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Results for “Avoidance Learning”

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PubMed2006

Parallel incentive processing: an integrated view of amygdala function.

The amygdala is a heterogeneous structure that has been implicated in a wide variety of functions, most notably in fear conditioning. From this research, an influential serial model of amygdala processes has emerged in which aversive learning is mediated by the amygdala basolateral nucleus whereas performance, in this case of various defensive reflexes, is mediated by the central nucleus. By contrast, recent evidence from appetitive conditioning studies suggests that the basolateral and central nuclei operate in parallel to mediate distinct incentive processes: the basolateral nucleus encodes emotional events with reference to their particular sensory-specific features, whereas the central nucleus encodes their more general motivational or affective significance. Given that there is little if any direct behavioral evidence for the serial model, we suggest that more attention should be given to the claims of the parallel view.

Amygdala↗

PubMed1997

Effects of piracetam on membrane fluidity in the aged mouse, rat, and human brain.

In vitro preincubation of brain membranes of aged mice with piracetam (0.1-1.0 mmol/L) enhanced membrane fluidity, as indicated by decreased anisotropy of the membrane-bound fluorescence probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Piracetam had similar in vitro effects on brain membranes of aged rats and humans, but it did not alter brain membrane fluidity in young mice. Chronic treatment of young and aged rats with piracetam (300 mg/kg once daily) significantly increased membrane fluidity in some brain regions of the aged animals, but had no measurable effect on membrane fluidity in the young rats. The same treatment significantly improved active avoidance learning in the aged rats only. It is suggested that some of the pharmacological properties of piracetam can be explained by its effects on membrane fluidity.

Aged↗

PubMed2002

Psychophysiological and subjective indicators of aversive pavlovian conditioning in generalized social phobia.

Aversive conditioning has been proposed as an important etiologic mechanism in social phobia; however, empirical evidence is scarce and has not relied on a detailed analysis of the acquisition and extinction of the conditioned emotional response. Fourteen men sustaining generalized social phobia and 19 healthy control subjects participated in differential aversive conditioning with two neutral faces as conditioned stimuli and an aversive odor as unconditioned stimulus. Subjective and peripheral physiological responses were obtained. Both groups were successfully conditioned as reflected by differential subjective (valence, arousal, subjective unconditioned stimulus expectancy) and peripheral physiological responses (skin conductance, startle response). There was no evidence for an enhanced conditionability in the social phobics; however, they showed an enhanced unconditioned stimulus expectancy, especially for the nonreinforced conditioned stimuli during acquisition, and a delayed extinction of the conditioned skin conductance response as well as a certain dissociation between subjective and physiological responses.The enhanced unconditioned stimulus expectancy during acquisition and the overall elevated subjective arousal suggest that, under threat, subjects with generalized social phobia may be more prone to associate neutral social cues and an aversive outcome. Furthermore, delayed extinction of the conditioned response seems to contribute to the etiology and maintenance of generalized social phobia.

Adult↗

PubMed1999

A behavioral and neuroanatomical assessment of an inbred substrain of 129 mice with behavioral comparisons to C57BL/6J mice.

The inbred 129 substrains have been characterized as poor learners that display hypoplasia of the corpus callosum. However, they are used extensively as a source of embryonic stem (ES) cells for creating mice carrying altered copies of a targeted gene ('knockout mice'). The present research investigated callosal agenesis and behavior in the 129/SvEvTac substrain and compared their behavior to that of C57BL/6J mice. In addition, the degree to which callosal agenesis affected behavior was assessed. Nearly 80% of 129/SvEvTac mice in the current sample exhibited callosal hypoplasia, although this was not subsequently found to be associated with any measure of cognition. They learned the Morris maze and a non-spatial pattern discrimination task, though at a level inferior to C57BL/6J mice. They were unable to learn shuttlebox avoidance or the Lashley III maze. The only measure on which they performed better than C57BL/6J mice was a simple water escape task. Thus, 129/SvEvTac mice, in addition to displaying aberrant neuroanatomy, perform poorly on many behavioral tasks, resulting in potential interpretational difficulties.

Agenesis of Corpus Callosum↗

PubMed2003

Effects of T-82, a novel acetylcholinesterase inhibitor, on impaired learning and memory in passive avoidance task in rats.

Effects of 2-[2-(1-benzylpiperidin-4-yl)ethyl]-2,3-dihydro-9-methoxy-1H-pyrrolo[3,4-b]quinolin-1-one hemifumarate (T-82), a new quinoline derivative, on drug- and basal forebrain lesion-induced amnesia models were examined in rats. Scopolamine (0.5 mg/kg, i.p.) and cycloheximide (1.5 mg/kg, s.c.) shortened the step-through latency in the passive avoidance task. T-82 significantly ameliorated amnesia induced by scopolamine or cycloheximide at the dose of 0.03, 0.1 and 0.3 mg/kg, p.o., and 0.3 and 1.0 mg/kg, p.o., respectively. Basal forebrain lesions with ibotenic acid shortened the step-through latency in passive avoidance task. An acute (0.1 and 0.3 mg/kg, p.o.) or subacute (0.03-0.3 mg/kg, p.o., for 7 days) treatment of T-82 significantly reversed the shortened latency. These results suggest that T-82 may ameliorate the impairment of memory induced by acetylcholinergic dysfunction.

Amnesia↗

PubMed2003

Prior exposure to a single stress session facilitates subsequent contextual fear conditioning in rats. Evidence for a role of corticosterone.

Previous studies showed that exposure of rats to chronic restraint stress for 21 days enhances subsequent contextual fear conditioning. Since recent evidence suggest that this effect is not dependent on stress-induced neurodegenerative processes, but to elevated training-elicited glucocorticoid release in chronically stressed animals, we aimed to explore here whether a single exposure to restraint stress, which is not expected to induce neuronal damage, would also affect contextual fear conditioning. We also questioned whether post-training corticosterone levels might be associated with any potential effect of stress on fear conditioning. Adult male Wistar rats were exposed to acute restraint stress for 2 h and, two days later, trained in the contextual fear conditioning task, under training conditions involving either moderate (0.4 mA shock) or high (1 mA shock) stress levels. The results showed that acute stress enhanced conditioned freezing at both training conditions, although data from the 1 mA shock intensity experiment only approached significance. Stressed animals were shown to display higher post-training corticosterone levels. Furthermore, the facilitating effect of prior stress was not evident when animals were trained in the hippocampal-independent auditory-cued conditioning task. Therefore, these findings support the idea that stress experiences preceding exposure to new types of stressors facilitate the development of contextual fear conditioning. They also indicate that not only repeated, but also a single exposure to aversive stimulation is sufficient to facilitate context-dependent fear conditioning, and suggest that increased glucocorticoid release at training might be implicated in the mechanisms mediating the memory facilitating effects induced by prior stress experiences.

Acoustic Stimulation↗

PubMedDate not supplied

Perceptual effects of a flattened fundamental frequency at the sentence level under different listening conditions.

UNLABELLED: The purpose of this series of experiments was to examine the effect of a flattened fundamental frequency (F0) contour on the intelligibility of sentence length material in different listening environments. Eight speakers of different genders and ages produced sentences from the Speech Perception in Noise Test (SPIN). Each utterance was subjected to a resynthesis technique that allowed flattening of the fundamental frequency while maintaining the timing and spectral characteristics of the utterances. To avoid learning effects two groups of listeners were chosen to complete word transcription and interval scaling tasks of the unmodified and flattened F0 utterances under different listening conditions (competing white noise or multi-speaker babble) to obtain measures of speech intelligibility. Results were that a flattened fundamental frequency contour negatively influences speech intelligibility regardless of the nature of the competing background noise. LEARNING OUTCOMES: (1) To appreciate the role fundamental frequency variation plays in speech intelligibility. (2) To understand the importance of considering environmental noise in clinical speech intelligibility testing.

Adult↗

PubMed2003

Alpha 2-adrenoceptors in the basal ganglia have a role in memory consolidation and reinforcement.

This study demonstrates a role for alpha(2)-adrenoceptors in the basal ganglia in the consolidation of memory using weakly and strongly reinforced models of discriminated avoidance learning in the chick. The memory enhancing action of noradrenaline injected into the basal ganglia (lobus parolfactorius-LPO) was reduced in the presence of the alpha(2)-adrenoceptor antagonist yohimbine, but when noradrenaline was injected into the multi-modal association area (intermediate medial hyperstriatum ventrale-IMHV), yohimbine failed to prevent memory enhancement. Yohimbine injected into the LPO prevented, whereas the alpha(2)-adrenoceptor agonists oxymetazoline and clonidine enhanced, consolidation of memory. The timing of the inhibitory effect of yohimbine in the LPO suggested that alpha(2)-adrenoceptor involvement occurs 10-15 min after training, and that stimulation of alpha(2)-ARs in LPO is necessary for subsequent consolidation of memory. Oxymetazoline, being hydrophilic, was ineffective injected into IMHV, whereas the action of the lipophilic alpha(2)-adrenoceptor agonist clonidine in the IMHV was interpreted as an action at a site more distal in the brain, probably the LPO. The results suggest that noradrenaline release in the basal ganglia in the chick stimulates alpha(2)-adrenoceptors, which modulate and consolidate memory formation mediated by beta(2)- or beta(3)-ARs in the association area. The LPO may be responsible for the reinforcement of memory in the IMHV.

Adrenergic Agonists↗

PubMedDate not supplied

Differential effect of free intake versus oral perfusion of sucrose in conditioned taste aversion in rats.

Five experiments were designed to investigate LiCl-induced conditioned taste aversion (CTA) obtained in rats whether after free intake of a sucrose solution (active mode) or after forced administration through an intraoral cannula (passive mode). It was found in Experiment 1 that actively conditioned rats showed a slower extinction rate as revealed by repeated two-bottle tests (active testing) as opposed to passively conditioned ones. As these rats underwent a mode change between conditioning and testing, the differential extinction rate might have arisen from this change inducing a generalization decrement effect or acting as a contextual shift. In Experiment 2, no evidence for any generalization decrement was found. The possibility that the mode of sucrose delivery could have contextual properties in CTA through a "renewal test" after extinction and a latent inhibition experiment was further tested in Experiments 3 and 4. When active testing followed passive extinction, a CTA was afresh obtained in rats actively conditioned in active conditions. Latent inhibition was attenuated in rats preexposed in passive conditions and conditioned in active conditions (i.e., when a shift in the drinking mode occurred between preexposure and conditioning). In Experiment 5, intraoral perfusion was used in both groups. The active subjects had to nose poke for intraoral administration of sucrose. The yoked control passive subjects received simultaneously the same amount of sucrose. The levels of CTA differed also from the actively to the passively conditioned subjects. Results are discussed in terms of free intake activity acting as a contextual modulator of CTA.

Animals↗

PubMed2003

Wheel running produces conditioned food aversion.

Previous investigations of conditioned taste aversion (CTA) induced by wheel running have used flavored liquids such as conditioned stimuli (CSs). Assuming that classical conditioning mediates activity anorexia, it is expected that CTA induced by physical activity should extend to food stimuli. The main purpose of the present experiment was to investigate this possibility. Rats were given a 60-min access to a running wheel [unconditioned stimulus (US)] either before or after being exposed to a novel distinctive flavored food (CS). An additional group had access to running wheels 4 h after receiving the CS food. Results from the present experiment indicate that regimented and contingent periods of wheel running decrease consumption of a food available before wheel running in nondeprived rats.

Analysis of Variance↗

PubMed1997

Reinforcer revaluation and conditioned place preference.

Conditioned place preference (CPP) tests provide a novel way of testing an animal's ability to respond to direct manipulation of its motivational state. In the first of two studies, rats exhibited an appropriate preference for a place previously paired with either food or fluid, depending on their current motivational state (hungry or thirsty). Preference was independent of the animal's prior exposure to the relevant reinforcer in that motivational state. In the second experiment, a sucrose solution was used to generate a place preference and was subsequently devalued using a LiCl taste aversion procedure. One group (B) received two CTA sessions and two further groups received a single CTA session either with (R), or without (N), a further nonreinforced opportunity to drink sucrose. Group B exhibited a substantial place aversion and a considerable reduction in sucrose consumption in a test following assessment of place preference. A weak place aversion was found in group N and a weak place preference was shown by group R; sucrose consumption in a test following measurement of place preference followed a similar pattern. These two studies indicate that performance on a place preference task is directly sensitive to both shifts in motivational state and reduction in reinforcer value.

Animals↗

PubMed1997

Remote and proximal US preexposure and aging effects in taste aversion learning in rats.

Age as a factor in the effect of proximal and remote unconditioned stimulus (US) preexposure on conditioned taste aversion in weanling, young adult, and old rats was studied in 2 experiments. In Experiment 1, 6 daily US preconditioning exposures attenuated conditioning in weanlings and young adults, but not in old rats. In Experiment 2, exposure to a single US 1 h before the conditioning trial curtailed conditioning at all age levels. These results are explained in terms of age differences in familiarity with the conditioning context and Wagner's information-processing model for self- and retrieval-generated disruption of conditioning.

Aging↗

PubMed1997

Extinction of a conditioned taste aversion in rats: I. Behavioral effects.

The literature is divided over whether a conditioned taste aversion (CTA) can be fully extinguished. In Experiment 1, we created a powerful aversion in 54 rats by pairing the taste of 0.0025 M NaSaccharin (CS) with intraperitoneal injections of 127 mg/kg LiCl (US) on 3 occasions. We then offered 23-h deprived rats NaSaccharin for 10 min/day to observe the course of recovery. Extinction occurred in three phases: static, dynamic, and asymptotic. During the static phase (mean = 9.6 days), rats consumed the CS at < 10% of their preconditioned rate. With dynamic recovery (6.0 days), they increased acceptance to > 80% of preconditioning levels. Finally, they achieved asymptote (3.1 days) at 100% acceptance. In Experiment 2, we used 8 additional conditioned rats and 8 unconditioned controls. We followed the same 1-bottle extinction procedure and, again, obtained 100% acceptance. Then we offered both NaSaccharin and water for 8 days at 23 h/day and monitored lick patterns every 6 s to determine taste preferences. The conditioned animals consumed less NaSaccharin than controls on Day 1, and less NaSaccharin as a percentage of total fluid as late as Day 3. For the last 5 days of 2-bottle preference testing, there were no significant differences between the groups with regard to 1. volume of NaSaccharin or water consumed, 2. percentage of total fluid taken as NaSaccharin, 3. consumption of each fluid associated with a meal or taken spontaneously, 4. intake during the light or dark periods, or 5. the characteristics of ingestion, including number of drinking bouts, duration of bouts, number of licks/bout, and rate of licking. Therefore, a robust CTA is subject to complete behavioral extinction.

Animals↗

PubMed1997

Antiemetic inhibits conditioned taste aversion, but not the hypophagia induced by epinephrine.

It has been shown that relatively high doses of epinephrine (E) injected intraperitoneally (IP) produce hypophagia and conditioned taste aversion (CTA) in rats. We examined the possibility that E effects involve malaise. For this purpose, changes in saccharin preference induced by E injected IP (100 microg/kg) were determined after a previous administration of trimethobenzamide (TMB, 5 mg/kg), an antiemetic agent. E alone decreased saccharin preference by 54% (p < 0.01), but only by 16% (not significant) in the presence of TMB. In contrast, the injection of 75 or 100 microg/kg E reduced food intake by 50 and 85%, respectively (p < 0.01), regardless of previous injection of TMB. In conclusion, the results suggest that E-induced malaise is not the direct cause of the hypophagia it elicits.

Animals↗

PubMed2002

One-trial tolerance to midazolam is due to enhancement of fear and reduction of anxiolytic-sensitive behaviors in the elevated plus-maze retest in the rat.

The anxiolytic-like effects of benzodiazepines (BZDs) in rats is reduced after a single exposure to the elevated plus-maze test (EPM). Several hypotheses have been formulated but no conclusive explanation exists for this phenomenon called "one-trial tolerance." In this study, we examined this phenomenon further by carrying out an ethopharmacological analysis of the behavior of rats submitted to the EPM in two trials. Rats injected with saline before both trials (control), treated with 1.0 mg/kg of midazolam before both trials (MM), or only before Trial 2 (SM), were exposed to the EPM. The SM group did not differ from the controls in the Trial 1 and Trial 2 conditions. The MM group showed a clear anxioselective profile in Trial 1 and no anxiolytic-like effects in Trial 2. Whereas midazolam injected before the first trial caused no significant change in immobility, there was a pronounced increase in immobility during Trial 2 for all three conditions. These data suggest that the anxiolytic-like action of midazolam in the first trial gives way to the fear-related insensitive behaviors (phobic/avoidance responses) responsible for the one-trial tolerance to BZDs in Trial 2. Furthermore, an additional experiment showed that midazolam does not seem to affect the acquisition of the learned avoidance response since it is present upon retesting even after midazolam administration in Trial 1 (MS group). Rather, the present data suggest an emotional shift from Trial 1 to Trial 2, which leads to change in the responsiveness of the animals to BZDs.

Animals↗

PubMed2003

Time-dependent effects of cycloheximide on long-term memory in the cuttlefish.

When shown prawns in a glass tube, cuttlefish promptly learn to inhibit their predatory behavior and retain this ability for a long time. The cellular and molecular mechanisms of this long-term memory (LTM) are not yet known. In this study, we analyzed the dependency of LTM on de novo brain protein synthesis. Cycloheximide (CXM), a protein synthesis inhibitor, is injected intravenously immediately, 1 h, 3 h, 4 h or 6 h after the training. Retention is tested 24 h posttraining. The injections of CXM revealed one period of memory sensitivity to pharmacological intervention. CXM administered immediately or 6 h after training has no effect on LTM. Conversely, injections given between 1 and 4 h posttraining resulted in amnesia. Taken together, findings of this study establish for the first time in Sepia officinalis that de novo protein synthesis is an essential and time-dependent event for LTM formation of this form of associative learning.

Animals↗

PubMed1984

Changes in alcohol intake resulting from prior experiences with alcohol odor in young rats.

Twenty-one day old rats were exposed to either alcohol or lemon odor, paired or unpaired with lithium chloride (LiCl) induced toxicosis, and were tested 7 days later for odor preferences and ethanol intake. Additional control groups received neither the conditioned nor the unconditioned stimuli and were merely tested on either odor preference or alcohol consumption. Ethanol odor exposure per se resulted in an enhanced ingestion of a 5.6% ethanol solution. This effects was attenuated by pairing such exposure with internal malaise. Furthermore, ethanol odor-LiCl pairings decreased olfactory preferences for ethanol relative to lemon odor, whereas lemon-LiCl pairings increased ethanol odor preference relative to lemon odor. Order of testing also affected odor preferences. Rats previously tested on ethanol consumption demonstrated a strong rejection of the alcohol odor when compared to rats initially tested in the olfactory task. These results suggest that early learned and unlearned experiences with alcohol odor can not only affect subsequent ethanol odor preferences but can also lead to significant changes in alcohol consumption.

Alcohol Drinking↗

PubMed1997

Drug disruption of short-term memory in Drosophila melanogaster.

Recent work on operant visual learning and memory in Drosophila has suggested at least three distinct memory phases. Trying to disrupt memory pharmacologically, we fed flies with ouabain or the depolarizing drugs potassium chloride (KCl), lithium chloride (LiCl) and monosodium glutamate for some specific time before training. The depolarizing drugs abolished memory very soon after training. Ouabain exerted no effect on memory within the first 20 min but abolished it more than 30 min after training. These drugs had no diminishing effects on the visual discrimination and behavioral performance of the flies during training. This result suggests that memory disruption may not be induced by nonspecific effects of the drugs. In addition, reversal training of the KCl-fed flies indicates that KCl appears not to impair the retrieval mechanism of flies. These results suggest that the specific disruptive effects of the drugs on memory formation and the existence of a short-term memory phase, are susceptible to disruption of the depolarizing drugs but unaffected by ouabain.

Animals↗