cues produced significantly better recovery of the visual avoidance response than either reversed intensity noise training or retraining with the original task. Training with a reversed intensity visual cue produced relearning deficits. In the second experiment, control conditions eliminated re-exposure to the test environment, the shock-response relationship, and compound conditioning as possible explanations for these findings. These results indicated that rats are capable of cross-modality transfer after posterior cortical lesions and that this transfer effect can facilitate recovery of behavioral function. The clinical implications of these findings are also discussed.

Animals↗

PubMed1975

Neonatal locomotor and long-term behavioral effects of d-amphetamine in the rat.

Locomotor activity in the neonatal rat was found to increase from birth until the beginning of the 3rd week of life, at which time it peaked and then subsequently declined. Subcutaneous injections of both .25 and 2.0 mg/kg of d-amphetamine increased activity in rats 1-21 days of age, with the maximum effect observed at 4 days of age. No tolerance to d-amphetamine was observed after 6 daily injections beginning at 1, 7, or 14 days of age. The decline in the excitatory effects of the drug thus reflected maturational changes in response to it. Consistent with other observations from this laboratory, no persisting effects of the neonatal drug treatment was observed on adult 2-way avoidance learning.

Age Factors↗

PubMed1981

Perinatal methylmercury intoxication: behavioral effects in rats.

Sprague-Dawley rats were subjected to perinatal (4th gestational day until Postnatal Day 21) methylmercury intoxication to determine the long-term behavioral effect of the mercury poisoning. Experimental and control animals were evaluated at 110-140 days of age. Compared to controls, the methylmercury animals demonstrated significant behavioral deficits characterized by hypoactivity and by reduced appetitive, escape, and avoidance learning.

Animals↗

PubMed1976

Early malnutrition and postnatal changes in brain and behavior in the mouse.

The effects of early undernutrition were studied by rearing mice in small, intermediate or large litters (respectively 4, 8 or 16 pups). Measures of reflexes and electrocorticographic activity applied from birth to weaning indicated that malnutrition resulted in a clear ontogenetic retardation which was followed by permanent body and brain stunting. The mice from the large litters were characterized by increased exploratory activity and by lower avoidance learning ability as measured 45 days after nutritional rehabilitation.

Animals↗

PubMed1975

Graded acquisition of an instrumental avoidance response by the spinal rat.

Eight pairs of spinal rats were exposed to an instrumental conditioning paradigm in which one animal served as the experimental and the other as a yoked control animal. An electrode, inserted into the experimental animal's foot, contacted an aqueous solution delivering shock to both animals. Leg flexion terminated the shock. Following two consecutive min without shock, the experimental animal's solution was raised an additional millimeter and training was re-instated. This procedure was repeated 4 times, or until the experimental animal failed to reach the 2 min criterion. In Run 1, one leg was trained; during Run 2, the contralateral leg was used. In addition, the animal which served as the experimental in Run 1 served as the yoked control in Run 2 and vice versa. The results indicate that the spinal rat is capable of acquiring successively higher criteria in an instrumental conditioning routine. In conjunction with previous results, these findings suggest that instrumental avoidance learning can occur in the spinal cord.

Animals↗

PubMed2006

Different molecular cascades in different sites of the brain control memory consolidation.

To understand cognition, it is important to understand how a learned response becomes a long-lasting memory. This process of memory consolidation has been modeled extensively using one-trial avoidance learning, in which animals (or humans) establish a conditioned response by learning to avoid danger in just one trial. This relies on molecular events in the CA1 region of the hippocampus that resemble those involved in CA1 long-term potentiation (LTP), and it also requires equivalent events to occur with different timings in the basolateral amygdala and the entorhinal, parietal and cingulate cortex. Many of these steps are modulated by monoaminergic pathways related to the perception of and reaction to emotion, which at least partly explains why strong and resistant consolidation is typical of emotion-laden memories. Thus memory consolidation involves a complex network of brain systems and serial and parallel molecular events, even for a task as deceptively simple as one-trial avoidance. We propose that these molecular events might also be involved in many other memory types in animals and humans.

Animals↗

PubMed1998

CS modality transfer of two-way avoidance in rats with central and basolateral amygdala lesions.

Post-lesion acquisition of two-way avoidance and subsequent transfer to two warning signals (conditioned stimulus, CS) of different modality were investigated in 60 rats. In Experiment I the animals were originally trained with less salient (darkness) CS, then transferred to more salient compound (darkness and white noise), and finally to white noise CS. The opposite arrangement of the conditioned stimuli (CSi) during the subsequent stages was employed in Experiment II. In control animals, avoidance acquisition was faster and the intertrial responding (ITR) rate lower with the auditory than with the visual CS. Lesioned rats learned avoidance responses more slowly, independently of CS modality. The transfer to other CSi revealed dramatic between-group difference in the level and consistency of avoidance response, shuttle-box latencies and ITR rate. In control animals, transfer to more salient CSi enhanced avoidance performance, whereas change to less salient CS decreased it. Rather small changes in shuttle-box performance and consistency of avoidance response due to CS modality were seen in rats with the basolateral lesions. In contrast, central nucleus injury caused a strong deterioration in the avoidance transfer, especially when the visual CS followed the acoustic one. The results indicate differential involvement of the basolateral and central amygdala nuclei in stimulus-processing mechanisms of instrumental defensive behavior.

Acoustic Stimulation↗

PubMed2004

The effects of the duration of adaptation to laboratory conditions on the formation of a passive avoidance reflex in rats.

The level of adaptation of rats to their new living conditions was studied during formation of a passive avoidance habit using a single combination. A short acclimation period (3 days) had positive influences on the ability of rats to retain a memory trace. There was a negative correlation between step-through latency and measures of anxiety behavior in the elevated cross maze. A change in the adaptation period to nine days decreased the state of anxiety and the level of performance of the conditioned response. There were no correlations between these measures. The modulating role of the level of adaptation to living conditions, associated with different levels of anxiety, in a passive one-session avoidance learning model was assessed.

Adaptation, Psychological↗

PubMed1968

Reinforcement magnitude as a determinant of performance decrement after electroconvulsive shock.

The intensity of a foot shock may be a determinant of the rate at which an avoidance response becomes resistant to disruption by electroconvulsive shock. Mice were trained, one trial a day, in a passive avoidance learning task, with one of three foot-shock intensities. Electroconvulsive shock was administered at various intervals after each trial. At all foot-shock intensities, electroconvulsive shock given 10 seconds after each training trial was eflective in disrupting learning. Where electroconvulsive shock was given at longer intervals after each trial, those animals learning at low intensities of foot shock showed greater impairment of performance than those learning at high intensities.

Analysis of Variance↗

PubMed1979

Central mediation of hormonal influences on instrumental avoidance conditioning.

Two behaviorally active hormones of the pituitary-adrenal system are adrenocorticotropic hormones (ACTH) and corticosterone, and their behavioral effects are facilitation and inhibition of performance of previously learned avoidance responses, respectively. Their uptake, distribution and effects on central nervous system are reviewed. Hypothalamic neurotransmitter control of corticotropin releasing hormone (CRH) is described together with hypothalamic and extra-hypothalamic (hippocampal) regulation of pituitary-adrenal activity. Extra-hypothalamic mediation of the behavioral effects of ACTH is evaluated. Recent isotopic mappings of the efferents of the hippocampal formation have identified pathways from hippocampal subiculum to hypothalamus and posterior lateral and anterior thalamic nuclei. The evidence reviewed suggests a complex circuit involving hippocampal subiculum, thalamus and hypothalamus may be involved both in regulating pituitary-adrenal responses to stress and in mediating the effects of ACTH on avoidance behavior.

Adrenocorticotropic Hormone↗

PubMed1984

Behavioral effects of piracetam in rats with isolation syndrome.

Piracetam in doses of 300 and 600 mg/kg i.p. administered for 5 days in Wistar rats with isolation syndrome produced a transient inhibition of mouse-killing behavior. Its anti-aggressive effect was most pronounced on days 2 and 3 of drug administration. On day 5 all aggressive rats again exhibited mouse-killing behavior. Piracetam in both doses was less effective in avoidance learning of aggressive rats. These results suggest that piracetam has a slight effect on the aggressive behavior of rats with isolation syndrome. No relationship exists between the antiaggressive and the learning-facilitating effects of piracetam.

Aggression↗

PubMed1993

Altered synaptic plasticity and memory formation in nitric oxide synthase inhibitor-treated rats.

Nitric oxide (NO) is a messenger molecule that is produced in the brain from the metabolism of L-arginine to L-citrulline. Growing evidence suggests a physiological role for NO in long-term potentiation (LTP). Since LTP is a form of synaptic plasticity thought to be involved in learning and memory, we have tested whether inhibition of endogenous NO production affects memory capacities of rats. We found that the NO synthase [L-arginine, NADPH:oxygen oxidoreductase (nitric oxide-forming), EC 1.14.13.39] inhibitor N omega-nitro-L-arginine, at doses blocking LTP in hippocampal slices, impairs spatial learning in a radial arm maze and olfactory memory in a social recognition test. In contrast, N omega-nitro-L-arginine left shock-avoidance learning unaffected. These results indicate that NO is involved in some but not all forms of memory and further support the existence of a causal link between LTP and spatial learning.

Amino Acid Oxidoreductases↗